Vocab Set 2 - AP BIO

Polar molecule

Polar molecule

A molecule (such as water) with an uneven distribution of charges in different regions of the molecule.

Hydrogen bond

A type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule.

Cohesion

The linking together of like molecules, often by hydrogen bonds.

Adhesion

The clinging of one substance to another, such as water to plant cell walls by means of hydrogen bonds.

Surface tension

A measure of how difficult it is to stretch or break the surface of a liquid. Water's is high because of the hydrogen bonding of surface molecules.0

Specific heat

The amount of heat that must be absorbed or lost for 1 g of a substance to change its temperature by 1°C

Evaporative cooling

The process in which the surface of an object becomes cooler during evaporation, a result of the molecules with the greatest kinetic energy changing from the liquid to the gaseous state.

Hydrophilic

Having an affinity for water.

Hydrophobic

Having no affinity for water; tending to coalesce and form droplets in water.

Polymer

A long molecule consisting of many similar or identical monomers linked together by covalent bonds.

Monomer

The subunit that serves as the building block of a polymer.

Hydrolysis

A chemical reaction that breaks bonds between two molecules by the addition of water; functions in disassembly of polymers to monomers.

Dehydration reaction

A chemical reaction in which two molecules become covalently bonded to each other with the removal of a water molecule.

Carbohydrate

A sugar (monosaccharide) or one of its dimers (disaccharides) or polymers (polysaccharides).

Lipid

Any of a group of large biological molecules, including fats, phospholipids, and steroids, that mix poorly, if at all, with water.

Protein

A biologically functional molecule consisting of one or more polypeptides folded and coiled into a specific three-dimensional structure.

Nucleic acid

A polymer (polynucleotide) consisting of many nucleotide monomers; serves as a blueprint for proteins and, through the actions of proteins, for all cellular activities. The two types are DNA and RNA.

Nucleotide

The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a nitrogenous base and one or more phosphate groups.

Antiparallel

Referring to the arrangement of the sugar-phosphate backbones in a DNA double helix (they run in opposite 5′ → 3′ directions).

Denaturation

In proteins, a process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions, thereby becoming biologically inactive; in DNA, the separation of the two strands of the double helix. It occurs under extreme (noncellular) conditions of pH, salt concentration, or temperature.

Prokaryotic cell

A type of cell lacking a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with prokaryotic cells (bacteria and archaea) are called prokaryotes.

Eukaryotic cell

A type of cell with a membrane-enclosed nucleus and membrane-enclosed organelles. Organisms with these types of cells (protists, plants, fungi, and animals) are called eukaryotes.

Endosymbiont theory

The theory that mitochondria and plastids, including chloroplasts, originated as prokaryotic cells engulfed by an ancestral eukaryotic cell. The engulfed cell and its host cell then evolved into a single organism.

Vesicle

A membranous sac in the cytoplasm of a eukaryotic cell.

Plasma membrane

The membrane at the boundary of every cell that acts as a selective barrier, regulating the cell's chemical composition.

Phospholipid

A lipid made up of glycerol joined to two fatty acids and a phosphate group. The hydrocarbon chains of the fatty acids act as nonpolar, hydrophobic tails, while the rest of the molecule acts as a polar, hydrophilic head. They form bilayers that function as biological membranes.

Selective permeability

A property of biological membranes that allows them to regulate the passage of substances across them.

Fluid mosaic model

The currently accepted model of cell membrane structure, which envisions the membrane as a mosaic of protein molecules dri+fting laterally in a fluid bilayer of phospholipids.

Integral protein

A transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane (or lining the channel in the case of a channel protein).

Peripheral protein

A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer.

Transport protein

A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.

Glycoprotein

A protein with one or more covalently attached carbohydrates.

Diffusion

The spontaneous movement of a substance down its concentration or electrochemical gradient, from a region where it is more concentrated to a region where it is less concentrated.

Concentration gradient

A region along which the density of a chemical substance increases or decreases.

Passive transport

The diffusion of a substance across a biological membrane with no expenditure of energy.

Hypertonic solution

Referring to a solution that, when surrounding a cell, will cause the cell to lose water.

Hypotonic solution

Referring to a solution that, when surrounding a cell, will cause the cell to take up water.

Isotonic solution

Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell.

Osmosis

The diffusion of free water across a selectively permeable membrane.

Turgid

Swollen or distended, as in plant cells. (A walled cell becomes like this if it has a lower water potential than its surroundings, resulting in entry of water.)

Flaccid

Limp. Lacking turgor (stiffness or firmness), as in a plant cell in surroundings where there is a tendency for water to leave the cell. (A walled cell becomes like this if it has a higher water potential than its surroundings, resulting in the loss of water.)

Plasmolysis

A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.

Facilitated diffusion

The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.

Aquaporin

A channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of free water across the membrane.

Active transport

The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy.

Exocytosis

The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.

Endocytosis

Cellular uptake of biological molecules and particulate matter via formation of vesicles from the plasma membrane.

Phagocytosis

A type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells).

Pinocytosis

A type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes.

Receptor-mediated Endocytosis

The movement of specific molecules into a cell by the inward budding of vesicles containing proteins with receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.

Contractile vacuole

A membranous sac that helps move excess water out of certain freshwater protists.

Osmoregulation

An animal that controls its internal osmolarity independent of the external environment.

Catabolic pathway

A metabolic pathway that releases energy by breaking down complex molecules to simpler molecules.

Anabolic pathway

A metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules.

Oxidation

The complete or partial loss of electrons from a substance involved in a redox reaction.

Reduction

The complete or partial addition of electrons to a substance involved in a redox reaction.

Exergonic

A spontaneous chemical reaction, in which there is a net release of free energy.

Endergonic

A nonspontaneous chemical reaction, in which free energy is absorbed from the surroundings.

ATP

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.

Catalyst

A chemical agent that selectively increases the rate of a reaction without being consumed by the reaction.

Enzyme

A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. Most are proteins.

Activation energy

The amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation.

Substrate

The reactant on which an enzyme works.

Active site

The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.

Competitive inhibitor

A substance that reduces the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics.

Noncompetitive inhibitor

A substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme's shape so that the active site no longer effectively catalyzes the conversion of substrate to product.

Allosteric regulation

The binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.

Feedback inhibition

A method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway.

Cellular respiration

The catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules and use an electron transport chain for the production of ATP.

Photosynthesis

The conversion of light energy to chemical energy that is stored in sugars or other organic compounds; occurs in plants, algae, and certain prokaryotes.

Chemiosmosis

An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Under aerobic conditions, most ATP synthesis in cells occurs by this process.

Citric acid cycle (Krebs cycle)

A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; together with pyruvate oxidation, the second major stage in cellular respiration.

Glycolysis

A series of reactions that ultimately splits glucose into pyruvate. It occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration.

Substrate-level

The enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism.

Phosphorylation

The process of generating ATP from ADP and phosphate by means of chemiosmosis, using a proton-motive force generated across the thylakoid membrane of the chloroplast or the membrane of certain prokaryotes during the light reactions of photosynthesis.

Oxidative phosphorylation

The production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration.

Electron transport chain

A sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make ATP.

Mitochondrion

An organelle in eukaryotic cells that serves as the site of cellular respiration; uses oxygen to break down organic molecules and synthesize ATP.

Aerobic

A catabolic pathway for organic molecules, using oxygen (O2) as the final electron acceptor in an electron transport chain and ultimately producing ATP. This is the most efficient catabolic pathway and is carried out in most eukaryotic cells and many prokaryotic organisms.

Anaerobic

A catabolic pathway in which inorganic molecules other than oxygen accept electrons at the "downhill" end of electron transport chains.

Light reactions

The first of two major stages in photosynthesis (preceding the Calvin cycle). These reactions, which occur on the thylakoid membranes of the chloroplast or on membranes of certain prokaryotes, convert solar energy to the chemical energy of ATP and NADPH, releasing oxygen in the process.

Calvin cycle

The second of two major stages in photosynthesis (following the light reactions), involving fixation of atmospheric CO2 and reduction of the fixed carbon into carbohydrate.

Chlorophyll

A green pigment located in membranes within the chloroplasts of plants and algae and in the membranes of certain prokaryotes. Type a participates directly in the light reactions, which convert solar energy to chemical energy.

Chloroplast

An organelle found in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.

Stomata (stoma, singular)

A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant.

Signal transduction pathway

The linkage of a mechanical, chemical, or electromagnetic stimulus to a specific cellular response.

Positive feedback

A form of regulation in which an end product of a process speeds up that process; in physiology, a control mechanism in which a change in a variable triggers a response that reinforces or amplifies the change.

Negative feedback

A form of regulation in which accumulation of an end product of a process slows the process; in physiology, a primary mechanism of homeostasis, whereby a change in a variable triggers a response that counteracts the initial change.

Chromosome

A cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each consists of one very long DNA molecule and associated proteins. (In bacteria, they usually consist of a single circular DNA molecule and associated proteins. They are found in the nucleoid region, which is not membrane bounded.)

Mitosis

A process of nuclear division in eukaryotic cells conventionally divided into five stages: prophase, prometaphase, metaphase, anaphase, and telophase. It conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei.

Cytokinesis

The division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II.

Sister chromatids

Two copies of a duplicated chromosome attached to each other by proteins at the centromere and, sometimes, along the arms. While joined, two sister chromatids make up one chromosome. Chromatids are eventually separated during mitosis or meiosis II.

Interphase

The period in the cell cycle when the cell is not dividing. During this phase, cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase. It often accounts for about 90% of the cell cycle.

G0 phase

A nondividing state occupied by cells that have left the cell cycle, sometimes reversibly.

G1 phase

The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.

G2 phase

The second gap, or growth phase, of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.

S phase

The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.

Checkpoint

A control point in the cell cycle where stop and go-ahead signals can regulate the cycle.

Cyclin

A cellular protein that occurs in a cyclically fluctuating concentration and that plays an important role in regulating the cell cycle.

Cyclin-dependent kinase

A protein kinase that is active only when attached to a particular cyclin.