Intro to metabolism Flashcards
What is the action of the liver relating to glucose?
Coverts fructose and galactose into glucose
Excess glucose converted (anabolised) into glycogen as an energy store
Glycogen stored in liver, muscle or combined with AAs to make fat
What are the proteases and where do they act/come from?
Pepsinogen/pepsin from stomach
Trypsin, chymotrypsin, elastase and carboxypeptidase from pancreas
Aminopeptidases in SI
What is protein broken down into in digestion?
Amino acids
how are amino acids absorbed and used?
absorbed into intestinal capillaries and transported to liver via hepatic portal vein
Modified to keto acids (for energy) and plasma bodies
Most AAs enter systemic circulation via caudal vena cava unaltered
AAs synthesised into different proteins in cells for intracellular functions or export from cells (e.g., enzymes)
how are triglycerides broken down?
emulsified by bile salts
hydrolysed by enzymes into monoglycerides which are dissolved into micelles
Micelles freely enter intestinal cells where triglycerides are re-synthesis from glycerol and fatty acid
triglycerol + cholesterol + lipoproteins = chylomicron
what hormones regulate storage and recycling of blood sugar?
Insulin from b-cells from Islets of Langerhans in pancreas
Glucagon from a-cell from Islets of Langerhans in pancreas
What is the action of insulin?
acts on liver =>converts glucose to glycogen (glycogenesis)
Acts on tissue cells => take up glucose from blood
lowers blood sugar
what is the action of glucagon?
Acts on liver => stimulates glycogen breakdown into glucagon (glycogeolysis)
Raises blood sugar
what are some non-carbohydrate energy substates?
during exercise - muscle glycogen broken down into lactate => liver => become substrate in gluconeogenesis
During fasting - fat broken down (lipolysis) => releases free fatty acids + glycerol => liver => used as substrate for gluconeogenesis
What is the fate of excess amino acids?
disposed via deamination
AAs then enter energy production pathways as pyruvate, acetyl CoA or components of Kreb’s cycle
Deamination releases ammonia (toxic) => converted to urea in liver and excreted in urine
What is the fate of lipids?
chylomicrons carried by lacteals into lymphatics and bloodstream => stored as adipose tissue
Some chylomicrons circulate to liver for:
- storage if there is an overwhelming influx in adipocytes as triacylglycerol
- converted to other molecules
- used as an energy substrate
what is the by-product and effect of fat metabolism?
ketone bodies produced by liver
source of energy but cause ketosis if they build up - acidic
What enzymes control fat metabolism?
Hormone sensitive lipase (HPL):
- hydrolyses fatty acid from triacylglycerol molecule => fatty acid and diglyceride
- or hydrolyses fatty acid from diacylglycerol molecule => fatty acid and monoglyecride
- Releases lipid from storage
Lipoprotein lipase (LPL):
- degrades circulating triglycerides in bloodstream to be taken up by tissues
- Storage of lipids in tissues
What gland controls metabolic rate?
thyroid gland under hypothalamus and pituitary influence
what are the signs that the liver is not functioning in its metabolic role?
Liver cells swell => hepatomegaly
Compromised liver cells release cell markers into blood:
- liver enzymes
- alkaline phosphatase (ALP)
- alanine aminotransferase (ALT)
