| Question | Answer |
| AA | -1/2 syn -1/2 diet -40-50g daily requirement |
| protein degradation | -all involve proteinases
-in cyt.
-catalysed by calpains or proteasomes |
| cathepsins | -lysosomal proteinases
-recycle aa from protiens |
| digestion of AA | -pepsin digestion
-acid denaturation & hydrolysis |
| pepsin | -secreted as pepsinogen(inactive zymogen)
-stomach acids modify (active) |
| enterokinase attaches... | -to membrane of enterocyte which activate trypsinogen
-causes cascade of proteinases |
| Active chymotrypsin | -N-term + charge
-forms ionic link W aspartic acid |
| action of peptidases | -hydrolyse peptide bonds
-in brush borders
-active/facilitated diffusion |
| Digestibility of proteins | -high efficiency
-proteinase inhibitors prevents digestion |
| Turnover of proteins | -7/8 essential aa recycled
-300g aa endogenous
-100g from diet |
| Nitrogen balance (-ve) | -starvation
-short term
-decr intake
-red. GI fn |
| Nitrogen balance (+) | -children & pregnant
-utilise to support protein syn. & growth |
| equilibrium | -healthy adults
-min=30-50g |
| essential AA | -must be oresent in diet
-his,leu,met,thr,val,ile,lys,phe,trp |
| his&arg | -semi-essential
-adults make enough but rate is too low |
| requirement for met... | -can be made by cysteine + CH3 + v.v |
| Tyr can be made from | -phe |
| limiting AAs | -all aa must be present for syn.
-continually supplied from diet
-aa catabolised if not used |
| complementary proteins | -2 low quality -combine to give overall aa balance |
