cell-respiration

ATP and Cellular Respiration

Structure of ATP

  • Adenine: Key nitrogenous base in ATP

  • Contains multiple nitrogen and carbon structures:

    • NH2, N, C, C, N, C CH

  • Ribose: A five-carbon sugar

  • Phosphate groups: Key for energy storage and transfer

Importance of ATP

  • Function: Primary energy currency in cells

    • ATP is generated through cellular respiration

  • Purpose: To make ATP for energy needs

Thermodynamics in Biology

First Law of Thermodynamics

  • Energy cannot be created or destroyed, only transformed

  • Living systems must acquire and transform energy to survive

  • Free energy: Energy in a system available for work

Second Law of Thermodynamics

  • Every energy transformation increases entropy (disorder)

  • The loss of order or free energy leads to death

Coupling Cellular Processes

  • Organisms maintain order by coupling cellular processes

    • Use reactions that increase entropy to power those that decrease entropy

    • Energy coupling is crucial for cellular function

Types of Reactions in Metabolism

Exergonic vs. Endergonic Reactions

  • Exergonic reactions:

    • Energy is released

    • Example: Digestion

  • Endergonic reactions:

    • Energy is absorbed

    • Example: Synthesis

  • Free energy change (ΔG):

    • Indicates the ability to do work

Metabolic Reactions

Bond Formation and Breakdown

  • Dehydration synthesis: Forming bonds by removing water (endergonic)

  • Hydrolysis: Breaking bonds by adding water (exergonic)

Energy Needs for Life

  • Organisms require energy for:

    • Synthesis of biomolecules

    • Reproduction

    • Active transport

    • Movement

    • Temperature regulation

Living Economy of ATP

  • Energy source: High energy organic molecules from food

  • Catabolism: Process of breaking down food to capture energy

  • ATP acts as a short-term energy storage molecule

Synthesis and Function of ATP

  • ATP structure:

    • Composed of adenosine (adenine + ribose) and three phosphate groups

    • ATP = ADP + Pi (involves energy input)

  • Negative charges in phosphate groups make ATP a high-energy molecule

  • Energy stored particularly in the third phosphate group

Energy Transfer via ATP

  • ATP release energy when converted to ADP

  • Process of phosphorylation:

    • Addition of phosphate groups to other molecules

  • Enzymes called kinases are responsible for this process

ATP/ADP Cycle

  • ATP cannot be stored; it's too reactive and transfers phosphate groups easily

  • Cells recycle 10 million ATPs per second through metabolic processes

Redox Reactions in Cellular Respiration

Oxidation and Reduction

  • Oxidation: Removal of electrons, resulting in energy release (exergonic)

  • Reduction: Addition of electrons, storing energy (endergonic)

  • Example of a redox reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

Harvesting Energy from Fuels

  • Digest large molecules into smaller ones

  • Electrons carry energy as they move and participate in redox reactions

  • Energy can be released as heat or captured as ATP

Electron Transport in Living Systems

  • Electrons are part of H atoms, thus moving H also moves electrons

  • Cellular systems utilize redox reactions in the breakdown of glucose

Electron Carriers

  • NAD+ and FAD: Important electron carriers in cellular respiration

  • When reduced (NADH, FADH2), they store high-energy electrons

Overview of Cellular Respiration

  • Consists of three stages:

    1. Glycolysis: Anaerobic breakdown of glucose in the cytosol

    2. Krebs Cycle: Aerobic respiration in the mitochondria

    3. Electron Transport Chain: Produces ATP using an H+ gradient

  • Overall equation: C6H12O6 + 6O2 ➜ 6CO2 + 6H2O + ~40 ATP

Glycolysis Basics

  • Process: Breaking down glucose into pyruvate

  • Occurs in cytosol, generating 2 ATP per glucose molecule

  • Inefficient resource use, yet vital for all forms of cellular respiration

Energy Investment & Payoff in Glycolysis

  • Energy investment phase: Glucose is phosphorylated, requiring 2 ATP

  • Energy payoff phase: Produces 4 ATP (net gain 2 ATP), 2 NADH, and 2 pyruvate

Evolutionary Perspective

  • First organisms: Prokaryotes that used glycolysis without O2 in the ancient atmosphere

  • Glycolysis remains a fundamental process for all modern life forms

Pyruvate Utilization

  • Branching point:

    • In the presence of O2: Pyruvate enters aerobic respiration

    • In absence of O2: Converts to ethanol or lactate through fermentation

Krebs Cycle

  • Produces large quantities of electron carriers (NADH, FADH2)

  • Cycles through multiple stages; glucose is completely oxidized to CO2

Electron Transport Chain

  • Located in the inner mitochondrial membrane

  • Generates H+ gradient crucial for ATP synthesis via ATP synthase

  • Transfers electrons from NADH and FADH2 to oxygen, creating water as a byproduct

Fermentation

  • Occurs in absence of O2; allows for regeneration of NAD+

  • Different pathways in yeast and animal cells, yielding ethanol and lactic acid, respectively

Summary of Cellular Respiration

  • Glucose inhaled contributes to metabolic processes, generating CO2 and water, alongside high ATP yields.

  • Overall, the processes of glycolysis, Krebs cycle, and oxidative phosphorylation are fundamental for energy production in living organisms.