BIOENERGETICS

These flashcards cover key vocabulary and concepts related to bioenergetics, energy transformations, cellular respiration, and photosynthesis.

Bioenergetics

The study of how energy flows through living systems.

Enthalpy (H)

The total energy of a system, including internal energy and the energy associated with pressure and volume.

Entropy (S)

A measure of disorder or randomness in a system.

Free energy (G)

The amount of energy available to do work in a system at constant temperature and pressure.

Activation energy (EA)

The minimum energy required to initiate a chemical reaction.

Metabolism

The sum of all chemical reactions occurring in a living organism.

Catabolism

The metabolic pathway that breaks down molecules into smaller units and produces energy.

Anabolism

The metabolic pathway that builds complex molecules from simpler ones, consuming energy in the process.

Glycolysis

The metabolic pathway that converts glucose into pyruvate, producing ATP and NADH.

Krebs Cycle

A series of reactions that produce energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

Electron Transport Chain (ETC)

A series of protein complexes in the inner mitochondrial membrane that transfer electrons and pump protons to generate a proton gradient used to make ATP.

Chemiosmosis

The process by which ATP is produced by the movement of protons across a membrane during cellular respiration or photosynthesis.

ATP (Adenosine Triphosphate)

The primary energy carrier in all living organisms.

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.

Aerobic respiration

A type of cellular respiration that requires oxygen to produce ATP from glucose.

Anaerobic respiration

A type of cellular respiration that occurs without oxygen, producing ATP through fermentation.

Fermentation

A metabolic process that converts sugar to acids, gases, or alcohol in the absence of oxygen.

Cyclic electron flow

A photosynthetic process in which electrons are recycled within Photosystem I to produce ATP without the production of NADPH.

Noncyclic electron flow

A photosynthetic process that involves both Photosystems I and II, resulting in the production of ATP and NADPH.

RUBISCO

An enzyme (ribulose-1,5-bisphosphate carboxylase/oxygenase) that catalyzes the first step of carbon fixation in the Calvin cycle.

Calvin Cycle

The series of biochemical reactions in photosynthesis that convert carbon dioxide into glucose, using ATP and NADPH from the light reactions.

First Law of Thermodynamics

The principle stating that energy cannot be created or destroyed, only transformed or transferred.

Second Law of Thermodynamics

The principle stating that every energy transfer or transformation increases the entropy (S) of the universe.

Exergonic reaction

A spontaneous chemical reaction in which there is a net release of free energy (\Delta G < 0).

Endergonic reaction

A non-spontaneous chemical reaction in which free energy is absorbed from the surroundings (\Delta G > 0).

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.

Substrate-level Phosphorylation

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

NADH and FADH2

Coenzymes that act as electron carriers, transporting high-energy electrons to the Electron Transport Chain (ETC).

Photorespiration

A metabolic pathway that consumes oxygen and ATP, releases carbon dioxide, and decreases photosynthetic output, occurring when RUBISCO binds O2 instead of CO2.

C4 Plants

Plants that preface the Calvin cycle with an alternate mode of carbon fixation that forms a four-carbon compound as its first product to minimize photorespiration.

CAM Plants

Plants that use Crassulacean Acid Metabolism, opening their stomata at night to take up CO_2 and storing it as organic acids until the daytime for photosynthesis.

Gibbs Free Energy Equation

The mathematical relationship used to determine the spontaneity of a chemical reaction: \Delta G = \Delta H - T\Delta S.

Enzymes

Biological catalysts, typically proteins, that speed up chemical reactions by lowering the activation energy (E_{A}).

Active Site

The specific region of an enzyme where substrate molecules bind and undergo a chemical reaction.

Competitive Inhibition

A form of enzyme inhibition where a molecule other than the substrate binds to the active site, preventing the substrate from binding.

Allosteric Inhibition

A type of noncompetitive inhibition where a regulatory molecule binds to a site other than the active site, changing the enzyme's shape and reducing its activity.

Pyruvate Oxidation

The intermediate step between glycolysis and the Krebs cycle where pyruvate is converted into acetyl-CoA, releasing CO_{2} and NADH.

Thylakoid

A flattened, membrane-bound sac inside a chloroplast where the light-dependent reactions of photosynthesis occur.

Stroma

The fluid-filled space within a chloroplast that surrounds the thylakoids; the site of the Calvin cycle reactions.

Mitochondrial Matrix

The innermost compartment of the mitochondrion where the enzymes for the Krebs cycle are located.