Cellular Respiration

Cellular Respiration Overview

  • Lecture focus on cellular respiration and its connection to photosynthesis, key power cycles of life.

  • Goals include:

    • Studying energy in cells

    • Comparing methods for obtaining carbon and energy

    • Distinguishing energy transport methods in cells

    • Defining cellular respiration steps

    • Applying knowledge to scientific research.

Energy and Carbon Sources

  • All organisms require two essential sources:

    • Energy Source

      • Light (absorption: phototrophs)

      • Chemical Compounds (consumption: chemotrophs)

    • Carbon Source

      • Carbon Dioxide (CO2): autotrophs

      • Organic Compounds (consumed food): heterotrophs

  • Organism Types:

    1. Photoautotrophs: Light + CO2

    2. Chemoautotrophs: Chemical + CO2

    3. Photoheterotrophs: Light + Organic Compounds

    4. Chemoheterotrophs: Chemical + Organic Compounds

  • Humans are Chemoheterotrophs (energy and carbon from food).

Interaction of Organisms

  • Photoautotrophs undergo photosynthesis (producing oxygen, organic molecules).

  • Chemoheterotrophs consume oxygen and organic molecules, making ATP and releasing CO2.

  • Metabolic cycles of photosynthesis and respiration are interconnected.

Cell Respiration Basics

  • Definition: Catabolic pathway (breaking down molecules, releasing energy).

  • **Types of Respiration:

    1. Aerobic:** Requires oxygen

    2. Anaerobic:** Does not require oxygen.

  • Common misconception: "Cell respiration" often refers to aerobic respiration.

Aerobic Respiration Chemical Reaction

  • Inputs: Glucose (C6H12O6) + Oxygen

  • Outputs: Carbon Dioxide (CO2) + Water (H2O) + ATP

  • Memorization not necessary for numbers, but need to know inputs/outputs and their significance.

Who Undergoes Cellular Respiration?

  • All eukaryotic cells undergo cellular respiration (including fungi, plants, animals).

  • Important true/false to note: Not exclusive to animal or plant cells.

Energy Transfer in Cellular Respiration

  • Stored energy is transferred by moving energized electrons.

  • Electrons can move between shells (energy states) with energy absorption and release.

  • Analogy: Excited electrons gaining energy to move higher (akin to going out for various activities).

Redox Reactions

  • Electrons moving between atoms leads to oxidation (losing electrons) and reduction (gaining electrons).

  • Gaining electrons makes a molecule more negative (reduced) while losing electrons makes it more positive (oxidized).

Electron Carriers in Cellular Respiration

  • NADH and FADH2 are key electron carriers.

  • NADH: High energy state; generated and used in various pathways.

  • FADH2: Another high-energy electron carrier, noted in Krebs cycle.

ATP Production in Cellular Respiration

  • Two main methods of ATP production:

    1. Substrate-level phosphorylation: Adding a phosphate group to ADP via enzymes.

    2. Oxidative phosphorylation: Involves H+ concentration gradient (chemiosmosis).

Steps of Cellular Respiration

  1. Glycolysis:

    • Location: Cytosol (cytoplasm)

    • Breakdown of glucose into 2 pyruvates (3-carbon molecules).

    • Inputs: 1 glucose

    • Outputs: 2 pyruvate, NADH, ATP (net gain).

    • Note: Does not require oxygen.

  2. Pyruvate Decarboxylation:

    • Moves pyruvate to mitochondria, converting to Acetyl CoA.

    • Byproduct: Carbon dioxide (CO2).

    • Inputs: 2 pyruvates

    • Outputs: 2 Acetyl CoA, NADH, CO2.

  3. Krebs Cycle (Citric Acid Cycle):

    • Location: Mitochondrial matrix

    • Input: 2 Acetyl CoA (2 carbons each)

    • Outputs: NADH, FADH2, ATP, CO2, hydrogen ions.

  4. Electron Transport Chain:

    • Location: Inner mitochondrial membrane (cristae).

    • Utilizes NADH and FADH2 for electron transport, driving H+ pumping, creating a gradient.

    • Need for oxygen is critical here, as it combines with electrons and H+ to form water (H2O).

    • Outputs: Significant ATP yield and H2O.

Importance of Mitochondria

  • Evolved from endosymbiotic bacteria, allowing aerobic respiration, which produces more ATP (36 vs. 2 ATP from glycolysis alone).

Anaerobic Respiration and Fermentation

  • Occurs when oxygen is limited, primarily utilizes glycolysis.

  • Lactic Acid Fermentation: Occurs in muscle cells, produces lactic acid.

  • Alcohol Fermentation: Conducted by yeast, creating ethanol and CO2 from pyruvate.

Historical Context

  • Glycolysis is an ancient metabolic pathway, predating aerobic processes when oxygen was scarce.

Diet and Cellular Respiration

  • Other macromolecules (proteins, fats) can be broken down for energy; not just glucose.

Regulation of Cellular Respiration

  • Feedback mechanisms regulate rates based on energy needs (ATP or ADP/AMP concentrations).

Summary of Power Cycles

  • Emphasize understanding the synergistic relationship between photosynthesis and cellular respiration, fueling life processes.

VO2 Max Paper Overview

  • Increasing oxygen uptake is necessary for improved exercise capacity and avoiding anaerobic fermentation.

  • Consistent exercise can increase VO2 max by 1 liter/minute.

  • Factors influencing VO2 max include body size and health status.

  • Importance of experimental controls in exercise research and implications for athletic training.

Conclusion

  • Review cellular respiration pathways and acknowledge the intricacies of energy production in biology.

  • Encourage questions and discussions in subsequent classes for deeper understanding.