Biochemistry: Energy and Mitochondria

What is Energy?

• Energy is required for living things to maintain order, grow and reproduce
• Bioenergetics is the branch of biochemistry focusing on how cells transform energy
• Chemical energy is stored in the bonds of molecules and can be released and transformed by metabolic pathways
• Free Energy (G) is the chemical energy available to do work

Why Life Requires a Highly Ordered System?

• Living organisms require a highly ordered system to maintain life

Mitochondria

• Mitochondria are often referred to as the “powerhouses of the cell”
• Discovered by Rudolph Albert von Kolliker in 1857

Mitochondria Structure

• Two separate membranes: an inner and outer membrane
• Three compartments: intermembrane space, cristae space, and matrix

Outer Membrane

• Acts as a molecular sieve allowing only small molecules to diffuse through

Inner Membrane

• Folds to form cristae that divide the organelle into three compartments
• Where the third stage of cellular respiration, the Electron Transport Chain, takes place

Intermembrane Space

• Located between the inner and outer membrane
• Involved in regulating respiration and metabolic functions

Cristae

• High curvature structures in the inner mitochondrial membrane (IMM) that are crucial for ATP production

Matrix

• Space enclosed by the inner membrane
• The second stage of cellular respiration, the Krebs Cycle, takes place in the matrix

Antoine Lavoisier

• Related chemistry to the science of bodies, physiology, and the study of metabolism and respiration

Coupled Reactions

• A class of organic reactions that involve the joining of two chemical species
• Increase entropy

Krebs Cycle

• Also known as the Citric Acid Cycle
• Second stage of cellular respiration
• Pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions
• Discovered by British biochemist, Hans Adolf Krebs, in 1937

Tricarboxylic Acid (TCA) Cycle/Krebs Cycle

• The three-carbon pieces are pulled apart bit by bit to release the energy stored in the covalent bonds
• Most of the CO2 is formed in this process
• Citric acid is formed in the initial reactions of the cycle

Two Types of Organisms

• Autotrophs make their own food
• Heterotrophs obtain food from other organisms

Food-Making Processes of Autotrophs

• Photosynthesis: captures energy from sunlight to produce carbohydrates
• Chemosynthesis: captures energy from small inorganic chemicals in the environment, can occur without oxygen

Adenosine Triphosphate (ATP)

• The energy currency of the cell
• Composed of adenine, ribose, and three phosphate groups

Hydrolysis of ATP

• Endergonic (requires energy)
• Active transport
• Cell movements
• Anabolism

Synthesis of ATP

• Exergonic (releases energy)
• Cell respiration
• Catabolism

Catabolism

• The metabolic breakdown of complex molecules into simpler ones and the release of energy

Cellular Respiration

• Cells trap and release chemical bond energy step by step in a series of chemical reactions
• Breaks down glucose and produces ATP
• Food is the raw material that provides energy for body function
• Cells use food to synthesize new molecules for life processes

Aerobic Respiration

• Chemical process in which oxygen is used to make energy from carbohydrates
• Oxygen is the final electron acceptor

Anaerobic Respiration

• Type of cellular respiration that does not use oxygen to produce energy

Equation for Aerobic Respiration

• 6O2 + C6H12O6 → 6CO2 + 6H2O + energy (ATP)
• Oxygen + glucose → carbon dioxide + water + energy

Equation for Anaerobic Respiration

• C6H12O6 → 2C3H6O3 + energy (ATP)
• Glucose → lactic acid + energy

Major Stages of Aerobic Respiration

• Glycolysis
• Krebs cycle
• Electron Transport Chain

Glycolysis

• Breakdown of a glucose molecule into two three-carbon molecules (pyruvate)
• Occurs in the cytoplasm of the cell

Nicotinamide Adenine Dinucleotide (NAD+)

• The oxidized form of NAD+ undergoes reduction by reacting with 2H (two hydrogen ions and two electrons)

Krebs Cycle

• Second stage of cellular respiration
• Pyruvic acid is broken down into carbon dioxide
• Occurs in the mitochondrial matrix
• Also known as the Citric Acid Cycle

Electron Transport Chain

• The third and final stage of aerobic respiration
• Occurs in the inner mitochondrial membrane
• Produces the most ATP

Explore the fundamental concepts of energy in living organisms and the role of mitochondria as the cell's powerhouses. This quiz delves into bioenergetics, the structure of mitochondria, and their importance for maintaining life. Test your understanding of how energy transformations occur at the cellular level.