Cellular Respiration Overview

Cellular Respiration

• Cellular respiration is the process by which cells generate energy from nutrients, converting chemical energy into ATP.
• The general equation for cellular respiration is: Glucose + Oxygen → Carbon Dioxide + Water + ATP.

Steps of Cellular Respiration

• Glycolysis: 6-carbon glucose is converted into 2 3-carbon molecules of pyruvate, producing ATP and NADH.
• Formation of Acetyl CoA: Pyruvate is oxidized into a 2-carbon molecule (acetyl CoA), producing NADH and releasing CO2.
• Citric Acid Cycle: Acetyl CoA binds to a 4-carbon molecule (oxaloacetate), producing a 6-carbon molecule (citrate), releasing energy into ATP, NADH, and FADH2.
• Electron Transport Chain: Electrons from glucose are passed through a chain of electron acceptors, pumping Hydrogen ions across the inner mitochondrial membrane, forming a proton gradient, which is used to produce ATP through chemiosmosis.

Glycolysis

• Glycolysis means "sugar splitting" and does not require oxygen.
• It involves 10 steps, converting glucose into pyruvate, producing ATP and NADH.

Formation of Acetyl CoA

• Catalyzed by enzyme pyruvate dehydrogenase.
• One carbon dioxide molecule is released, and the remaining 2-carbon fragment is oxidized, transferring electrons to NAD+.

Citric Acid Cycle

• Also known as the Tri-carboxylic acid cycle or Krebs cycle.
• Produces 6 CO2 molecules, 10 NADH molecules, and 2 FADH2 molecules per glucose molecule.

Electron Transport Chain

• Takes place in the inner mitochondrial membrane (eukaryotes) and plasma membrane (prokaryotes).
• ATP is produced through Oxidative Phosphorylation, which is coupled to redox reactions involving oxygen.

ATP Production

• Each NADH results in approximately 3 ATP.
• Each FADH2 gives 2 ATP.

Anaerobic Respiration

• Occurs in the absence of oxygen.
• Facultative anaerobes can switch between aerobic and anaerobic respiration.
• Fermentation is the anaerobic degradation of glucose, producing ATP through the conversion of glucose into lactic acid.

Examples of Anaerobic Respiration

• Lactic acid bacteria ferment glucose to lactate.
• Mammalian skeletal muscle cells ferment glucose to lactic acid during prolonged contraction when oxygen is limited.