Respiration

Respiration Study Guide

Course Information

  • Course: Biol 1106

  • Semester: Fall 2024

Learning Objectives

  • Differentiate between aerobic and anaerobic respiration, along with their processes.

  • Measure carbon dioxide production during anaerobic respiration.

  • Understand the effects of inhibitors, intermediate compounds, and cofactors in anaerobic respiration.

Energy Flow in Ecosystems

  • Energy stored in organic molecules, derived from food, ultimately comes from sunlight.

  • Energy flows into an ecosystem as sunlight and exits as heat.

  • In contrast, essential chemical elements for life are recycled.

Respiration

  • All living organisms utilize respiration to release energy from organic molecules and capture it into ATP.

  • Classification of organisms based on oxygen requirement:

    • Aerobes - require oxygen to respire.

    • Anaerobes - do not require oxygen for respiration.

  • The process of respiration has evolved as a mechanism to prevent membrane damage in primordial Earth conditions.

Types of Respiration

  • Aerobic Respiration

    • Defined as the complete breakdown of organic molecules using oxygen.

  • Anaerobic Respiration

    • Defined as the incomplete breakdown of organic molecules without using oxygen.

Glycolysis

  • Glycolysis is the initial step of respiration, occurring irrespective of the presence of O2.

  • It involves the oxidation of glucose to pyruvate, thus harvesting chemical energy.

  • Glycolysis Definition: Means “sugar splitting.”

  • Process Details:

    • Glucose (a 6-carbon sugar) is divided into two pyruvate molecules (3-carbon sugars).

  • Products of Glycolysis:

    • 2 pyruvate molecules

    • 2 water molecules (H₂O)

    • Gross products: 4 ATP; Net products: 2 ATP

    • 2 NADH molecules

Aerobic Respiration Overview

  • Pathway of Aerobic Respiration:

    1. Glycolysis

    2. Pyruvate Oxidation

    3. Citric Acid Cycle

    4. Oxidative Phosphorylation (Electron transport and chemiosmosis)

  • Electrons are carried via NADH and FADH₂ throughout the process.

  • Locations in the Cell:

    • Glycolysis occurs in the cytosol.

    • Pyruvate oxidation and the Krebs cycle occur in the mitochondrion.

Pyruvate Oxidation

  • Under aerobic conditions, pyruvate moves into the mitochondria.

  • Pyruvate is then oxidized to form Acetyl CoA.

  • During this process, a carboxyl group is removed from the pyruvate, which is replaced with coenzyme A.

Citric Acid Cycle (Krebs Cycle)

  • The Acetyl group from Acetyl CoA combines with oxaloacetate to produce citrate.

  • Products Per Turn of the Cycle:

    • 2 CO₂ molecules

    • 3 NADH molecules

    • 1 ATP molecule

    • 1 FADH₂ molecule

Electron Transport Chain

  • The electron transport chain comprises a series of proteins embedded in the inner mitochondrial membrane.

  • It facilitates the transfer of electrons through a series of protein complexes.

Process of Electron Transport Chain

  1. Electron Transport: Electrons are moved along the chain.

  2. Proton Pumping: Protons (H⁺ ions) are pumped across the membrane, creating a gradient.

  3. Chemiosmosis: ATP synthase allows H⁺ ions to flow back, producing ATP through oxidative phosphorylation.

Summary of ATP Production

  • From glycolysis, 2 ATP are generated by substrate-level phosphorylation.

  • From the citric acid cycle, another 2 ATP are produced.

  • Total ATP Yield: Approximately 30 to 32 ATP from one glucose molecule, depending on the shuttle used to transport electrons from NADH in the cytosol.

Fermentation

  • Fermentation enables the production of ATP without the need for oxygen.

  • It presents two main types:

    • Alcohol Fermentation:

    • Pyruvate is converted to ethanol, producing carbon dioxide as a byproduct; this process allows bread to rise.

    • Lactic Acid Fermentation:

    • Pyruvate is converted into lactic acid.

Processes in Fermentation

  1. Alcohol Fermentation:

    • Pyruvate → Ethanol + CO₂

    • General Equation:

      ext{Glucose}
      ightarrow 2 ext{Ethanol} + 2 ext{CO}_2 + 2 ext{NAD}^+

  2. Lactic Acid Fermentation:

    • Pyruvate → Lactic Acid

    • General Equation:

      ext{Glucose}
      ightarrow 2 ext{Lactate} + 2 ext{NAD}^+

Today's Experiment

  • Objective: Measure carbon dioxide production during anaerobic respiration through alcohol fermentation using yeast.

  • Key Components:

    • Glucose: A common energy source for respiration.

    • Pyruvate: The product of glycolysis, acting as an activator for respiration.

    • Magnesium Sulfate: A cofactor that activates glycolysis enzymes.

    • Sodium Fluoride: Acts as an inhibitor for certain enzymes.

Experimental Setup: Tube Composition

  • Tube 1:

    • 3M Pyruvate: -

    • 0.1M MgSO₄: -

    • 0.1M NaF: -

    • 5% Glucose: 4 mL

    • DI H₂O: 3 mL

    • Yeast: –

  • Tube 2:

    • Same as Tube 1 except:

    • 1 mL Pyruvate

    • 3 mL Glucose

    • 3 mL Yeast

  • Further Tubes:

    • Continue similar adjustments for Tubes 3 to 6, altering concentrations appropriately while maintaining a standard amount of yeast in each.

Today's Assignment

  • Complete Procedure 12.1

  • Prepare a Predicted Results Table

  • Answer Question 3a-i