Aerobic Cellular Respiration in Biochemistry

Energy Coupling in Cells

• Cells manage energy resources by energy coupling, which uses an exergonic process to drive an endergonic one.
• Most energy coupling in cells is mediated by ATP.

Aerobic Cellular Respiration

• The major stages of aerobic cellular respiration are glycolysis, the citric acid cycle, and oxidative phosphorylation.
• Glucose enters glycolysis, where it is converted into smaller organic molecules, producing a small amount of ATP.
• The final product of glycolysis enters the citric acid cycle, where redox reactions move electrons to the electron carriers NADH and FADH2.
• The electron carriers feed their electrons to molecules in the oxidative phosphorylation process, synthesizing a large amount of ATP.

Glucose Breakdown

• Glucose is broken down into smaller molecules, such as sugars, fats, and amino acids, which are fed into the cellular respiration process.
• Glucose is the most important fuel for cellular respiration, generating a large amount of ATP during its complete breakdown.

ATP and Energy

• ATP is a good energy source because it can be easily converted into energy.
• Example: ATP is used to perform muscle contractions.
• ATP consists of a molecule of adenosine to which three phosphate groups are attached.
• Energy carried by ATP is released when one of the phosphate groups is broken down.

Bioenergetics and Related Terms

• Bioenergetics: the study of energy transformations in living organisms.
• Open system: a system that exchanges energy and matter with its surroundings.
• Free energy: energy available to do work.
• Equilibrium: a state where the rates of forward and reverse reactions are equal.
• Photoautotrophic producer: an organism that produces its own food using sunlight.
• Heterotrophic consumers: organisms that consume other organisms or organic matter for energy.
• Aerobic process: a process that requires oxygen.
• Anaerobic process: a process that does not require oxygen.

Exergonic and Endergonic Reactions

• Exergonic reactions: energy-releasing reactions, where energy is released from the reactants.
• Endergonic reactions: energy-requiring reactions, where energy is absorbed by the reactants.

Cell Work

• The three main kinds of work performed by cells are:
  • Mechanical work: muscle contractions.
  • Transport work: transporting molecules across cell membranes.
  • Chemical work: biosynthesis.

Energy Yield

• One gram of fat yields 9 kcal or 38 kJ, while one gram of carbohydrate yields 4 kcal.

Cellular Respiration

• Cellular respiration takes place in several steps to avoid releasing a large amount of heat at once, which would likely destroy the cell.
• The energy released is controlled, and more energy is captured and converted to ATP, with less energy lost as heat.

Electron Carriers

• The electron carriers involved in the citric acid cycle are NADH and FADH2.