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Cellular Respiration Study Notes

Introduction to Cellular Respiration

  • Presenter: Mr. Andersen
  • Main Focus: Distinguishing between respiration (breathing) and cellular respiration.
    • Respiration: Just breathing in oxygen.
    • Cellular Respiration: Process that occurs at the cellular level, specifically in the mitochondria, using oxygen to break down food to produce ATP.

Cellular Respiration in Different Organisms

  • Bacteria and Respiration:
    • Bacteria do not need mitochondria to perform respiration.
    • They can utilize their outer membranes for aerobic respiration.

Human Example of Cellular Respiration

  • Track Athlete Example:
    • Referencing Usain Bolt to illustrate the necessity of ATP for muscle movement during running events.

Study on World Records and Running Pace

  • Conducted analysis of world records from 100m to 10,000m races.
    • Findings:
    • Pace (meters per second) drops off quickly during sprints but stabilizes over longer distances (marathon).
    • Sprinting leads to rapid fatigue due to intense energy demands.

Types of Respiration

  • Aerobic Respiration:
    • Respiration that occurs in the presence of oxygen.
  • Anaerobic Respiration:
    • Functions as a 'turbo button' for temporary energy bursts, valid during high-intensity efforts.
    • Excessive anaerobic activity results in lactic acid buildup, causing muscle fatigue and pain (e.g., encountered during 400m sprints).

Muscle Fatigue Lab Example

  • Class experiment where students squeezed a tennis ball:
    • Outcome: Average of 25 squeezes in ten seconds, demonstrating rapid fatigue.
    • As anaerobic respiration starts, lactic acid build-up became noticeable.

Purpose of Cellular Respiration

  • Heterotrophs:
    • Organisms (like animals, fungi, and bacteria) that rely on organic compounds to produce ATP through respiration.
    • Process: Organic compounds combined with oxygen yield carbon dioxide, water, and ATP.
  • Autotrophs:
    • Organisms (like plants and algae) convert carbon dioxide and water into organic materials through photosynthesis.
    • Important Note: Autotrophs also perform cellular respiration to extract energy from their organic compounds.

Cellular Respiration Equation

  • Basic Equation:
    • ext{C}6 ext{H}{12} ext{O}6 + 6 ext{O}2
      ightarrow 6 ext{CO}2 + 6 ext{H}2 ext{O} + ext{ATP}
    • Energy Source: Hydrogens in glucose provide energy by attaching to oxygen to form water.
    • ATP serves as the primary energy currency in cells.

Energy Generation and Oxygen's Role

  • Role of Oxygen:
    • Functions as a powerful electron acceptor, enabling the release of significant energy when interacting with electrons.
    • Controlled Process: Cellular respiration's controlled environment prevents uncontrolled energy release (e.g., fire from direct combustion).

Mitochondrial Structure

  • Critical components of mitochondria include:
    • Cristae: Inner folds that increase surface area for energy production.
    • Membranes:
    • Inner Membrane: Site for electron transport and ATP synthesis.
    • Outer Membrane: Encases the mitochondria.
    • Intermembrane Space: The space between the inner and outer membranes.
    • Mitochondria replicate via binary fission and contain their own DNA and ribosomes.

Steps of Cellular Respiration

  1. Glycolysis:
    • Occurs in the cytoplasm; breaks down glucose (6-carbon) into two pyruvate molecules (3-carbon).
    • Produces a net gain of 2 ATP and reduces NAD+ to NADH (high-energy electron carrier).
  2. Conversion to Acetyl CoA:
    • Pyruvate enters mitochondria to get converted into Acetyl CoA, releasing CO2 as a by-product.
  3. Krebs Cycle (Citric Acid Cycle):
    • Occurs in the mitochondrial matrix; Acetyl CoA is further broken down, yielding:
      • Carbon dioxide (released),
      • 2 ATP,
      • Additionally generates high-energy carriers NADH and FADH2 for the next stage.
  4. Electron Transport Chain:
    • NADH and FADH2 donate their electrons to a series of proteins creating a proton gradient across the inner membrane.
    • Protons are pumped into the intermembrane space, creating a positive charge.
    • Electrons eventually combine with oxygen to form water, and the energy released is used to convert ADP to ATP through ATP synthase.
    • Energy output from this process is significant, producing approximately 32-34 ATP.

ATP Synthase Mechanism

  • ATP synthase acts as a protein channel through which protons flow back into the mitochondria, generating ATP through rotary motion of the enzyme that attaches phosphates to ADP.

Consequences of Anaerobic Respiration

  • If oxygen is absent:
    • Glycolysis can occur producing 2 ATP, but cannot continue due to lack of NAD+.
  • Lactic Acid Fermentation in Muscles:
    • When exertion levels are high and oxygen is limited, pyruvate converts to lactate, enabling recycling of NAD+ and continued ATP production.
    • Lactic acid buildup leads to fatigue.
  • Alcoholic Fermentation in Yeast:
    • Similar process occurs, resulting in the production of ethanol and carbon dioxide while recycling NAD+.
    • Used in the production of alcoholic beverages; ethanol is the by-product of fermentation.

Summary of Cellular Respiration

  • Production of Energy: Cellular respiration serves as a mechanism for converting various types of food into energy, utilized by a broad range of organisms from bacteria to plants.
  • It is a fundamental biological process integral to life, enabling energy acquisition through organic compound breakdown.