Cellular Respiration pt 2

Cellular Respiration Overview

• ATP Generation:

  • Cellular respiration is the primary process of ATP production in the presence of oxygen, utilizing glucose.

  • Defined as an eroding process, breaking down glucose to extract energy.

Fermentation

• Alternative Pathway:

  • In absence of oxygen, cells resort to fermentation.

  • Produces less ATP compared to cellular respiration, but allows for energy extraction.

Main Focus Areas in Cellular Respiration

• Key Steps:

  • Focus on three primary steps:

  1. Glycolysis

  2. Pyruvate Oxidation (Pyruvate Processing)

  3. Possibly the Citric Acid Cycle

Energy Extraction from Glucose

• Energy Graphs:

  • Cellular respiration involves extracting high-potential chemical energy from glucose.

  • Energy Release:

  • A total of 686 kilocalories per mole is released during glucose oxidation.

  • Use of energy:

  • Energy extracted is utilized for cellular processes such as anabolic reactions.

ATP Hydrolysis

• ATP Usage:

  • Cells hydrolyze ATP to access energy for metabolic processes.

  • High-energy phosphate molecules facilitate energy transfer.

  • Example:

  • Phosphorylation of glutamic acid increases its free energy.

Redox Reactions in Cellular Respiration

• Definition and Explanation:

  • Redox stands for Reduction-Oxidation which describes the loss and gain of electrons.

  • Oxidation: Loss of electrons (electron donors).

  • Reduction: Gain of electrons (electron acceptors).

  • Example: Chloride accepting electrons becomes reduced.

• Common Compounds:

  • NAD+ (Nicotinamide adenine dinucleotide) is utilized in the first three steps of cellular respiration for electron transport.

Glycolysis

• Overview:

  • Starting molecule: Glucose (6 carbons).

  • Final products: Two pyruvate molecules (3 carbons each).

  • Investment Phase:

  • Requires an input of ATP to initiate glycolysis (energy investment).

  • Output:

  • Net production of 2 ATP after accounting for the 2 ATP invested.

• Details of Glycolysis:

  • Not required to memorize all intermediates.

  • Each step facilitates the gradual oxidation of glucose, breaking down bonds to extract energy.

Pyruvate Oxidation

• Conversion Process:

  • Pyruvate molecules enter mitochondria and undergo oxidation.

  • Removal of one carbon yields carbon dioxide as a byproduct.

  • Energy capture: Electrons stripped from pyruvate generate NADH.

  • Coenzyme A (CoA) attaches to the remaining two-carbon fragment, forming Acetyl CoA.

Citric Acid Cycle (Krebs Cycle)

• Introduction:

  • Each Acetyl CoA from pyruvate oxidation enters the cycle.

  • Initial reaction: Acetyl CoA combines with oxaloacetate (4 carbons) to form citrate.

• Key Features:

  • Carbon atoms released: Over the cycle, two carbon dioxide molecules are released for every Acetyl CoA that enters.

  • Electron carriers: Produces NADH and FADH2 which store energy.

  • Substrate Level Phosphorylation:

  • One ATP is produced directly during the cycle.

  • Cycle Regeneration:

  • Oxaloacetate is regenerated for the cycle to continue.

• Summary of Products:

  • Energy Capture:

  • Two ATPs directly usable by the cell, with more energy stored in NADH and FADH2.

Mitochondrial Structure and Oxidative Phosphorylation

• Structure:

  • Mitochondria have a double membrane with an inner and outer layer.

  • Inner membrane hosts folds called cristae.

• Oxidative Phosphorylation:

  • Occurs on the cristae membrane.

  • Involves the electron transport chain where NADH and FADH2 drop off electrons, leading to ATP synthesis.