Cellular Respiration and Enzyme Energetics

Vocabulary flashcards covering energy forms, thermodynamics, enzymes, cellular respiration steps, and fermentation based on the lecture notes.

Activation energy

Energy needed to start a chemical reaction.

Catalyst

A substance that speeds up a reaction without being used up.

Enzyme characteristics

Proteins that act as biological catalysts, being specific, reusable, and affected by temperature and pH.

Substrate

The specific molecule an enzyme acts on, which fits into the enzyme's active site.

Denature

The process where an enzyme loses its shape and stops working properly due to extreme temperature or pH.

Competitive inhibitor

A molecule that blocks the active site of an enzyme by competing with the substrate.

Allosteric inhibitor

A molecule that binds somewhere other than the active site and changes the enzyme's shape.

Kinetic energy

Energy of motion, such as molecular movement related to heat.

Potential energy

Stored energy that can be used later, such as $H^+$ ions concentrated on one side of a membrane.

Entropy

A measure of disorder or randomness in a system.

Free energy

Energy available to perform work in a cell, such as making ATP.

Thermodynamics

The study of energy and energy changes during cellular reactions.

Exergonic

A reaction that releases free energy and usually has a negative $\boldsymbol{\nabla G}$ ($\boldsymbol{\nabla G}$ is negative).

Endergonic

A reaction that requires or absorbs free energy and has a positive $\boldsymbol{\nabla G}$.

Metabolic heat

Heat released during chemical reactions that is not stored as ATP.

Oxidation

The loss of electrons during a chemical reaction (OIL: Oxidation Is Loss).

Reduction

The gain of electrons during a chemical reaction (RIG: Reduction Is Gain).

Glycolysis

The process taking place in the cytoplasm that breaks glucose into 2 pyruvate molecules, yielding 2 ATP net, 2 $NADH$, and 2 pyruvate.

Pyruvate oxidation

The conversion of pyruvate into Acetyl-CoA in the mitochondrial matrix, producing $NADH$ and $CO_2$.

Krebs cycle

A cycle in the mitochondrial matrix where Acetyl-CoA enters to produce $NADH$, $FADH_2$, ATP, and $CO_2$.

Electron Transport Chain (ETC)

A chain of proteins in the inner membrane of mitochondria that uses electrons from $NADH$ and $FADH_2$ to pump $H^+$ protons into the intermembrane space.

Chemiosmosis

The movement of $H^+$ ions from the intermembrane space to the matrix through ATP synthase to synthesize ATP.

Oxidative phosphorylation

The process of making large amounts of ATP using the ETC, an $H^+$ gradient, and ATP synthase.

Substrate-level phosphorylation

The direct creation of ATP by transferring a phosphate group to ADP during glycolysis and the Krebs cycle.

Mitochondrial matrix

The innermost space of the mitochondria where pyruvate oxidation and the Krebs cycle occur.

Intermembrane space

The space in mitochondria where $H^+$ ions build up to form a concentration gradient.

Final electron acceptor

Oxygen ($O_2$) in aerobic cellular respiration, which accepts electrons and $H^+$ to form $H_2O$.

Alcoholic fermentation

An anaerobic pathway that converts pyruvate into ethanol and $CO_2$ to regenerate $NAD^+$ in organisms like yeast.

Lactic acid fermentation

An anaerobic pathway in animal cells when oxygen is limited that converts pyruvate into lactate to regenerate $NAD^+$

Oxaloacetic acid (OAA)

A molecule in the Krebs cycle that combines with Acetyl-CoA to start the cycle and is regenerated at the end.

ATP

Adenosine triphosphate, a high-energy molecule used to power cellular work like active transport, movement, and building molecules.

ADP

Adenosine diphosphate, the lower-energy form that combines with phosphate and energy to form ATP.