MG

Recording-2025-03-12T12:58:50.447Z

Overview of Cellular Respiration

  • Definition: Cellular respiration is a metabolic pathway that breaks down glucose and converts it into usable energy in the form of ATP (adenosine triphosphate).

  • Common Misconception: Many associate cellular respiration only with breathing (oxygen intake and carbon dioxide release), but it also involves intricate biochemical processes.

Key Concepts

Metabolic Pathways

  • Definition: A series of chemical reactions where the product of one reaction becomes the reactant for the next.

  • Importance: Metabolic pathways allow organisms to efficiently produce energy and regulate cellular processes.

Energy Currency of the Cell

  • ATP (Adenosine Triphosphate): The primary energy carrier in cells.

    • Derived from breaking chemical bonds in glucose during cellular respiration.

    • Essential for various cellular functions and processes.

Processes of Cellular Respiration

Types

  1. Aerobic Respiration (requires oxygen)

    • Main process for ATP production in the presence of oxygen.

  2. Anaerobic Respiration (does not require oxygen; associated with fermentation)

    • Occurs in environments lacking oxygen.

The Cellular Respiration Process

Step 1: Glycolysis

  • Location: Cytoplasm

  • Process:

    • Breakdown of one glucose (6 carbons) into two pyruvate molecules (3 carbons each).

    • Requires an initial investment of 2 ATP but produces 4 ATP (net gain of 2 ATP) and 2 NADH.

Step 2: Transition Reaction (Oxidation of Pyruvate)

  • Location: Mitochondrial Matrix

  • Process:

    • Each pyruvate (3 carbons) is converted into Acetyl CoA (2 carbons), releasing one carbon dioxide and producing NADH.

    • Important as Acetyl CoA enters the citric acid cycle.

Step 3: Citric Acid Cycle (Krebs Cycle)

  • Location: Mitochondrial Matrix

  • Process:

    • Acetyl CoA combines with oxaloacetate to form citrate (6 carbons).

    • Through a series of transformations:

      • Produces: 3 NADH, 1 FADH2, 1 ATP, and releases 2 CO2 molecules for each Acetyl CoA present.

  • Total products from one glucose (yielded from 2 Acetyl CoA): 6 NADH, 2 FADH2, 2 ATP, and 4 CO2.

Step 4: Oxidative Phosphorylation (Electron Transport Chain)

  • Location: Inner mitochondrial membrane

  • Process:

    • Electron carriers NADH and FADH2 donate electrons to the electron transport chain.

    • Electrons are passed through several proteins, releasing energy, which pumps H+ ions into the intermembrane space (active transport).

    • H+ ions then flow back into the mitochondrial matrix through ATP synthase, generating ATP (chemiosmosis).

  • Final Electron Acceptor: Oxygen, which combines with electrons and protons to produce water.

Definitions

  • Redox Reactions: Chemical reactions involving the transfer of electrons; reduction (gain of electrons) and oxidation (loss of electrons) occur simultaneously.

  • Electron Carriers: Molecules that transport electrons during cellular respiration (e.g., NADH, FADH2).

Summary of Key Stages

  1. Glycolysis: Converts glucose into pyruvate, with a small yield of ATP.

  2. Transition: Converts pyruvate into Acetyl CoA while producing NADH.

  3. Krebs Cycle: Processes Acetyl CoA, yielding NADH, FADH2, ATP, and CO2.

  4. Oxidative Phosphorylation: Produces the majority of ATP via the electron transport chain and chemiosmosis.

Second Law of Thermodynamics

  • When energy is converted from one form to another, some energy is lost as heat, reducing the efficiency of energy transfer in cellular respiration.