AP Biology Unit 3: Cellular Energetics

Overview

• Focus on key topics: Enzymes, Cellular Energy, ATP, Photosynthesis, and Cellular Respiration.
• Lecture by Glenn Wokenfeld (Mr. W), retired AP Biology teacher.
• Resources: Learn-Biology.com, BioMania app, downloadable checklist.

Enzymes (Topics 3.1 to 3.3)

Key Properties

• Enzymes are mainly proteins; some RNAs act as enzymes.
• Catalyze reactions by lowering activation energy.
• Specific to substrates due to active site shape/charge.
• Function optimally within narrow environmental conditions (pH, temperature, ion concentration).

Environmental Impact on Enzyme Activity

• pH: Enzymes have an optimal pH range; deviation leads to denaturation.
• Temperature: Activity increases with temperature up to a point; high temperatures denature enzymes.

Denaturation

• Reversible: Function restored upon returning to optimal conditions.
• Irreversible: Permanent loss of function (cooking egg analogy).

Substrate Concentration

• Low concentration results in low reaction rate; increases with concentration up to saturation point.

Inhibition

• Competitive: Inhibitor competes for active site.
• Non-Competitive: Inhibitor binds to allosteric site, altering active site.

Cellular Energy (Topic 3.4)

Metabolic Pathways

• Series of enzyme-catalyzed reactions (e.g., Glycolysis, Kreb Cycle, Calvin Cycle).
• Pathways can be linear or cyclical.

Organisms

• Autotrophs: Produce own food; include photoautotrophs (plants, cyanobacteria) and chemoautotrophs.
• Heterotrophs: Rely on organic compounds from other organisms.

Reactions

• Exergonic: Release energy (e.g., cellular respiration).
• Endergonic: Require energy (e.g., photosynthesis).

ATP Structure & Function

• Composed of ribose, adenine, and 3 phosphate groups.
• Stores/releases energy through adding/removing phosphate groups.

Energy Coupling

• Links exergonic and endergonic reactions (e.g., ATP synthesis).

Photosynthesis

Overview

• Converts light energy to chemical energy.
• Formula: 6 CO2 + 6 H2O + light → C6H12O6 + 6 O2.
• Endergonic reaction: increases organization.

Evolution & Impact

• Evolved ~3.5 billion years ago.
• Created an oxygen-rich atmosphere, enabling aerobic metabolism and life on land.

Phases

• Light Reactions: Convert light energy to ATP and NADPH; occur in thylakoids.
• Calvin Cycle: Uses ATP and NADPH to synthesize carbohydrates from CO2.

Chlorophyll

• Absorbs light (blue & red wavelengths); reflects green.
• Associated with chloroplasts' thylakoid membranes.

Light Reactions

• Convert light to chemical energy (ATP & NADPH).
• Involve electron transport chain, producing ATP through chemiosmosis.
• Water splitting produces oxygen as a byproduct.

Calvin Cycle

• Carbon Fixation: CO2 combines with RuBP.
• Energy Investment/Harvest: Produces G3P (sugar precursor).
• Regeneration: Reform RuBP from G3P.

Cellular Respiration

Overview

• Chemical equation: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP.
• Occurs in mitochondria; exergonic reaction releasing energy.

Phases

• Glycolysis: Glucose → pyruvate; occurs in cytoplasm.
• Link Reaction: Pyruvate → Acetyl CoA in mitochondria.
• Kreb Cycle: Generates electron carriers (NADH, FADH2) and ATP.
• Electron Transport Chain: Produces most ATP; oxygen as final electron acceptor.

Anaerobic Respiration & Fermentation

• Anaerobic: Occurs without oxygen; includes glycolysis and fermentation.
• Fermentation: Regenerates NAD+; alcohol and lactic acid fermentation types.

Comparisons

• Aerobic vs Anaerobic: Aerobic requires oxygen, produces more energy.
• Fermentation Types: Alcohol (yeast, CO2 release) vs Lactic Acid (muscle tissue).

Study Tips

• Utilize resources like Learn-Biology for comprehensive study tools and interactive learning.
• Engage with music and songs related to cellular energetics for better retention.

Note: These notes aim to provide a summary and study guide for AP Bio Unit 3, focusing on cellular energetics, key reactions, and processes involved in cellular respiration and photosynthesis.