Biological Processes: Photosynthesis and Cellular Respiration

Photosynthesis vs. Chloroplasts

  • Photosynthesis

    • Process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose.
    • Takes place primarily in the chloroplasts of plant cells.

  • Chloroplasts

    • Organelles found in plant cells and eukaryotic algae.
    • Contain chlorophyll, which captures light energy.
    • Structures involved in photosynthesis include:
    • Light-dependent reactions (LDR)
    • Calvin cycle

Light-Dependent Reactions (LDR)

  • Definition: The first stage of photosynthesis that requires light to produce ATP and NADPH.
  • Location: Occurs in the thylakoid membranes of chloroplasts.
  • Process:
    • Light energy is absorbed and used to generate ATP through photophosphorylation.
    • Water molecules are split, releasing oxygen as a by-product.

Calvin Cycle

  • Definition: A series of biochemical reactions that take place in the chloroplasts during photosynthesis.
  • Purpose: Uses ATP and NADPH produced in the LDR to convert carbon dioxide into glucose.
  • Key Steps:
    • Carbon fixation
    • Reduction phase
    • Regeneration of RuBP (Ribulose bisphosphate)

Cellular Respiration

  • Definition: The process by which cells convert glucose into ATP, releasing energy.

  • Key Structures:

    • Mitochondria: The organelles where cellular respiration occurs.

  • Major Stages of Cellular Respiration:

    1. Glycolysis
    • Definition: The breakdown of glucose into pyruvate, producing ATP and NADH.
    • Location: Cytoplasm.
    1. Krebs Cycle (Citric Acid Cycle)
    • Definition: Chemical reactions that generate energy through oxidation of acetyl-CoA.
    • Location: Mitochondrial matrix.
    1. Electron Transport Chain (ETC)
    • Definition: Series of protein complexes that transfer electrons and pump protons to produce ATP.
    • Location: Inner mitochondrial membrane.

ATP (Adenosine Triphosphate)

  • Definition: The energy currency of the cell.
  • Composition:
    • Made up of adenine, ribose (a sugar), and three phosphate groups.
  • Function:
    • Stores energy in the bonds between its phosphate groups.
    • Energy is released when ATP is converted to ADP (Adenosine Diphosphate) through the breaking of bond.

Types of Respiration

  • Aerobic Respiration

    • Definition: A process that requires oxygen to produce ATP.
    • Outcome: More efficient ATP production.
    • Reaction: Glucose + Oxygen → Carbon Dioxide + Water + ATP

  • Anaerobic Respiration

    • Definition: A process that occurs without oxygen.
    • Outcome: Less efficient ATP production, leading to fermentation.

  • Fermentation

    • Definition: A metabolic process that converts sugar to acids, gases, or alcohol in the absence of oxygen.
    • Example: Lactic acid fermentation, which occurs in muscle cells during intense exercise when oxygen levels are low.