Oxidative Phosphorylation

Introduction to Oxidative Phosphorylation

  • The discussion begins with an overview of transitions in cellular respiration, specifically moving from the Citric Acid Cycle (TCA cycle) to Oxidative Phosphorylation.

  • The instructor mentions they will start with tutorial questions to engage the audience.

Audience Engagement

Vevox Tools

  • Vevox is introduced as an audience engagement tool.

  • Participants are instructed to enter a Meeting ID (117217947) to join the session.

Interactive Polls Regarding Cellular Metabolism

Poll #1: Location of Pyruvate Production

  • Question: "Pyruvate is produced in the cytoplasm."

    • Options: True or False.

Poll #2: Fuel of TCA Cycle

  • Question: "The 'fuel' of the TCA cycle is:"

    • Options include:

    1. Glucose

    2. Pyruvate

    3. Acetyl CoA

    4. NADH

    5. FADH2

    6. CO2

Entry of Pyruvate into Mitochondria

  • Pyruvate moves from the cytoplasm (Cytosol) into the mitochondria, which is the point of entry for the TCA cycle.

Pyruvate Decarboxylase

Enzymatic Reaction

  • Pyruvate Decarboxylation: Pyruvate is oxidatively decarboxylated by the enzyme pyruvate decarboxylase.

  • This reaction involves a series of steps that convert pyruvate into Acetyl CoA.

  • Enzyme Complexes Involved:

    • E1 (Pyruvate Dehydrogenase): Catalyzes the oxidative decarboxylation. Prosthetic group: TPP.

    • E2 (Dihydrolipoyl Transacetylase): Transfers the acetyl group to CoA. Prosthetic group: Lipoamide.

    • E3 (Dihydrolipoyl Dehydrogenase): regenerates the oxidized form of lipoamide. Prosthetic group: FAD.

  • Products: Acetyl CoA, CO2, and electrons (e−). Total: 2 e−, 2 CO2 produced per cycle.

TCA Cycle Conditions

Polls on TCA Cycle

  • Polls assess understanding of:

    • Whether the TCA cycle requires oxygen (True/False).

    • Whether the TCA cycle produces Glucose, ATP, Pyruvate, Acetyl CoA, NADH, FADH2, CO2, and O2.

Overview of Biomolecules and Metabolism

  • Oxidative Phosphorylation is introduced as a critical metabolic pathway.

  • It is emphasized that high-energy and low-energy molecules play roles in the metabolism, illustrated by the reduction of NADH to NAD+.

Cellular Respiration Overview

Processes Involved

  • Two main processes discussed:

    1. Citric Acid Cycle

    2. Oxidative Phosphorylation

  • Correlation illustrated between:

    • Substrates: Fatty acids, Glucose, Amino acids to Acetyl CoA.

    • Final Products: ATP, Water (H2O), CO2, and electrons.

  • Key diagram showing cycle of NADH and FADH2 and their roles in driving ATP production via oxidative phosphorylation.

Electron Transport Chain and Energy Production

Description of Electron Transport Chain

  • The electron transport chain (ETC) is likened to a bicycle chain.

  • The mechanism of transferring energy from carbon oxidation to create a proton gradient.

  • Specifics on proton pumps and functional complexity:

    • Four large protein complexes embedded in the inner mitochondrial membrane.

    • Mechanism: Proton pumping from matrix into intermembrane space creates a proton gradient used to synthesize ATP.

Thermodynamics of Electron Transport

  • This section outlines how ATP synthesis is indirectly related to chemical reactions in the mitochondrial membrane.

  • Detailed explanation of redox reactions:

    • General reaction formula for oxidation and reduction: Oxidized + Reduced ⇌ Reduced + Oxidized.

Proton Gradients and ATP Synthesis

Chemiosmotic Hypothesis

  • Introduced ATP synthase and its mechanism to exploit the proton gradient.

  • Breakdown of the processes of electron transport to ATP synthesis:

    • The pH gradient and membrane potential create a proton motive force for ATP production.

NADH Entry into Mitochondria

  • Different methods for cytosolic NADH to enter mitochondria:

1. Glycerol 3-Phosphate Shuttle

  • NADH transports electrons via conversion of dihydroxyacetone phosphate to glycerol 3-phosphate.

  • This allows entry into the mitochondrial electron transport chain.

2. Malate-Aspartate Shuttle

  • Involves conversion of oxaloacetate to malate for transport into mitochondria.

  • Upon reoxidation, allows recycling of NADH/oxaloacetate.

Energy Yield Calculation from Glucose

  • Complete oxidation of glucose is quantified:

    • Yielding approximately 30 ATP molecules.

    • ATP usage in glycolysis accounted and NADH contribution from mitochondrial processes noted.

Oxidative Phosphorylation Regulation

  • ATP demand drives the rate of oxidative phosphorylation.

Alcohol Fermentation

Pasteur Effect

  • Discussion on yeast fermentation in absence and presence of oxygen, illustrating differences in ATP yield and products.

    • With oxygen: CO2 and H2O, producing ATP via aerobic respiration.

    • Without oxygen: CO2 and Ethanol, producing limited ATP via fermentation.

Warburg Effect and Cancer Metabolism

  • Overview of differences in aerobic and anaerobic metabolism in differentiated versus proliferative tissues (tumors).

  • Notable ATP production differences provided:

    • Aerobic respiration: 36 moles ATP/mole glucose.

    • Anaerobic glycolysis results in only 2 moles ATP/mole glucose.

Hypoxia and Transcription Factors

  • Advanced explanation of how hypoxia affects metabolic pathways and transcription factors that regulate these pathways.

  • Increased activity in glycolytic enzymes and fatty acid metabolism noted in response to low oxygen conditions.

Here are some fill-in-the-blank questions based on the notes:

  1. Pyruvate is produced in the .

  2. The 'fuel' of the TCA cycle is .

  3. Pyruvate is oxidatively decarboxylated by the enzyme .

  4. The enzyme complex E2 in pyruvate decarboxylase is called .

  5. The products of pyruvate decarboxylation include Acetyl CoA, CO2, and .

  6. The electron transport chain complexes are embedded in the mitochondrial membrane.

  7. Proton pumping from the matrix into the intermembrane space creates a gradient used to synthesize ATP.

  8. The two main methods for cytosolic NADH to enter mitochondria are the Shuttle and the Shuttle.

  9. Complete oxidation of glucose yields approximately ATP molecules.

  10. In the Warburg Effect, aerobic respiration produces moles ATP per mole glucose, while anaerobic glycolysis results in only moles ATP per mole glucose.