Aerobic Cellular Respiration and Fermentation

Mitochondria and Cellular Respiration Overview

General Information

  • Cellular Respiration: The biochemical process by which organisms convert food to adenosine triphosphate (ATP), an essential energy molecule.

  • Breathing: The physical act of gas exchange. Unlike breathing, cellular respiration is a chemical process generating energy.

Aerobic Cellular Respiration

Key Differences Between Processes

  • Aerobic Cellular Respiration: Requires oxygen.

  • Anaerobic Respiration: Occurs without oxygen.

  • Purpose: To produce ATP, carbon dioxide, and water as byproducts.

Chemical Reactions and Pathways

  1. Overall Reaction:

    • The formula for aerobic cellular respiration:
      C(6)H(12)O6 + 6 O(2) — > 6CO(2)+ 6 H(2)O + energy

  2. Pathways Involved:

    • Glycolysis: Occurs in the cytosol and does not require oxygen.

    • Pyruvate Oxidation (Transition Reaction): Takes place in the mitochondrion matrix.

    • Krebs Cycle (Citric Acid Cycle): Also located in the mitochondrial matrix.

    • Electron Transport Chain (Oxidative Phosphorylation): Located on the cristae of the mitochondrion.

Pathways of Energy Production

  • Glycolysis:

    • Input: Glucose, 2 ADP, 2 Pi

    • Output: 2 Pyruvate, 2 ATP, 2 NADH

  • Pyruvate Oxidation:

    • Input: 2 Pyruvate

    • Output: 2 Acetyl CoA, 2 CO₂, 2 NADH

  • Krebs Cycle:

    • Input: 2 Acetyl CoA

    • Outputs: 6 NADH, 2 FADH₂, 2 ATP, 4 CO₂

  • Electron Transport Chain:

    • Input: 10 NADH, 2 FADH₂, O₂

    • Output: 32 ATP, 6 H₂O

Storage and Utilization of Energy

  • Plants: Store glucose as starch, which can be converted back to glucose when energy is needed.

  • Animals: Store glucose as glycogen in liver and muscle cells. Glycogen can also be converted to glucose in energy-demanding situations.

Physiological Context of Cellular Respiration

  • Mitochondrion Structure:

    • Outer Membrane: Encloses the mitochondrion.

    • Inner Membrane (Cristae): Location of the electron transport chain.

    • Matrix: Site for the Krebs cycle and pyruvate oxidation.

Effects of Exercise on Cell Respiration

Experimental Context

  • Measurements: Heart rate (beats/minute), breathing rate (breaths/minute), and carbon dioxide output post-exercise.

  • BTB Indicator: Changes color based on pH, indicating CO₂ levels.

    • BTB is blue (basic), green (neutral), yellow (acidic).

    • CO₂ is added to water {H(2)O} producing a weak acid - carbonic acid: H(2)CO(3)
      ightleftharpoons H2CO3
      ightleftharpoons H^+ + HCO_3^-

Results Analysis

  1. Effect of Exercise on Color Change:

    • Longer time for color change post-exercise indicates reduced CO₂ production.

  2. Carbon Dioxide in Exhaled Breath:

    • Increased levels of CO₂ post-exercise due to muscle activity.

  3. Breathing Rate:

    • Increases during exercise to supply more oxygen and remove CO₂.

  4. Heart Rate:

    • Increases to deliver oxygen to muscles and remove metabolic wastes like CO₂.

Fermentation

Process Overview

  • Fermentation: An anaerobic metabolic process allowing glycolysis to produce ATP without oxygen.

Key Definitions

  1. Anaerobic: Refers to processes that occur without oxygen.

  2. Types of Fermentation:

    • Lactic Acid Fermentation: Produces lactic acid (in animals).

    • Alcohol Fermentation: Produces ethanol and CO₂ (in yeast).

Pathways in Fermentation

  • Glycolysis: Initial step producing pyruvate, which is then converted during fermentation.

  • Lactic Acid Pathway: Pyruvate is reduced to lactic acid:

    • C6H{12}O6 + 2 ADP + 2 Pi
      ightarrow 2 ext{Lactic Acid} + 2 ATP

  • Ethanol Pathway: Pyruvate is converted to acetaldehyde and then to ethanol:

    • C6H{12}O6 + 2 ADP + 2 Pi
      ightarrow 2 ext{Ethanol} + 2 CO_2 + 2 ATP$$

Experimental Investigations in Fermentation

Rate of Fermentation with Different Sugars

  • Objective: To measure CO₂ production by yeast during fermentation using various sugars: glucose, maltose, sucrose, and lactose.

Observations

  1. Fastest Fermentation: Maltose produced the largest bubble size, indicating the highest fermentation rate.

  2. No Fermentation: Lactose demonstrated no bubbles, indicating no fermentation took place.

Post-Lab Conclusions

  1. Role of Cellular Respiration: Converts food into usable energy (ATP).

  2. Gas Exchange: CO₂ from respiration is exhaled as a waste product.

  3. Hypotheses:

    • Cellular Respiration: Oxygen is consumed and CO₂ is produced.

    • Fermentation: Maltose ferments fastest; lactose does not ferment.

  4. Yeast Application: Yeast is used to create alcoholic beverages by fermenting sugars, producing CO₂ that carbonates the beverage, while the resulting ethanol gives the drink its alcoholic content.