AP Biology Unit 3: Cellular Energetics Lecture Notes

Introduction

• AP Biology Unit 3 covers cellular energetics, focusing on cellular respiration and photosynthesis.
• The goal is to understand these topics thoroughly for exams including the AP Bio test.

Overview of Topics

1. Enzymes
2. Cellular Energy and ATP
3. Photosynthesis
   • Light reactions
   • Calvin cycle
4. Cellular Respiration
   • Glycolysis
   • Link reaction
   • Krebs cycle
   • Electron transport chain

Enzymes (Topics 3.1 to 3.3)

Key Properties of Enzymes

• Composition: Mostly proteins, some RNAs.
• Function: Catalyze reactions by lowering activation energy, increasing reaction rates.
• Specificity: Active site complements substrate's shape and charge.
• Structure: Secondary, tertiary, and quaternary structures involving hydrogen and ionic bonds.

Enzyme Activity Factors

• pH: Each enzyme has an optimum pH; deviations can cause denaturation.
• Temperature: Activity increases with temperature to a point; excessive heat causes denaturation.
• Substrate Concentration: Reaction rate increases with more substrate until saturation is reached.
• Inhibition:
  • Competitive: Inhibitor competes for active site.
  • Non-competitive: Inhibitor binds elsewhere, altering active site.

Cellular Energy (Topic 3.4)

Metabolic Pathways

• Definition: Linked enzymatic reactions in a cell.
• Examples: Glycolysis, Krebs cycle, Calvin cycle.

Autotrophs vs. Heterotrophs

• Autotrophs: Produce own food (photosynthesis/chemosynthesis).
• Heterotrophs: Consume organic matter for energy.

Types of Reactions

• Exergonic Reactions: Release energy and increase entropy.
• Endergonic Reactions: Require energy input and decrease entropy.

ATP

• Structure: Ribose, adenine, and three phosphate groups.
• Function: Powers cellular work, storing and releasing energy by forming/breaking phosphate bonds.
• Energy Coupling: Exergonic reactions drive endergonic processes.

Photosynthesis

Big Picture

• Process: Converts light energy to chemical energy, producing glucose and oxygen.
• Equation: 6CO2 + 6H2O + light → C6H12O6 + 6O2
• Endergonic: Increases organization, reduces entropy.

Evolution and Impact

• Origin: ~3.5 billion years ago.
• Consequences: Oxygenated atmosphere, aerobic metabolism, ozone layer formation.

Phases

Light Reactions

• Convert light energy to ATP and NADPH in thylakoid membranes.
• Key Components: Photosystems, electron transport chains, ATP synthase.
• Z Scheme: Describes energy changes during electron transport.

Calvin Cycle

• Uses ATP/NADPH to convert CO2 into carbohydrates.
• Phases:
  1. Carbon Fixation
  2. Energy Investment & Harvest
  3. Regeneration of RuBP

Cellular Respiration

Big Picture

• Equation: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP
• Exergonic: Energy release and organization decrease.

Phases

Glycolysis

• Location: Cytoplasm
• Process: Glucose breakdown into pyruvate.
• Yield: Net 2 ATP, 2 NADH.

Link Reaction

• Converts pyruvate to Acetyl CoA, releasing CO2 and generating NADH.

Krebs Cycle

• Location: Mitochondrial matrix
• Output: 3 NADH, 1 FADH2, 1 ATP per Acetyl CoA.

Electron Transport Chain

• Location: Mitochondrial inner membrane
• Process: Uses NADH/FADH2 to create proton gradient and synthesize ATP.

Anaerobic Respiration & Fermentation

• Types: Alcohol fermentation, lactic acid fermentation.
• Result: Regenerates NAD+ allowing glycolysis to continue under low oxygen conditions.

Conclusion

• Engage with online resources like Learn-Biology.com for practice and mastery of AP Biology concepts.
• The preferred learning strategy involves interaction, feedback, and thorough review to excel in the AP Bio exam.