Protein biochem overview Flashcards
List a number of different ways to categorize amino acids.
chemical properties (acidic/basic, polar/non), essential vs non-essential, side chain structures, usage in other metabolic pathways
What are conditionally essential amino acids
These amino acids can be made by the body, but the capacity for their synthesis is limited, and in states of high consumption, deficiency may develop.
Which metabolic pathways can aa be used in
gluconeogenesis, ketogenesis
Describe how proteins are broken down to amino acids in the gut and in tissues.
Gut: broken down by peptidases activated in the gut lumen. Break down long peptides into amino acids which are absorbed and enter circulation. Tissues: ubiquination (proteasome degradation) and degradation in lysosomes
Describe the flow of nitrogen from an amino acid to urea.
Transamination rxns are bidirectional- NH2 is removed from aa or added to carbon skeleton to mak an aa. AA donates NH2 to alpha-ketoglutarate (aminotransferase) > forms L-glutamate and alpha keto acid > release of NH3 and regeneration of alpha ketoglutarate > NH3 (ammonia) leaves via urea cycle
generally describe urea cycle
Ammonia from transamination >converted to carbamoyl phosphate (carbamoyl phosphate synthase 1) > N enters urea cyle and is combined with ammonia to form urea
glutamine importance
aa which can accept N from other aa in peripheral tissues, carry it to the liver and kidney where it is donated to glutamate, then to alpha ketoglutarate
list sulfur containing aa
cysteine and methionine
cysteine importance
Forms disulfide bridges that change protein conformation. Glutathione (tri peptide containing cysteine) serves as redox buffer and protects against free radical injury
Importance of methionine
S-adenosylmethionine (SAM) is an energy source for a number of important biochemical reactions. In addition, it is a methyl donor. SAM is also a precursor for homocysteine which is important in vascular dz, wound healing and B12/folate metabolism
