Photosynthesis & Cellular Respiration In-Depth Notes

General Outcomes

  • Photosynthesis: Relates to the storage of energy in organic compounds.
  • Cellular Respiration: Explains the role of releasing potential energy from organic compounds.
  • ATP: Summarize and explain its role in cellular metabolism.

Complementary Processes

  • Photosynthesis is an energy-storing reaction.
  • Cellular Respiration is an energy-releasing reaction.
  • Relationship: Products of one are reactants of the other.

Matter and Energy Pathways in Living Systems

  • Photosynthesis occurs in: Chloroplasts.
  • Cellular respiration occurs in: Mitochondria.
  • ATP - Adenosine Triphosphate: Main energy source for cellular processes.

Key Equations

  • Photosynthesis:
    ext{6 CO}2(g) + ext{6 H}2O(l) + ext{light energy}
    ightarrow ext{C}6 ext{H}{12} ext{O}6(s) + ext{6 O}2(g)
  • Cellular Respiration:
    ext{C}6 ext{H}{12} ext{O}6(s) + ext{6 O}2(g)
    ightarrow ext{6 CO}2(g) + ext{6 H}2 ext{O}(l) + 36 ext{ ATP energy}

Types of Organisms

  • Photoautotrophs: Use solar energy to synthesize carbohydrates.
  • Heterotrophs: Obtain carbohydrates by consuming other organisms.

ATP and Energy

  • Role of ATP: Provides energy for synthetic reactions, active transport, muscle contraction, and nerve impulses.
  • ATP Cycle: Continuous regeneration from ADP + Pi.

Cellular Activities Using ATP

  1. Active transport of ions and molecules.
  2. Movement of chromosomes.
  3. Cilia and flagella movement.
  4. Muscle contraction.
  5. Synthesis of macromolecules (carbohydrates, proteins, fats, nucleic acids).
  6. Heat production for temperature regulation.

Metabolic Pathways

  • Involve: Controlled reactions where products of one become reactants for another.
  • Enzymes: Special proteins that catalyze reactions by lowering activation energy.

Metabolism Overview

  • Anabolic Pathways: Synthesize larger molecules from smaller ones, require energy (e.g., photosynthesis).
  • Catabolic Pathways: Break down larger molecules to release energy (e.g., cellular respiration).

Oxidation-Reduction Reactions

  • Oxidation: Loss of electrons.
  • Reduction: Gain of electrons.
  • Example: In photosynthesis, ext{CO}2 is reduced to form glucose, while in respiration glucose is oxidized to produce ext{CO}2.

Photosynthesis Overview

  • Light-dependent Reactions: Capture solar energy and convert it into ATP and NADPH; occur in thylakoids.
  • Light-independent Reactions (Calvin Cycle): Synthesize carbohydrates using ATP and NADPH; occur in stroma.

Light-Dependent Reactions Steps

  1. Light Absorption by Photosystems.
  2. Electron Transport Chain generates proton gradient for ATP synthesis.
  3. NADPH formation.

Light-Independent Reaction (Calvin Cycle)

  1. Carbon Fixation: CO2 combines with RuBP.
  2. Reduction: ATP and NADPH reduce 3-PGA to PGAL.
  3. Regeneration: RuBP is regenerated for the cycle to continue.

Cellular Respiration Overview

  • Two Types: Aerobic (with O2) and Anaerobic (without O2).
  • Key Stages in Aerobic Respiration:
    1. Glycolysis: Breakdown of glucose to pyruvate (cytoplasm).
    2. Krebs Cycle: Processes acetyl CoA in the mitochondrial matrix.
    3. Electron Transport Chain: Produces ATP via oxidative phosphorylation (inner mitochondrial membrane).

Aerobic Respiration Equation

ext{C}6 ext{H}{12} ext{O}6 + 6 ext{O}2
ightarrow 6 ext{CO}2 + 6 ext{H}2 ext{O} + 36 ext{ ATP}

Anaerobic Respiration Examples

  • Alcohol Fermentation: ext{C}6 ext{H}{12} ext{O}6 ightarrow 2 ext{C}2 ext{H}5 ext{OH} + 2 ext{CO}2 + 2 ext{ATP} (used by yeast).
  • Lactic Acid Fermentation: ext{C}6 ext{H}{12} ext{O}6 ightarrow 2 ext{C}3 ext{H}6 ext{O}3 + 2 ext{ATP} (used in muscle cells under low oxygen).

Efficiency of Respiration

  • Aerobic respiration converts up to 36% of energy content of glucose -> ATP; the remainder lost as heat.
  • Efficiency varies with processes - cellular respiration more efficient than combustion in cars.

Summary

  • Photosynthesis: Traps solar energy to produce glucose.
  • Cellular Respiration: Releases stored energy in glucose to produce ATP.
  • Energy Flow: Photosynthesis stores energy as glucose; respiration converts it to usable ATP.

Importance of ATP in Cellular Metabolism

  • Central to making energy available for cellular activities such as transport, synthesis, and muscle contraction.