Lecture on Cell Respiration

Introduction

• Cell Respiration (also known as Cellular Respiration)
  • One of the two major energy processes (the other is photosynthesis).
  • Carried out by all living organisms (prokaryotes and eukaryotes).
  • Converts energy from food into ATP, the energy currency for cells.
  • Not an either/or with photosynthesis; all organisms do cell respiration.
• Photosynthesis
  • Not all organisms can perform photosynthesis.
  • Involves transforming light energy into chemical energy, typically producing glucose and oxygen.

Key Concepts of Cell Respiration

• Process of ATP Production
  • ATP is made by phosphorylating ADP (adding a phosphate group).
  • Two methods: Substrate level phosphorylation and Oxidative phosphorylation.
  • Involves electron carriers like NAD+ and FADH.

The Stages of Cell Respiration

1. Glycolysis
   • Takes place in the cytoplasm.
   • Splits glucose into two molecules of pyruvate.
   • Produces a net of 2 ATP via substrate level phosphorylation.
   • Can occur with or without oxygen.
   • Produces electron carriers (2 NADH).
2. Pyruvate Oxidation
   • Occurs in the mitochondrial matrix.
   • Converts pyruvate into acetyl CoA, releasing 2 CO2 and producing 2 NADH.
   • No ATP produced.
3. Citric Acid Cycle (Krebs Cycle)
   • Also takes place in the mitochondrial matrix.
   • Completes the breakdown of glucose, releasing 4 CO2.
   • Produces 2 ATP by substrate level phosphorylation.
   • Generates electron carriers (6 NADH, 2 FADH2).
4. Oxidative Phosphorylation
   • Involves the entire mitochondrion (except the outer membrane).
   • Produces 32 ATP on average through chemiosmosis.
   • Involves electron transport chain and ATP synthase.
   • Final electron acceptor is oxygen, forming water.

Important Components

• Electron Carriers
  • NAD+ and FADH2, critical in transferring electrons and establishing a concentration gradient.
• ATP Synthase
  • Enzyme facilitating ADP to ATP conversion as protons move down the concentration gradient.

Concept of Fermentation

• Anaerobic Respiration (Fermentation)
  • Occurs when there is insufficient oxygen.
  • In animals, produces lactic acid; in yeasts, produces ethanol.
  • Only 2 ATP produced per glucose molecule.
  • Fermentation is accelerated, burning glucose at a higher rate.

Application and Importance

• Energy Conversion
  • Essential for life, driving cellular reactions.
  • Energy is packaged as ATP for use anywhere in the cell.
• Health Implications
  • Cyanide and other poisons can block respiration stages.
  • Carbohydrates are the preferred fuel for efficient ATP production.

Summary

• Cell respiration is a complex process necessary for the survival of all living organisms, enabling them to convert food energy into usable ATP.
• Structured into four main stages, each contributing to the overall energy yield.
• Understanding these basics can be expanded upon in more advanced biological studies.