week10 : postmortem Flashcards
what is the basic unit of collagen
tropocollagen
how is made type 1 collagen
from two alpha 1 chains and one alpha 2.
in type III collagen there is ___ alpha ___
three alpha 1
what are the most common amino acids found in collagen
glycine proline alanine hydroxyproline hydroxylysine.
what is the repeating unit of amino acids in collagen
gly-proline-hydroxyproline or hydroxylysine
what type of collagen is this : side by side arrays and colaent cross-linking to stabilize and strengthen the structure.
striated (fibrous)
when you get older, the number of cross-linking ____ in collagen fibers
increase
t or f : in collagen fibrils, the structure is old together by hydrogen cross-linking
false, it is covalent cross-linking
what is the most common amino acids of elastin
glycine
Elastin has ____ and ____ cross-linking
lysinorlysine and desmosine cross-linkage
Lysinorlysine is from the cross-link between ___ and ____
allysine and lysine
how is formed allysine
from the oxidation of lysine from the enzyme lysyl oxidase
What is particular of the desmosine cross-linking ?
derived from four lysine chains.
what is the cross-linkage mostly responsible for restoring the elastin shape
desmosine (4 lysine chains attached to phenylalanine).
why is there rigor mortis
because of the lack of ATP meaning that there is no way to reduce the Ca2+ levels and so the muscles are stuck in the contraction.
how long is the delay phase
12h
how long is the resolution phase
from few days to 2 weeks
what are the different phases in muscle conversion to meat
delay phase
rigor phase
resolution phase
what is p94
it is a calpain-3, activated by submicromolar calcium concentrations
where are concentrated the calpains in the skeletal muscles
in the z-disk
what is the target of the calpains
z disk
the calpains degrade ____ and __ and _____ proteins as well as other proteins ____
titin
troponin-T
nebulin
other proteins in the Z disk
T or F : the cathepsins are mediated by calcium levels
false, only the calpains are
the ___ is involved in th degradation of actin and myosin
proteosome
The final pH (5.5) is close to the isoelectric point of ___
myosin
Why is there water excuding of meat?
The final pH (5.5) is close to the isoelectric point of myosin so there is a aggregation of the proteins and a decrease in the water holding capacities of meat.
what is dark meat
meat that has a final pH that is high because of early termination of glycolysis since there is not a lot of glycogen.
T or F : myoglobin is one of the most heat stable muscle proteins and retain structure up to 50˚C
true
