SAT Subject Bio Glossary Crack SAT Flashcards
abiotic
Nonliving materials in the environment—such as elements, sunlight, and soil—that influence and are influenced by living (biotic) entities on the planet.
Acetylcholine
A neurotransmitter released from the axons of nerve cells to excite an action potential or trigger a muscle to contract.
active immunity
Protective immunity to a disease in which the individual produces antibodies as a result of previous exposures to the antigen.
Acids
Hydrogenion (H+) donors. Acids are very important in the chemical reactions of life because they are highly reactive. Acids have pH values below 7. They are the opposite of bases.
actin
Protein filaments that, along with myosin, allow muscles to contract.
active site
The part of an enzyme that interacts with, or binds to, a substrate.
active transport
The movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration. Because active transport involves moving the molecule against the natural flow of the concentration gradient, the process requires energy.
adaptive radiation
The evolutionary process by which ancestral forms of an organism are diversified through adaptation to new environments.
adenosine triphosphate (ATP)
The energy storage molecule for the cell. ATP consists of an adenosine molecule bonded to three phosphate groups. Each phosphate bond contains energy; by breaking these bonds, the cell can get the energy it needs for chemical
reactions. Cells build ATP during cell respiration, using the raw material of glucose.
adrenal glands
Two glands, the adrenal cortex (cortisone, aldosteron) and adrenal medulla (adrenaline) located on the kidney.
aerobic respiration
A form of cell respiration requiring oxygen(as opposed to an aerobic respiration, which does not need oxygen). Aerobic respiration is much more efficient than anaerobic respiration; it produces 36 ATP for every molecule of glucose. Aerobic respiration proceeds in three stages: glycolysis ,the Krebs cycle, and the electron transport chain
allantois
The extra embryonic membrane of birds, reptiles, and mammals that serves as an area of gaseous exchange and as a site for the storage of noxious excretion products.
allele
A specific form or possible version of a gene having multiple versions. Alleles may be dominant or recessive.
allelic frequency
The frequency with which a particular allele for a certain characteristic appears among all possible alleles for that characteristic in a population.
alternation of generations
The fluctuation between the diploid(sporophyte) and haploid(gametophyte) life stages that occur in plants.
alveolus
An air sac in the lung, the site of respiratory exchange.
amino acid
The monomer of a protein. A central carbon attached to an amino group(–NH2), a carboxyl group (–COOH), and a hydrogen atom(–H). The fourth group is variable and defines the amino acid’s chemical identity.
Amnion
The extra embryonic membrane in birds, reptiles, and mammals that surrounds the embryo, forming an amniotic sac.
anaerobic respiration
A form of cell respiration that does not use oxygen(as opposed to aerobic cell respiration). Anaerobic respiration is less efficient than the aerobic variety and produces just 2 ATP per molecule of glucose. Anaerobic respiration has two stages: glycolysis and fermentation.
analogous trait
A trait that is morphologically and functionally similar to that of a different species but that arose from a distinct, ancestral condition.
anaphase
The stage of mitosis in which sister chromosomes are separated and pulled to opposite ends of the cell by microtubules; the fourth stage of the first meiotic division(meiosis I), during which maternal and paternal homologous pairs are separated on microtubules; the fourth stage of the second meiotic division(meiosis II), during which either maternal or paternal sister chromatids are separated on microtubules.
androgen
A male sex hormone. (e.g.testosterone)
Angiosperm
Avascular flowering plant in which seeds are enclosed inside protective ovaries, such as fruit or flowers. Angiosperms can be monocots or dicots.
Anther
Pollen-producing structure at the top of the stamen, the male reproductive organ of flowers.
Anticodon
The sequence of three nucleotides on tRNA that pairs with a codon of mRNA at the A site of a ribosome during translation. (tRNA, mRNA)
Antigen
A protein coat on the surface of red blood cells; a red blood cell may have a protein coat of typeA, B, or AB. If the cell has no antigens, it is called type O. The presence of a foreign antigen in a body will cause blood to clot.
Aorta
The largest artery in the body; carries oxygenated blood from the left ventricle of the heart.
aphotic zone
Literally, zone without light. The aphotic zone is part of the marine pelagic zone and begins 600 feet below the surface of the ocean. Only chemosynthetic organisms, scavengers, and predators are able to survive in this habitat.
Appendage
A structure that extends from the trunk of an organism and is capable of active movements.
Artery
Vessel that carries blood away from the heart and has thick, elastic, muscular walls that can dilate or contract to control blood pressure within the vessels. Blood in arteries is oxygenated, with the exception of the blood in the pulmonary artery.
autonomic nervous system
The involuntary half of the peripheral nervous system. The autonomic nervous system is in two antagonistic parts: the sympathetic and parasympathetic nervous systems. Their interactions control smooth and cardiac muscle, glands, and organs, and processes such as heartbeat, the movements of the digestive tract, and the contraction of the bladder.
Autosome
Any chromosome that is not a sex chromosome. Humans have 44 autosomes, in 22 homologous pairs. The two sex chromosomes are the twenty-third pair of chromosomes.
Autotroph
An organism that can produce the organic molecules and energy necessary for life through the processes of photosynthesis or chemosynthesis. Autotrophs do not rely on other organisms for food. In a food web, autotrophs
are producers.
Auxin
One in a class of plant hormones that stimulates (among other things) cell elongation, secondary tissue growth, and fruit development.
Base
An ion or compound that removes H+ ions from solution. Often bases are substances that release hydroxide ions (OH–). Bases have pH values above 7. They are the opposite of acids.
Bile
An emulsifier of fats secreted by the liver and stored in the gallbladder for release in the small intestine.