Flashcards in Metabolic Pathways and ATP Production 2 (Cholesterol/Hormonal control) Deck (13):
Recall four examples of blood-borne hormones which act as metabolic regulators
Explain glucagon's mode of action
Stimulates production of glucose:
Explain adrenaline's mode of action
Makes more glucose available to body for 'fight or flight' response
Similar mechanisms to glucagon
Explain glucocorticoids' mode of action
- Increase synthesis of enzymes concerned with glucose availability.
- Increases glucose available since rate of glucose-providing mechanisms increases
Explain insulin's mode of action
Stimulates uptake and use of glucose
Promotes storage of glucose as glycogen and fat
List the mechanisms of action for metabolic hormones
- Product inhibition
- Enzyme phosphorylation
- Allosteric effectors
- Change in enzyme levels
Explain the metabolic abnormalities in diabetes types 1 and 2 and describe the overall effect on the body's metabolism
Type 1 = Make insufficient insulin
Type 2 = Reduced responsiveness to insulin
Overall effect is that body metabolism becomes primed as if for starvation, regardless of dietary intake.
Summarise the synthesis of cholesterol from acetyl-CoA
1) Acetyl CoA (2C) -> Mevalonate (6C)
2) Mevalonate (6C)-> Isopentenyl-PP (5C)
3) Isopentenyl-PP (5C) elongated to squalene (30C)
4) Squalene undergoes cyclisation and demethylation to form Cholesterol.
Summarise the synthesis of steroid hormones
- Synthesised from pregnenolone (cholesterol)
- Pregnenolone generated by cholesterol desmolase
- Levels of steroid hormones are controlled by rate of synthesis and hence the rate of pregnenolone production
Summarise the synthesis of bile salts and acids
- Synthesised in the liver
- Regulated step is the conversion of cholesterol into 7-alpha-hydroxycholesterol involving cytochrome P450 monooxygenase
- Further reactions occur to form conjugated bile salts, excreted in aqueous form into GI tract
Explain the mechanism for transport of cholesterol around the body
Packaged inside a phospholipid monolayer with cholesterol and hydrophilic proteins making the hydrophilic inside. Cholesterol and other uncharged insoluble lipids travel around the body in the hydrophobic core of these packages.
What is the mechanism for cholesterol uptake in the body?
Endocytosis - LDL receptor trafficking