Liver & GI

Question 1

“Briefly outline the functions of the liver”

Syllabus + past question

Answer 1

	1. Storage
	- Metabolic fuel: Glycogen- ~100g & fat
	- Fat soluble vitamins
		○ Vitamin A → stored in stellate cells --> converted to retinol (active form). Contains 1-2yr supply
		○ Vitamin D → ~ 1-4 month supply
		○ Vitamin E & vitamin K - minimal
	- Vitamin B12 + folate (50% of body's storage for both)
	- Trace elements - iron (as ferritin), zinc, copper, selenium
	- Blood reservoir - ~ 500mL of blood

	2. Synthetic
	- Plasma proteins- albumin, α+ β globulins, fibrinogen
	- Nutrients - glucose, ketones, lipids, cholesterol, amino acids
	- Regulatory molecules (thrombopoetin, angiotensinogen)
	- Bile acids → stored in gallbladder

	3. Metabolic
	- Carbohydrate metabolism
		○ Liver is a glucostat -->  maintains strict BSL
			§ in conditions of ↑ glucose, glycogenesis & FFA synthesis will normalise BSL
			§ in conditions of ↓ glucose, gluconeogenesis will normalise BSL 
	- Lipid metabolism → free fatty acids (FFA). synthesised & packaged with as lipoproteins be transported to adipose tissue for storage 
			§ FFA oxidation will also produce energy. 
	- Protein Metabolism - amino acids can be transaminated, deaminated or decarboxylated to give acetyl- CoA

	4. Detoxification & excretion
	- Immunological detoxification:
		○ Kupfer cells act as scavengers & phagocytes & secrete prostaglandins
	- Ammonia → urea conversion via urea cycle
	- Conjugation of bilirubin & excretion in bile
	- Processing of drugs via:
		○ Phase I (oxidation & hydrolysis) and
		○ Phase II (conjugation) reactions