Photosynthesis and ATP Overview

Photosynthesis

• Photosynthesis is the process where plants, algae, and some bacteria convert light energy into chemical energy, storing it in glucose.
• It occurs in chloroplasts, specifically the thylakoid membranes and stroma.
• Chlorophyll absorbs sunlight, a crucial pigment in this process.
• Photosynthesis has two main stages:
  • Light-Dependent Reactions:
    • Takes place in the thylakoid membrane.
    • Inputs: Light, water (H₂O), ADP, NADP⁺.
    • Outputs: Oxygen (O₂), ATP, NADPH.
  • Calvin Cycle (Light-Independent Reactions):
    • Occurs in the stroma.
    • Inputs: Carbon dioxide (CO₂), ATP, NADPH.
    • Outputs: Glucose (C₆H₁₂O₆), ADP, NADP⁺.

ATP (Adenosine Triphosphate)

• ATP is the primary energy currency of cells.
• Structurally, it consists of adenine, ribose sugar, and three phosphate groups.
• ATP releases energy when a phosphate group is removed (ATP → ADP + Pᵢ).
• This released energy powers cellular functions like muscle contraction, active transport, and chemical reactions.

Reactants and Products of Photosynthesis

• Reactants: Carbon dioxide (CO₂), water (H₂O), light energy.
• Products: Glucose (C₆H₁₂O₆), oxygen (O₂).

Cellular Respiration

• Cellular respiration is the process where cells convert glucose into usable energy (ATP).
• It has three key stages:
  • Glycolysis:
    • Takes place in the cytoplasm.
    • Inputs: Glucose.
    • Outputs: 2 Pyruvate, 2 ATP, 2 NADH.
  • Krebs Cycle (Citric Acid Cycle):
    • Occurs in the mitochondrial matrix.
    • Inputs: Pyruvate (converted to Acetyl-CoA).
    • Outputs: CO₂, NADH, FADH₂, 2 ATP.
  • Electron Transport Chain (ETC):
    • Happens in the inner mitochondrial membrane.
    • Inputs: NADH, FADH₂, O₂.
    • Outputs: Water, ~32-34 ATP.

Reactants and Products of Cellular Respiration

• Reactants: Glucose (C₆H₁₂O₆), oxygen (O₂).
• Products: Carbon dioxide (CO₂), water (H₂O), ATP.

Key Comparisons: Photosynthesis and Cellular Respiration

Study Tips

• Memorize the equations for both photosynthesis and cellular respiration.
• Understand ATP's role and how it's used in cells.
• Relate reactants and products between photosynthesis and cellular respiration.
• Review the organelles—chloroplasts for photosynthesis and mitochondria for cellular respiration.
• Use diagrams to visualize processes like the Calvin cycle and ETC.