Cell Metabolism and Respiration Notes

Cell Metabolism and Respiration

Overview of Cellular Respiration

• Cellular respiration is the process by which cells convert glucose (C6H12O6) and oxygen (O2) into carbon dioxide (CO2), water (H2O), and ATP (adenosine triphosphate).
• The overall reaction for cellular respiration can be summarized as:
  • C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

Role of ATP

• ATP Production: Energy from food is used to produce ATP from ADP (adenosine diphosphate) and inorganic phosphate.
• Energy Release: The energy stored in ATP is released to perform cellular work, regenerating ADP and phosphate.
• Cellular Work Includes:
  • Mitosis (cell division)
  • DNA replication
  • Protein synthesis
  • Other metabolic reactions (rxns)

Energy Storage in Cells

• Two types of energy storage:
  • Short-term storage: Similar to cash (immediate use)
  • Example: ATP
  • Long-term storage: Analogous to a savings account (future use)
  • Examples: Fats, Glycogen

Phases of Cellular Respiration

There are three main phases of cellular respiration:

1. Glycolysis

   • Location: Cytosol
   • Process:
     • Breakdown of glucose into pyruvate.
     • Generates 2 ATP through substrate-level phosphorylation.
     • Produces NADH by transferring electrons.

2. Citric Acid Cycle (Krebs Cycle)

   • Location: Mitochondrion
   • Process:
     • Converts pyruvate into acetyl-CoA before entering the cycle.
     • Generates NADH and FADH₂ from electron transfers.
     • Also produces 2 ATP through substrate-level phosphorylation.

3. Oxidative Phosphorylation

   • Location: Inner mitochondrial membrane
   • Process:
     • Involves the electron transport chain.
     • Electrons from NADH and FADH₂ are passed through proteins, releasing energy used to pump H+ ions into intermembrane space.
     • Creates a proton gradient that drives ATP production via ATP synthase, resulting in the generation of approximately 34 ATP.

Structure of Mitochondria

• Outer Membrane: Selectively permeable, surrounds the mitochondrion.
• Inner Membrane: Folds inward (forming cristae), increasing surface area for cellular respiration reactions.
• Intermembrane Space: Area between inner and outer membranes where protons are pumped during the electron transport chain.
• Matrix: The inner space of the mitochondria where the citric acid cycle occurs.

Electron Transport Chain

• Located in the inner mitochondrial membrane.
• Key components include:
  • Complex proteins that transfer electrons (NADH, FADH₂)
  • Oxygen serves as the final electron acceptor, forming water (H2O).
• Pumps protons (H+) into the intermembrane space, contributing to the proton gradient used in ATP production.