Class13

Introduction to Cellular Respiration

  • Understanding the energy extraction from glucose by organisms.

Agenda Overview

  • Introduction to the stages of cellular respiration:
    • Glycolysis
    • Transition Reaction
    • Citric Acid Cycle
    • Oxidative Phosphorylation

Learning Objectives

  • Explain how redox reactions in catabolic pathways yield energy by oxidizing organic fuels.
  • Describe:
    • Inputs
    • Processes
    • Products
    • Aerobic cellular respiration overall and individual stages (glycolysis, transition reaction, citric acid cycle, oxidative phosphorylation).
  • Predict effects on cellular respiration due to perturbations in inputs and processes of:
    • Glycolysis
    • Transition Reaction
    • Citric Acid Cycle
    • Oxidative Phosphorylation.
  • Trace the origin of specific atoms and energy found in the products of cellular respiration.

Endergonic Reactions in Cells

  • Endergonic reactions require energy input:
    • Synthesis of glucose
    • Synthesis of DNA
    • Protein synthesis
    • Active transport (against concentration gradient)
    • Muscle contraction.
  • Energy for these reactions is derived from exergonic reactions, notably ATP hydrolysis.

Cellular Respiration as ATP Generation

  • Big Idea: Cellular respiration converts energy from food into ATP:
    • Reaction: ext{Glucose} + 6 ext{O}2 ightarrow 6 ext{CO}2 + 6 ext{H}_2 ext{O}
    • Mass transformation: Glucose & O2 to CO2 & H2O.
    • Energy transformation: Bonds in Glucose to Bonds in ATP
    • Reaction: ext{ADP} + ext{Pi}
      ightarrow ext{ATP}

Overview of Cellular Respiration

  • Reactants: 1 Glucose + 6 O2
  • Products: 6 CO2 + 6 H2O
  • Change in free energy: extΔG=−686extkJ/molext{ΔG} = -686 ext{ kJ/mol}
  • Composition of reactants and products:
    • Reactants: 6 carbons, 18 oxygens, and 12 hydrogens.
    • Products: 6 carbons, 18 oxygens, and 12 hydrogens.
  • High-energy electrons in glucose ultimately transferred to oxygen, settling to a low energy state, releasing energy.

ATP Production from Glycolysis

  • Conversion of glucose via glycolysis results in the production of ATP:
    • Overall ATP yield through glycolysis: About 38 ATP
    • Important process: Chemiosmosis where energy from glucose is used to produce ATP across different stages of cellular respiration:
    • Glycolysis
    • Transition Reaction
    • Citric Acid Cycle
    • Electron Transport Chain

Benefits of Using ATP

  • ATP vs. Carbohydrates:
    • ATP is the direct energy currency of the cell, while energy in carbohydrates is indirect.
    • Metaphor: Energy in sugar is like a check, while energy in ATP is akin to cash (a $20 bill).

Four Stages of Cellular Respiration

  1. Glycolysis: Splits glucose into 2 pyruvate molecules; occurs in cytoplasm, producing 2 ATP and NADH.
  2. Transition Reaction: Converts pyruvate to Acetyl CoA; occurs in the mitochondrial matrix, generating CO2 and NADH.
  3. Citric Acid Cycle (Krebs Cycle): Fully oxidizes Acetyl CoA; CO2, ATP, NADH, and FADH2 produced.
  4. Oxidative Phosphorylation (Electron Transport Chain and Chemiosmosis): Uses NADH and FADH2 in the presence of oxygen to produce approximately 26 to 28 ATP per glucose molecule.

Summary of ATP Production per Process

  • **Glycolysis