BType of nutrition characteristic of all fungi. Fungi release enzymes into their substrate and absorb dissolved nutrients.
Ec[000000]f[16]LBactin
BOne of two proteins found in microfilaments. Actin molecules have binding sites for both ATP and myosin. Actin acts as a catalyst to activate the ATPase activity of myosin. Actin and myosin are usually found in association.
Ec[000000]f[16]LBactive transport
BThe ability of membranes to bind and transport certain molecules and ions at the expense of cellular energy.
Ec[000000]f[16]LBadjacent
BNext to or close to.
Ec[000000]f[16]LBADP
BThe scientific designation for adenosine diphosphate. ADP and inorganic phosphate are the result of ATP breakdown.
Ec[000000]f[16]LBaerobe
BAn organism that requires free oxygen for metabolism. An obligate aerobe must have oxygen; a facultative aerobe uses free oxygen when it is available, but may switch to other chemical reactions in the absence of free oxygen.
Ec[000000]f[16]LBaerobic
BRequiring oxygen. Aerobic chemical reactions require oxygen. Anaerobic chemical reactions do not require oxygen.
Ec[000000]f[16]LBaggregate
BA collection that is massed together. Aggregate proteins are linked or bonded together. In membranes, aggregate proteins are formed by interactions between integral proteins or between integral and peripheral proteins.
Ec[000000]f[16]LBalcoholB
An organic compound with a hydroxyl group attached to a carbon atom. Examples include ethanol and methanol.
Ec[000000]f[16]LBaldehydeB
A highly reactive organic compound obtained by oxidation of primary alcohols.
Ec[000000]f[16]LBalgae
BA general term for various groups of photosynthetic protists; sometimes also applied to a phylum of monerans--the cyanobacteria, or blue-green algae.
Ec[000000]f[16]LBallele
BA specialized gene. Alleles are genes that transmit specific genetic information.
Ec[000000]f[16]LBalpha-helix
BThe shape formed by amino acid chains in membrane proteins. This shape is a regular coiled formation that is rigid and unbending.
Ec[000000]f[16]LBamino acid groupB
A functional group found in organic compounds, primarily in proteins; it consists of an NHBS2BS group.
Ec[000000]f[16]LBamino acids
BThe building blocks of proteins. Amino acids are assembled into proteins through a process known as protein synthesis. The order of amino acids in a protein chain determines the function of the protein. The assembly of proteins is regulated by DNA molecules that carry hereditary information.
Ec[000000]f[16]LBamoeba
BA single-celled organism found in fresh and salt water, soil, some plants, and on animals as parasites. The amoeba moves by extending its protoplasm into a pseudopod.
Ec[000000]f[16]LBamoeboid cells
BCells that move by means of pseudopodia. An amoeba is an amoeboid.
Ec[000000]f[16]LaBmphipathic
BHaving both hydrophobic and hydrophilic properties. A chemical or biological substance that has both of these properties is amphipathic in nature. An amphipathic substance is dually soluble and must adopt a shape in which both solubility preferences are satisfied.
Ec[000000]f[16]LBamphoteric
BFrom a Greek work that means "either of two," this word may be used to describe compounds that are polar and nonpolar, such as phospholipids, or that can act as either an acid or a base.
Ec[000000]f[16]LBanaerobe
BAn organism whose metabolism does not require free oxygen. An obligateI Ianaerobe cannot tolerate the presence of free oxygen; facultative anaerobe is synonymous with facultative aerobe.
Ec[000000]f[16]LBanalog
BSomething that is similar in many respects to something else; also spelled analogue.
Ec[000000]f[16]LBanaphase
BA phase of cellular reproduction in which the chromosomes move to the poles. Anaphase occurs in both mitotic reproduction and in meiotic reproduction. In meiosis, metaphase happens twice: metaphase I and metaphase II.
Ec[000000]f[16]LBanimal
BOne of the five kingdoms. A multicellular organism that develops from a blastula formed after a large egg is fertilized by a smaller motile sperm. Animals are heterotrophic, metabolizing food produced by other organisms.
Ec[000000]f[16]LBantheridium
BThe male sex organ of algae, fungi, bryophytes, and pteridiphyta.
Ec[000000]f[16]LBantibodies
BProteins in the blood that attack foreign bodies, such as blood and other disease-producing organisms.
Ec[000000]f[16]LBanticodon
BA group of three adjacent nucleotide bases on transfer RNA. An anticodon corresponds to a complementary codon on messenger RNA, specifying one amino acid.
Ec[000000]f[16]LBaqueous
BMade with or from water. An aqueous environment is one in which water is present. A nonaqueous environment is one in which water is absent.
Ec[000000]f[16]LBarchegonium
BThe multicellular, water-retaining structure in which a single egg is produced and fertilized in the liverworts, mosses, and hornworts.
Ec[000000]f[16]LBAscomycetes
BThe fungal phylum characterized by the production of ascospores in an ascus, following sexual conjugation of two strains. Many Ascomycetes also may produce asexual spores in one of a variety of ways.
Ec[000000]f[16]LBascus
BThe pouch in which ascospores are produced; the expanded cell wall of the original zygote nucleus formed after conjugation.
Ec[000000]f[16]LBasexual
BRefers to reproduction that takes place without male and female gametes; nonsexual reproduction.
Ec[000000]f[16]LBasexual reproduction
BReproduction that does not involve the fusion of genetic material from two individuals; vegetative reproduction. The binary fission of protists, such as amoeba and paramecium,I Iis a type of asexual reproduction, as is the growth of daughter colonies within IVolvoxI and the production Ec[000000]f[16]LFand development of zoospores among many algae.
Ec[000000]f[16]LBasymmetric
BUneven distribution on either side of a midpoint. Membranes are asymmetric because they have different distributions of proteins and lipids in the two halves of the bilayer.
Ec[000000]f[16]LBATP
BThe scientific designation for adenosine triphosphate. ATP is called the energy molecule because it furnishes energy for growth, reproduction, muscle contraction, and other chemical processes. The breakdown of the ATP molecule provides energy that is converted from chemical Ec[000000]f[16]LFenergy to mechanical energy for growth or movement. ATP is broken down into ADP and phosphate.
Ec[000000]f[16]LBautotroph
BA producer. An organism that produces its own food, most commonly thorough photosynthesis, but in the case of some bacteria, through chemosynthesis.
Ec[000000]f[16]LBaxoneme
BThe bundle of microtubules that form the central axis of flagella and cilia. The arrangement of microtubules is uniform and gives scientists the most abundant information about the structure and function of microtubules.
Ec[000000]f[16]LBbacteria
BThe smallest living organisms. These one-celled organisms lack a nucleus with a distinct membrane, making them procaryotic cells.
Ec[000000]f[16]LBbase pairs
BThe two nitrogenous compounds in nucleotides that match each other and can hydrogen-bond to help form the double helix of DNA molecules.
Ec[000000]f[16]LBBasidiomycetes
BThe fungal phylum characterized by the production of basidiospores on a basidium.
Ec[000000]f[16]LBbasidium
BA club-shaped reproductive structure with several spores attached to its tip; basidia repacked along the gills or pores of typical mushrooms.
Ec[000000]f[16]LBbenzene
BA molecule composed of six carbon atoms connected in a ring or hexagon. Each carbon atom has a hydrogen atom attached to it. Benzene is a colorless, toxic liquid and is used as a solvent.
Ec[000000]f[16]LBbilayer
BA layer composed of two distinct parts. A membrane bilayer is composed of two layers of lipids. The fatty acid chains line up end to end in the inside of the bilayer, forming a hydrophobic region that excludes water molecules. The phosphate and alcohol groups face the surrounding water.
Ec[000000]f[16]LBbiochemical
BRelating to the chemistry of biological processes.
Ec[000000]f[16]LBblastula
BA hollow ball of cells formed after a zygote undergoes a sequence of cell divisions in the very early embryology of animals.
Ec[000000]f[16]LBbryophyte
BNonvascular plant.
Ec[000000]f[16]LBcapping
BThe active movement of some proteins through cell membranes. The accumulation of molecules within the cell is called the cap. Energy must be expended by the cell in this kind of active transport.
Ec[000000]f[16]LBcarbohydrate
BA chemical compound such as sugar or starch. Carbohydrates are composed of carbon, hydrogen, and oxygen. They can attach to the lipids and proteins of interior and exterior cellular membranes, and they make up the cellulose that is used to build the cell wall.
Ec[000000]f[16]LBcarbonB
A nonmetallic element with a vast number of compounds in its forms. Organic chemistry is a branch of chemistry devoted to the study of carbon.
Ec[000000]f[16]LBcarbonyl group
BAn important functional group in organic chemistry; it contains a carbon atom double-bonded to an oxygen atom (CO).
Ec[000000]f[16]LBcarboxyl group
BAn important functional group in organic chemistry; it contains a carbon atom double-bonded to an oxygen atom, and single-bonded to an oxygen atom that is in turn single-bonded to a hydrogen atom (COOH).
Ec[000000]f[16]LBcartilage
BA tough, elastic tissue that is mostly replaced by bone in many developing vertebrate embryos (such as our own). The mouth of lampreys and hagfishes is supported by cartilage, which forms the entire skeleton of sharks and rays.
Ec[000000]f[16]LBcatalyst
BA compound that speeds the reaction time between two other compounds but remains unchanged after the reaction is completed.
Ec[000000]f[16]LBcell
BThe smallest unit of life. It exhibits all the properties associated with life, such as reproduction, chemical activity, and responsiveness. Cells can be grouped into two classes: procaryotes and eucaryotes.
Ec[000000]f[16]LBcell cycle
BThe cycle of growth, synthesis, and division that a cell undergoes during reproduction. The cell cycle is a never-ending process.
Ec[000000]f[16]LBcell membrane
BThe cell membrane surrounds the cell and divides the cell from its surroundings. It is the site of much chemical activity. It is also a site for communication between the cell and its surroundings. It allows certain molecules to enter the cell while preventing other molecules from entering. Ec[000000]f[16]LFThe cell membrane is also known as the plasma membrane.
Ec[000000]f[16]LBcell plate
BThe structure that divides a plant cell during cell division. The cell builds the plate out of membranous vesicles that fuse together across the cell and split it in half.
Ec[000000]f[16]LBcell wall
BA structure found outside the cell membrane. Cell walls are found in plant cells and in procaryotes. Most animal cells lack cell walls. Cell walls are rigid but porous.
Ec[000000]f[16]LBcellulose
BThe substance used to create the cell wall of plant cells. Cellulose is composed of carbohydrate fibers laid down in a crisscross network.
Ec[000000]f[16]LBcentrioles
BMicrotubules that form the poles of the spindle apparatus. Centrioles are found in animal cells and are bundled in nine groups of three microtubules.
Ec[000000]f[16]LBcentromere
BThe point at which two chromatids are attached. This is also the point at which the fiber from the spindle apparatus attaches to the chromosome.
Ec[000000]f[16]LBchemistryB
The scientific study of elements and compounds, with the atoms and molecules of which they are composed, and with the reactions between them.
Ec[000000]f[16]LBchiasmata
BThe point at which two homologous chromosomes join together in crossover. The chromosomes are attached at the chiasmata. Longer chromosomes have more chiasmata than shorter chromosomes.
Ec[000000]f[16]LBchloroplast
BGreen, photosynthetic organelle that contains chlorophyll.
Ec[000000]f[16]LBchromosomes
BSubcellular structures found in the nucleus of the cell; they contain DNA molecules, which carry the genetic code. They are composed of alleles and genes and condense out of chromatin to form two strands that are attached at a point, called a centromere.
Ec[000000]f[16]LBcilium
BUsually refers to a relatively short cellular appendage with a circular arrangement of nine pairs of microtubules with another pair in the center. A cilium is surrounded by the cell membrane and filled with cytoplasm.
Ec[000000]f[16]LBcirculatory system
BThe human blood system. The circulatory system flows throughout the body, carrying food and oxygen to cells and removing waste products from cells. Hormones are carried to their destinations via the circulatory system.
Ec[000000]f[16]LBcleavage
BThe act of splitting apart. Cleavage in cellular terms refers to the splitting apart of the cell. The cell cleaves in two during cell division.
Ec[000000]f[16]LBcoagulate
BTo turn a liquid into a semi-solid or solid mass.
Ec[000000]f[16]LBcodon
BA group of three adjacent nucleotide bases on messenger RNA. A codon specifies which amino acid should come next in the sequence during protein synthesis.
Ec[000000]f[16]LBCoelenterates
BPhylum of animals that contains the hydroids: jellyfish, sea anemones, coral, and comb jellies. All are aquatic, mostly marine.
Ec[000000]f[16]LBcoelom
BA membrane-lined sac between the digestive tube and the body wall of several phyla of animals. The lining forms from mesoderm tissue during embryological development.
Ec[000000]f[16]LBcoenocytic
BDescribes large cells with many nuclei. In coenocytic cells, mitosis occurs without cell division or cytokinesis, resulting in one large cell with many nuclei.
Ec[000000]f[16]LBcomatose
BIn a coma; not responding to external stimuli; unconscious.
Ec[000000]f[16]LBcomb jellies
BCharacterized by radial-body symmetry, the comb jellies are propelled mouth forward through the water by the movement of bands of cilia that resemble combs. While comb jellies have muscle tissue with some control over their mouths, the coelenterates do not have muscle tissue.
Ec[000000]f[16]LBcomplement
BTo complete or make whole; in nucleic acids, nucleotide bases that can form a stable pair with another nucleotide base through hydrogen bonding complement that base.
Ec[000000]f[16]LBcomplementary
BIn nucleic acids, nucleotide bases that can form a stable match through hydrogen bonding.
Ec[000000]f[16]LBcondensation
BThe process of reducing the size or volume of something; in biochemistry, condensation reactions combine two molecules by removing a water molecule. Condensation is the opposite of hydrolysis.
Ec[000000]f[16]LBconformational change
BA structural change. The interaction between ATP molecules and microtubules or microfilaments causes a structural change in each.
Ec[000000]f[16]LBconjugate base-acid
BA compound capable of dissociating with a hydrogen ion and acting as a base, and then associating with a hydrogen ion and acting as an acid. Conjugate base/acid systems serve as buffers to resist changes in pH when a strong acid or base is added to a solution.
Ec[000000]f[16]LBconjugation
BA type of sexual reproduction that usually leads to the fusion of a pair of similar nuclei as one cell donates its nucleus to another.
Ec[000000]f[16]LBcontract
BTo make smaller. During muscle contraction, the H-bands become narrower.
Ec[000000]f[16]LBcontraction
BThe act of contracting; in muscles, contraction is the shortening of muscles as they are put to work.
Ec[000000]f[16]LBcotyledons
BThe first leaves of a plant, often strikingly different from later leaves. In some plants, like the bean, they contain large quantities of stored food that get the embryo off to a good start until it can shift for itself. Cotyledons are the two halves of the bean seed, which usually persist for only a short while after germination.
Ec[000000]f[16]LBcovalent bondB
A bond in which two atoms share a pair of electrons. Most bonds in organic molecules are covalent bonds.
Ec[000000]f[16]LcBross-bridge
BThe connection between microtubules and microfilaments that is responsible for the sliding motion of each. In microtubules, the cross-bridge is formed by the dynein arms. In microfilaments, the cross-bridge is formed by myosin.
Ec[000000]f[16]LBcrossover
BThe process in which homologous chromosomes exchange bits of hereditary information. Crossover insures genetic variability within the species.
Ec[000000]f[16]LBcyanobacteria
BBlue-green algae.
Ec[000000]f[16]LBcycads
BLarge, palmlike, tropical, cone-bearing plants that have long, fernlike clusters of leaves emanating from the top of a trunk or an underground stem.
Ec[000000]f[16]LBcysteine
BAn amino acid, found primarily in hair, that contains a sulfur atom. The sulfur atoms of two cysteine amino acids may bond, forming a disulfide bridge that connects a protein to itself as it folds.
Ec[000000]f[16]LBcytokinesis
BThe term used to specify the division of cytoplasm in cellular reproduction. During cytokinesis, the cell actually splits apart, dividing up the cytoplasm and the organelles.
Ec[000000]f[16]LBcytology
BThe branch of biology that deals with the structure, function, and formation of cells. Cytologists are scientists that study cells.
Ec[000000]f[16]LBcytoplasm
BThe gelatinous substance outside the nucleus of cells. The substance inside the nucleus of cells is called nucleoplasm. Together, cytoplasm and nucleoplasm are called protoplasm.
Ec[000000]f[16]LBdalton
BA unit that measures the weight of single molecules.
Ec[000000]f[16]LBdehydration
BThe process of removing water from something; the condensation reaction can be considered a form of dehydration and is often called dehydration synthesis.
Ec[000000]f[16]LBdenature
BTo change the character of something. In biochemistry, a denatured protein is no longer able to function properly. Protein molecules are denatured by changes in temperature or pH, which disrupt the fragile bonds that keep them folded properly.
Ec[000000]f[16]LBDeuteromycetes
BThe fungal phylum characterized by a lack of sexual reproduction. Occasionally, a mycologist discovers a sexual reproduction in a deuteromycete. At that point, the sexual form is placed into whichever other phylum its mode of reproduction dictates.
Ec[000000]f[16]LBdeuterostome
BA few phyla of animals in which the blastopore formed during early embryology develops in the anus rather than the mouth. These phyla are thought to share fairly recent common ancestry based on this same feature. Chordates are among the deuterostome phyla.
Ec[000000]f[16]LBdinucleotide
BA molecule made of two nucleotides bonded together.
Ec[000000]f[16]LBdiploid
BContaining paired chromosomes in the nucleus, rather than a single set. Also see haploid.
Ec[000000]f[16]LBdiscernible
BAble to be seen or understood.
Ec[000000]f[16]LBDNA
BDeoxyribonucleic acid. Genetic material in the nucleus of eucaryotic cells and the nucleoid are composed of long strings of varying sequences of four nucleotides. The degree of similarity of these sequences in the DNA of various organisms can be an indication of the Ec[000000]f[16]LFextent of their shared ancestry. When a sufficient catalog of these sequences has been determined among many organisms, direct comparison should indicate relative times for the divergence of different groups of organisms from common ancestors.
Ec[000000]f[16]LBdormant
BThe state of a plant when it is not growing, or it is in suspended development.
Ec[000000]f[16]LBdouble helix
BThe name given to the shape of a DNA molecule. DNA molecules are composed of two chains of chemical compounds. Each compound in one chain is attracted to its counterpart on the other chain. The two chains coil around each other to form the shape of a helix.
Ec[000000]f[16]LBdoublet
BTwo microtubules that are connected together by a shared wall. The two microtubules of the doublet are called the A subtubule and the B subtubule. The A subtubule is complete within itself. The B subtubule, however, is not a complete microtubule. It is an incomplete circle in Ec[000000]f[16]LFcross section and is attached to the A subtubule to make it enclosed.
Ec[000000]f[16]LBdynein arm
BMicrotubular arms that extend from the A subtubules and come in contact with adjacent B subtubules during flagellar bending. The dynein arms bind and break down ATP molecules to produce energy. They then slide the attached B subtubule to a new position, causing movement in the flagella.
Ec[000000]f[16]LBIE. coliBI
A bacterium studied by scientists. IE. coliI cells reproduce in a way similar to sexual reproduction.
Ec[000000]f[16]LBechinoderm
BAnimals that are characterized by a five-part radial symmetry; illustrated by the five arms of a starfish and seen in the sections of a sand dollar or sea urchin's skeleton.
Ec[000000]f[16]LBectoderm
BOutermost germ layer of animal embryo, developing into epidermis, nerve tissue, and sense organs.
Ec[000000]f[16]LBeffectors
BMolecules that bind to proteins and affect their functioning.
Ec[000000]f[16]LBelater
BA hygroscopic attachment to a horsetail spore.
Ec[000000]f[16]LBelectron microscope
BA mechanical device used to observe cells and subcellular structures. The electron microscope uses electrons, rather than visible light, to illuminate the cell. The pictures taken by this apparatus are called electron micrographs. A cell must be killed, stained with chemicals, and sliced Ec[000000]f[16]LFvery thin in order to be observed with an electron microscope.
Ec[000000]f[16]LBelectron spin resonance
BAn experimental technique used to study the fluid state of membranes. In this technique, phospholipid molecules are tagged by combining them with chemical groups containing unpaired electrons. A magnetic field is applied, and the tagged groups produce a distinct absorption Ec[000000]f[16]LFcurve, allowing researchers to watch tagged groups travel through membranes.
Ec[000000]f[16]LBelectronegative
BAble to attract electrons.
Ec[000000]f[16]LBelectronegativityB
The tendency of an atom to draw electrons. Atoms with electronegativity tend to attract atoms with a slightly positive charge, resulting in hydrogen bonds.
Ec[000000]f[16]LBelement
BIn chemistry, a substance made of atoms that have the same number of protons in their nucleus.
Ec[000000]f[16]LBelongate
BTo make longer. The spindle apparatus elongates during cell division, and some microtubules and microfilaments can elongate by growing.
Ec[000000]f[16]LBelongation
BThe act of making longer; in protein synthesis, this includes the activities necessary to add an amino acid to the growing chain of amino acids.
Ec[000000]f[16]LBembryo
BA rudimentary plant formed after sexual reproduction; a young sporophyte. The embryo is formed in the ovule of seed plants and in the archegonium on the gametophyte of plants, such as mosses and ferns.
Ec[000000]f[16]LBendoderm
BThe second of the primary germ layers in a blastula that develops into the lining of the lungs, pancreas, liver, and the digestive and respiratory systems.
Ec[000000]f[16]LBendoplasmic reticulum
BAn organelle within the cell that is a site of protein synthesis. The endoplasmic reticulum, also known as the ER, can be either rough or smooth. It is made rough by the many ribosomes covering its surface. Smooth ER is associated with the synthesis of hormones.
Ec[000000]f[16]LBendoskeleton
BSupporting structure within the body. Our own endoskeleton is living tissue that grows as we grow. Some endoskeletons, sponges for instance, are secreted structures that slowly grow by means of added secretions.
Ec[000000]f[16]LBenzyme
BProtein molecule whose function is to accelerate, or catalyze, chemical reactions at the cellular level. The manufacturing of enzymes is regulated by DNA molecules in a process called protein synthesis. Certain types of enzymes perform specific functions. For example, Ec[000000]f[16]LFsome cells use enzymes to transmit nerve impulses while other cells use different enzymes to manufacture hormones.
Ec[000000]f[16]LBequator
BThe middle point of the spindle apparatus. The equator of the spindle apparatus is analogous to the equator of the earth. It encircles the cell at the midpoint. Chromosomes line up at the equator before beginning their journey to the poles.
Ec[000000]f[16]LBErlenmeyer flasks
BA laboratory vessel with a wide, flat bottom tapering to a narrow neck; named after the German chemist who originated the shape, Emil Erlenmeyer, 1825-1909.
Ec[000000]f[16]LBethanol
BAn organic molecule, CBS2BSHBS5BSOH; also called ethyl alcohol or alcohol. It is the intoxicating substance in fermented beverages such as beer, wine, and liquor.
Ec[000000]f[16]LBeucaryote
BA cell containing many internal organelles. Eucaryotic cells form higher organisms, such as plants and animals, and are complex.
Ec[000000]f[16]LBeucaryotic
BHaving a cell nucleus where DNA is contained, like most cells. Also spelled eukaryotic.
Ec[000000]f[16]LBexoskeleton
BExternal supporting structure, such as the hard, crunchy covering of a beetle or crab. Exoskeletons are shed periodically as organisms grow.
Ec[000000]f[16]LBexperimentation
BThe processes of testing hypotheses to determine whether they are reliable.
Ec[000000]f[16]LBextent
BDegree or range of application or coverage.
Ec[000000]f[16]LBextrinsic proteins
BMembrane proteins that come in contact with the membrane surface. Extrinsic proteins are also called peripheral proteins. Extrinsic proteins can be removed from membranes by relatively mild treatments, such as changing the salt concentration or acidity of the aqueous medium surrounding the membrane.
Ec[000000]f[16]LBfacilitated
BMade easier or removed obstacles.
Ec[000000]f[16]LBfat
BA type of lipid used primarily as a way for animals and some plants to store energy; fats are made up of three fatty acids attached to one glycerol molecule.
Ec[000000]f[16]LBfatty acids
BLong chains of hydrocarbons, each containing a carboxyl group on the end; fats are made of three fatty acids attached to one glycerol molecule.
Ec[000000]f[16]LBfermented
BA sugar that has been split into carbon dioxide and alcohol by a yeast.
Ec[000000]f[16]LBfertilization
BThe process of fusion between two gametes. The sperm cell fertilizes the egg cell when the two cells fuse together to produce a zygote.
Ec[000000]f[16]LBfibers
BThe elongated, cylindrical or ribbonlike cells in muscles. Striated muscle fibers get their appearance from the striations of the myofibrils.
Ec[000000]f[16]LBfilament
BA thin fiber or threadlike appendage. Microfilaments are organelles within animal cells.
Ec[000000]f[16]LBfive-kingdom classification system
BOne of many classifications systems used by biologists to group living things. This system was proposed by R.H. Whittaker in the 1950s. According to this classification system, all life forms fall into one of five large groups called kingdoms. The Monera kingdom is composed of Ec[000000]f[16]LFprocaryotes, bacteria, and blue-green algae. The Protista kingdom includes protozoa and some single-celled algae. The remaining three kingdoms, which include all higher life forms, are the Fungi kingdom, the Plantae (plants) kingdom and the Anamalia (animals) kingdom.
Ec[000000]f[16]LBflagella
BHairlike projections from the surface of a cell that propel the cell. Flagella are also called cilia when they are found in large numbers.
Ec[000000]f[16]LBflagellar bending
BThe apparent motion that a flagellum makes. The motion is called "apparent" because the flagellum does not actually bend. The interior microtubules slide further into the tip, causing the movement.
Ec[000000]f[16]LBflagellum
BA relatively long cellular appendage. In procaryotes, it is composed of packed proteinaceous filaments and is embedded in the cell membrane and wall, rather than surrounded by the membrane as in eucaryotes.
Ec[000000]f[16]LBflatulence
BGas in the intestinal tract.
Ec[000000]f[16]LBfleeting
BPassing quickly; evanescent.
Ec[000000]f[16]LBfluctuates
BVaries or shifts inconsistently.
Ec[000000]f[16]LBfluid
BA substance that is able to flow and take the shape of its container. Cellular membranes are in a fluid state, meaning they are able to flow.
Ec[000000]f[16]LBfluid mosaic model
BThe model of membrane structure used today. According to the fluid mosaic model, proteins are suspended as globular units in a fluid lipid bilayer. This model also asserts that membranes are asymmetric.
Ec[000000]f[16]LBfree-floating
BUnattached to a cell membrane, wall, or organelle; floating freely in the cytoplasm.
Ec[000000]f[16]LBfreeze-fracture
BA scientific technique for observing membrane structure. In this technique, an artificial phospholipid bilayer or living tissue is quickly frozen and fractured with a knife edge. A replica of the fractured surface is made by coating it with a carbon and platinum film. The tissue is Ec[000000]f[16]LFthen thawed and dissolved away with acid, and the replica is observed with an electron microscope.
Ec[000000]f[16]LBfructose
BA six-carbon sugar found primarily in fruits and honey.
Ec[000000]f[16]LBfruit
BSwollen, ripe ovary or ovaries containing the seeds of angiosperms.
Ec[000000]f[16]LBfunctional group
BA specific group of atoms that serves a certain function in molecules.
Ec[000000]f[16]LBfungus
BOne of the five kingdoms. A fungus has absorptive nutrition and reproduces by means of spores.
Ec[000000]f[16]LBfurrow
BAn indentation that circles a cell before cell division. The furrow in animal cells results from the progressive sliding of microfilaments that constrict the cell until it splits into two parts.
Ec[000000]f[16]LBfuse
BTo mix together or blend, as if by melting. Two gametes fuse together and blend their internal materials during fertilization.
Ec[000000]f[16]LBgalactose
BA six-carbon sugar, found primarily in milk as part of the larger sugar molecule lactose.
Ec[000000]f[16]LBgamete
BThe egg or sperm cells necessary for fertilization and reproduction. The egg cell is of maternal origin, and the sperm cell is of paternal origin. Gametes participate in sexual reproduction, or meiosis. Gametes have a haploid number of chromosomes.
Ec[000000]f[16]LBgene
BA hereditary unit that occupies a specific position on a chromosome. Genes contain the hereditary information that is transmitted from the parent cell to the offspring cell.
Ec[000000]f[16]LBgenetic
BRelating to the original source of inherited cellular information.
Ec[000000]f[16]LBglobular
BNearly spherical or globe shaped. Membrane proteins are globular particles.
Ec[000000]f[16]LBglucose
BA six-carbon sugar that almost all living organisms use as a source of energy. Starch, cellulose, and table sugar all contain glucose.
Ec[000000]f[16]LBglycerol
BA type of alcohol that contains three hydroxyl (OH) groups. Glycerol is soluble in water.
Ec[000000]f[16]LBglycocalyx
BThe cell surface layer of carbohydrates. The carbohydrate groups extend from the cell surface into the surroundings. The appearance is called a sugar coating.
Ec[000000]f[16]LBglycogen
BOften called "animal starch," glycogen is manufactured in the liver of animals to store excess energy; like starch and cellulose, this is a glucose polymer.
Ec[000000]f[16]LBGolgi apparatus
BAn organelle within the cell that resembles a stack of squashed balloons with connecting tubes. The Golgi apparatus packages materials manufactured by the cell.
Ec[000000]f[16]LBGram stain
BA procedure developed by Hans Gram whereby bacteria with two distinct types of cell wall structure can be quickly identified under the microscope. The Gram stain was developed for medical use, but it is helpful in taxonomy because the cell wall difference indicates a basic ancestral division.
Ec[000000]f[16]LBgranum
BA stack of lamellae--or thin, platelike structures--found in the chloroplasts of plant cells. Granum means grain.
Ec[000000]f[16]LBGTP
BGuanosine triphosphate; a cofactor in energy metabolism. It contains the base guanine, the sugar ribose, and three phosphates attached together in a chain. Like ATP, it is a ready source of energy in many biochemical reactions.
Ec[000000]f[16]LBguanine
BOne of five nucleotide bases, it pairs with the nucleotide base cytosine. It was named after guano (bat excrement), where it was found.
Ec[000000]f[16]LBgut
BThe intestinal tract or alimentary canal.
Ec[000000]f[16]LBH-band
BThe open space between the thin filaments that run along the thick filaments in myofibrils. H-bands run transversely across the center of each sarcomere. When muscles contract, the H-band narrows.
Ec[000000]f[16]LBhaploid
BOne-half the number of chromosomes normally found in a somatic cell. Cells that have a haploid number of chromosomes have one set of chromosomes as opposed to two sets of chromosomes.
Ec[000000]f[16]LBhelix
BA spiral.
Ec[000000]f[16]LBhereditary
BHaving come from a predecessor; transferred genetically.
Ec[000000]f[16]LBheterotroph
BA consumer. An organism that fuels its metabolism with food it acquires from other organisms.
Ec[000000]f[16]LBhexagon
BA six-sided figure. The hexagon is the formation taken by the carbon atoms in benzene molecules. Also, the thick and thin filaments of myofibrils form a double hexagon. The thick filaments are surrounded by thin filaments in a hexagon. The thick filaments, in turn, are arranged in a hexagon.
Ec[000000]f[16]LBhomologous
BSimilar in structure and function.
Ec[000000]f[16]LBhormone
BA substance in the human body that is secreted by the glands, carried through the circulatory system, and deposited in target tissues. Hormones stimulate activity through chemical means. Different hormones have different purposes within the body.
Ec[000000]f[16]LBhydrocarbon
BA long chain of primarily hydrogen and carbon atoms; the hydrocarbon chains in fatty acids make up a large portion of fats.
Ec[000000]f[16]LBhydrogen bond
BA bond in which the hydrogen atom of one molecule is attracted to an electronegative atom in another molecule.
Ec[000000]f[16]LBhydrolysis
BA process that uses a water molecule to split a molecule. Hydrolysis is the opposite of condensation.
Ec[000000]f[16]LBhydrophilic
BHaving a preference for water or an aqueous environment. Chemical or biological substances with a hydrophilic nature prefer an aqueous environment. Phosphate and alcohol groups have a hydrophilic nature.
Ec[000000]f[16]LBhydrophobic
BHaving an aversion to water or an aqueous environment. Chemical or biological substances with a hydrophobic nature tend to avoid water or aqueous environments. Hydrocarbons of fatty acid chains have a hydrophobic nature.
Ec[000000]f[16]LBhydroxyl group
BA functional group that contains an oxygen atom and a hydrogen atom (OH). Hydroxyl groups are common in sugars and alcohols.
Ec[000000]f[16]LBhyphae
BStrands of fungal cells. Many hyphae together form a mycelium. Hyphae penetrate a fungus's substrate and absorb nutrients. Some yeasts, such as brewer's yeast, do not have hyphae.
Ec[000000]f[16]LBincapacitate
BTo make useless or without power.
Ec[000000]f[16]LBinert
BNot reactive with other elements; capable of forming few or no chemical compounds.
Ec[000000]f[16]LBingesting
BTaking food into the body.
Ec[000000]f[16]LBintegrity
BThe act of being sound and without flaws or having a tendency to stick to moral rules.
Ec[000000]f[16]LBinterphase
BThe phase that precedes mitotic cell division. An interphase also occurs between meiosis I and meiosis II. During interphase, the chromosomes are long and thin. During the interphase before both mitosis and meiosis, the chromosomes duplicate.
Ec[000000]f[16]LBintoxicating
BInducing a series of deteriorating states of mind, from euphoria to stupor, usually by drinking alcohol.
Ec[000000]f[16]LBintracellular
BOccurring or existing inside cells.
Ec[000000]f[16]LBintrinsic proteins
BProteins that are deeply embedded in the lipid bilayer of membranes; also called integral proteins. These proteins can be removed from membranes by treatments with detergents or solvents.
Ec[000000]f[16]LBisomer
BA molecular compound with the same atoms as another compound but with a different molecular structure.
Ec[000000]f[16]LBketone
BAn organic compound that contains an oxygen double-bonded to an internal carbon atom.
Ec[000000]f[16]LBkinetic
BHaving to do with motion.
Ec[000000]f[16]LBlay person
BSomeone without special skill or knowledge of a particular subject.
Ec[000000]f[16]LBlegume
BA plant of the pea family, an economically and ecologically important group. Also refers to a fruit type characteristic of this plant group.
Ec[000000]f[16]LBlenticel
BA lenslike formation of cells in the bark layer of a plant; a pore for gas exchange.
Ec[000000]f[16]LBlichen
BA symbiotic association between a fungus and an alga, or cyanobacterium. The fungus obtains all of its nourishment from the photosynthesis of its partner. Most of the fungi involved in these symbioses are Ascomycetes, but they occur only as lichens.
Ec[000000]f[16]LBlipid
BA large organic molecule that is generally insoluble in water. Examples include fats, which store energy in animal cells, and waxes, which coat and protect plant leaves.
Ec[000000]f[16]LBlipids
BA large group of organic compounds that are insoluble in water. They form the basic framework of membranes. Membrane lipids arrange themselves in two layers, called a bilayer, so that their dual property of solubility is satisfied. The lipid bilayer is in a fluid state.
Ec[000000]f[16]LBlumen
BThe central channel inside a microtubule wall. The microtubule wall is about four to five nanometers in thickness.
Ec[000000]f[16]LBlysis
BThe dissolution of the cell wall or membrane, thereby causing the destruction of a cell.
Ec[000000]f[16]LBlysosome
BMembrane-bound vesicles that contain enzymes and other chemicals that are capable of breaking down cellular molecules and structures. Lysosomes are found almost exclusively in animal cells.
Ec[000000]f[16]LBmaternal
BOf, or pertaining to, the mother. Chromosomes of maternal origin come from the mother.
Ec[000000]f[16]LBmeiosis
BReductive cell division; the type of cell division found in the reproductive cells of sexual organisms. Meiosis is a series of two divisions and results in the creation of gametes, which have a haploid number of chromosomes, or one-half the original number of chromosomes.
Ec[000000]f[16]LBmembrane
BA thin, pliable tissue. Membranes are found in cells in a variety of forms. Some are vesicles, while others surround the cell as an outside layer.
Ec[000000]f[16]LBmeristem
BIn younger parts of plants, the undifferentiated, growing cellular tissue.
Ec[000000]f[16]LBmesoderm
BThe third of the three primary germ layers in blastula. It develops into the muscles, skeleton, heart, blood, blood vessels, ovaries or testes, and kidneys.
Ec[000000]f[16]LBmetabolic products
BChemical compounds produced within organisms as they extract energy from food molecules.
Ec[000000]f[16]LBmetabolize
BRefers to the chemical action a cell performs to convert food into energy.
Ec[000000]f[16]LBmetaphase
BA phase of cellular reproduction in which the chromosomes line up on the equator of the spindle apparatus. Metaphase occurs in both mitotic reproduction and in meiotic reproduction. However, in meiotic reproduction, there are two metaphases, metaphase I and metaphase II.
Ec[000000]f[16]LBmethane
BA simple hydrocarbon gas, often one of the final products of the decomposition of organic matter; one of the major components of the natural gas we use as fuel.
Ec[000000]f[16]LBmicrobodies
BSmall organelles found in both plant and animal cells. Their function is not well understood, but they seem to aid in chemical reactions and in the breakdown of harmful cellular wastes.
Ec[000000]f[16]LBmicrofibrils
BExtremely thin threads of material, such as the microfilaments that make up plant fibers.
Ec[000000]f[16]LBmicrofilament
BExtremely thin threads of material, such as the microfilaments that make up muscles.
Ec[000000]f[16]LBmicrofilaments
BExtremely fine, unbranched fibers of variable length. Microfilaments participate in cellular movements. They are also responsible for the contractile movements of striated and smooth muscle cells in animals, and for the streaming motions of the cytoplasm during cell division.
Ec[000000]f[16]LBmicrograph
BThe picture taken by an electron microscope. Through micrographs, scientists can view the inner structure of a cell. Cells must be killed and stained so that their organelles will show up in the micrograph.
Ec[000000]f[16]LBmicrotubules
BLong, thin protein rods found in eucaryotic cells. They can be quickly assembled and disassembled. Microtubules act as supporting rods, aid in the creation of the cell wall, and aid the cell in movement as subunits of flagella and cilia.
Ec[000000]f[16]LBmicturition
BThe act of urinating.
Ec[000000]f[16]LBmitochondria
BThe cellular organelle that is responsible for breaking food down and releasing the energy, or ATP, molecule. Mitochondria are composed of folded membranes called cristae with material between the folds called the matrix.
Ec[000000]f[16]LBmitosis
BCell division found in somatic cells; cellular reproduction that results in two identical offspring cells.
Ec[000000]f[16]LBmoleculeB
The smallest particle of a chemical compound; the simplest structural unit of a chemical compound that retains the characteristics and properties of a compound.
Ec[000000]f[16]LBmonera
BOne of the five kingdoms. All the procaryotes are monerans. A moneran has no nucleus in its cell. Its genetic material is loosely arranged in a nonbound nucleoid.
Ec[000000]f[16]LBmotility
BA synonym for movement. A motile organism is capable of movement.
Ec[000000]f[16]LBmRNA
BMessenger RNA; the form of RNA that carries the code for a specific protein.
Ec[000000]f[16]LBmulticellular
BDescribes an organism with more than one cell. Most higher life forms, including plants and animals, are multicellular organisms.
Ec[000000]f[16]LBmycelium
BThe main body of a fungus, usually formed from a network of hyphae and often fused together into thicker strands or masses.
Ec[000000]f[16]LBmycologist
BA scientist who studies fungi.
Ec[000000]f[16]LBmycorrhizae
BStructures composed of symbioses between solid fungi and the roots of plants. Ectomycorrhizae stick out from root hairs, and endomycorrhizae are embedded in root cells. Both types contribute to the health of plants.
Ec[000000]f[16]LBmyofibrils
BLong, fibrous strands within striated muscle cells. The myofibrils are responsible for the striations, alternating light and dark transverse bands, that give the muscle its name.
Ec[000000]f[16]LBmyosin
BOne of two proteins found in microfilaments; the other is actin. Myosin molecules are formed from a double head connected to a long tail. The myosin head is the center of ATPase activity.
Ec[000000]f[16]LBnexin link
BA microtubular connector that runs from the A subtubule to the B subtubule of the next microtubule. The name is derived from a Latin word meaning "to bind."
Ec[000000]f[16]LBnine plus two
BThe arrangement of microtubules within one flagella. There are nine pairs of microtubules with two single microtubules in the center.
Ec[000000]f[16]LBnm
BNanometer. A nanometer is one-billionth of a meter. Nanometers are used to measure extremely small distances, like those in membranes, microtubules, and microfilaments.
Ec[000000]f[16]LBnonpolar
BWithout opposed or opposite ends; a molecule that is nonpolar does not carry a charge, positive or negative, that might make it attractive to water molecules. This means that it is not able to dissolve in or mix with water.
Ec[000000]f[16]LBnotochord
BA flexible rod of tissue that forms the longitudinal support structure in embryonic chordates. During vertebrate development, the notochord becomes the spinal column.
Ec[000000]f[16]LBnucleic acid
BEither DNA or RNA; the blueprints for life and one of the four major types of organic molecules found in living cells.
Ec[000000]f[16]LBnucleolus
BA dark sphere within the nucleus where DNA, protein, and other chemicals congeal and ribosomes are assembled.
Ec[000000]f[16]LBnucleotide
BOne of the building blocks of the nucleic acids RNA and DNA. Nucleotides contain a base, a sugar, and a phosphoric acid group.
Ec[000000]f[16]LBnucleotide base
BThe protein base that is one of three key components of nucleotides, the units that make up RNA and DNA. The other two units are a phosphate group and a five-carbon sugar, either ribose or deoxyribose.
Ec[000000]f[16]LBnucleus
BA dark, spherical structure located in some cells. The nucleus directs the cell's activities. The nucleolus is a structure within the nucleus that contains DNA molecules, which carry hereditary information. The primary function of the nucleus is information storage.
Ec[000000]f[16]LBoptical diffraction
BA technique used to observe the structure of microfilaments. In this technique, a beam of light is projected through the electron micrograph of an axoneme. The light splits into smaller beams as it comes in contact with the connecting elements of the microtubules. The resultant light Ec[000000]f[16]LFpattern can be used to reconstruct the microtubules.
Ec[000000]f[16]LBorganelle
BA subcellular body that performs a function in a cell.
Ec[000000]f[16]LBorganelles
BSmall structures with specific functions located inside the cell. Examples of organelles are the nucleus, the ribosomes, and the Golgi apparatus.
Ec[000000]f[16]LBorganic
BIn chemistry, of or pertaining to compounds containing carbon; characteristic of living organisms.
Ec[000000]f[16]LBorganism
BAny living entity, such as a plant or an animal.
Ec[000000]f[16]LBosmosis
BThe diffusion of water through a membrane. Osmosis is a form of passive transport.
Ec[000000]f[16]LBovary
BThe base of a pistil in an angiosperm flower; a structure that houses the ovules.
Ec[000000]f[16]LBovule
BFemale reproductive structure that becomes the seed in seed plants.
Ec[000000]f[16]LBovum
BThe reproductive cell of maternal origin; the egg cell, or female gamete. The ovum contains half the number of chromosomes present in normal, or somatic, body cells. When the ovum is fertilized by a sperm cell, the two join to become a zygote.
Ec[000000]f[16]LBoxidation
BA chemical reaction in which substances combine with oxygen to form other substances.
Ec[000000]f[16]LBoxygenB
A gaseous element that is colorless, odorless, and tasteless. It also may take the form of liquid oxygen, which is pale blue in color. Almost all life depends on oxygen.
Ec[000000]f[16]LBparasite
BAn organism that lives on or in another living organism and robs it of nutrients without furnishing anything in return.
Ec[000000]f[16]LBparasitic
BLiving in or on another organism and obtaining nourishment at the host organism's expense. Parasitic protists, monerans, and fungi may cause diseases in the hosts they infect.
Ec[000000]f[16]LBpassive transport
BThe ability of membranes to allow molecules to diffuse through them. Passive transport expends no cellular energy.
Ec[000000]f[16]LBpaternal
BOf, or pertaining to, the father. Chromosomes of paternal origin come from the father.
Ec[000000]f[16]LBpeptide
BAmino acids that are linked to each other through special bonds, called peptide bonds. Small peptides are classified according to the number of amino acids in the chain. Larger peptides are called polypeptides. Peptides with more than fifty amino acids are usually classified as proteins.
Ec[000000]f[16]LBpeptide bond
BThe bond that forms between two amino acids, specifically between the carboxyl group of one amino acid and the amino group of another.
Ec[000000]f[16]LBperipheral
BOn the outside. Peripheral proteins are found on the outside surface of membranes. Peripheral doublets are found on the outside of the axoneme.
Ec[000000]f[16]LBperpendicular
BForming a right, or ninety-degree, angle. H-bands run perpendicular to myofibril microfilaments, meaning that they transverse the microfilament.
Ec[000000]f[16]LBphagocytosis
BA process in which cells take in food. The cell surrounds the food particle, encases the particle in a membranous vesicle, empties some lysosomes into the vesicle to break down the particle, then absorbs the food.
Ec[000000]f[16]LBpharyngeal clefts
BA feature found in all chordates at some stage of their development; sometimes called gill slits.
Ec[000000]f[16]LBphloem
BFood-conducting tissue in vascular plants.
Ec[000000]f[16]LBphosphate group
BA chemical group that contains at least one phosphate atom. Phosphate groups are found in most membrane lipids. Those lipids are collectively called phospholipids.
Ec[000000]f[16]LBphospholipid
BMembrane lipids containing a phosphate group. Phosphoglycerides are a subgroup of phospholipids built on a framework of glycerol, a three-carbon molecule that has three binding sites.
Ec[000000]f[16]LBphospholipids
BA type of lipid that serves as one of the primary components of cell membranes. Unlike most lipids, these molecules have a polar head and two nonpolar tails, which makes them both polar and nonpolar, or amphoteric.
Ec[000000]f[16]LBphosphoric acid group
BA functional group that contains a phosphorus atom double-bonded to one oxygen, single-bonded to two oxygen atoms, and single-bonded to a hydroxyl group. This group is an important component of nucleic acids.
Ec[000000]f[16]LBphotosynthesis
BA process in which plants take in energy from the sun and convert it into food energy. Photosynthesis occurs only in plants, not in animals.
Ec[000000]f[16]LBphylum
BA taxonomic grouping smaller than a kingdom and larger than a class.
Ec[000000]f[16]LBphytosterols
BThe predominant sterol found in plant cell membranes. Cholesterol is also found in plant cell membranes, but in a much smaller amount.
Ec[000000]f[16]LBpK
BA measure of the extent to which acids dissociate from hydrogen ions. The less apt an acid is to dissociate, the weaker it is, and the higher its pK is. The more apt an acid is to dissociate, the stronger it is, and the lower its pK is.
Ec[000000]f[16]LBplant
BOne of the five kingdoms. A plant is a muticellular organism that develops from a diploid embryo nourished by parental tissue. This definition applies to many animals as well, but plants do not develop as blastulas; all animals do. Most plants are green food producers.
Ec[000000]f[16]LBplasma membrane
BAlso called the cell membrane; it surrounds the cell and delineates it from its surroundings. It is a site of much chemical activity. It is also a site for communication between the cell and its surroundings. It has a property called selective permeability that allows selective Ec[000000]f[16]LFmolecules to enter the cell while preventing other molecules from doing the same.
Ec[000000]f[16]LBplasmolysis
BCell shrinkage caused by water loss during osmosis.
Ec[000000]f[16]LBplastid
BAn organelle in a plant cell. Different plastids have different functions. For example, some plastids store materials. The chloroplast contains chlorophyll, the substance that allows plants to capture sunlight and produce food energy.
Ec[000000]f[16]LBpolar
BHaving opposed or opposite ends. Polar molecules carry a charge, positive or negative, that makes them attractive to water molecules. Thus, they are able to dissolve in or mix with water.
Ec[000000]f[16]LBpoles
BThe end points of the spindle apparatus, analogous to the poles of the earth. The poles are the ultimate point to which the chromosomes journey during anaphase. Once the chromosomes have arrived at the poles, nuclear membranes surround the chromosomes, forming the nuclei of the new daughter cells.
Ec[000000]f[16]LBpollen
BMale gametophyte in seed plants. Pollen performs the reproductive role filled by swimming sperm in nonseed plants.
Ec[000000]f[16]LBpollination
BThe transfer of pollen from the anther to the stigma. Most flowers are insect- or wind-pollinated. Insect-pollinated flowers have petals and nectar that attract insects. The pollen tends to be sticky and clings more easily to insect bodies. Wind-pollinated flowers either lack petals, or the Ec[000000]f[16]LFpetals are relatively inconspicuous. They seldom produce nectar. Pollen is light and dry and sometimes has membranous appendages, making it easier to become wind borne. Windblown pollen is produced in large quantities, enhancing the chances for pollination.
Ec[000000]f[16]LBpolyethylene
BAn organic polymer of ethylene molecules used to make many plastics.
Ec[000000]f[16]LBpolyhedron
BA solid figure with many sides.
Ec[000000]f[16]LBpolyhydroxy aldehyde
BA sugar; the name for all sugars that describes their functional chemical groups is polyhydroxy aldehydes and ketones.
Ec[000000]f[16]LBpolymer
BA large compound formed when many smaller molecules unite.
Ec[000000]f[16]LBpolymerization
BA chemical reaction in which smaller molecules synthesize into larger molecules, creating chains of repeating units.
Ec[000000]f[16]LBpolynucleotide
BA chain of several nucleotides bonded together between the phosphate group of one nucleotide and a hydroxyl group from the sugar ring of the next.
Ec[000000]f[16]LBpolypeptide
BA chain of amino acids bonded together between the carboxyl group of one amino acid and the amino group of another.
Ec[000000]f[16]LBpolysaccharides
BA chain of sugar molecules. Starch, cellulose, and glycogen are all examples of polysaccharides.
Ec[000000]f[16]LBpolysome
BA combination of one mRNA strand and two or more ribosomes.
Ec[000000]f[16]LBprocaryote
BA cell containing no membrane-bounded nucleus, or an organism composed of such cells.
Ec[000000]f[16]LBprocaryotes
BCells that lack internal organelles. Procaryotic cells are simple, one-celled organisms. Bacteria and blue-green algae are procaryotes.
Ec[000000]f[16]LBprocaryotic
BWithout a cell nucleus. Procaryotic cells, such as bacteria and blue-green algae, have their DNA in a nuclear region that is not enclosed by a membrane. Also spelled prokaryotic.
Ec[000000]f[16]LBproduct
BThe molecule or molecules produced when an enzyme catalyzes a reaction between substrates.
Ec[000000]f[16]LBprophase
BThe first phase in cell division. Prophase occurs once in mitosis. In meiosis, there are two prophases, prophase I and prophase II.
Ec[000000]f[16]LBprotein
BComplex combination of amino acids that forms the basis for all living tissues. Proteins can be synthesized in plants but not in animals. Protein synthesis is the process in which proteins are created. DNA molecules carry the hereditary information that directs the amino acids to Ec[000000]f[16]LFform proteins. The numbers, types, and positions of amino acids in a chain dictate the protein's structure, and different proteins have different functions. For example, some proteins may be enzymes whereas other proteins may be hemoglobin in the human blood stream.
Ec[000000]f[16]LBprotein synthesis
BThe process by which proteins are created out of amino acids at the cellular level. DNA molecules carry the hereditary information that directs the formation of various proteins. Different proteins have different functions. For example, some proteins may be enzymes, whereas other Ec[000000]f[16]LFproteins may be hemoglobin in the human bloodstream.
Ec[000000]f[16]LBprothallium
BThe independent, free-living gametophyte generation of a nonseed plant, such as a fern, usually attached to the soil by rhizoids.
Ec[000000]f[16]LBprotist
BOne of the five kingdoms, probably the most difficult to define. Protists are all the unicellular eucaryotes and those multicellular organisms that seem more directly derived from them than related to the animals, plants, or fungi.
Ec[000000]f[16]LBprotonema
BThe filamentous or thallose early growth from a bryophyte spore.
Ec[000000]f[16]LBprotoplasm
BThe jellylike material that makes up cells. The term has become largely obsolete in the scientific community, being replaced by newer terms, such as cytoplasm. However, the term may be used in very general cases.
Ec[000000]f[16]LBprotostome
BSeveral phyla of animals in which the blastopore develops in the mouth during embryology. The arthropods are one of the protostome phyla.
Ec[000000]f[16]LBprotozoa
BSingle-celled organisms that are very similar to simple animal organisms. The word means "first animal."
Ec[000000]f[16]LBprotozoan
BA microscopic, single-celled organism. The name means "first animal," but protozoa and animals are classified differently.
Ec[000000]f[16]LBpseudocoel
BA pocket of space between the digestive tube and the body wall. In nematodes, the space is filled with fluids. A pseudocoel does not have a lining derived from mesoderm tissue (as a coelom does); pseudocoels may have developed independently along different lines of animal evolution.
Ec[000000]f[16]LBpseudopod
BAn extension of cellular protoplasm. The word IpseudopodI means "false foot." The cell extends its protoplasm forward into a pseudopod, which propels the organism and surrounds food to draw it into the cell.
Ec[000000]f[16]LBpurine
BAny of several organic compounds derived from the crystalline compound CBS5BSHBS4BSNBS4BS, such as caffeine, adenine, and guanine.
Ec[000000]f[16]LBpyrimidine
BAny of several organic compounds derived from the basic compound CBS4BSHBS4BSNBS2BS, such as thymine, cytosine, and uracil.
Ec[000000]f[16]LBquaternary
BHaving four of something, or fourth in order. The quaternary structure of a protein is the way in which protein molecules interact with other protein molecules.
Ec[000000]f[16]LBred cell ghosts
BThe name given to red blood cells that have been emptied of their contents.
Ec[000000]f[16]LBreplicate
BTo repeat or duplicate. Scientists use this term to describe the duplication process of hereditary information during cellular reproduction.
Ec[000000]f[16]LBrespiration
BThe cellular process in which energy is released by chemical reaction. The energy molecule is called the ATP molecule.
Ec[000000]f[16]LBrhizoid
BFilaments that function like roots for attachment and absorption.
Ec[000000]f[16]LBribosome
BA small organelle at the site of protein synthesis.
Ec[000000]f[16]LBribosomes
BAn organelle within the cell that is capable of synthesizing proteins. Ribosomes are generally found on the endoplasmic reticulum, or ER. Cells that produce a great deal of protein generally have many ribosomes.
Ec[000000]f[16]LBrigor mortis
BThe stiffness of animal limbs after death. Rigor mortis is the result of ATP deprivation that locks muscle microfilaments. The cross-bridges lock in place at a forty-five-degree angle at the end of their power stroke.
Ec[000000]f[16]LBRNA
BRibonucleic acid; a chemical substance that helps transmit genetic information from parent to offspring. RNA molecules are messengers that transmit the genetic code to proteins during protein synthesis.
Ec[000000]f[16]LBRNA mapping
BDetermining nucleotide sequences in RNA (ribonucleic acid). Taxonomists predict that comparison of ribosomal-RNA nucleotide sequences among groups of organisms will provide a guide to distant relationships (kingdoms and phyla). Ribosomal-RNA is considered more useful Ec[000000]f[16]LFfor this process than DNA sequencing because ribosomal-RNA changes very little over long periods of time.
Ec[000000]f[16]LBrRNA
BRibosomal RNA; the form of RNA that associates with various proteins to form ribosomes.
Ec[000000]f[16]LBsaprobe
BAn organism that feeds on the remains of other organisms. A saprobe is a decomposer.
Ec[000000]f[16]LBsarcomere
BThe repeating units within myofibrils. The boundaries of the sarcomere are called the Z-lines.
Ec[000000]f[16]LBscienceB
knowledge that deals with a body of facts or truths systematically arranged and showing the operation of general laws; systematic knowledge of the physical or material world gained through observation and experimentation
Ec[000000]f[16]LBsegregation
BThe appropriation of subcellular structures during cell division. Segregation is one of the steps in the cell cycle. During this step, the organelles are separated so that they will end up in one of the daughter cells.
Ec[000000]f[16]LBselective permeability
BA property of the cell membrane that allows some molecules to enter and exit a cell while preventing others from doing the same. In this way, the cell membrane controls the chemical activity of a cell.
Ec[000000]f[16]LBSendai virus
BA virus used by Frye and Edidin to create supercells. Human cells and mouse cells were exposed to the virus, so that they could fuse together into one large cell containing the nuclei and cytoplasm of both cells.
Ec[000000]f[16]LBseptum
BA wall between cells on fungal hyphae. Many fungi have incomplete septa that permit the flow of cytoplasm between cells.
Ec[000000]f[16]LBserine
BA nitrogenous alcohol group that is linked to membrane phospholipids in red blood cells. L.L.M. Van Deenen used serine-attacking enzymes in his experiments on membranes.
Ec[000000]f[16]LBsexual reproduction
BType of reproduction involving the fusion of genetic material from two individuals to produce haploid cells before the next sexual fusion.
Ec[000000]f[16]LBsinglet
BA single microtubule that is complete within itself. Central singlets are found in the center of the axoneme.
Ec[000000]f[16]LBsolubility
BThe ability of substances to dissolve in a solvent. Solubility is important in both passive and active transport of molecules through a membrane. Substances that are soluble in lipids easily pass through membranes.
Ec[000000]f[16]LBsoluble
BAble to dissolve into another compound, especially water.
Ec[000000]f[16]LBsolute
BA compound that is dissolved into another. When sugar is dissolved into water, sugar is the solute, and water is the solvent.
Ec[000000]f[16]LBsolvent
BA liquid compound that dissolves another. When sugar is dissolved into water, sugar is the solute, and water is the solvent.
Ec[000000]f[16]LBsomatic cells
BBody cells; cells that are not sex cells. Somatic cells reproduce by mitosis.
Ec[000000]f[16]LBsoredium
BA dispersal structure of lichens, consisting of a few fungal hyphae surrounding some algae cells.
Ec[000000]f[16]LBspecies
BGenerally, organisms that can interbreed and produce fertile offspring constitute a species. A species is the least subjective taxonomic classification because nature has made the distinctions for us. All larger taxonomic placements are guesses based on the best available evidence of ancestral relationships.
Ec[000000]f[16]LBsperm
BThe male gamete or reproductive cell. The sperm cell contains one-half the number of chromosomes of a normal body cell. The sperm cell must fuse with an ovum cell in order to create a zygote.
Ec[000000]f[16]LBspicule
BA hard, sharp, tiny bit of silica, or calcium carbonate, secreted by sponges. Spicules provide some skeletal support and discourage predators.
Ec[000000]f[16]LBspindle apparatus
BThe subcellular structure created by the cell to house the chromosomes for cell division. The spindle apparatus consists of two poles and an equator. Chromosomes begin at the equator then move to the poles where they form the nuclei of daughter cells. The cell divides Ec[000000]f[16]LFat the equator of the spindle, forming the two daughter cells.
Ec[000000]f[16]LBspindle fibers
BMicrotubules that stretch out from the spindle apparatus and attach themselves to the chromosomes at the centromere. It is not clear whether the fibers push or pull the chromosomes apart.
Ec[000000]f[16]LBspoke
BA microtubule-connecting element that connects each of the peripheral doublets to the central hub of the axoneme.
Ec[000000]f[16]LBspore
BA dispersal structure common to all fungi. Some fungi produce both sexual and asexual spores.
Ec[000000]f[16]LBstarch
BA long chain of carbohydrates made of repeating glucose molecules. Plants make starch to store excess energy; animals make a similar compound called glycogen. Both can also be called polysaccharides.
Ec[000000]f[16]LBstationary
BNot moving. Stationary proteins are not moving. For example, aggregate proteins are locked in place and are therefore stationary.
Ec[000000]f[16]LBsterol
BA solid, mostly unsaturated alcohol that is found in plant and animal tissue.
Ec[000000]f[16]LBsterols
BA kind of membrane lipid formed on a framework of carbon rings. Sterols are responsible for keeping the membrane interior in a fluid state at reduced temperatures. They also enhance the hydrophobic property of the membrane interior. Cholesterol is the predominant sterol in animal cell membranes.
Ec[000000]f[16]LBstriated muscle
BMuscle cells denoted by their striated, or lined, appearance. Striated muscles exist in almost all animals. Striated muscles of the human body provide the voluntary movements of limbs, such as the lips and the eyelids.
Ec[000000]f[16]LBstymied
BTo be confounded, or have one's progress blocked.
Ec[000000]f[16]LBsubstrate
BThe surface or substance on which an organism occurs. A fungal substrate may be a log, an apple, a human hair, or other items. A fungus generally feeds on its substrate.
Ec[000000]f[16]LBsubtubule
BOne of the microtubules in a doublet. The subtubules are named A and B; the A subtubule is a complete microtubule, and the B subtubule is incomplete. The B subtubule is attached to the A subtubule to enclose it.
Ec[000000]f[16]LBsucrose
BTable sugar, which is made of one glucose molecule and one fructose molecule.
Ec[000000]f[16]LBsymbiont
BAn organism that lives on, in, near, or with some organism of another species; each organism derives some benefit from the other's presence, and the degree of benefit is often unevenly weighted.
Ec[000000]f[16]LBsymbiotic
BLiving together in an intimate association, each participant deriving some benefit from the other.
Ec[000000]f[16]LBsymmetry
BIn zoology, symmetry refers to the basic body plan of an animal. Some animals have radial symmetry, and others, bilateral.
Ec[000000]f[16]LBsynthesis
BThe biochemical process within cells whereby small molecules are combined to create larger ones. Proteins are created out of amino acids in a process called protein synthesis.
Ec[000000]f[16]LBsynthesized
BThe forming of a compound from its elements or simpler compounds.
Ec[000000]f[16]LBsynthetic
BMade by a process other than a natural process; man-made.
Ec[000000]f[16]LBtaxonomy
BA cataloging of organisms, with the categories based on supposed evolutionary relationships. As new knowledge comes to light, biological taxonomy changes to reflect it.
Ec[000000]f[16]LBtelophase
BThe phase in cellular reproduction during which the cell divides. Cytoplasm and organelles are apportioned to each daughter cell. Telophase occurs twice in meiosis.
Ec[000000]f[16]LBtemplate
BA model or pattern for making or copying something.
Ec[000000]f[16]LBtermination
BThe act of ending. It is the last step in protein synthesis, where the process of adding amino acids is ended and the complete protein is released.
Ec[000000]f[16]LBtertiary
BThird in order. The tertiary structure of a protein is the total three-dimensional structure of a single protein molecule.
Ec[000000]f[16]LBtestis
BThe male reproductive gland. The testis of a grasshopper is often used to study meiotic cell division.
Ec[000000]f[16]LBtetrad
BA complex of four chromatids, or two homologous chromosomes attached through crossover.
Ec[000000]f[16]LBtetrahedron
BA three-dimensional figure having four sides; a four-sided pyramid.
Ec[000000]f[16]LBthick filament
BMuscle microfilaments composed of myosin. Thick filaments and thin filaments work together during muscle contraction.
Ec[000000]f[16]LBthin filament
BMuscle microfilaments composed of actin. Thin filaments slide across thick filaments during muscle contraction.
Ec[000000]f[16]LBthylakoids
BStacks of membranes that are active in photosynthesis. Thylakoids, also known as lamellae, are found in the chloroplast organelle of plant cells.
Ec[000000]f[16]LBthymine
BOne of five nucleotide bases, it pairs with the nucleotide base adenine. It is found only in DNA, not in RNA. In RNA, uracil pairs with adenine.
Ec[000000]f[16]LBThyone
BA species of echinoderm studied by Lewis Tilney. The Thyone sperm contains microfilaments that assemble into a projection, uniting the sperm and egg cells.
Ec[000000]f[16]LBtRNA
BTransfer RNA; the form of RNA that brings amino acids to the site of protein synthesis.
Ec[000000]f[16]LBtubulin
BThe protein used to create the subunits of microtubules. Tubulin is the collective name given to two different but similar proteins: alpha and beta tubulin. One alpha tubulin and one beta tubulin link together to form the dumbbell-shaped microtubular subunit.
Ec[000000]f[16]LBuracil
BOne of five nucleotide bases, it pairs with the nucleotide base adenine. It is found only in RNA, not in DNA. In DNA, thymine pairs with adenine.
Ec[000000]f[16]LBurea
BA powdery, white compound found dissolved in the urine of mammals. It can be made in the laboratory from ammonia and carbon dioxide. It is used commercially in fertilizer, animal feed and resins.
Ec[000000]f[16]LBvacuole
BA membranous bag used by the cell for storage and transportation of wastes and other products. Vacuoles in plants contain pigments and, when expanded, are responsible for plant growth.
Ec[000000]f[16]LBvacuum chamber
BA chamber that has been emptied of its contents. Specimens are placed in vacuum chambers in order to be observed under an electron microscope.
Ec[000000]f[16]LBvalence
BThe ability of an atom to bond with other atoms.
Ec[000000]f[16]LBvascular system
BFood- and water-conducting system of many plants and animals.
Ec[000000]f[16]LBvertebrate
BAnimals with a backbone. Humans and most higher animal organisms are vertebrates.
Ec[000000]f[16]LBvesicle
BA membranous bag produced by some cells. Some cells have secretion vesicles into which they place waste. The vesicles then move to the cell membrane and dump their contents outside the cell. Other vesicles contain enzymes that, when discharged, destroy cellular debris. Some Ec[000000]f[16]LFcells use vesicles to surround food particles that are then broken down and absorbed by the cell.
Ec[000000]f[16]LBvirus
BOne of the smallest organisms, consisting of only a strand of nucleic acid and a protein coat. Viruses live and reproduce inside the cells of other organisms.
Ec[000000]f[16]LBwavelength
BThe distance between two points on a wave, such as a light wave. Light waves are measured in microns.
Ec[000000]f[16]LBwax
BA lipid found in plants. It coats the leaves of plants and is part of tree bark. Because it is insoluble in water, it helps hold moisture inside these structures.
Ec[000000]f[16]LBwhitefish
BA type of freshwater fish whose cells are used by scientists to study cellular reproduction.
Ec[000000]f[16]LBwoody stems
BStems with three major functions: first, they conduct water upward from the roots to the leaves and conduct dissolved food materials downward from the leaves to the roots; second, they produce and support leaves and flowers; third, they provide the mechanisms for the storage of food.
Ec[000000]f[16]LBX-chromosome
BThe sex chromosome; one of the two chromosomes that denote gender.
Ec[000000]f[16]LBX-ray diffraction
BA laboratory process used to determine the structure of proteins.
Ec[000000]f[16]LBxylem
BWater-conducting tubes of vascular plants, reinforced by lignin.
Ec[000000]f[16]LBZ-line
BThe boundary lines of the sarcomere within myofibrils. The Z-lines appear as dark transverse bands.
Ec[000000]f[16]LBZygomycetes
BThe fungal phylum characterized by a lack of septa between cells in the hyphae. The only septa are those that separate spore-producing structures from the rest of the organism.
Ec[000000]f[16]LBzygote
BA fertilized egg cell. Two gametes--a sperm and an ovum--must fuse together to form a zygote. Once cell division begins in the zygote, the new body is called an embryo.
