Cell Biology Lecture Week 4

Apoptosis

• Apoptosis is a process of programmed cell death.
• Apoptosis was first described in 1972.
• After apoptosis, macrophages play a role in removing the dead cells.
• The nematode worm Caenorhabditis elegans provided significant knowledge about apoptosis.

Proteins and Pathways

• Proteins that initiate apoptosis in mammals are called pro-apoptotic proteins.
• Caspases play a role in apoptosis by acting as executioner proteins.
• The intrinsic pathway of apoptosis involves the mitochondria.
• p53 is a tumor suppressor protein that plays a role in apoptosis by triggering cell death in response to DNA damage.
• The extrinsic pathway of apoptosis is triggered by the binding of death ligands to death receptors.

Metabolic Pathways

• Enzymes play a key role in metabolic pathways by catalyzing reactions.
• Anabolic pathways are referred to as synthetic pathways because they build complex molecules from simpler components.
• Coupling exergonic and endergonic reactions in a cell allows for the transfer of energy from one reaction to another.
• Catabolic pathways break down complex macromolecules into simpler components.
• The sum total of all reactions happening in a cell at the same time is referred to as metabolism.
• Endergonic reactions have a positive ΔG because they require energy input.
• ATP hydrolysis involves the breakdown of ATP into ADP and inorganic phosphate.

ATP Structure and Function

• The structure of ATP consists of a central ribose, a nitrogenous base called adenine, and three phosphate groups linked by a phosphoanhydride bond.
• Each cell in the body uses approximately 1-2 million ATP molecules per minute.
• Approximately 1-2 pounds of ATP are produced per day.
• Oxidation plays a key role in ATP production by generating energy through the breakdown of glucose.
• During a highly exergonic reaction, glucose is converted into ATP and carbon dioxide.
• The energy released from glucose oxidation drives the formation of ATP from ADP and Pi.