SACE Biology: Cell Metabolism Study Notes

Cell Metabolism Overview

• Cell metabolism: sum of all biochemical processes in cells.

• Eukaryotic cells engage in thousands of processes; prokaryotes depend on hundreds.

Internal Membranes and Organelles

• Eukaryotic cells contain membrane-bound organelles where reactions are catalyzed by enzymes.

• Mitochondria: internal membranes (cristae) increase surface area for ATP synthesis.

• Chloroplasts: thylakoid stacks (grana) host chlorophyll for trapping light energy in photosynthesis.

Glycolysis and Enzymatic Importance

• Example of glycolysis highlights the importance of enzymes in metabolic pathways.

• ATP production is a critical aspect; bioprocesses must generate manageable heat.

Energy in Reactions

• Exergonic reactions: energy release when stable bonds form (heat produced).

• Endergonic reactions: energy uptake leads to cooling.

Environmental Influences on Metabolism

• Environmental factors affect enzyme-catalyzed reactions and metabolic processes.

Chemical Interference

• Chemicals can impede metabolism (poisons) with varying effects on organisms.

• Irreversible inhibitors alter enzyme structure, impacting cell function.

• Cyanide: disrupts cytochrome in the electron transport chain; affects ATP production.

• Acetylcholine mimicking toxins block nerve transmission, causing paralysis.

Specific Toxins and Their Effects

• Novichok: inhibits acetylcholinesterase, causing muscle contractions.

• Antibiotics (e.g., tetracycline, rifampicin) target bacterial metabolic processes but can lead to resistance.

Harmful Effects and Usage of Chemicals

• DDT: a bioaccumulating insecticide with serious ecological effects but used for malaria prevention.

• Sulfur dioxide: used in food preservation, poses allergy risks.

• Thalidomide: past effectiveness for morning sickness resulted in severe birth defects; now limited use for cancer treatment.

• Antibiotics: revolutionized medicine but risk of antibiotic resistance rises.