Download SSN SBPM Workshop~ Exam 3

SSN SBPM Workshop~ Exam 5
Multiple Choice Questions
**Last year’s handouts are available at
http://cpmcnet.columbia.edu/student/ssn/sbpmd/block5.htm
1. Which GI hormone is released in response to mechanical stretch?
A. CCK
B. Secretin
C. Gastrin
D. GIP
E. Motilin
2. Joe goes to famiglia and eats a delicious slice of Sicilian pizza. Less than 20 minutes
later in anatomy lab he strongly feels the urge to defecate. What is the most likely
mechanism?
A.
B.
C.
D.
Fundo-sigmoidal reflex
Gastro-colic reflex
Ileo-colic reflex
Flatulative reflex
3. Chronic administration of which of the following types of drugs would lead to a
sustained increase in serum gastrin levels?
A.
B.
C.
D.
Proton Pump Inhibitor
Anticholinergic
H2 receptor antagonist
Beta blocker
4. The delivery of chyme into the proximal small intestine will
A. Increase gastric acid secretion
B. Decrease pancreatic bicarbonate secretion
C. Increase gastric emptying of solids
D. Decrease circulating CCK levels
5. Which one of the following statements is correct?
A. Pepsin is inactivated at a pH of 3 and below
B. Gastric acid secretion is greatest during the cephalic phase of digestion
C. Somatostatin increases antral G cell gastrin release
D. Maximal acid output may be increased in a patient with duodenal ulcer
disease
6. Pyruvate is converted to acetyl CoA in the:
A.
B.
C.
D.
E.
Mitochondrial matrix
Cytosol
Smooth endoplasmic reticulum
Rough endoplasmic reticulum
Nucleus
7. When insulin levels are elevated, PFK2 acts as a ___________, levels of fructose-2,6bisphosphate are ___________ and glycolysis is ____________.
A.
B.
C.
D.
E.
Phosphorylase; low; inhibited
Kinase; high; inhibited
Phosphorylase; low; stimulated
Kinase; high; stimulated
Phosphorylase; high; inhibited
8. After secretion of trypsinogen into the duodenum, the enzyme is converted to its active
form, trypsin, by:
A.
B.
C.
D.
E.
Enteropeptidase
Procarboxypeptidase
Pancreatic lipase
Previously secreted trypsin
An alkaline pH
9. The transport protein responsible for entry of glucose into the intestinal enterocyte is
called:
A.
B.
C.
D.
E.
GLUT-2
GLUT-5
SGLT1
SGLT2
SGLT5
10. Which of the following sugars is absorbed from the small intestine by facilitated
diffusion?
A.
B.
C.
D.
E.
Glucose
Galactose
Fructose
Sucrose
A and B
11. Severe inflammation of the ileum may be accompanied by:
A.
B.
C.
D.
E.
Decreased vitamin B12 absorption
Decreased bile acid pool size
Increased colon absorption of water
Increased absorption of dietary fatty acids
A and B
12. Which is not a final destination of amino acid carbons?
A.
B.
C.
D.
E.
Glucose
Urea
CO2
Ketones
Tissue Protein
13. Which of the following enzymes catalyzes an irreversible reaction in Amino Acid
metabolism?
A. Glutamate Dehydrogenase
B. Transaminases
C. Glutamate Synthetase
14. Which of the following enzymes is not involved in the production of ammonia?
A.
B.
C.
D.
E.
Glutamate Dehydrogenase
Amino Acid Oxidase
Transaminase
Urease
Threonine Dehydrogenase
SSN SBPM Workshop~ Exam 5
Answers to Multiple Choice Questions
1. C
2. B
3. A.
Gastric acid secretion by parietal cells occurs in response to neural (acetylcholine),
hormonal (gastrin), and paracrine (histamine) excitatory inputs. Secretion of the parietal
cell involves the H+-K+-ATPase actively pumping H+ out of a cell in exchange for K+
entering the cell. Inhibition of pump activity leads to a prolonged increase in gastric pH
and the removal of the inhibitory effect of low pH (<3.0) on gastrin release.
4. C
The delivery of food into the proximal small intestine is accompanied by the appearance
of segmenting intestinal contractions. It also initiates neural reflexes and the release of
hormones that affect a variety of GI processes. It's inhibitory to gastric secretion and
emptying, stimulates pancreatic and hepatobiliary secretions (CCK, secretin), and
increases small intestine segmentation. The latter is responsible for mixing chyme with
bile and the digestive enzymes.
5. D
Gastric juice contains a number of secretions including HCl, intrinsic factor, pepsinogen,
water, and electrolytes. Gastric secretion can be studied during the interdigestive (basal
phase) or the digestive (cephalic, gastric, and intestinal phases of acid secretion) periods.
Increased acid output is the result of neural (ACh), hormonal (gastrin), and paracrine
(histamine) stimuli acting on the oxynitic cell. Feedback regulation )inhibition) of acid
secretion occurs as the result of ion-stimulated release of somatostation from paracrine
cells located near the gastrin-containing antral G cells and as the result of the presence of
chyme in the small intestine. The latter limits acid secretion via neural and hormonal
pathways. Removal of the intestinal inhibitory feedback leads to increased acid output.
6. A
Pyruvate dehydrogenase is a mitochondrial enzyme
7. D
High levels of insulin activate intracellular phosphatases. Dephosphorylated PFK2 is
most active as a kinase, so it phosphorylates fructose-6-phosphate to F-2,6-P. Increased
levels of F-2,6-P in turn allosterically activate phosphofructokinase-1, which is the key
glycolytic regulatory enzyme. This should make sense because insulin--secreted in the
fed state--stimulates the conversion of ingested carbohydrate into triglyceride by
converting glucose to pyruvate and onward.
8. A
9. C
10. C
11. E
12. B
The Nitrogen from amino acids becomes urea NOT the carbons
13. C
The irreversibility of the glutamate synthetase reaction limits ammonia toxicity,
especially in the brain.
14. C
SSN SBPM Workshop~ Exam 5
Short Answer Questions
Note: These questions may not be similar to the on-line short
answer questions for your exam. The purpose of these questions is
to explain topics in more detail than is allowed by the Multiplechoice format. Also, these questions offer an opportunity to go over
some topics that the SSN teachers do not have time to teach during
the SSN session.
1. Acidification of the duodenal mucosa results in…
The main response to acidic fluid in the duodenum is the stimulation of
secretin, which stimulates both the gall bladder & pancreas to release
bicarbonate. Secretin also slows gastric emptying to allow time for the
contents of the small intestine to be neutralized before even more acidic stuff
from the stomach enters.
2. Explain why, after a night of many beers, a person can become hypoglycemic the
next morning (helping to explain some of their righteous hangover).
Hint: One molecule of ethanol is metabolized in the body to one acetyl CoA, and in
the process, forms 2 molecules of NADH.
High levels of NADH are going to build up with ethanol ingestion. In this
heavily reducing environment, there will be a tendency for pyruvate to be
converted to lactate (remember that a buildup of NADH slows glycolysis
because free NAD+ is needed for the glyceraldehyde-3-P dehydrogenase
reaction). Also, lactate itself, a gluconeogenic precursor, will not be
converted back to pyruvate because of all the excess NADH. This isn't the
only reason why alcohol can lead to hypoglycemia, but it is an important
contributing factor.
3. What is the difference between feed-forward and feed-back regulation? Why is
one more common in disposal pathways?
In feed-back regulation, a downstream product of the pathway inhibits the
initiation of the pathway. In feed-forward, the downstream product stimulates
the pathway. Disposal pathways (such as the urea cycle) often involve feedforward stimulation, because as the amount of substrate increases, so does the
need for its disposal. Production pathways usually use feed-back inhibition to
limit the amount made.