AP Biology Unit 3

enzyme

A protein that acts as a biological catalyst by lowering the activation energy needed in a reaction

active site

a region on an enzyme that binds to a substrate

substrate

A specific reactant acted upon by an enzyme

catalyst

substance that speeds up the rate of a chemical reaction

activation energy

the minimum amount of energy required to start a chemical reaction

denature/denaturation

A change in the shape of a protein that makes it unable to function

competitive inhibitor

A substance that reduces the activity of an enzyme by binding to the enzyme's active site in place of the substrate.

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 it no longer binds to the substrate.

allosteric regulation

When a protein's function at one site is affected by the binding of a regulatory molecule to a separate site.

laws of thermodynamics

1) energy can not be created or destroyed, only converted from one form to another, 2) each time you convert one form of energy to another, some energy is converted to a non-usable form (more energy efficient to consume plants because they exist very close to the initial source of energy)

exergonic reaction

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

endergonic reaction

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

photosynthesis

Conversion of light energy from the sun into chemical energy.

cyanobacteria

Bacteria that can carry out photosynthesis

light dependent reactions

reactions of photosynthesis that use energy from light to produce ATP and NADPH

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

NADPH

electron carrier that provides high-energy electrons for photosynthesis

chlorophyll

Green pigment in plants that absorbs light energy used to carry out photosynthesis

Photosystems I and II

contain chlorophyll and absorb light energy during the light dependent reactions

electron transport chain (ETC)

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

Electrochemical/proton gradient

Electrochemical gradient resulting from a difference in proton concentration across a membrane and the potential difference (membrane potential) across the membrane. Such a gradient is established across the inner mitochondrial membrane during oxidative phosphorylation in mitochondria, and across the thylakoid membrane during photophosphorylation in chloroplasts.

ATP synthase

Large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP

photophosphorylation

The process of generating ATP from ADP and phosphate by means of a proton-motive force generated by the thylakoid membrane of the chloroplast during the light reactions of photosynthesis.

calvin cycle

reactions of photosynthesis in which energy from ATP and NADPH is used to build high-energy compounds such as sugars

fermentation (anaerobic)

Process by which cells release energy in the absence of oxygen

lactic acid

product of fermentation in many types of cells, including human muscle cells

cellular respiration (aerobic)

Process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

NADH & FADH2

electron carriers in cellular respiration

chemiosmosis

A process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme.

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.

glycolysis

first step in releasing the energy of glucose, in which a molecule of glucose is broken into two molecules of pyruvic acid

Krebs cycle

second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions