MCB 150 Lecture 10: Introduction to Cellular Respiration

Flashcards covering key concepts in Cellular Respiration.

Cellular Respiration

The breakdown of glucose to CO2 and H2O through multiple reactions in 3 distinct pathways: Glycolysis, Pyruvate oxidation and Krebs cycle, and Oxidative phosphorylation.

Glycolysis

The first phase in making ATP from glucose. Starts with a 6-carbon sugar (glucose), ends with two 3-carbon molecules (pyruvate).

Glycolysis Steps

A process where 2 steps are endergonic and 3 steps are exergonic, harnessing and saving energy for later, including 2 SLP (Substrate-Level Phosphorylation) reactions.

Aerobic Respiration

If oxygen (O2) is present, cells will undergo this process.

Anaerobic Respiration

If oxygen (O2) is absent but an alternative terminal electron acceptor exists, cells will undergo this process.

Fermentation

If oxygen (O2) is absent and no terminal electron acceptor exists, cells might be able to undergo this process.

Aerobic Respiration

Carbon source (2 molecules of pyruvate) completely converted to carbon dioxide; occurs in mitochondria of eukaryotes and cytoplasm/plasma membrane of prokaryotes.

Inner Membrane (Mitochondria)

Principal site of ATP generation in mitochondria, with >70% protein and impenetrable to ions & small molecules except by transporters.

Matrix (Mitochondria)

Contains Krebs enzymes, DNA & ribosomes within the mitochondria.

Pyruvate Oxidation

Pyruvate is oxidized to acetyl CoA and CO2. Acetyl CoA enters the Krebs cycle.

Krebs Cycle (Citric Acid Cycle)

Acetyl CoA is oxidized, releasing CO2 and producing ATP, NADH, and FADH2.

Oxidative Phosphorylation

NADH and FADH2 are oxidized, providing electrons for the electron transport chain, which generates a proton gradient used to produce ATP.

Electron Transport Chain (ETC)

A series of protein complexes that transfer electrons from electron donors to electron acceptors via redox reactions, and couples this electron transfer with the transfer of protons across a membrane.

ATP Synthase

Enzyme that uses the proton gradient generated by the ETC to synthesize ATP from ADP and inorganic phosphate (Pi).

Substrate-Level Phosphorylation (SLP)

Direct transfer of a phosphate group from an organic substrate to ADP, producing ATP.

Oxidative Phosphorylation ATP Yield

Produces approximately 26-28 ATP molecules per glucose molecule.

Total ATP Yield from Cellular Respiration

The theoretical maximum ATP yield is approximately 30-32 ATP molecules per glucose molecule (including glycolysis, pyruvate oxidation, and oxidative phosphorylation).