AP Biology - Unit 3: Cellular Energetics

Enzyme Function

• Enzymes: Protein catalysts that speed up reactions without being consumed.
• Structure of Proteins:
  • Primary Structure: Sequence of amino acids.
  • Secondary Structure: Folding of polypeptide backbone (alpha helices, beta sheets).
  • Tertiary Structure: 3D folding due to side chain interactions.
  • Quaternary Structure: Overall protein shape from multiple polypeptides.
• Denaturation: Loss of protein shape due to pH, temperature, and salt concentration changes.
• Chaperonins: Assist in protein folding.
• Active Site: Region where substrate binds on enzyme.
• Induced-fit Model: Enzyme changes shape to better fit the substrate.
• Cofactors & Coenzymes: Assist enzyme function (minerals and vitamins).
• Enzyme Inhibition:
  • Competitive: Non-reactant blocks substrate from active site.
  • Noncompetitive: Molecule binds elsewhere, changing shape and function.
  • Feedback Inhibition: End product inhibits enzyme activity early in the pathway.

Environmental Impacts on Enzyme Function

• Factors Affecting Active Sites:
  • Temperature, pH, enzyme/substrate concentration.
• Regulatory Molecules:
  • Allosteric Regulation: Can inhibit or stimulate enzymes.
  • Cooperativity: Substrate binding increases activity at other sites.
• ATP & ADP: ATP inhibits, ADP activates enzymes.

Cellular Energy

• ATP: Primary energy molecule.
• Organisms:
  • Heterotrophs: Obtain energy externally.
  • Autotrophs: Produce energy from solar energy.
• Photosynthesis:
  • Convert light energy to chemical energy (glucose).
  • Chlorophyll: Key pigment in absorbing light.
  • Reactions:
    • Light-dependent: Use light energy.
    • Light-independent (Calvin Cycle): Do not require light, use CO2.
• Cellular Respiration: Glucose breakdown to release energy.
  • Opposite of photosynthesis.

Photosynthesis Details

• Structures:
  • Mesophyll: Leaf tissue with chloroplasts.
  • Thylakoids: Membranes where light reactions occur.
  • Stomata: CO2 enters, O2 exits.
• Processes:
  • Calvin Cycle: Uses ATP and NADPH for glucose production.
  • Electron Transport Chain: Creates H+ gradient.
  • ATP Synthase: Produces ATP from ADP and P.

Cellular Respiration

• Glycolysis: Breaks glucose into pyruvate, produces ATP and NADH.
• Pyruvate Oxidation: Converts pyruvate to Acetyl CoA.
• Citric Acid Cycle: Completes glucose breakdown, produces CO2, NADH, FADH2.
• Oxidative Phosphorylation: Uses electron transport chain for ATP production.
• Comparison to Photosynthesis: Reverse processes, photosynthesis stores energy, respiration releases it.

Sources

• Khan Academy: www.khanacademy.org