Cell Homeostasis
To describe the ~composition and control of intracellular fluid and the~ mechanisms by which cells maintain their homeostasis and integrity
Cellular respiration describes the production of ATP through a series of redox reactions. Oxygen is used as the oxidising agent, whilst the catabolic fuel may be glucose, fat, or protein.
Cellular respiration can be broken down into:
- Glycolysis/Lipolysis/Proteolysis
- Citric Acid Cycle
- Electron Transport Chain
Glycolysis
Glycolysis, or the Embden-Meyerhof pathway, describes the production of pyruvate from glucose. Glycolysis:
- Occurs in the cytoplasm
- Begins with the phosphorylation of glucose to glucose-6-phosphate
- Produces:
- 2 ATP
- 2 Pyruvate
- 2 NADH
- Note that oxygen is not consumed and carbon dioxide is not produced
- In aerobic conditions:
NADH exchanges electrons across the mitochondrial wall, regenerating NAD+ and allowing glycolysis to continue - In anaerobic conditions:
NAD+ is regenerated through the production of lactate
Citric Acid Cycle/Kreb's Cycle
- Takes place in the mitochondria
- Complicated
- Can take many various substrates:
- Acetyl CoA
Produced by β-oxidation of fatty acids and pyruvate. - Pyruvate
- Ketoacids
- Acetyl CoA
- Does not consume oxygen but also doesn't function under anaerobic conditions, due to its requirement on fresh NAD+ from the ETC
- Produces:
- NADH
- FADH2
- CO2
Electron Transport Chain
- Final stage of carbohydrate, fat, and protein catabolism
- ETC consists of five protein complexes
- Electrons are passed along the chain and combine with oxygen, releasing energy which stimulates the movement of hydrogen ions
- Each time a hydrogen ion crosses the mitochondrial matrix, an ATP is produced
- This is called coupled phosphorylation
- Uncoupled phosphorylation allows hydrogen ions to travel down their gradient without generating ATP, which produces excess heat instead
- 36-38 ATP are produced by aerobic glycolysis
Sources disagree on exactly how much ATP is produced.- 2 from the Embden-Meyerhof pathway
- 34-36 from the CAC and ETC
References
- Chambers D, Huang C, Matthews G. Basic Physiology for Anaesthetists. Cambridge University Press. 2015.