Protein Metabolism and Nitrogen Balance Flashcards
(32 cards)
How are proteins absorbed
- absorbed in ileum as amino acids via secondary active transport
- digestion is slow ( hours )
Describe protein concentration in tissues and what happens to excess
- high turnover between tissues = rapid distribution
- will be expelled in urine if there is too much and proximal tube can’t reabsorb
Describe the metabolism of proteins
- broken into amino acids which are used for energy
- Amino acids undergo deamination which breaks it into glucose, fatty acids and ketone and Ammonia
- ammonia is expelled in urea
How are amino acids stored? what happens when protein is needed?
- free amino acids can’t be stored so they combine to form peptides and intracellular proteins
- when protein is needed intracellular proteins are degraded into amino acids and the transported in blood
Where are proteins stored
- liver stores most proteins along with kidneys and intestinal mucosa
- can’t be stored by cells unless AA convert to fat/glycogen
What influences the storage of amino acids
- hormone and insulin increases protein synthesis
- glucocorticoid mobilize amino acids for energy
What are the 4 plasma proteins and their function
- Albumin : generates osmotic pressure
- Globulins : innate and acquired immunity
- Transferrin : carry ferrous ions
- Fibrinogen: mediates clot formation and repairs leaks in Circulation
What produces plasma protein and what can affect the rate of production
- plasma is formed by the liver
- in stress conditions production increases
- in liver disease it decreases and thus causes oedema
List the 4 stages of protein metabolism in liver
1- Transamination
2- Deamination
3- Oxidation
4- Excretion
Describe Transamination & the main substrate used
- amino group transferred from amino acid to alpha keto acid by aminotransferase
- glutamine amino is usually used
What is the effect of aminotransferase on protein synthesis
aminotransferase used vitamin B6 which decreases protein synthesis
Describe Deamination
- amino group is removed from amino acids
- amino acid is converted to ammonia which is excreted in urea
Describe role of alpha ketoglutarate
- amino acid and alpha ketoglutarate through aminotransferase will make glutamate and alpha keto acid.
- glutamate will make ammonia
- alpha ketoglutarate can also enter TCA cycle (gluconeogenesis )
Explain Gluconeogenesis and amino acids
- alpha ketoglutarate will enter TCA cycle which contains amino acids
- amino acids can also generate pyruvate
Explain Ketogenesis and amino acids
- amino acids can create Acetyl CoA
- synthesise ketones and lipids
What are the 5 classes of amino acids
1- Essential 2- Non-essential 3- Glucogenic 4- Ketogenic 5- Glucogenic and Ketogenic
How is Urea formed
- Ammonia released from deamination is ionized with carbon dioxide to create ammonium ( NH4)
- one amino from ammonium makes citrulline that combines with amino from aspartate to make arginine that with water becomes urea
What does Urea contain
Ornithine Carbamoyl phosphate ( reactor ) Citrulline Aspartate ( reactor ) Arginiosuccinate fumarate arginine = urea
What is the purpose of Urea
prevents toxic build up of ammonium
how is Protein used as a source of energy and when
- used for gluconeogenesis
- only used if all carb and fat stores are used
What happens with liver phosphorylase deficiency
- will not be able to mobilize glycogen from liver and thus gluconeogenesis and ketogenesis will be used for fuel
Growth hormone effect protein metabolism
- promotes synthesis of cellular protein
- increase amino acid membrane transport
- increase RNA transcription
Insulin effect on protein metabolism
- promotes cellular uptake of AA
- inhibits protein catabolism
- increase RNA transcription
- decrease gluconeogenesis
What hormones are needed for protein synthesis
- growth hormone and insulin
- needed TOGETHER
