Exam 2 Collaborative Quizlet

Activation Energy

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

Active Site

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

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.

Anabolic Pathway

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

Catabolic Pathway

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

Catalyst

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

Chemical Energy

Energy available in molecules for release in a chemical reaction; a form of potential energy.

Competitive Inhibitor

A molecule that structurally resembles an enzyme's substrate and binds to the enzyme's active site, preventing the actual substrate from binding and thus slowing down or stopping the reaction.

Endergonic Reaction

A reaction that requires the input of energy.

Energy Coupling

In cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction.

Entropy

A measure of the disorder or randomness within a biological system. It quantifies the number of possible states or configurations that a system's energy and matter can take on.

Enzyme

Specialized proteins that serve as catalysts by stabilizing substrates and lowering activation energy.

Exergonic Reaction

A reaction that releases energy.

Feedback Inhibition

Metabolic pathway acts as an inhibitor of an enzyme within that pathway.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed in a reaction.

Free Energy

The amount of energy in a system that is available to do work.

Metabolism

A set of biochemical reactions that will transform biomolecules and transfers energy.

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.

Potential Energy

Energy that is not associated with movement, but rather is stored.

Second Law of Thermodynamics

The total entropy (disorder) only increases over time - never decreases.

Spontaneous Process

A physical or chemical change that occurs naturally under specific conditions without the need for continuous external energy input, driven by a tendency toward increased entropy (disorder) and lower Gibbs free energy.

Phosphorylation

The biochemical process of adding a phosphate group to a molecule, such as a protein or a sugar. This addition acts as a regulatory switch, modifying the molecule's function, activity, and cellular location.

Substrate

the substance in which an organism can act

acetyl CoA

Acetyl coenzyme A; the entry compound for the citric acid cycle in cellular respiration, formed from a two-carbon fragment of pyruvate attached to a coenzyme.

aerobic respiration

A catabolic pathway for organic molecules, using oxygen (O2) as the final electron acceptor in an electron transport chain and ultimately producing ATP.

alcohol fermentation

Glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD+ and releasing carbon dioxide.

ATP synthase

potential energy stored in the proton gradient is converted to mechanical energy as protons move down their concentration gradient

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.

citric acid cycle

Oxidation of glucose into carbon dioxide

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.

Fermentation

metabolic pathways in which the terminal electron acceptor is an organic molecule, in contrast to aerobic cellular respiration in which the terminal electron acceptor is oxygen.

Glycolysis

the breakdown of glucose by enzymes, releasing energy and pyruvic acid

Lactic acid fermentation

anaerobic metabolic reaction in which glucose or other sugar molecules are converted into lactic acid and energy.

Oxidation

loss of electrons

oxidative phosphorylation

A metabolic process that occurs in the mitochondria that converts ATP to ADP through a series of redox reactions.

redox reaction

/ oxidation-reduction reaction: chemical reaction involving the transfer of electrons between two species

Reduction

gain of electrons

substrate-level phosphorylation

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

Autotroph

organisms that make their own energy

Calvin cycle

Uses ATP and NADPH to fix CO2 into organic molecules through the processes of carbon fixation, reduction, and regeneration.

carbon fixation

The initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism.

Carotenoid

An accessory pigment, either yellow or orange, in the chloroplasts of plants and in some prokaryotes.

Chlorophyll

the main photosynthetic pigment that absorbs visible light/ solar energy; absorbs violet and red and reflects green; once chlorophyll absorbs light, an electron is elevated and passes onto the next adjacent chlorophyll

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.

glyceraldehyde 3-phosphate (G3P)

A three-carbon carbohydrate that is the direct product of the Calvin cycle; it is also an intermediate in glycolysis.

Heterotroph

organisms that must ingest other organisms to make energy

light-harvesting complex

A complex of proteins associated with pigment molecules (including chlorophyll a, chlorophyll b, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem.

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.

linear electron flow

process in photosynthesis where electrons are transferred through a series of proteins in the thylakoid membrane, ultimately leading to the production of ATP and NADPH

Mesophyll

the inner tissue of a leaf, containing many chloroplasts

Photophosphorylation

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.

Photosynthesis

Process that converts solar energy into chemical energy

Photosystem

A light-capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes, consisting of a reaction-center complex surrounded by numerous light-harvesting complexes. There are two types of photosystems, I and II; they absorb light best at different wavelengths.

photosystem II (PS II)

absorbs wavelengths of 680 nm and the reaction center in chlorophyll a is p680

photosystem I (PS I)

A light-capturing unit in a chloroplast's thylakoid membrane or in the membrane of some prokaryotes; it has two molecules of P700 chlorophyll a at its reaction center.

primary electron acceptor

whatever accepts electrons at the end of the electron transport chain, oxygen for aerobic respiration

reaction-center complex

A complex of proteins associated with a special pair of chlorophyll a molecules and a primary electron acceptor. Located centrally in a photosystem, this complex triggers the light reactions of photosynthesis. Excited by light energy, the pair of chlorophylls donates an electron to the primary electron acceptor, which passes an electron to an electron transport chain.

Rubisco

Ribulose bisphosphate (RuBP) carboxylase-oxygenase, the enzyme that normally catalyzes the first step of the Calvin cycle (the addition of CO2 to RuBP). When excess O2 is present or CO2 levels are low, rubisco can bind oxygen, resulting in photorespiration.

Stoma

(plural, stomata) 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.

Stroma

The dense fluid within the chloroplast surrounding the thylakoid membrane and containing ribosomes and DNA; involved in the synthesis of organic molecules from carbon dioxide and water.

Thylakoid

A flattened, membranous sac inside a chloroplast. Thylakoids often exist in stacks called grana that are interconnected; their membranes contain molecular 'machinery' used to convert light energy to chemical energy.