Mcat Biological Sciences Definitions

a muscle that moves a limb away from the center of the body; compare to adductor

charge separation due to asymmetric distribution of electrons

a cell or an organism that has more than two allele per trait

the loss of electrons or hydrogen from an atom, ion, or molecule; the addition of oxygen to an atom, ion, or molecule

becomes positive or more positive

refers to fatty tissue, fat-storing, or fat within cells

a polymer composed of many amino acids linked together by peptide bonds

a white blood cell that transforms into a macrophage in the presence of foreign invaders

in genetics, an area or region of a chromosome

compounds of the general formula Cn(H2O)n

intermediate between the two chair conformations in cyclohexane; similar to the boat conformation except it is more stable because the twist relieves eclipsing

a segment of DNA consisting of a promoter, operator, and structural genes. the structural genes code for products of a specific biochemical pathway; their transcription is regulated by a repressor protein

compounds of the general formula RCHO

the chain of cytochroms in the mitochondria that transfers electrons from NADH to oxygen with the release of energy, which is then used to synthesize ATP via oxidative phosphorylation

elimination reaction whose kinetics are second-order. a base removes a proton, and the leaving group simultaneously departs, forming a double bond

the inhalation and exhalation of gases and their exchange at a respiratory surface

packaging unit of DNA in eukaryotic cells consisting of DNA and histone proteins complexed together

a term for the phenotype characteristic of the majority of individuals in a particular species

the central cavity in the gastrula stage of embryological development; it is lined by endoderm and ultimately gives rise to the adult digestive tract

any reproductive process that involves the fusion of gametes, resulting in the passage of combined genetic information to offspring

the portion of the central nervous system consisting primarily of myelinated axons

the set of cells surround a developing or mature ovum. secretes nutrients and estrogen and atrophies into the corpus luteum after ovulation

the release of the mature ovum from the ovarian follicle

refers to an allele in a diploid cell whose pheotypic effect is the same in both homozygotes and heterozygotes

the process by which the body defends itself in response to an antigen (e.g., production of antibodies)

carbon atom that possesses a formal positive charge (lacks an electron)

a genetic in which the phenotype of a heterozygote is a reflection of both alleles at a particular locus

fluid released during ejaculation consisting of sperm cells suspended in seminal fluid

the embryonic stage of characterized by the presence of endoderm, ectoderm, the blastocoel, and the archenteron. the early gastrula is two layered; later a thin layer, the mesoderm developes

unlined genes within a primary germ cell separate randomly during gametogenesis

a solution that, when compared to another, has a lower concentration of solute particles, and consequently, a lower osmotic concentration

a spherically symmetrical electron orbital centered on the nucleus

temperature at which the solid compounds with at least two chiral centers but with a plane of symmetry resulting in a mirror image that is superimposable on the original molecule

chain reaction in which a radical abstracts a substituent from a molecule (usually hydrogen) and replaces it with another substituent, often a halogen, forming the product and a free radical. these are characterized by three steps: initiation, propagation, and termination

the synthesis of ATP using the energy released from the reactions of the electron transport chain

cell lacking a nuclear membrane-bound organelles, such as a bacterium

the breaking apart of a molecule by addition of water

a mass of similar cells and support structures organized into a functional unit

the synthesis of RNA molecules from a DNA template

a type of endocytosis in which small particles or liquids are engulfed by a cell

the coiled tube in which sperm gains motility and is stored after its production in the testes

the reduced form of NAD+

a solution of salts, pigments, and cholesterol produced by the liver and stored in the gall bladder; it emulsifies large fat droplets when secreted into the small intestine via the bile duct

a type of genetic mutation in which one of the bases in the DNA template is deleted during replication

reaction in which a halogen atom is incorporated into a substrate through an addition, free-radical, or substitution reaction

the tube leading from outer extremity of the ovary to the uterus; generally the site of fertilization

reactive molecules or molecule pieces that are formed during a reaction and quickly proceed to subsequent steps of the reaction sequence

a tiny organism - like particle composed of protein-encased nucleic acid; viruses are obligate parasites

delocalization of electrons within a compound. such compounds may be represented by various electron configurations and have a true electron configuration somewhere between the various possibilities. because the electrons are spread out over the molecule, the structure gains added stability

muscle cell membrane capable of propaga

the amino acid sequence of a protein

a type of white blood cell involved in an organism's immune response

function to eliminate the antigen, either by releasing antibodies (in the case of B cells), cytotoxic granules (cytotoxic T cells) or by signaling to other cells of the immune system (helper T cells).

a hormone produced in the alpha cells of the pancreas that increases the concentration of blood glucose

noradrenaline; a hormone secreted by the adrenal medulla that stimulates the fight - or - flight response; a neurotransmitter

stereoisomers of sugars that differ only in configuration about the C-2 carbon atom

ability of an atom to attract electrons, resulting in polarized bonds

term used to describe the rotation of plane polarized light by an optically active molecule in a clockwise or +ve direction

species that is a "nucleus lover" and thus tends to donate an electron pair to an electrophile

series of events immediately following initiation in a chain reaction. a reactive intermediate reacts with a stable molecule to form another reactive intermediate, thereby continuously regenerating the reaction species. this enables the reaction to continue until completion

a protein found in muscle cells that functions in muscle contraction. their fibers are also called thick filaments

first segment of the small intestine; the contents of the stomach and the pancreatic and bile ducts empty into it. site of digestion and some absorption

a cell that conducts electricity impulses; the functional unit of the nervous system

stereroisomers that are nonsuperimposable mirror images of one another. for example, if there is one chiral center, then the R and S isomers are enantiomers

substrate - binding region of an enzyme

double - ringed nitrogenous bases such as adenine and guanine

an organism that requires performed organic nutrients because it cannot form them from inorganic precursors

the fluid - filled central cavity of the blastula

unstable intermediate between ketone and ketal; containing one -OR group and one -OH group on the same carbon atom

sperm or ovum; a cell that has half the number of chromosomes of a somatic cell -haploid - and can fuse with another gamete to form a zygote

the outer layer of the forebrain, consisting of gray matter; it is the site of higher cognitive functions in humans. their neurons initiate voluntary muscle action and constitute the final reception are for sensory impulses

an atom or molecule with a net negative or positive charge

a phagocytic white blood cell

slowest step in a multistep reaction. the rate of the reaction is dependent only on this step

points on myelinated axon that are not covered by myelin

shifting of substituents with their electrons to a new location on the same molecule, leaving behind a more stable molecule - e.g., methyl and hydride shifts

chromosomes in a diploid cell that carry corresponding genes for the same traits at corresponding loci

chemical messengers secreted by cells of one part of the body and carried by the bloodstream to cells elsewhere in the body, where they regulate biochemical activity

mechanism that prevents genetic exchange between individuals of different species or populations

flat depiction of cyclic molecules. for sugars, the oxygen atom is always at the back right corner of a haworth projection, and the hemiacetal carbon is at the far right

the union of gametes

a sugar consisting of one monomer - e.g., glucose, fructose, galactose

a substance that speeds up a chemical reaction by lowering the activation energy, without being altered or consumed during the reaction

compounds of the general formula RCOR

a polypeptide hormone secreted by the thyroid; it causes deposition of calcium and phosphate in bones and thus lowers their concentration in the blood

substance that kills or inhibits the growth of bacteria or fungi - usually by disrupting cell wall assembly or by binding to ribosome, thus inhibiting synthesis

white blood cell; the four principle types are granulocytes, macrophages, monocytes, and lymphocytes

the large vesicle at the head of a sperm cell containing enzymes that degrade the ovum cell membrane to allow fertilization

organ in the mammalian female reproductive system that is the site of embryonic development

a reaction generating a free radical

the anterior pituitary hormone that stimulates spermatogenesis and the maturation of ovarian follicles

unimolecular nucleophillic substitution

it is characterized by two steps: (1) dissociation of a molecule into a carboncation and a leaving group; (2) combination of a nucleophile with the carbocation, no inversion of configuration occurs, but a loss of stereochemistry does occur because of the formation of a planar intermediate

the structure formed by the wall of the uterus and the chorion of the embryo, containing a network of capillaries through which exchange between maternal and fetal circulation occurs

a small, hollow tube composed of two types of protein subunits; serves numerous function in the cell (e.g., microtubules comprise the internal structures of cilia and flagella)

in test tube or in a culture

rule defining aromaticity, stating that cyclic conjugated molecules will exhibit unusual stability if they contain 4n+2 pi electrons

incorporation of atmospheric nitrogen into inorganic nitrogen compounds. performed by bacter

nonprotein molecules required by many enzymes for activity

the genetic composition of an entire organism or reference to a particular trait

the movement of a substance across a membrane without the expenditure of energy

immune or protective protein evoked by the presence of foreign substances (antigens) in the body. each antibody binds to a specific antigen in an immune response

embryonic germ layer; it later gives rise to the linings of the alimentary canal and of the digestive and respiratory organs

an inheritable change in the genetic composition of an organism

the part of the eye that contracts or dilates to regulate the amount of light passing through the pupil

loss of secondary and tertiary structure of protein, caused by an increase in temperature of a pH change. denaturing agents disrupt hydrogen bonding, inactivating proteins

vertebrate organ that regulates water and salt concentration in the blood and is responsible for urine formation

a gland found in mammalian males that produces seminal fluid

organic compounds containing only carbon and hydrogen

nucleic acid composed of monomers consisting of the five - carbon sugar deoxyribose, a phosphate group, and a nitrogenous base (adenine, cytosine, guanine, or thymine); contains the cell's genetic information

a collection of filamentous hyphae that makes up a fungus

dense body visible in a nondivding nucleus. site of ribosomal RNA synthesis

female sex hormone that stimulates the development of secondary sequal characteristics and is secreted by the ovarian follicle

tendency for certain alleles to be inherited together due to proximity on the same chromosome

compounds with the same molecular formula but different connections between atoms

organisms that maintain a constant internal temperature

a type of asexual reproduction in which the offspring starts out as an outgrowth of the parent that subsequently splits off to exist as an independent organism

situated towards the back of an organism

the development of structure and form in an organism

the network of capillaries encapsulated by bowman's capsule. acts as a filter for blood entering the nephron

group that is replaced in a substitution reaction, which must be a weaker nucleophile than the species that will replace it. the best leaving groups form the most stable anions in solution

the anterior portion of the hindbrain of vertebrates; it includes the cerebellum and the pons

the insoluble protein that forms the bulk of a blood clot

small, enucleated, disk - shaped blood cells that play an important role in blood clotting

the physical manifestation of an organism's genotype

pathway by which a reaction occurs, describing all reactant, intermediates and products and the conditions that must be present for the reaction to take place

uptake and incorporation of "naked" DNA by a recipient bacterial cell

combination of two or more molecules, often with the loss of a small molecule such as water or alcohol

temperature at which the solid and liquid phases of a compound are in equilibrium

solution whose PH changes only slightly upon addition of either acid or base. the solution contains a conjugate acid - or base pair that consumes any added base or acid

strain in a molecule produced by repulsion of groups adjacent or close to one another. hindrance increases as size and bulk increase

dienes whose two c-c double bonds are adjacent (not separated by any single bonds)

the stage of mitosis or meiosis characterized by the migration of chromatids or homologous chromosomes to opposite poles of the dividing cells

a coenzyme that functions in cell respiration

any region in the central nervous system that consists largely of neuron cell bodies, dendrites, and synapses

weal electrostatic interaction between a hydrogen atom bonded to an electronegative atom, such as N, O, or F and the lone pairs of other electronegative atoms

compounds with two alcohol groups. geminal have two -OH groups on the same carbon atom; vicinal, also known as glycols, have the two -OH groups on adjacent carbons

a firm, elastic, translucent connective tissue produced by cells called chondrocytes

standardized system of nomeclature promoted by the international union of pure and applied chemistry

electron pair donor

the middle embryonic germ layer; it gives rise to the muscular, skeletal, urogenital, and circulatory systems

having only one of each chromosome per cell

reaction who's rate depends on the concentration of only one reactant

rate = k * reactant

covalent bond formed by parallel overlap of two hybridized atomic p - orbitals, as in a carbon - carbon double bond

in disubstituted benzene rings, the configuration in which the two functional groups are located in the 1,2 or 1,6 positions on the ring

a hormone synthesized by the adrenal medulla; it stimulates the fight or flight response

it is also a neurotransmitter in the sympathetic nervous system

the initiation of cell differentiation in a developing embryo due to the influence of other cells

fusion of the nuclei of two gametes

light in which all electric fields vibrate in one plane

clusters of molecules possessing hydrophilic ionic heads facing the surface of a sphere, where they can interact with water, and possessing hydrophobic hydrocarbon tails in the interior. soap forms micelles, facilitating the dissolution of oils and fats

organelles that play a role in the packaging and secretion of protein and other molecules produced intracellularly

a small projection from the wall of the small intestine that increases the surface area for digestion and absorption

the fundamental unit of the vertebrate kidney

level of protein structure characterized by inter - and intramolecular hydrogen bonding

e.g. alpha - helix and beta - pleated sheet

a specialized cytoplasmic structure

a cavity open only at one end, such as the blind pouch (diverticulum) at the junction of the large and small intestine

a developing organism that has passed the early developmental stages. in humans, the term refers to an embryo from the third month of pregnancy until birth

the release of metabolic wastes by an organism

an asexual reproductive cell that can endure extreme environmental conditions and develop into an adult organism when conditions become favorable

an organic cofactor required for enzyme activity

a neurotransmitter found throughout the nervous system (e.g., somatic motor neurons, preganglionic parasympathetic and sympathetic nerves, and post ganglionic parasympathetic nerves). it is metabolized by acetylcholinesterase

a series of mitotic divisions of the zygote immediately following fertilization, resulting in progressively small cells with increased nucleus - to - cytoplasm ratios

the short interval between the application of a stimulus to a muscle and the contraction of the muscle

a type of asexual reproduction in which an organism replaces lost body parts

an electron acceptor / donor system that functions, primarily, in biosynthetic processes

configuration about a double bond in which the two largest groups are on the same side of the molecule

a microscopic, whiplike filament that functions in locomotion of sperm cells and some unicellular organisms; composed of microtubules

the chemical breakdown of complex substances - macromolecules - to yield simpler substances and energy

any male sex hormone e.g. testosterone and diihydrotestosterone

compounds of the general formula RCOOR

the junction between two neurons into which neurotransmitters are released

pH at which the number of positive charges and the number of negative charges on a compound - e.g. an amino acid - are equal

an amine with two hydrogen and one hydrocarbon substituents (i.e. RNH2)

a virus that invades bacteria and sometimes uses bacterial RNA and ribosomes to self-replicate

a metabolic pathway used in cellular respiration in which acetyl -CoA combines with oxaloacetic acid to form citric acid, which then undergoes a series of reactions to yield NADH, FADH, ATP, and CO2

occurs in aerobes

at the site / origin of

double membrane enveloping the nucleus, interrupted periodically by pores; found in eukaryotic cells only

the female sex chromosome

red blood cell; a biconcave, disk - shaped cell that contains hemoglobin and has no nucleus

the layer of skin cells under the epidermis. contains sweat glands, hair follicles, fat, and blood vessels

tension experienced by cyclic compounds due to the bending and stretching of bonds in order to fulfill geometric/angular and steric requirements

the class of RNA that is product of the transcription process and acts as a template for the synthesis of polypeptides

terminal portion of the small intestine

the thin, transparent layer that covers the front of the eye

the anaerobic catabolism of glucose to pyruvic acid

the pairing of homologous chromosomes during prophase 1 of meiosis

the building blocks of proteins, each containing an amino group, a carboxylic acid group, and a side chain - or R group - attached to the alpha carbon

a type of asexual reproduction characteristic of prokaryotes in which there is equal nuclear and cytoplasmic division

rhythmic waves of muscular contraction that moves a substance through a tube - food through the digestive tract

the stage between successive nuclear division; it is divided into the G1, S, and G2 stages. cell growth and DNA replication occur during this stage

a ring shaped muscle that closes and opens a tube - ex. the pyloric sphincter

compounds containing two double bonds

a hormone secreted by the anterior pituitary that stimulates hormone production in the adrenal cortex

simple sugar that cannot be hydrolyzed to simpler compounds

the representation of a three - dimensional chiral structure in two dimensions. the vertical lines indicate bonds that project into the plane of the paper, whereas the horizontal lines represent bonds that project out of the plane of the paper

the electrical potential of a neuron at rest, approximately 70 mV across the axon membrane

a gland found in mammalian males that produces seminal fluid

compounds of the general formula ROH

spherically shaped bacteria

an atom with a net positive or negative charge

orientation of atoms in a molecule that can be altered by rotation about a C-C single bond

the subdivision of the autonomic nervous system involved in rest or homeostasis

dienes whose two C-C double bonds are separated by one single bond and are therefore subject to electron delocalization

addition of an electrophile to an electron-rich species. a typical example is the addition of BR2 to an alkene

any change in an organism's internal or external environment that changes the organism's activity

a body part composed of a group of tissues that form a functional and structural unit

the cup-like structure of the nephron; it collects the glomerula filtrate and channels it into the proximal convoluted tubule

ovary or testis; the reproductive organ in which gametes are produced

a behavioral pattern based on a 24-hour cycle

positive and negative ions linked by electrostatic attraction. a salt is the neutralization product of an acid and a base

bacteriophage infectio involving the destruction - lysis - of the host bacterium

carbon atom that possesses a formal positive charge - lacks an electron

interaction of protein subunits to form a large complex; the highest form of protein structure

the genetic composition of an entire organism or reference to a particular trait

bonds lying in the plane of a ring

four-ringed organic lipid molecules that make up many hormones and vitamins

the period of relaxation of cardiac muscle during which the atrioventricular valves open and the ventricles fill with blood

the difference in the number of e- possessed by an atom in a molecule and its elemental state

dienes whose two C-Cdouble bonds are adjacent - not separated by any single bonds

an electron withdrawing or electron attracting effect transmitted through sigma bonds in response to a dipole

measurable energy change accompanying the addition of an electron to an atom

allowing solutes to pass through; a term typically applied to biological membranes

an intracellular participant in one of the mechanisms of hormonal action; synthesized from ATP by aenylate cyclase. aka secondary messenger

the subdivision of the autonomic nervous system that produces the "flight - or fight" respnse

the movement of alleles into and out of a population's gene pool

compounds containing a 3 membered cyclic ether