CR

Overview of Cellular Respiration

  • Definition: Cellular respiration is a metabolic process that converts biochemical energy from nutrients into ATP (adenosine triphosphate), and then releases waste products.
  • Main Stages: The process involves several key stages:
    • Glycolysis
    • Krebs Cycle
    • Electron Transport Chain

Glycolysis

  • Location: Occurs in the cytoplasm of the cell.
  • Initial Process: Breaks down glucose (C6H12O6) into pyruvate.
  • Key Outputs:
    • ATP (net gain of 2 ATP)
    • NADH (electron carrier)
    • Pyruvate (converted to Acetyl-CoA for Krebs Cycle)

Krebs Cycle (Citric Acid Cycle)

  • Location: Takes place in the mitochondrial matrix.
  • Key Inputs:
    • Acetyl-CoA
    • NAD+
    • FAD
  • Major Outputs:
    • NADH
    • FADH2
    • 2 ATP
    • Carbon dioxide (CO₂)
  • Function: Processes pyruvate and generates high-energy electron carriers for the next stage.

Oxidation and Reduction Reactions

  • Electrons Transfer: Essential for energy production.
  • Oxidation: Loss of electrons (e-), often resulting in a release of energy.
  • Reduction: Gain of electrons, resulting in an increase in energy.
  • Key Concept:
    • Oxidation is Loss, Reduction is Gain (OIL RIG).

Electron Transport Chain (ETC)

  • Location: Embedded in the inner mitochondrial membrane.
  • Function:
    • Receives high-energy electrons from NADH and FADH2.
    • Establishes a proton (H+) gradient across the inner mitochondrial membrane.
  • Process:
    • Electrons are transferred through protein complexes, moving to lower energy states.
    • Energy released is used to pump protons into the intermembrane space.
    • H+ ions flow back into the mitochondrial matrix through ATP synthase, generating ATP (chemiosmosis).

ATP Synthase

  • Function: Enzyme that synthesizes ATP from ADP and inorganic phosphate (Pi) using the proton gradient.
  • Process: As protons flow through, ATP synthase rotates and catalyzes ATP formation.
  • Net ATP Yield: Approximately 32 ATP molecules produced per glucose molecule during aerobic respiration.

Chemiosmotic Phosphorylation (Oxidative Phosphorylation)

  • Definition: The process by which ATP is formed as protons flow down their concentration gradient across the inner membrane of mitochondria.
  • Connection to ETC: Directly linked to the functioning of the electron transport chain and ATP synthase.

Modern Weight Loss Drugs and DNP

  • Connection to Hormones: Modern weight loss drugs, such as Ozempic (semaglutide), work by mimicking hormones to suppress appetite.
  • DNP (2,4-Dinitrophenol):
    • Historical use in dieting pills in the 1930s due to its metabolic enhancement properties.
    • Mechanism: Increases metabolic rate dramatically and tricks mitochondria into working harder to produce ATP, resulting in heat (extreme hyperthermia).
  • Health Risks:
    • Notable fatalities reported linked to DNP usage (e.g., Sarah Houston's death).
    • DNP is banned for weight loss due to health risks.

Ethical Implications and Risks of DNP

  • Case Study:
    • Sarah Houston, a medical student, died after taking DNP.
    • Symptoms included temperature spikes and breathlessness prior to death.
    • The coroner highlighted the danger of online dealers targeting vulnerable individuals.
  • Public Awareness: The need for increased awareness campaigns regarding the dangers of using banned substances, such as DNP, for weight loss.