Photosynthesis and Cellular Respiration

Key Comparison:

• These processes are essentially reverse reactions of each other

• What's produced in one process becomes input for the other

II. Photosynthesis

A. Basic Information

• Location: Chloroplast

• Organisms: Autotrophs only

• Input: Water, carbon dioxide, light energy

• Output: Oxygen, glucose

B. Chloroplast Structure & Processes

1. Thylakoid Reactions (Light-Dependent)

   • Location: Thylakoid membrane

   • Grana = stacks of thylakoids

   • Process:

     • Chlorophyll absorbs light

     • Electrons become excited

     • Electrons flow through ETC

     • Water splits → oxygen released

     • NADP+ accepts electrons → NADPH formed

     • ATP synthase creates ATP as protons diffuse to stroma

2. Stroma Reactions (Light-Independent)

   • Location: Stroma fluid

   • Inputs: Carbon dioxide

   • Outputs: Glucose

   • Uses ATP and NADPH from light-dependent reactions

III. Cellular Respiration

A. Basic Information

• Location: Primarily in mitochondria

• Organisms: Both autotrophs and heterotrophs

• Input: Oxygen, glucose

• Output: Water, carbon dioxide, ATP

B. Stages and Locations

1. Glycolysis

   • Location: Cytoplasm

   • Inputs:
     

     • Glucose

     • 2 ATP

   • Outputs:
     

     • Net 2 ATP

     • Pyruvate

     • NADH

2. Linking Step

   • Location: Mitochondrial matrix

   • Input: Pyruvate

   • Output: Acetyl CoA

3. Krebs Cycle

   • Location: Mitochondrial matrix

   • Input: Acetyl CoA

   • Outputs:
     

     • CO2

     • 2 ATP

     • NADH

     • FADH2

4. Electron Transport Chain (ETC)

   • Location: Inner mitochondrial membrane

   • Inputs:
     

     • NADH

     • FADH2

     • O2

   • Outputs:
     

     • ~30-32 ATP

     • Water

   • Process:
     

     • Electrons flow through chain

     • Final electron acceptor is oxygen

     • ATP synthase creates ATP

IV. Key Relationships

A. Energy Flow

• Photosynthesis: Light energy → Chemical energy (glucose)

• Cellular respiration: Chemical energy (glucose) → ATP

B. Product-Reactant Relationship

• Photosynthesis products (glucose, O2) become cellular respiration reactants

• Cellular respiration products (CO2, H2O) become photosynthesis reactants

C. Location Differences

• Photosynthesis: Chloroplasts

• Cellular respiration: Primarily mitochondria

D. Organism Distribution

• Photosynthesis: Autotrophs only

• Cellular respiration: All living organisms

V. Important Notes

1. Both processes involve electron transport chains

2. Both use ATP synthase for ATP production

3. Both involve multiple stages in different cellular locations

4. Together they form a crucial cycle in nature

5. Understanding both processes is key to understanding energy flow in ecosystems