who typically has a positive nitrogen balance? correct answers young children and pregnant women
what is negative nitrogen balance a sign of? correct answers disease or starvation
what is nitrogen balance? correct answers the amount of daily nitrogen intake is equal to the amount of nitrogen ...
Bioc 385 module 7 || Already Passed.
who typically has a positive nitrogen balance? correct answers young children and pregnant
women
what is negative nitrogen balance a sign of? correct answers disease or starvation
what is nitrogen balance? correct answers the amount of daily nitrogen intake is equal to the
amount of nitrogen lost by excretion
when food enters the stomach through the esophagus, it stimulates the release of _____, a small
peptide hormone synthesized in the mucosal cells that line the stomach correct answers gastrin
gastrin triggers the release of gastric juices containing hydrochloric acid from parietal cells and
the secretion of pepsinogen from chief cells; pepsinogen is in the _____ state, or zymogen, of the
protease pepsin. the resulting increase in acidity (pH~2) in the stomach denatures the dietary
proteins resulting in greater exposure of peptide bonds for _____. the low pH in the stomach also
results in the activation of the protease by autocatalytic cleavage of _____ to expose the protease
active site, and now it is in the active form known as _____, that is maximally active at a pH
value of ~2 and preferentially cleaves polypeptide bonds on the amino-terminal side of aromatic
amino acids Phe, Trp, and Tyr correct answers inactive; hydrolysis; pepsinogen; pepsin
the highly acidic slurry of digested food, called _____, leaves the stomach by passing through
the pyloric valve and into the _____, which is the first section of the small intestine correct
answers chyme; duodenum
what is the role of secretin? correct answers stimulates the pancreas to release an alkaline fluid
containing bicarbonate (HCO3-), which neutralizes the chyme
when chyme leaves the stomach, the release of which two hormones is the result? correct
answers secretin and cholecystokinin
what protease that specifically activates several proteolytic zymogens released from the pancreas
is also secreted by the duodenum? correct answers enteropeptidase
enteropeptidase is able to cleave a pancreatic zymogen called _____ to form the endopeptidase
trypsin at a pH of ~7 correct answers trypsinogen
an activated trypsin enzyme cleaves numerous pancreatic zymogens to amplify the proteolytic
cascade. what are they? correct answers chymotrypsinogen, proelastase, procarboxypeptidase,
trypsinogen
the combined activity of the pancreatic proteases and the _____ and _____, which are located on
the membrane of intestinal mucosal cells, generates peptides and amino acids correct answers
aminopeptidases; dipeptidases
, the peptides and amino acids generated are transported into intestinal epithelial cells before being
exported to where? correct answers the blood
what are the two pathways of degradation by eukaryotic cellular proteins? correct answers 1. an
ATP-independent process that degrades proteins inside lysosomes, which are derived from Golgi
membranes
2. an ATP-dependent process that degrades proteins containing a polymer of ubiquitin protein,
occurring in a proteasome
degradation of eukaryotic cellular proteins is mediated by _____ and _____ correct answers
lysosomes; proteasomes
lysosomes contain acidic proteases that nonselectively digest protein particles derived to
lysosomes by _____ or _____ correct answers phagocytosis; endosomal fusion
proteasomes degrade ubiquitinated proteins by using three different protease activities located
within the _____ correct answers central core
the proteasome consists of a _____ core particle and two _____ regulatory particles, which serve
as caps to regulate protein entry into and exit from the proteolytic core correct answers 20S; 19S
the 19S complexes contain binding sites for ubiquitinated proteins and also encode _____
hydrolyzing enzymes that function in protein unfolding, which is required before the polypeptide
can enter the internal chamber and be degraded correct answers ATP
the intact proteasome, consisting of _____ regulatory subunits and the proteolytic core, has a
sedimentation coefficient of _____ correct answers two; 30S
what are the three classes of proteins involved in ubiquitination? correct answers 1. E1 enzymes
that attach ubiquitin to E2 enzymes
2. E2 enzymes that attach ubiquitin to target proteins
3. E3 proteins that facilitate ubiquitination of target proteins by forming heterotrimeric
complexes with E2 enzymes and target proteins
what is the first step of attachment of ubiquitin to a target protein? correct answers ubiquitin
covalently attached to cysteine residue in E1 active site through ATP-dependent reaction,
involving Gly76
what is the second step of attachment of ubiquitin to a target protein? correct answers E1
associates with E2 enzyme and transfers the ubiquitin to cysteine residue in E2 active site
what is the third step of attachment of ubiquitin to a target protein? correct answers each E2-
ubiquitin complex binds to E3 enzyme to form E2-ubiquitin-E3 complex
what is the fourth step of attachment of ubiquitin to a target protein? correct answers complex
attaches ubiquitin to target proteins recognized by the complex
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