Protein digestion Flashcards
exam 4
source of nitrogen-containing substances in the body, including proteins, heme, nucleic acids
Amino acids
used for fuel or for making glucose
excess amino acids
aa pool of blood supplies aa’s to
tissues
where is pepsin found?
stomach
where is trypsin found?
small intestine
where is chymotrypsin found?
small intestine
where is elastase found?
small intestine
where is carboxypeptidase found?
small intestine
propetide of pepsin binds at
high pH
pepsin is active at
low pH
which organ secretes bicarbonate to neutralize stomach contents?
Pancreas
pancreas is stimulated by ____ to release bicarbonate
CCK
key enzyme to convert zymogens to active enzyme
trypsin
released from the cells lining the small intestine to initiate trypsinogen conversion to trypsin
enteropeptidase
biochemical basis of inherited forms of pancreatitis stems from
overactive trypsin
mutations in trypsin
reduce binding to its inhibitor
transported across membranes using transporters that are specific for groups of aa
amino acids
amino acids are brought into cells typically using a
sodium-linked transporter
disease that results from a
defective transport
defective transport in cystinuria also leads to
elevated lysine because it uses the same transporter
build up of cystein leads to
cystine-based deposits in the kidney
loss of tryptophan because of a defective transporter
Hartnup
hartnup leads to
tryptophan deficiency
made from tryptophan
Niacin
D3: dementia, diarrhea, dermatitis
deficiency in niacin- Pellagra
difference btween Pellagra and Hartnup?
high tryptophan in urine in Hartnup
intracellular proteins recognized by _____________ and are tagged by _____________ and degraded by the ________
intracellular proteins recognized by E3 ubiquitin-ligase and are tagged by polyubiquitin and degraded by the proteasome
An initiating ______ ligates uniquitin to an E3 bound substrate
E2
signals for protein to be tagged can be
within the amino acid sequences
example of a signal within aa
identity of the N-terminal aa
HPV E6 protein to recruit E6-AP, an E3 ubiquitin ligase
facilitator protein
recognizes and ubiquitinates p53
E6-AP
products of proteosome are
short peptides
the short peptides are degraded to aa by
cellular proteases
example of an E3-type ubiquitin ligase that is associated with Parkinson’s disease
Parkin
re-used
ubiquitin
doesn’t allow ubiquitin recycling and might contribute to Parkinson’s
lack of deubiquintinase
more protein is ______ and _______ than used in the diet
broken down and re-made
amino acid pool turns over
frequently
disease of inadequate protein
kwashiorkor
has a lower ‘chemical’ score
vegetable-based protein
PVT TIM HALL
P- phenylalanine
V- valine
T- tryptophan
T- Threonine
I- Isoleucine
M- methionine
H- histidine
A- arginine
L- Leucine
L- Lysine
Over the course of a day, where does most of the tryptophan in the free amino acid pool come from in humans? (have to assume a typical American diet)
A. degradation of body protein
B. dietary meat
C. dietary vegetables
D. synthesis from a glycolytic intermediate
A. degradation of body protein (yes, about 3/4)
Parietal cells secrete
H+
Chief cells secreate
pepsinogen
acid release of parietal cells will activate
pepsinogen
Pancreas releases ___________ and _________ to neutralize the acid of the stomach
zymogen proteolytic enzymes and bicarbonate
pesinogen is activated to
pepsin
at higher pH, ____________ segment interferes with active site
pro-peptide
_________ will digest peptides
activated pepsin
mucosal cells will release ___ and ______ when acidic chyme passes through small intestine to duodenum
secretin and cck
cck causes bile duct of gall bladder to release
bile
secretin inhibits __________ function and stimulates ductal cells of pancreas to create _______
inhibits parietal cell and creates bicarbonate
pancrease releases ___________ and _________
bicarbonate and zymogens
the activating enzyme for trypsinogen is
enteropeptidase
trypsinogen is activated into
trypsin
trypsin cleaves at
lysine/arginine
cleaves ar large hydrophobic aa
chymotrypsin
cleaves small hydrophobic aa
elastase
cleaves sat the C-terminus
carboxypeptidase
all digestive proteolytic enzymes have the ability to degrade themselves
YEs
Which enzyme is tightly controlled in the pancrease
trypsin
inhibited trypsin can lead to
pancreatitis
nor hereditary of the pancreas
duct blockage
hereditary pancreas
mutation in trypsin
oligopeptides undergo action by _________ before absorption
aminopeptidase
when proteins finally meet enterocytes, they arrive as ______ or _______
a.a. or oligopeptides
in the enterocytes will catalyze the final breakdown into single AAs
peptidases
defective kidney transporter for cystine
cystinuria
due to lack of tryptophan transportation
Hartnup
lysosomal proteases that degrade extracellular proteins
cathepsins
pathway for intracellular protein degradation
ubiquitin-proteasome pathway
poly-ubi tag on protein is recognized by
proteasome
MHC I cells use _________________ to present peptide on extracellular surface
Tag transporter
recycles ubiquitin
deubiquitinase
proteasome has a _________ and a _______
regulatory particle and core particle
via proteolysis, the ______ of the proteasome will generate short peptides
core particle
edits wrongly tagged proteins
polybiquitin
which N-terminal is degraded the slowest
methionine
facilitates the degradation of p53
HPV E6
ubiquitation signals,
in the protein sequence and not variable
- N-end rule
- PEST sequence
- Destruction boxes
ubiquitation signals,
external factors and more variable
- phosphorylation
- denaturation/damage
- facilitators/chaperones
characterized by Lewy bodies in the brain which cause loss of neuronal cells and loss of dopamine
Parkinson’s disease
tagged by Parkin
Protein X
protein X deubiquitinase
UCH-L1
E3- ubiquitin ligase that with a mutation can lead to protein deposits
Parkin
characterized by incomplete protein or insufficient protein but sufficient calories
Kwashiorkor
How are essential AA attained?
from diet or degradation of body stores
higher chemical store
animal protein
