Cellular Respiration

Cellular respiration

A metabolic pathway that rearranges the atoms in food molecules, making stored energy available to the cell.

NADH

An electron carrier that transfers electrons removed from food molecules to oxygen.

ATP

A key energy currency of the cell, produced from energy released during cellular respiration.

Glycolysis

The first part of cellular respiration where glucose is oxidized into two molecules of pyruvate.

Krebs Cycle

Also known as the tricarboxylic acid cycle, continues oxidation of glucose intermediates and produces CO2.

Oxidative phosphorylation

Transfers electrons from electron carriers to an electron transport chain to produce ATP.

Exergonic

A chemical process that releases energy, such as cellular respiration.

Decarboxylation

The removal of carbon and oxygen atoms from intermediates, releasing them as CO2.

Substrate level phosphorylation

The process of producing ATP by transferring a phosphate group from an intermediate to ADP.

Lactic acid fermentation

A process that converts pyruvate into lactic acid, allowing glycolysis to continue under anaerobic conditions.

Alcohol fermentation

A process used by yeasts to convert pyruvate into ethanol and CO2, recycling NAD+.

Electron transport chain

A series of proteins embedded in a membrane that transfer electrons and pump hydrogen ions to generate ATP.

Chemiosmosis

The process by which hydrogen ions flow back across a membrane, driving ATP production in the mitochondria.

Pyruvate

A three-carbon molecule produced from glycolysis that enters the Krebs cycle.

Acetyl-CoA

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

FAD

A reduced electron carrier similar to NAD+, involved in transferring electrons in cellular respiration.

Oxaloacetate

A four-carbon molecule that combines with acetyl-CoA to begin the Krebs cycle.

Phosphofructokinase

An enzyme that catalyzes the first step in glycolysis and is inhibited by ATP.

Amylase

An enzyme that breaks down starch into individual glucose molecules.

Electron carriers

Molecules like NADH and FADH2 that transfer electrons during cellular respiration.

ATP synthase

An enzyme that synthesizes ATP as hydrogen ions move through it during oxidative phosphorylation.

Proton motive force

The potential energy stored as a result of hydrogen ion concentration gradients across a membrane.

Hydrogen atoms

Atoms that are removed from glucose during cellular respiration and added to oxygen to form water.

Feedback inhibition

A regulatory mechanism in metabolic pathways where the end product inhibits an earlier step.

Citrate

A six-carbon molecule that begins the Krebs cycle, formed from acetyl-CoA and oxaloacetate.

Glycerol

A three-carbon compound that can be converted to an intermediate in glycolysis from fat breakdown.

Deamination

The removal of the nitrogen-containing amino group from amino acids before entering cellular respiration.

ADP

A molecule that is converted to ATP during the process of cellular respiration.

Glyceraldehyde-3-phosphate

An intermediate produced in glycolysis which can also be converted from glycerol.

NAD+

An oxidized form of NADH that accepts electrons during glycolysis and the Krebs cycle.

Intermediates

Compounds that are formed during glycolysis and the Krebs cycle and used in various pathways.

Carbohydrates

Organic molecules that are broken down into simple sugars for energy during cellular respiration.

Lipids

Fats that can be metabolized for energy; glycerol can enter glycolysis after conversion.

Proteins

Molecules that can be broken down into amino acids and enter cellular respiration at various stages.

Enzymes

Proteins that catalyze biochemical reactions, lowering the activation energy needed.

Energy investment phase

The initial phase of glycolysis where ATP is used to phosphorylate intermediates.

Energy payoff phase

The phase of glycolysis that produces a net gain of ATP from substrate level phosphorylation.

Flavins

A group of coenzymes that participate in redox reactions during cellular respiration.

Carbon dioxide

A waste product produced during the Krebs cycle and released from the cell.

Water

A waste product formed when oxygen accepts electrons at the end of the electron transport chain.

Glucose-6-phosphate

An intermediate in glycolysis, formed when ATP donates a phosphate to glucose.

Phosphoenolpyruvate

An intermediate in glycolysis that donates a phosphate to ADP, forming ATP.

Malate

A four-carbon molecule that is oxidized to regenerate oxaloacetate in the Krebs cycle.

Acetaldehyde

An intermediate in alcohol fermentation produced from pyruvate.

Succinate

A four-carbon intermediate in the Krebs cycle formed from succinyl-CoA.

Fumarate

An intermediate in the Krebs cycle formed from the oxidation of succinate.

Isocitrate

A pivotal intermediate in the Krebs cycle converted from citrate.

Pyruvate oxidation

The conversion of pyruvate into acetyl-CoA before entering the Krebs cycle.

Intermembrane space

The space between the inner and outer membranes of the mitochondria where protons are pumped.

Citric acid cycle

Another name for the Krebs cycle, emphasizing its production of citric acid.

Lactate dehydrogenase

The enzyme that catalyzes the conversion of pyruvate to lactic acid in fermentation.

NADH + H+

The reduced form of NAD+ after it gains electrons during glycolysis and the Krebs cycle.

Complex carbohydrates

Polymers like starch that can be broken down into glucose for cellular respiration.