AP Biology Unit 3: Cellular Energetics Lecture Notes

Introduction

• Focus on Unit 3: Cellular Energetics in AP Biology
• Topics covered: Enzymes, Cellular Energy, Photosynthesis, and Cellular Respiration.
• Presenter: Glenn Wokenfeld (Mr. W), retired AP Biology teacher.
• Resources: Checklist available at APbios.c/checklist, Learn-Biology.com, and BioMania AP Bio app.

Enzymes (Topics 3.1 to 3.3)

Key Properties of Enzymes

• Enzymes are usually proteins but some RNAs act as enzymes.
• Function by lowering activation energy, increasing reaction rates.
• Highly specific active sites complement substrate's shape and charge.
• Function within narrow environmental conditions (temperature, pH, ion concentration).

Environmental Effects on Enzymes

• pH: Enzymes have an optimal pH range; deviations can lead to denaturation.
• Temperature: Increased temperature raises enzyme activity until denaturation occurs.
• Reversible/Irreversible Denaturation: Reversible denaturation allows restoration of function; irreversible does not.

Enzyme Inhibition

• Competitive Inhibition: Inhibitor competes with substrate for the active site.
• Non-Competitive Inhibition: Inhibitor binds at allosteric site, altering active site shape and function.

Cell Energy (Topic 3.4)

Metabolic Pathways

• Series of enzyme-catalyzed reactions within a cell.
• Can be linear (e.g., Glycolysis) or cyclical (e.g., Krebs Cycle, Calvin Cycle).

Autotrophs vs. Heterotrophs

• Autotrophs: Produce own food (e.g., plants - photosynthesis, certain bacteria - chemosynthesis).
• Heterotrophs: Obtain energy from organic compounds, dependent on other organisms.

Exergonic vs. Endergonic Reactions

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

ATP: Structure and Function

• Composed of ribose, adenine, and three phosphates.
• Stores and releases energy via phosphorylation and hydrolysis.
• Energy Coupling: Exergonic reactions drive endergonic processes.

Photosynthesis

Overview

• Converts carbon dioxide and water into glucose using light energy.
• Chemical Equation: 6 CO2 + 6 H2O + light → C6 H12 O6 + 6 O2.
• Endergonic due to energy conversion and entropy reduction.

Light Reactions

• Occur in the thylakoid membranes, produce ATP and NADPH.
• Convert light energy into chemical energy, release O2 as a byproduct.

Calvin Cycle

• Occurs in the stroma, uses ATP and NADPH to convert CO2 into sugars.
• Involves carbon fixation, energy investment, and regeneration phases.

Chlorophyll and Pigments

• Chlorophyll absorbs light for photosynthesis, reflects green light.
• Absorption Spectrum: Peaks in blue and red light regions.

Cellular Respiration

Overview

• Converts glucose and oxygen into CO2, water, and ATP.
• Chemical Equation: C6 H12 O6 + 6 O2 → 6 CO2 + 6 H2O + ATP.

Glycolysis, Link Reaction, Krebs Cycle

• Glycolysis: Occurs in cytoplasm, anaerobic, yields 2 ATP and 2 NADH.
• Link Reaction: Converts pyruvate to acetyl-CoA, releases CO2.
• Krebs Cycle: Occurs in mitochondrial matrix, produces NADH, FADH2, ATP.

Electron Transport Chain (ETC)

• Located in mitochondrial inner membrane.
• Uses NADH and FADH2 to create a proton gradient, produces ATP through chemiosmosis.
• Oxygen: Final electron acceptor, essential for aerobic respiration.

Anaerobic Respiration and Fermentation

• Anaerobic Respiration: Yields less ATP (2 per glucose) without oxygen.
• Fermentation: Regenerates NAD+ for glycolysis under anaerobic conditions.
• Types include alcohol fermentation (yeast) and lactic acid fermentation (muscles).

Summary

• Unit 3 encompasses vital processes for cell energy management including enzymatic reactions, photosynthesis, and cellular respiration.
• Understanding these processes is crucial for success in AP Biology and related exams.