Amino Acid Oxidation & the Urea Cycle (Biochemistry) Flashcards
What many amino acids are hydrophobic?
9
How many hydrophillic amino acids are there?
6
What are the charged amino acids that are acidic (negatively charged)
- Aspartic acid
- Glutamic acid
What are the charged amino acids that are basic (positively charged)
- Lysine
- Arginine
- Histidine
What is Autophagy?
Cells break down their own components
Why does Autophagy occur?
- Shortage of nutrients
- Break down worn out organelles
What occurs to dietary amino acids that exceed body’s protein syntehsis?
They are degraded
Where does protein degradation happen?
In the gastrointestinal track
What is the function of pepsin?
Cutting protein into peptides in the stomach
Where does Trypsin and chymotrypsin cut proteins or large peptides?
Small intestine
What does aminopeptidase and carboxypeptidase A and B does to peptide in the small intestine
Degrade peptide into amino acids
What is the transportation pathway for amino acids?
Intestinal epithelium -> Blood -> Liver
What aare the issues with amino group metabolism?
Produce ammonium (NH4+) which is toxic
What removes alpha amino acids in Enzymatic transamination?
Aminotransferases
What does all aminotransferases require?
Pyridoxal phosphate cofactor
What is L-Glutamate function in Enzymatic Transamination?
Act as a temporary storage of nitrogen
What alpha - ketoglutarate accepts amino groups with?
L-glutamate
What is Glutamine?
Non toxic transport form of ammonia
What is released when Glutamine enters liver mitochondrias?
Ammonium ion
What is the Glucose-Alanine Cycle?
Excess nitrogen in extrahepatic tissues travels to the liver as amino acids
How is pyruvate coverted to alanine?
Recieving an amino group from glutamate
In pyruvate what is ammonium group replaced by?
Oxygen
What happens in Glutamate Dehydrogenase Reaction?
Two-electron oxidation of glutamate followed by hydrolysis
What is the net process of glutamate?
Oxidative deamination
Where does Glutamate Dehydrogenase Reaction occur?
In the mitochondrial matrix
What can be used as an electron acceptor in Glutamate Dehydrogenase Reaction?
NAD+ or NADP+
What do aquatic vertebrates release into the environment?
Ammonia
What are the methods of ammonia release into the environment by aquatic vertebrates?
- Passive diffusion from epithelial cells
- Active transport via gills
What does terrestrial vertebrates and sharks excrete?
Urea
What does birds and reptiles excrete?
Uric acid
What are the upsides to urea?
- Less toxic than ammona
- Very soluble
What are the upsids to uric acid?
- Insouble
- Excretion as paste allows to conserve water
What are ammonotelic anaimals?
Most aquatic vertebrates (e.g bony fishes)
What are ureotelic animals?
Terrestrial vertebrates and sharks
What are uricotelic animals?
Birds and reptiles
What is the purpose of synthesis of carbamoyl phosphate?
Recapturing ammonia
What is the 1st step of the urea cycle?
Carbamoyl phosphate donates carbamoyl group to Ornithine
What is the second 2nd step of the urea cycle?
Entry of Aspartate into the urea cycle
- Requires ATP and move through an intermediate step
What is the second nitrogen acquiring reaction catalysed by?
Argininosuccinate synthetase
What is step 3 in urea cycle?
Argininosuccinate is cleaved releasing fumarate & arginine
What is the enzyme in step 3 of the urea cycle?
Argininosuccinase
What is the side reaction in step 3 of the urea cycle?
Can enter mitochodnria to join the pool of citric cycle intermediates
Arginine is cleaved to release urea and Ornithine. What stage of the urea cycle is this?
Step 4
What is the catalystic in stage 4 of the urea cycle
Arginase
How is the Urea Cycle regulated?
- Protein rich diet
- Starvation
What is the long term to urea cycle regulation?
Regulation of the 4 urea cycle enzymes and carbamoyl synthetse I in the liver (Higher synthesis rates in starving animals)
What is the short term regulation to urea cycle?
Activationr egulation of carbamoyl synthetase I via N-acetylglutamate synthase
What links the urea and citric acid cycle?
Arginosuccinate Shunt
How much does Arginosuccinate Shunt save?
3 ATP
What are the amino acids that are used in Acetyl-CoA?
Leu (Leucine),
Ile (Isoleucine),
Thr (Threonine),
Lys (Lysine),
Phe (Phenylalanine),
Trp(Tryptophan),
Tyr (Tyrosine)
What are the amino acids used in pyrvuate?
Ala (Alanine),
Thr (Threonine),
Trp(Tryptophan),
Cys (Cysteine),
Gly (Glyine),
Ser (Serine),
What is the amino acids used in succinyl-CoA?
Met (Methionine)
Val (Valine)
Ile (Isoleucine),
Thr (Threonine),
What are the amino acids used in alpha-ketoglutarate
Arg (Arginine)
Glu (Glutamic acid)
Gln (Glutamine)
His (Histidine)
Pro (Proline)
What are the two amino acids used in fumarate?
(Phe) Phenylalanine
(Tyr) Tyrosine
What molecules are ketogenic?
- Acetoacetyl-CoA
- Acetyl-CoA
What molecules are Glucogenic?
- Pyruvate
- OXaloacetate
- Fumarate
- Succinyl-CoA
- Alpha-Ketoglutarate
What amino acids are exclusively ketogenic?
Lecuine, Lysine
What molecule is exclusively Glucogenic?
Arginine,
What amino acid is both ketogenic and glucogenic?
Phenylalanine, Tryptophan, Isoleucine, TYrosine
