Abjad A
JEJAK
MAHASISWA
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Dibuat
12/19/2011 | ||||||||||||||
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| A | B | C | D | E | F | G | H | I | J | K | L | M | ||||
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A site
Aminoacyl-tRNA site; the binding site on a ribosome that holds the tRNA carrying the next amino acid to be added to a growing polypeptide chain.
abscisic acid
(ABA) (ab-SIS-ik) A plant hormone that generally acts to inhibit growth, promote dormancy, and help the plant tolerate stressful conditions.
absorption spectrum
The range of a pigment's ability to absorb various wavelengths of light.
abyssal zone
(uh-BIS-ul) The portion of the ocean floor where light does not penetrate and where temperatures are cold and pressures intense.
acclimatization
(uh-KLY-mih-ty-ZAY-shun) Physiological adjustment to a change in an environmental factor.
accommodation
The automatic adjustment of an eye to focus on near objects.
acetyl CoA
The entry compound for the Krebs cycle in cellular respiration; formed from a fragment of pyruvate attached to a coenzyme.
acetylcholine
One of the most common neurotransmitters; functions by binding to receptors and altering the permeability of the postsynaptic membrane to specific ions, either depolarizing or hyperpolarizing the membrane.
acid precipitation
Rain, snow, or fog that is more acidic than pH 5.6.
acid
A substance that increases the hydrogen ion concentration in a solution.
acoelomate
(a-SEEL-oh-mate) A solid-bodied animal lacking a cavity between the gut and outer body wall.
acrosome
(AK-ruh-some) An organelle at the tip of a sperm cell that helps the sperm penetrate the egg.
actin
(AK-tin) A globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other contractile elements in cells.
action potential
A rapid change in the membrane potential of an excitable cell, caused by stimulus-triggered, selective opening and closing of voltage-sensitive gates in sodium and potassium ion channels.
active site
The specific portion of an enzyme that attaches to the substrate by means of weak chemical bonds.
active transport
The movement of a substance across a biological membrane against its concentration or electrochemical gradient, with the help of energy input and specific transport proteins.
adaptive peak
An equilibrium state in a population when the gene pool has allele frequencies that maximize the average fitness of a population's members.
adaptive radiation
The emergence of numerous species from a common ancestor introduced into an environment, presenting a diversity of new opportunities and problems.
adenylyl cyclase
An enzyme that converts ATP to cyclic AMP in response to a chemical signal.
adhesion
The tendency of different kinds of molecules to stick together.
adrenal gland
(uh-DREE-nul) An endocrine gland located adjacent to the kidney in mammals; composed of two glandular portions: an outer cortex, which responds to endocrine signals in reacting to stress and effecting salt and water balance, and a central medulla, which responds to nervous inputs resulting from stress.
aerobic
(air-OH-bik) Containing oxygen; referring to an organism, environment, or cellular process that requires oxygen.
age structure
The relative number of individuals of each age in a population.
agnathan
(AG-naa-thun) A member of a jawless class of vertebrates represented today by the lampreys and hagfishes.
agonistic behavior
(ag-on-IS-tik) A type of behavior involving a contest of some kind that determines which competitor gains access to some resource, such as food or mates.
AIDS
(acquired immunodeficiency syndrome) The name of the late stages of HIV infection; defined by a specified reduction of T cells and the appearance of characteristic secondary infections.
aldehyde
(AL-duh-hyde) An organic molecule with a carbonyl group located at the end of the carbon skeleton.
aldosterone
(al-DAH-stair-own) An adrenal hormone that acts on the distal tubules of the kidney to stimulate the reabsorption of sodium (Na+) and the passive flow of water from the filtrate.
alga
(plural, algae) A photosynthetic, plantlike protist.
allantois
(AL-an-TOH-iss) One of four extraembryonic membranes; serves as a repository for the embryo's nitrogenous waste.
allele
(uh-LEEL) An alternative form of a gene.
allometric growth
(AL-oh-MET-rik) The variation in the relative rates of growth of various parts of the body, which helps shape the organism.
allopatric speciation
(AL-oh-PAT-rik) A mode of speciation induced when the ancestral population becomes segregated by a geographical barrier.
allopolyploid
(AL-oh-POL-ee-ploid) A common type of polyploid species resulting from two different species interbreeding and combining their chromosomes.
all-or-none event
An action that occurs either completely or not at all, such as the generation of an action potential by a neuron.
allosteric site
(AL-oh-STEER-ik) A specific receptor site on an enzyme molecule remote from the active site. Molecules bind to the allosteric site and change the shape of the active site, making it either more or less receptive to the substrate.
alpha helix
A spiral shape constituting one form of the secondary structure of proteins, arising from a specific hydrogen-bonding structure.
alternation of generations
A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants.
altruistic behavior
(AL-troo-IS-tik) The aiding of another individual at one's own risk or expense.
alveolus
(al-VEE-oh-lus) (plural, alveoli) (1) One of the deadend, multilobed air sacs that constitute the gas exchange surface of the lungs. (2) One of the milk-secreting sacs of epithelial tissue in the mammary glands.
amino acid
(uh-MEE-noh) An organic molecule possessing both carboxyl and amino groups. Amino acids serve as the monomers of proteins.
amino group
A functional group that consists of a nitrogen atom bonded to two hydrogen atoms; can act as a base in solution, accepting a hydrogen ion and acquiring a charge of +1.
aminoacyl-tRNA synthetases
A family of enzymes, at least one for each amino acid, that catalyzes the attachment of an amino acid to its specific tRNA molecule.
amniocentesis
(AM-nee-oh-sen-TEE-sis) A technique for determining genetic abnormalities in a fetus by the presence of certain chemicals or defective fetal cells in the amniotic fluid, obtained by aspiration from a needle inserted into the uterus.
amnion
(AM-nee-on) The innermost of four extraembryonic membranes; encloses a fluid-filled sac in which the embryo is suspended.
amnion
(AM-nee-on) The innermost of four extraembryonic membranes; encloses a fluid-filled sac in which the embryo is suspended.
amniotic egg
(AM-nee-AH-tik) A shelled, water-retaining egg that enables reptiles, birds, and egg-laying mammals to complete their life cycles on dry land.
Amphibia
The vertebrate class of amphibians, represented by frogs, salamanders, and caecilians.
amphipathic molecule
A molecule that has both a hydrophilic region and a hydrophobic region.
anaerobic
(an-air-OH-bik) Lacking oxygen; referring to an organism, environment, or cellular process that lacks oxygen and may be poisoned by it.
anagenesis
(AN-uh-JEN-eh-sis) A pattern of evolutionary change involving the transformation of an entire population, sometimes to a state different enough from the ancestral population to justify renaming it as a separate species; also called phyletic evolution.
analogy
The similarity of structure between two species that are not closely related; attributable to convergent evolution.
anaphase
The third stage of mitosis, beginning when the centromeres of duplicated chromosomes divide and sister chromotids separate from each other, and ending when a complete set of daughter chromosomes are located at each of the two poles of the cell.
androgen
(AN-droh-jen) The principal male steroid hormones, such as testosterone, which stimulate the development and maintenance of the male reproductive system and secondary sex characteristics.
aneuploidy
(AN-yoo-ploy-dee) A chromosomal aberration in which certain chromosomes are present in extra copies or are deficient in number.
angiosperm
(AN-jee-oh-spurm) A flowering plant, which forms seeds inside a protective chamber called an ovary.
anion
(AN-eye-on) A negatively charged ion.
annual
A plant that completes its entire life cycle in a single year or growing season.
anterior
Referring to the head end of a bilaterally symmetrical animal.
anther
(AN-thur) The terminal pollen sac of a stamen, inside which pollen grains with male gametes form in the flower of an angiosperm.
antheridium
(an-theh-RID-ee-um) In plants, the male gametangium, a moist chamber in which gametes develop.
antibiotic
A chemical that kills bacteria or inhibits their growth
antibody
An antigen-binding immunoglobulin, produced by B cells, that functions as the effector in an immune response.
anticodon
(AN-tee-CO-don) A specialized base triplet on one end of a tRNA molecule that recognizes a particular complementary codon on an mRNA molecule.
antidiuretic hormone
(ADH) A hormone important in osmoregulation.
antigen
(AN-teh-jen) A foreign macromolecule that does not belong to the host organism and that elicits an immune response.
aphotic zone
(ay-FOE-tik) The part of the ocean beneath the photic zone, where light does not penetrate sufficiently for photosynthesis to occur.
apical dominance
(AY-pik-ul) Concentration of growth at the tip of a plant shoot, where a terminal bud partially inhibits axillary bud growth.
apical meristem
(AY-pik-ul MARE-eh-stem) Embryonic plant tissue in the tips of roots and in the buds of shoots that supplies cells for the plant to grow in length.
apomorphic character
(AP-oh-MORE-fik) A derived phenotypic character, or homology, that evolved after a branch diverged from a phylogenetic tree.
apoplast
(AP-oh-plast) In plants, the nonliving continuum formed by the extracellular pathway provided by the continuous matrix of cell walls.
aposematic coloration
(AP-oh-so-MAT-ik) The bright coloration of animals with effective physical or chemical defenses that acts as a warning to predators.
aqueous solution
(AY-kwee-us) A solution in which water is the solvent.
Archaea
One of two prokaryotic domains, the other being the Bacteria.
Archaea
One of two prokaryotic domains, the other being the Bacteria.
archenteron
(ark-EN-ter-on) The endoderm-lined cavity, formed during the gastrulation process, that develops into the digestive tract of an animal.
Archezoa
Primitive eukaryotic group that includes diplomonads, such as Giardia; some systematists assign kingdom status to archezoans.
arteriosclerosis
A cardiovascular disease caused by the formation of hard plaques within the arteries.
artery
A vessel that carries blood away from the heart to organs throughout the body.
artificial selection
The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits.
ascus
(plural, asci) A saclike spore capsule located at the tip of the ascocarp in dikaryotic hyphae; defining feature of the Ascomycota division of fungi.
asexual reproduction
A type of reproduction involving only one parent that produces genetically identical offspring by budding or by the division of a single cell or the entire organism into two or more parts.
associative learning
The acquired ability to associate one stimulus with another; also called classical conditioning.
assortative mating
A type of nonrandom mating in which mating partners resemble each other in certain phenotypic characters.
asymmetric carbon
A carbon atom covalently bonded to four different atoms or groups of atoms.
atom
The smallest unit of matter that retains the properties of an element.
atomic number
The number of protons in the nucleus of an atom, unique for each element and designated by a subscript to the left of the elemental symbol.
atomic weight
The total atomic mass, which is the mass in grams of one mole of the atom.
ATP synthase
A cluster of several membrane proteins found in the mitochondrial cristae (and bacterial plasma membrane) that function in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen-ion concentration gradient to make ATP. ATP synthases provide a port through which hydrogen ions diffuse into the matrix of a mitrochondrion.
ATP
(adenosine triphosphate) (uh-DEN-oh-sin try-FOS-fate) An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed. This energy is used to drive endergonic reactions in cells.
atrioventricular valve
A valve in the heart between each atrium and ventricle that prevents a backflow of blood when the ventricles contract.
atrioventricular valve
A valve in the heart between each atrium and ventricle that prevents a backflow of blood when the ventricles contract.
autogenesis model
According to this model, eukaryotic cells evolved by the specialization of internal membranes originally derived from prokaryotic plasma membranes.
autoimmune disease
An immunological disorder in which the immune system turns against itself.
autonomic nervous system
(AWT-uh-NAHM-ik) A subdivision of the motor nervous system of vertebrates that regulates the internal environment; consists of the sympathetic and parasympathetic divisions.
autopolyploid
(AW-toe-POL-ee-ploid) A type of polyploid species resulting from one species doubling its chromosome number to become tetraploid, which may self-fertilize or mate with other tetraploids.
autopolyploid
(AW-toe-POL-ee-ploid) A type of polyploid species resulting from one species doubling its chromosome number to become tetraploid, which may self-fertilize or mate with other tetraploids.
autotroph
(AW-toh-TROHF) An organism that obtains organic food molecules without eating other organisms. Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones.
auxin 
(AWK-sins) A class of plant hormones, including indoleacetic acid (IAA), having a variety of effects, such as phototropic response through the stimulation of cell elongation, stimulation of secondary growth, and the development of leaf traces and fruit.
auxotroph
(AWK-soh-trohf) A nutritional mutant that is unable to synthesize and that cannot grow on media lacking certain essential molecules normally synthesized by wild-type strains of the same species.
Aves
The vertebrate class of birds, characterized by feathers and other flight adaptations.
axillary bud
(AKS-ill-air-ee) An embryonic shoot present in the angle formed by a leaf and stem.
axon
(AKS-on) A typically long extension, or process, from a neuron that carries nerve impulses away from the cell body toward target cells.
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