nitrogen balance, amino acid degradation, urea cycle, glucose-alanine cycle, lipids Flashcards
what are the 5 main roles of the liver?
storage
regulates hormones eg. oestrogen
immune
synthesis of proteins
digestion (produces bile)
what are the resident macrophages of the liver?
WBC that undergoes phagocytosis that lives in tissues of liver
kuppfer cells
what substances does the liver store?
fats
minerals eg. iron as ferritin
carbohydrates
what are the 3 types of proteins synthesised by the liver?
albumin (pasma proteins)
clotting factors
compliment proteins
what are the 2 roles of albumin?
to maintain oncotic pressure
carrier protein
what is oncotic pressure?
the force keeping blood in the blood vessel
achieved by albumin pressing on the walls
what is albumin a carrier protein for?
unconjugated bilirubin
insoluble, hydrophobic molecule
which clotting factor ISN’T produced by liver?
8
vonwillibrand factor
which clotting factors are dependent on vitamin K synthesis?
10,9,7,2
what do compliment proteins do?
they are involved in immune response - mark pathogens
what are excess proteins stored as?
fat
what are the 2 pathways for recycling faulty proteins in the liver?
ie. degrading macromolecules back into constituent AAs
ubiquitin dependent - protein in cytoplasm that selectively binds to protein and signals to proteases to break it down
lysosomal - Kupfer cells phagocytose the protein, and then the lysosomes of the kuppfer cells fuse and secrete enzymes that break it down
what is the difference between a protein, polypeptide and dipeptide?
depends on how many peptide bonds with the molecule
protein has 50>
polypeptide has <50 but still a lot
dipeptide has 1 (2 monomers)
what are the main functions of amino acids? (4)
1) bond via peptide bonds to form proteins and polypeptides
2) broken down to be used as intermediates in the Krebs cycle
3) form nitrogenous proteins eg. ammonia, which needs to be excreted
4) can be used to from glucose (C backbone)
intake of nitrogen (3)
diet
bodily protein (fasted state)
de novo (newly synthesised)
outake of nitrogen (3)
excreted as urine
faecel loss
skin, hair, sweat
what is a positive nitrogen balance?
when more nitrogen intake then outtake
eg. bodybuilders
what is a negative nitrogen balance?
when less intake then outtake
eg. essential amino acid deficiency
what is transamination?
metabolism of amino acids to create metabolic intermediates to feed into TCA/krebs cycle
what is the transamination reaction?
amino acid + alpha ketoacid → alpha keto acid + amino acid
- swaps amine group
- the a-kacid becomes an intermediate for Krebs
- the aa gets NH3 removed in urea cycle
what is the most common transamination reaction?
alanine + alpha-ketoglutatate → pyruvate + glutamate (aa)
what is the catalyst for transamination reaction?
alanine aminotransferease (ALT) with pyridoxal phosphate (PLP)
what is pyruvate?
an alpha keto acid metabolic intermediate (gluconeogenesis and aerobic respiration)
produced In transamination
what is oxidative deamination?
- process to excrete toxic NH3 in urea cycle
- hydrolyses amino acid whilst preserving carbon back bone
what are the chemicals involved in oxidative deamination?
- glutamate (aa product of transamination)
- water (because its a hydrolysis reaction)
- glutamate dehydrogenease (catalysts)
- alpha ketoglutemate (recycled and used in body)
- NH3 (free ammonia, toxic, goes into urea cycle)
what is the reaction of oxidative deamination?
glutamate (aa) + H20 → alpha ketoglutemate + NH3
what is the functional use of ammonia?
- product of oxidative deamination
- used in urea cycle
why is ammonia neurotoxic?
it can cross the BBB and deplete alpha-ketoglutate
this impairs aerobic respiration and impacts krebbs
what are the 3 main Amino acids to the urea cycle?
- arginine
- orthinine
- citrulline
what are the 3 main steps of the urea cycle?
arginine split by arginase to form ornithine and urea (non-toxic)
ammonia and CO2 feed in and ornithine turns into citrulline
ammonia feeds in to regenerate arginine
what is the glucose-alanine cycle?
cycle where liver produces glucose for energy for muscle contraction
alanine is the main amino acid involved
what is the 1st step of the glucose-alanine cycle?
- reverse transamination in muscles to produce alanine
what is the 2nd step of the glucose-alanine cycle?
- alanine transported to liver
what is the 3rd step of the glucose-alanine cycle?
- transamination in liver . produces glutamate and pyruvate. glutamate undergoes oxidative deamination. pyruvate undergoes glucogensies to become glucose in the liver.
what is the 4th step of the glucose-alanine cycle?
- glucose transported to muscle cells
what is the 5th step of the glucose-alanine cycle?
- glycolysis of glucose to produce pyruvate for step 1
what are lipids?
macromolecules
in what form are they mainly stored in the liver as?
in adipocytes in white adipose tissue (some brown from brith)
what is the main intake of lipids?
TAGs from diet
what is the structure of a triglyceride?
1 glycerol with 3 fatty acids (ester bonds)
lipids are also stored in the liver as phospholipids, cholesterol, and fat soluble vitamins. which are the fat soluble vitamins?
A
D
E
K
what are the main functions of lipids? (4)
- energy reserve (largest in body)
- hormone metabolism
- shock absorbant (protects liver)
- form cell membrane components
how do lipids relate energy?
fatty acid beta oxidation breaks down the FAs
releases energy
what are the 4 biggest energy reserves in body? in order from lowest to highest
give energy in killer calories
- blood glucose 400kcal
- glycogen 600kcal
- muscle protein 30,000
- lipids 100,000
