Biology 1002

Catabolism

A metabolic pathway that breaks down complex molecules and is exergonic.

Anabolism

A metabolic pathway that builds up molecules and is endergonic.

Fermentation

A partial degradation of sugars or other organic fuel that occurs without O2.

Aerobic respiration

The most efficient catabolic pathway in which cells use oxygen to break down glucose (food) to create a large amount of energy in the form of ATP, producing carbon dioxide and water as byproducts.

Anaerobic respiration

A metabolic process in which energy is generated from food molecules without using oxygen.

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.

Oxidation-reduction reactions

The transfer of one or more electrons from one reactant to another.

Oxidation

The loss of electrons from one substance

Reduction

The addition of electrons to another substance

Reducing agent

The electron donor

Oxidizing agent

The electron acceptor

Nicotinamide adenine dinucleotide

A derivative of the vitamin niacin and coenzyme that is an electron carrier of hydrogen atoms. Consists of two nucleotides joined together at their phosphate group.

NAD+

Oxidized form of nicotinamide adenine dinucleotide and most versatile electron acceptor in cellular respiration

NADH

Reduced form of nicotinamide adenine dinucleotide

Dehydrogenases

Enzymes that help NAD+ trap electrons from glucose by removing a pair of hydrogen atoms from glucose.

Electron transport chain

Respiration uses this to break the fall of electrons to oxygen into several energy-releasing steps. A collection of molecules embedded in the inner membrane of the mitochondrion in eukaryotic cells.

“Downhill” carrier

Capable of oxidizing and more electronegative

Glycolysis

Splitting sugar to make pyruvate

Pyruvate

A compound made by the breaking down of glucose.

Acetyl CoA

An oxidized pyruvate compound that enters the citric acid cycle.

Citric acid cycle

A chemical cycle that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA to carbon dioxide.

Oxidative phosphorylation

The production of (most) 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.

Energy investment phase

A phase of glycolysis that spends ATP.

Energy pay-off phase

A phase of glycolysis that produces of ATP by substrate-level phosphorylation.

Acetate

A compound formed from 2 oxidized carbons from pyruvate.

Prosthetic groups

Nonprotein components essential for the catalytic functions of certain enzymes.

Flavoprotein

The first molecule of the electron transport chain in complex I where electrons are transferred from NADH to this molecule by NAD+.

Ubiquinone

It is a small hydrophobic molecule, the only member of the electron transport chain that is not a protein.

Cytochromes

Proteins between ubiquinone and oxygen that make up most of the remaining electron carriers.

Heme group

This prosthetic group has an iron atom that accepts and donates electrons in the ECT.

Cyt a3

The last cytochrome of the ECT and passes its electrons to oxygen.

ATP synthase

A complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion (proton) concentration gradient to make ATP.

Chemiosmosis

An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work.

Uncoupling protein

A channel protein which allows protons to flow back down their concentration gradient without generating ATP.

Respiratory chain

Another name for the electron transport chain