22207424
Description
Flashcards by Evian Chai, updated more than 1 year ago
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Created by Evian Chai
over 4 years ago
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| Question | Answer |
| What are the 3 functions of protein in the body? | 1. Blood glucose during starvation 2. Protein 3. Special compound synthesis (eg. purines, carnitine, creatine, neurotransmitters) |
| Why do we need dietary protein? | There is no long term storage of protein, as is it constantly degraded and synthesised Dietary protein needed as a result |
| Amino acids are present in low concentrations in cells/bloodstream that make up the amino acid pool-where does the surplus go? | Catabolised into fats/carbs+nitrogen in the urea |
| What are the 20 essential amino acids? | Very Many (Hairy) Little Pigs live In The Toilet (Africa) -Valine, methionine, histidine, lysine, phenylalanine, leucine, isoleucine, threonine, tryptophan, arginine |
| How many of the essential amino acids are synthesised naturally in the human body? | 10 |
| When intake/protein synthesis>excretion/protein breakdown, the nitrogen balance is .... When does this occur? | The nitrogen balance is positive Occurs during growth, pregnancy, convalescence |
| When intake/protein synthesis<excretion/protein breakdown, the nitrogen balance is .... When does this occur? | Negative Occurs during starvation, illness, cancer, injury |
| How are endogenous (most) old/damaged proteins broken down? | Via the Uniquitin breakdown system which: - marks them via proteosome - alters location - alters protein interactions/cell activity |
| How are exogenous proteins (eg. muscle) broken down? What affects the rate of muscle breakdown? | 1. Taken into vesicles via endocytosis 2. Vesicles fuse with lysosomes 3. Proteolytic enzymes in lysosome break protein into amino acids Hormones eg. cortisol increase |
| What are 5 major roles the liver plays in protein metabolism? | 1. Remove AA/Glucose/Fats from blood 2. Absorb amino acids to make cellular/plasma proteins, haem/purins, pyrimidines for DNA/RNA 3. Degrade AA 4. Convert NH3 to urea, excreted in kidney 5. Transport of AA/Ammonia |
| How do the rates of structural/hormonal protein breakdown differ? | - Structural protein such as collagen have half lives of years - Hormones & digestive enzymes degrade very rapidly, with half lives of minutes |
| What are the two ways amino acids are broken down? | 1. Transamination 2. Deamination |
| What occurs during transamination, and what is this process important for? What catalyses this reaction? | The amino group on one amino acid is transferred to a carbon skeleton (keto acid) to form a new amino acid Important for creating amino acids not available Aminotransferase |
| What does an amino acid become once its amino group it removed? | Keto group (double bond O replaces amine group) |
| What occurs during oxidative deamination? Which amino acid (s) are capable of undergoing this? What enzyme catalyses this? | The amine group (NH2) is removed as NH3 (ammonia), which then goes to the urea cycle. Leaves behind a keto acid Glutamate Glutamate dehydrogenase |
| How is glutamate formed? The amino group from... is passed onto ... to form a carbon skeleton (...) and glutamate | Glutamate is formed via transamination Alanine Oxologlutarate Pyruvate |
| What happens to keto acids (formed after amino acids lose amino group)? What are these referred to as? Which two keto acids does this whole process not happen for? | First converted to acetyl CoA Then oxidised to CO2/H20 by TCA cycle to provide intermediates Ketogenic Amino acids Lysine and Leucine can only be degraded to acetyl CoA |
| Glucogenic Amino Acids are called this because | They can be converted back to glucose during periods of starvation by becoming pyruvate (Oxo acid)-->TCA Cycle-->Glucose+H20+CO2 |
| How many amino acids are glucogenic? Which two ketogenic amino acids also classify as glucogenic? | 13 Phenylalanine and tyrosine |
| Amino acids are transaminated in muscles and transported in the blood as these 4 amino acids: | 1. Alanine, which goes to the liver - removal of amino group from alanine produces pyruvate for glucose/used as acetyl CoA in the TCA cycle 2. Glutamate 3. Glutamine (both 2/3 carry NH3) 4. Aspartate - in urea cycle |
| What is the role of glutamate/glutamine, and why are they effective? | They are carrier proteins for ammonia to the liver, where it will be converted to urea for excretion They are - safe - Glutamine can carry 2 amino groups (2-oxoglutarate <--> glutamate <--> glutamine) |
| What is NH2 carried in the blood as? | Glutamine |
| What is glutamine's role in pH regulation? | Carries ammonia to kidney for pH regulation |
| What is the equation for the urea cycle? | NH4+ + CO2 + 2ATP to NH2CO(P)+ 2ADP+ Pi |
| What are the 4 end products of nitrogen metabolism? | 1. Urea from the urea cycle 2. Creatinine from creatinine phosphate breakdown (high energy phosphate reserve) 3. Uric acid from DNA/RNA breakdown 4. Ammonia from control of body pH |
| What is the simplified urea cycle? | Ornithine-->cirtrulline Citrulline+aspartate-->arginosuccinate via Arginosuccinate-->arginine + fumarate (back into TCA) Arginine-->Urea + ornithine |
| What can the neurotoxicity of ammonia lead to? | Cerebral oedema, coma, death, cell death |
| What is Hyperammonaemia? What are two things it is caused by? | Impaired conversion of NH3 to urea 1. Liver failure - Viral hepatitis - Ischaemia - Liver cirrhosis - Toxins (aflatoxin in moodily peanuts) 2. Genetic defects - Reduction in catalytic activity of any enzyme of the urea cycle - ornithine transcarbamoylase deficiency X linked inheritance (1 in 30,000 live births) |
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