Chapter 9: Glycolysis and Krebs Cycle

Sep 30, 2024

Lecture Notes: Cellular Respiration

Overview

  • Focus on completing cellular respiration
  • Photosynthesis to be studied independently
  • Two main topics: Cellular Respiration and Photosynthesis
    • Chapter 9: Cellular Respiration
    • Chapter 10: Photosynthesis

Cellular Respiration

  • Definition: Process of making energy in the cell
  • Main Stages:
    1. Glycolysis
    2. Krebs Cycle (Citric Acid Cycle)
    3. Electron Transport Chain (ETC)

Glycolysis

  • Meaning: Breakdown of glucose
  • Process:
    • Glucose (6-carbon) is split into two 3-carbon molecules called pyruvate
    • Requires initial energy input
    • Produces:
      • 2 ATP (Net gain - use 2 ATP, make 4 ATP)
      • 2 Pyruvate
      • 2 NADH (energized form, potential energy)
  • Location: Cytoplasm

NAD and NADH

  • Roles:
    • NAD: Non-energized, oxidized form
    • NADH: Energized form, carries hydrogen
  • Importance: NADH participates in electron transport chain for energy production

Pyruvate to Acetyl CoA

  • Conversion:
    • Pyruvate is modified with the addition of vitamin A
    • Becomes Acetyl CoA, ready for the Krebs Cycle
  • Transport:
    • Through mitochondrial membranes using transporters (TIM and TOM)
  • Transporter Characteristics:
    • Active but can sometimes function without energy
    • Subject of scientific studies

Mitochondria Structure

  • Components:
    • Inner and outer membranes
    • Cristae (infoldings)
    • Matrix (jelly-like substance)
  • Intermembrane Space: Site of hydrogen concentration gradient

Krebs Cycle (Citric Acid Cycle)

  • Occurs in: Mitochondrial matrix
  • Goals:
    • Produce reduced energy carriers: NADH, FADH2
    • Generate ATP (small amount)
  • Cycle Details:
    • Each Acetyl CoA enters the cycle, producing:
      • 3 NADH
      • 1 FADH2
      • 1 ATP
    • For one glucose molecule (2 turns):
      • 6 NADH
      • 2 FADH2
      • 2 ATP
  • Waste Product: CO2

Electron Transport Chain (ETC)

  • Final Stage: Produces the most ATP
  • Location: Cristae of mitochondria
  • Process:
    • Uses NADH and FADH2 to generate a hydrogen gradient
    • ATP produced via chemiosmotic phosphorylation
  • Components:
    • Protein transporters
    • Involves hydrogen transfer across the membrane
  • Important Notes:
    • Sensitive to poisons like carbon monoxide

Additional Information

  • Cellular Poisons: Some affect cycles, e.g., arsenic impacts the Krebs cycle
  • Mitochondria and Energy:
    • Mitochondria’s role in energy production is crucial
    • Has complex biochemistry involving many specific reactions and enzymes

Summary

  • Cellular Respiration: Converts glucose to ATP through a series of reactions
  • Cycle of Energy: NADH and FADH2 play critical roles as hydrogen carriers

Questions Discussed

  • Consumption of ATP directly in the body
  • The role of pyruvic acid and pyruvate
  • How poison like arsenic affects cellular respiration

These notes review the key points discussed about cellular respiration, emphasizing the biochemical pathways and components involved in ATP production within cells.