LIFE 102: Cellular Respiration Overview

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• Worksheet today

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• Homework & quiz due Sunday

• Exam review Friday online AND in-person

• Exam 2 on Monday, October 13

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  • Course: 2025FA-LIFE-102-003: Attributes of Living Systems

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• Live sessions schedule for LIFE 102-004:

  • Class time is from 1:00 pm - 1:50 pm on MWF

  • Specific class dates including:

  • August 25, August 27, August 29

  • September 3, September 5

  • Upcoming Live classes on October 3, October 6, October 8, October 10, and October 13

Cohort Tutor Groups

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Lecture Focus: Cellular Respiration

Part 3 of 3 on Cellular Respiration

• Title as referenced: Cellular Respiration (III)

• Current learning focus: metabolic pathway from glucose to ATP production

Overview of Energy Yield from Glucose

• From one molecule of glucose:

  • Net energy production: 2 ATP

• Glycolysis Process:

  • Inputs: 2 ATP, 1 Glucose

  • Outputs: 4 ATP, 2 NADH, 2 Pyruvate

Pyruvate Processing

• Pyruvate Oxidation:

  • Inputs: 2 Pyruvate

  • Outputs: 2 Acetyl-CoA, 2 NADH

Krebs Cycle Overview

• The Krebs Cycle:

  • Process overview:

  • Inputs: 2 Acetyl-CoA

  • Outputs: 2 Oxaloacetate, 6 NADH, 2 FADH2, 2 ATP

Electron Transport Chain (ETC) and Chemiosmosis

Overview of Pathway

• Following glycolysis and Krebs cycle, electron carriers (NADH, FADH2) proceed to the ETC.

Steps of Electron Transport Chain

• Location: Mitochondrial membrane

• Goal: To use harvested electrons to power proton pumps and generate an electrochemical gradient.

• Outputs from the ETC and Chemiosmosis:

  • Yield: Approximately 28 ATP and H2O

Details of Electron Transport Chain

• Components:

  • Composed of 3 membrane proteins that transport electrons across the mitochondrial membrane.

  • NADH donates electrons, becoming oxidized to NAD+.

  • FADH2 also donates electrons, becoming oxidized.

Final Electron Acceptor

• Oxygen acts as the final electron acceptor.

• Reaction:
  ext{O}2 + 4 ext{H}^+ + 4 ext{e}^- ightarrow 2 ext{H}2 ext{O}

Chemiosmosis

• The process uses the electrochemical gradient created by the ETC to synthesize ATP.

• ATP Synthase:

  1. Channel for H+ ions

  2. Protons flow through and activate the enzyme complex, converting ADP to ATP.

  3. Total outputs: Around 28 ATP from oxidative phosphorylation.

Implications of Oxygen Availability

Aerobic vs Anaerobic Respiration

• Discussed processes in absence of oxygen:

  • If there is no oxygen, anaerobic respiration occurs, utilizing alternative electron acceptors.

  • Efficiency dramatically reduced to yield approximately 9 ATP.

Fermentation Mechanisms

• Two types of fermentation:

  1. Lactic Acid Fermentation

  2. Ethanol Fermentation

• In absence of O2, pyruvate acts as the electron acceptor leading to NADH oxidation back to NAD+.

Summary of Key Pathways in Cellular Respiration

• Main stages:

  1. Glycolysis

  • Yield: 2 Pyruvate, Net Gain of 2 ATP

  1. Pyruvate Oxidation

  • Generates Acetyl-CoA, NADH

  1. Krebs Cycle

  • Yields various electron carriers and ATP

  1. Oxidative Phosphorylation

  • Includes both the ETC and Chemiosmosis, final ATP synthesis

Important Questions

Exam Preparation Questions

1. What are the products of glycolysis?

2. Where does the Krebs cycle take place?

3. What is the role of NADH in cellular respiration?

4. How does ATP Synthase function in cellular respiration?

5. What happens to pyruvate in anaerobic conditions?