Cellular Respiration and Redox Reactions

Vocabulary flashcards covering the concepts of redox reactions, the stages of cellular respiration (Glycolysis, Link Reaction, Citric Acid Cycle, and Oxidative Phosphorylation), and the roles of electron carriers and ATP synthase.

Oxidation-Reduction reactions (redox)

Chemical reactions in which there is a transfer of $1$ or more electrons ($e^-$) from one reactant to another.

"Oil Rig"

A mnemonic used to remember that Oxidation is losing and reduction is gaining.

Oxidation

The loss of electrons; if a molecule loses $H$, it is considered oxidized.

Reduction

The gain of electrons; if a molecule gains $H$, it is considered reduced.

Reducing agent

The substance that donates electrons and becomes oxidized during a redox reaction.

Oxidizing agent

The substance that accepts electrons and becomes reduced during a redox reaction.

NAD+

Nicotinamide adenine dinucleotide; a coenzyme derived from the vitamin niacin ($B3$) that acts as an electron acceptor (oxidizing agent) by accepting $H$.

NADH

The reduced form of Nicotinamide adenine dinucleotide, formed by the reaction $NAD^+ + H \rightleftharpoons NADH$. Produces approximately $2.5$ $ATP$ in the electron transport chain.

Glycolysis

The process of "sugar splitting" occurring in the cytoplasm where a six carbon sugar (glucose) is split into $2$, three carbon sugars (pyruvate).

Substrate-level phosphorylation

A process where an enzyme transfers a phosphate group from a substrate molecule to $ADP$ to make $ATP$.

Link Reaction (Pyruvate oxidation)

Occurs in the mitochondrial matrix; it oxidizes pyruvate ($3$ carbon molecule) to acetyl coenzyme A (acetyl CoA) ($2$ carbon molecule) by releasing $CO_2$.

Citric acid cycle (Krebs cycle)

An $8$ step cycle in the mitochondrial matrix that regenerates starting material and yields $4$ $CO_2$, $6$ $NADH$, $2$ $FADH$, and $2$ $ATP$ per glucose molecule.

Oxidative phosphorylation

The final stage of cellular respiration consisting of the electron transport chain and chemiosmosis, occurring on the inner membrane of the mitochondria.

Electron transport chain (ETC)

A collection of molecules (mostly proteins) embedded in the inner mitochondrial membrane where electrons are passed in a series of redox reactions.

Cristae

The foldings of the inner mitochondrial membrane that increase surface area to provide space for thousands of copies of electron transport chain molecules.

FADH2

An electron carrier that places its electrons further down the electron transport chain than $NADH$ and produces approximately $1.5$ $ATP$.

Oxygen

The final electron acceptor in the electron transport chain due to its high electronegativity, resulting in the production of water.

Chemiosmosis

A process where energy stored in the form of a $H^+$ ion gradient is used to drive cellular work, such as the synthesis of $ATP$.

ATP synthase

A protein complex (enzyme) embedded in the inner mitochondrial membrane containing a channel through which $H^+$ ions return down their gradient to attach a phosphate group to $ADP$.

Proton motive force

The usable energy released as $H^+$ ions return down their gradient into the matrix through $ATP$ synthase.