Lecture 17: Cellular Respiration

Cellular Respiration

• Cellular respiration: the process of generating energy for the cell through the breakdown of glucose and other molecules
• Involves many oxidation-reduction reactions, including the breakdown of glucose to CO2 and H2O

Energy Carriers

• ATP (Adenosine Triphosphate): the energy currency of the cell, holding energy temporarily in covalent bonds between phosphates
• ATP is generated in the presence (aerobic respiration) or absence (anaerobic respiration) of oxygen
• ~1 billion ATP molecules are in a cell at any one time, turned over every 1-2 minutes
• At rest, we produce our body weight in ATP every day; at maximal exercise, this number can increase to 0.5-1kg per minute

Anabolism and Catabolism

• Anabolism: the process of building molecules, such as the synthesis of glycogen from glucose
• Catabolism: the process of breaking down molecules, such as the breakdown of proteins to peptides
• Energy can be extracted from the breakdown of carbohydrates, proteins, and lipids

Cellular Respiration Pathways

• Glycolysis: a series of 10 reactions in the cytosol that produces 2 pyruvate molecules from 1 glucose molecule, producing 4 ATP molecules (net 2 ATP)
• Intermediate reaction: the process of pyruvate converting to Acetyl CoA, producing NADH and CO2
• Krebs Cycle: a series of 8 reactions in the mitochondrial matrix, producing 2 CO2, 3 NADH, one FADH2, and one ATP
• Electron Transport Chain: the process of electrons donated by NADH and FADH2 moving through protein complexes, generating ATP through the pumping of H+ and the formation of water

ATP Synthesis

• ATP synthase harnesses potential energy to generate ATP by combining ADP and Pi
• H+ are concentrated in the intermembrane space, creating an electrochemical gradient
• Energy is harvested from the flow of H+ down their electrochemical gradient through ATP synthase

Aerobic and Anaerobic Respiration

• Aerobic pathways: more efficient at producing ATP, producing 28-34 ATP molecules per glucose molecule
• Anaerobic pathways: less efficient, producing 2 ATP molecules per glucose molecule
• Glycolysis is faster but only produces net 2 ATP per glucose molecule, while the electron transport chain takes longer but produces 28-34 ATP molecules per glucose molecule