AP Biology Unit 3 (OpenStax Chapters 6-8)

activation energy

energy necessary for reactions to occur

active site

specific region of the enzyme to which the substrate binds

allosteric inhibition

inhibition by a binding event at a site different from the active site, which induces a conformational change and reduces the affinity of the enzyme for its substrate

anabolic

(also, anabolism) pathways that require an input of energy to synthesize complex molecules from simpler ones

ATP

adenosine triphosphate, the cell's energy currency

catabolic

(also, catabolism) pathways in which complex molecules are broken down into simpler ones

chemical energy

potential energy in chemical bonds that is released when those bonds are broken

competitive inhibition

type of inhibition in which the inhibitor competes with the substrate molecule by binding to the active site of the enzyme

denature

process that changes the natural properties of a substance

endergonic

describes chemical reactions that require energy input

exergonic

describes chemical reactions that release free energy

feedback inhibition

effect of a product of a reaction sequence to decrease its further production by inhibiting the activity of the first enzyme in the pathway that produces it

metabolism

all the chemical reactions that take place inside cells, including anabolism and catabolism

potential energy

type of energy that has the potential to do work; stored energy

substrate

molecule on which the enzyme acts

acetyl CoA

combination of an acetyl group derived from pyruvic acid and coenzyme A, which is made from pantothenic acid (a B-group vitamin)

aerobic respiration

process in which organisms convert energy in the presence of oxygen

anaerobic

process that does not use oxygen

anaerobic cellular respiration

process in which organisms convert energy for their use in the absence of oxygen

ATP synthase

(also, F1F0 ATP synthase) membrane-embedded protein complex that adds a phosphate to ADP with energy from protons diffusing through it

chemiosmosis

process in which there is a production of adenosine triphosphate (ATP) in cellular metabolism by the involvement of a proton gradient across a membrane

citric acid cycle

(also, Krebs cycle or TCA cycle) series of enzyme-catalyzed chemical reactions of central importance in all living cells. Hans Krebs first identified the steps in the pathway in the 1930s in pigeon flight muscles. Group name for citric acid, tricarboxylic acid (TCA)

fermentation

process of regenerating NAD+ with either an inorganic or organic compound serving as the final electron acceptor; occurs in the absence of oxygen

glycolysis

process of breaking glucose into two three-carbon molecules with the production of ATP and NADH

oxidative phosphorylation

production of ATP using the process of chemiosmosis and oxygen

phosphorylation

addition of a high-energy phosphate to a compound, usually a metabolic intermediate, a protein, or ADP

pyruvate

three-carbon sugar that can be decarboxylated and oxidized to make acetyl CoA, which enters the citric acid cycle under aerobic conditions; the end product of glycolysis

redox reaction

chemical reaction that consists of the coupling of an oxidation reaction and a reduction reaction

absorption spectrum

range of wavelengths of electromagnetic radiation absorbed by a given substance

Calvin cycle

light-independent reactions of photosynthesis that convert carbon dioxide from the atmosphere into carbohydrates using the energy and reducing power of ATP and NADPH

carbon fixation

process of converting inorganic CO2 gas into organic compounds

carotenoid

photosynthetic pigment that functions to dispose of excess energy

chlorophyll a

form of chlorophyll that absorbs violet-blue and red light and consequently has a bluish-green color; the only pigment molecule that performs the photochemistry by getting excited and losing an electron to the electron transport chain

chlorophyll b

accessory pigment that absorbs blue and red-orange light and consequently has a yellowish-green tint

chloroplast

organelle in which photosynthesis takes place

electron transport chain

group of proteins between PSII and PSI that pass energized electrons and use the energy released by the electrons to move hydrogen ions against their concentration gradient into the thylakoid lumen

granum

stack of thylakoids located inside a chloroplast

heterotroph

organism that consumes organic substances or other organisms for food

light-dependent reaction

first stage of photosynthesis where certain wavelengths of the visible light are absorbed to form two energy-carrying molecules (ATP and NADPH)

light-independent reaction

second stage of photosynthesis, though which carbon dioxide is used to build carbohydrate molecules using energy from ATP and NADPH

photosystem

group of proteins, chlorophyll, and other pigments that are used in the light-dependent reactions of photosynthesis to absorb light energy and convert it into chemical energy

reduction

gain of electron(s) by an atom or molecule

stoma

opening that regulates gas exchange and water evaporation between leaves and the environment, typically situated on the underside of leaves

stroma

fluid-filled space surrounding the grana inside a chloroplast where the light-independent reactions of photosynthesis take place

thylakoid

disc-shaped, membrane-bound structure inside a chloroplast where the light-dependent reactions of photosynthesis take place; stacks of thylakoids are called grana

thylakoid lumen

aqueous space bound by a thylakoid membrane where protons accumulate during light-driven electron transport