Biology Chapter: Aerobic Respiration

Study Notes

Aerobic Respiration Stages

Respiration consists of four main stages: Glycolysis, Link Reaction, Krebs Cycle, and Oxidative Phosphorylation.
Glycolysis converts one 6-carbon glucose into two 3-carbon pyruvate molecules.
The Link Reaction transforms pyruvate into carbon dioxide and acetyl coenzyme A (acetyl CoA).
Krebs Cycle involves acetyl CoA in a series of eight enzyme-catalysed reactions, producing reduced NAD, FAD, and ATP.
Oxidative Phosphorylation utilizes reduced NAD and FAD in the electron transport chain, requiring oxygen and producing water.

Anaerobic Respiration

Anaerobic respiration includes glycolysis but omits the Link Reaction, Krebs Cycle, and Oxidative Phosphorylation.
In mammals, pyruvate from glycolysis is converted into lactate.
In yeast, pyruvate is converted into ethanol and carbon dioxide.

Glycolysis Overview

Glycolysis occurs in the cytoplasm of all multicellular and many unicellular organisms.
It converts a hexose sugar (glucose) into two 3-carbon molecules (pyruvate), involving ten smaller enzyme-controlled reactions grouped into four stages.

Stages of Glycolysis

Activation of Glucose:
- Glucose is phosphorylated using two ATP molecules, forming fructose 1,6-bisphosphate; this makes glucose reactive and prevents its exit from the cell.
Splitting of Phosphorylated Sugar:
- Fructose 1,6-bisphosphate splits into two molecules of triose phosphate.
Oxidation of Triose Phosphate:
- Hydrogen is removed from triose phosphate and transferred to NAD+ to produce reduced NAD.
Production of ATP:
- Conversion of triose phosphate to pyruvate yields four ATP (net gain of two) and two molecules of reduced NAD.

Net Yield from Glycolysis

From one glucose molecule, glycolysis results in:
- Two net molecules of ATP.
- Two molecules of reduced NAD, which can produce more ATP.
- Two molecules of pyruvate.

Significance of Glycolysis

Glycolysis is one of the earliest biochemical pathways and operates without organelles or membranes.
It functions anaerobically, allowing organisms to utilize alternative pathways such as fermentation in the absence of oxygen.
Pyruvate can be further broken down in the Krebs Cycle to release additional energy, particularly in aerobic conditions.

Description

Explore the four essential stages of aerobic respiration, including glycolysis, the link reaction, and the Krebs cycle. This quiz will test your understanding of how glucose is transformed into energy within cells and the importance of each stage in the biological process. Strengthen your knowledge of cellular respiration and its significance in living organisms.