Glycolysis, Pyruvate -> Acetyl-CoA conversion, TCA, ETC

What is the main purpose of glycolysis?

To convert 1 glucose molecule into 2 pyruvate molecules, producing ATP and NADH in the process.

What are the products of glycolysis for each glucose molecule?

Input: Glucose (6C)

• 2 ATP

• 2 NAD+

• 2P

Output:

2 ATP (net), 2 NADH, 2 pyruvate.

What happens to pyruvate after glycolysis?

Pyruvate is either used in aerobic respiration (TCA cycle and ETC) or in fermentation, depending on oxygen availability.

Aerobic Respiration

Requires oxygen. Pyruvate enters the mitochondria, is converted to acetyl-CoA, and enters the TCA cycle.

Fermentation

Occurs when oxygen is absent. Replenishes NAD+ without using the electron transport chain. Pyruvate is converted into lactate or ethanol.

TCA Cycle Overview

Each acetyl-CoA molecule goes through the TCA (Krebs) cycle twice. Produces NADH, FADH2, and ATP, with CO2 as a byproduct.

TCA Cycle Products (per cycle)

• 3 NADH

• 1 FADH2

• 1 ATP

• 2 CO2

Electron Transport Chain (ETC)

Electrons from NADH and FADH2 are passed along the ETC, creating a proton gradient that drives ATP synthesis via ATP synthase (chemiosmosis).

Aerobic Respiration ATP Yield

• 1 NADH -> 3 ATP

• 1 FADH2 -> 2 ATP
  Total ATP from NADH (10x3) = 30 ATP; from FADH2 (2x2) = 4 ATP.

Chemiosmosis

Process by which the proton gradient, created by the ETC, drives the production of ATP via ATP synthase.

Electron Acceptors

• Aerobic respiration: O2 as electron acceptor

• Anaerobic respiration: Nitrogen or sulfur compounds as acceptors

What is the proton motive force?

The gradient of protons created across the membrane during the ETC, which is used to drive ATP synthesis.

Prokaryotic Summary Diagram

Proteins, Fat, and Sugars~ all of these can be used as a source of energy

Role of NAD+ in Respiration

NAD+ is regenerated in the ETC, allowing glycolysis and the TCA cycle to continue by accepting more electrons.