8+Cellular+Respiration+Lecture

Cellular Respiration Overview

• Definition: Cellular respiration is the process by which cells convert sugar and oxygen into energy (ATP), carbon dioxide, and water. It is a crucial metabolic pathway necessary for all forms of life.

Learning Objectives

• Understand energy and redox reactions.

• Compare reactants, products, and energy yield of the three stages of cellular respiration:

  • Glycolysis

  • Pyruvate Processing

  • Citric Acid Cycle

  • Electron Transport Chain

• Analyze relationship between electron transport chain and oxidative phosphorylation.

• Importance of oxygen in cellular respiration.

• Structure of mitochondria and its functional significance.

• Differentiate between cellular respiration and fermentation regarding inputs, outputs, and ATP production.

The Big Picture

• Role of Energy: All life requires energy, which is obtained through cellular respiration.

• Photosynthesis and Cellular Respiration:

  • Plants convert sunlight energy into chemical energy (sugars) through photosynthesis.

  • Both plants and animals utilize cellular respiration to convert sugars into ATP.

• Respiration Equation:

  • Formula: 6CO2 + 6H2O + energy ↔ C6H12O6 + 6O2 (indicating the conversion of glucose and oxygen to carbon dioxide and water while producing energy).

Energy in Chemical Reactions

• Kinetic Energy: Energy of motion, e.g., thermal energy from moving molecules (heat).

• Potential Energy: Stored energy in chemical bonds or concentration gradients.

• Energy Transformations: Energy is transformed from one type to another during biochemical processes.

Thermodynamics and Chemical Reactions

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

• Exothermic Reactions: Release energy; products have less potential energy than reactants.

• Endothermic Reactions: Absorb energy; products have higher potential energy than reactants.

Cellular Respiration and Metabolism

• Catabolic Pathways: Break down molecules to release energy (exothermic), primarily for ATP production.

• Anabolic Pathways: Use ATP to synthesize larger molecules from smaller components (endothermic).

Energy and Enzymes

• Enzymatic Functions: Enzymes direct metabolic reactions, facilitating cells' acquisition and use of energy.

• Metabolic Pathways: Series of enzyme-catalyzed reactions breaking down or building up biomolecules.

Overview of Cellular Respiration

• Definition: Process of harvesting chemical energy from organic molecules resulting in the generation of ATP.

• Aerobic Process: Requires oxygen for effective energy yield.

• Gas Exchange: Cells intake oxygen (O2) and release carbon dioxide (CO2) as waste.

Cellular Respiration Components

1. Glycolysis:

   • Occurs in cytoplasm.

   • Converts glucose to two pyruvate molecules, yielding 2 ATP and 2 NADH.

2. Pyruvate Processing:

   • Pyruvate is oxidized to form Acetyl CoA, producing CO2 and NADH.

3. Citric Acid Cycle:

   • Acetyl CoA is oxidized to CO2, resulting in NADH, FADH2, and ATP from substrate-level phosphorylation.

4. Electron Transport Chain and Oxidative Phosphorylation:

   • Electrons from NADH and FADH2 are transferred through the chain to form a proton gradient that drives ATP synthesis.

ATP: Energy Currency of Cells

• ATP Structure and Function: Essential for driving cellular processes; energy is released when phosphate bonds are broken during hydrolysis.

Electron Carriers and Redox Reactions

• Role of Electron Carriers: NAD+ and FAD accept electrons during glycolysis and the citric acid cycle, becoming NADH and FADH2.

• Redox Reactions: Involve electron transfers; oxidation (loss of electrons) and reduction (gain of electrons) occur together.

Regulation of Glycolysis and Pyruvate Processing

• Feedback Inhibition: High ATP levels inhibit glycolysis and pyruvate processing pathways to prevent excess energy production.

Citric Acid Cycle Process

• Acetyl CoA contributes to CO2 production, energy carrier accumulation (NADH, FADH2), and ATP synthesis.

Summary of Energy Production

• Complete glucose oxidation yields CO2, ATP, NADH, and FADH2. Total yield is approximately 29 ATP per glucose molecule.

Fermentation as an Alternative Pathway

• Definition: Anaerobic process when oxygen is absent; regenerates NAD+ for glycolysis.

• Types of Fermentation:

  • Lactic Acid Fermentation: Occurs in muscle cells, producing lactate and reopening NAD+.

  • Alcohol Fermentation: Involves yeast and generates ethanol and CO2.

• Efficiency: Fermentation is less efficient than cellular respiration, generating only 2 ATP per glucose compared to respiration's 29 ATP.