AP Biology- Unit 3: Cellular Energetics

First Law of Thermodynamics

Energy cannot be created or destroyed, only transferred.

Second Law of Thermodynamics

Energy transfer leads to increased disorder, or entropy.

Exergonic Reactions

Reactions where the products have less energy than the reactants.

Endergonic Reactions

Reactions where the products have more energy than the reactants.

Enzymes

Biological catalysts that speed up reactions by lowering activation energy.

Activation Energy

The minimum amount of energy required to start a chemical reaction.

Enzyme Specificity

Each enzyme catalyzes only one specific kind of reaction.

Substrates

Molecules that enzymes target during enzymatic reactions.

Active Site

The special region on an enzyme where substrate binding occurs.

Induced-fit Model

The concept that enzymes change shape slightly to better fit their substrates.

Cofactors

Factors that assist enzymes in catalyzing reactions, can be organic or inorganic.

Enzyme Denaturation

The alteration of an enzyme's structure, often due to extreme temperature or pH.

Saturation Point

The concentration of substrate at which all enzyme active sites are occupied.

Competitive Inhibition

When an inhibitor competes with the substrate for the active site.

Noncompetitive Inhibition

When an inhibitor binds to an allosteric site, distorting the enzyme shape.

Cellular Respiration

A metabolic process that breaks down glucose and produces ATP, involving either aerobic or anaerobic processes.

Aerobic Respiration

A type of respiration that requires oxygen to produce ATP, involving glycolysis, acetyl-CoA formation, the Krebs cycle, and oxidative phosphorylation.

Glycolysis

The first stage of cellular respiration that splits glucose into two pyruvic acid molecules, producing a net of 2 ATP and 2 NADH.

Acetyl-CoA

A two-carbon molecule formed from pyruvic acid that enters the Krebs cycle.

Krebs Cycle (Citric Acid Cycle)

A series of reactions in the mitochondrial matrix that produces ATP, NADH, and FADH2 by oxidizing acetyl-CoA.

Oxidative Phosphorylation

The final stage of cellular respiration where ATP is produced using the energy from electrons passed down the electron transport chain.

Electron Transport Chain

A series of protein carriers in the inner mitochondrial membrane that transfer electrons and pump hydrogen ions, leading to ATP production.

Chemiosmosis

The process through which ATP is generated by the movement of hydrogen ions across a membrane.

Fermentation

An anaerobic process that allows glycolysis to continue, producing lactic acid or ethanol instead of ATP when oxygen is not available.

NADH

An electron carrier molecule that is reduced from NAD+ during glycolysis and used in the Krebs cycle and oxidative phosphorylation.

FADH2

An electron carrier produced in the Krebs cycle that contributes to ATP production during oxidative phosphorylation.

Proton Gradient

A difference in the concentration of hydrogen ions across a membrane, which powers ATP synthesis during oxidative phosphorylation.

Oxygen Debt

A condition resulting from intense exercise where the demand for oxygen exceeds supply, leading to anaerobic respiration in muscles.

Pyruvic Acid

A three-carbon compound that is produced from glycolysis and converted to acetyl-CoA in aerobic respiration or to lactic acid or ethanol in anaerobic respiration.

ATP Synthase

An enzyme that synthesizes ATP from ADP and inorganic phosphate, driven by the flow of protons down their gradient.

Lactic Acid

A product of anaerobic respiration in muscle cells that occurs when pyruvic acid is converted due to lack of oxygen.

Ethanol

A product of anaerobic respiration in yeast cells, resulting from the conversion of pyruvic acid.