PCOL 838 COMPLETE EXAMINATION TEST
QUESTIONS WITH VERIFIED SOLUTIONS
●● How much protein should be consumed each day? (11/19)
Answer: Humans are dependent on essential amino acids & adequate
total protein. Both quantity and quality of the dietary protein is very
important. Requirements are 0.8g protein/Kg body weight; 56g for
average male and 44 g for average female; average US consumption is
about 120 g per day.
●● What is the function of proteases? (11/19)
Answer: Proteases breakdown proteins into peptides and amino acids in
the stomach and intestine.
●● What causes Kwashiorkor? What are the signs? (11/19)
Answer: Protein deficiency despite of adequate calories
- Edema and distended abdomen
- Muscle wasting due to the lack of essential amino acids
- Compounded by inability to make digestive enzymes and new
intestinal epithelial cells
●● What initiates protein breakdown in the stomach? (11/19)
Answer: Pepsin initiates the protein breakdown in the stomach
,●● How is pepsinogen activated? (11/19)
Answer: Gastric parietal cells produce HCl which causes a
conformational change to activate pepsinogen to pepsin, an autocatalytic
process. Acid is also important in denaturing dietary proteins and
unfolding them.
●● Where does pepsinogen come from? (11/19)
Answer: Pepsinogen is secreted by the chief cells of the stomach.
●● Bicarbonate is responsible for _____. (11/19)
Answer: neutralizing the stomach acid that has reached the small
intestine
●● Bicarbonate is first released from the pancreas then the pancreatic
enzymes, besides digesting the proteins what else are they capable of
digesting? (11/19)
Answer: The digestive enzymes digest
themselves too.
- They also digest the intestinal cells, which are constantly replaced by
the precursor cells
●● What is inspissation? What does it lead to in the pancreas? (11/19)
,Answer: Inspissation (drying and thickening) of pancreatic exocrine
secretions
- Leads to obstruction of ducts
- Inability of pancreatic enzymes to enter intestinal lumen
- enzymes can't reach the small intestine because of the mucus buildup,
causing pancreatitis
●● Which zymogen is especially important to activate the rest of the
zymogens? (11/19)
Answer: trypsinogen (zymogen) --(enteropeptidase)--> trypsin (active
enzyme)
●● How is carbamoyl phosphate synthesized? (11/26)
Answer: Carbamoyl phosphate is a high energy compound, requiring 2
ATPs for formation from carbon dioxide and ammonium ion.
-first step of the urea cycle
●● Which enzyme catalyzes the first step of the urea cycle? (11/26)
Answer: Carbamoyl phosphate synthetase I (CPSI), the enzyme that
catalyzes this first step of the urea cycle, is found mainly in
mitochondria of the liver and intestine. CPSII, located in the cytosol, is
for pyrimidine biosynthesis.
, ●● Which products of the urea cycle can cross the mitochondrial
membrane? (11/26)
Answer: Ornithine and citrulline are exchanged for one another across
the mt membrane
●● Ornithine is an amino acid, why does it not appear in proteins?
(11/26)
Answer: ornithine is very abundant, but no codon matches for ornithine,
so it does not happen in nature
not an essential amino acid
●● How is ornithine synthesized? (11/26)
Answer: Ornithine is normally regenerated by the urea cycle.
Ornithine also can be synthesized de novo by a transamination reaction
catalyzed by ornithine aminotransferase under specific conditions in the
intestine. Note: PLP is needed.
●● When comparing the urea cycle to the TCA cycle, what would be
analogous to oxaloacetate? Why? (11/26)
Answer: Ornithine functions analogously to oxaloacetate in TCA cycle
as it initiates the cycle and is also reformed in the cycle
●● Where are the first and second nitrogens donated in the urea cycle?
(11/26)
QUESTIONS WITH VERIFIED SOLUTIONS
●● How much protein should be consumed each day? (11/19)
Answer: Humans are dependent on essential amino acids & adequate
total protein. Both quantity and quality of the dietary protein is very
important. Requirements are 0.8g protein/Kg body weight; 56g for
average male and 44 g for average female; average US consumption is
about 120 g per day.
●● What is the function of proteases? (11/19)
Answer: Proteases breakdown proteins into peptides and amino acids in
the stomach and intestine.
●● What causes Kwashiorkor? What are the signs? (11/19)
Answer: Protein deficiency despite of adequate calories
- Edema and distended abdomen
- Muscle wasting due to the lack of essential amino acids
- Compounded by inability to make digestive enzymes and new
intestinal epithelial cells
●● What initiates protein breakdown in the stomach? (11/19)
Answer: Pepsin initiates the protein breakdown in the stomach
,●● How is pepsinogen activated? (11/19)
Answer: Gastric parietal cells produce HCl which causes a
conformational change to activate pepsinogen to pepsin, an autocatalytic
process. Acid is also important in denaturing dietary proteins and
unfolding them.
●● Where does pepsinogen come from? (11/19)
Answer: Pepsinogen is secreted by the chief cells of the stomach.
●● Bicarbonate is responsible for _____. (11/19)
Answer: neutralizing the stomach acid that has reached the small
intestine
●● Bicarbonate is first released from the pancreas then the pancreatic
enzymes, besides digesting the proteins what else are they capable of
digesting? (11/19)
Answer: The digestive enzymes digest
themselves too.
- They also digest the intestinal cells, which are constantly replaced by
the precursor cells
●● What is inspissation? What does it lead to in the pancreas? (11/19)
,Answer: Inspissation (drying and thickening) of pancreatic exocrine
secretions
- Leads to obstruction of ducts
- Inability of pancreatic enzymes to enter intestinal lumen
- enzymes can't reach the small intestine because of the mucus buildup,
causing pancreatitis
●● Which zymogen is especially important to activate the rest of the
zymogens? (11/19)
Answer: trypsinogen (zymogen) --(enteropeptidase)--> trypsin (active
enzyme)
●● How is carbamoyl phosphate synthesized? (11/26)
Answer: Carbamoyl phosphate is a high energy compound, requiring 2
ATPs for formation from carbon dioxide and ammonium ion.
-first step of the urea cycle
●● Which enzyme catalyzes the first step of the urea cycle? (11/26)
Answer: Carbamoyl phosphate synthetase I (CPSI), the enzyme that
catalyzes this first step of the urea cycle, is found mainly in
mitochondria of the liver and intestine. CPSII, located in the cytosol, is
for pyrimidine biosynthesis.
, ●● Which products of the urea cycle can cross the mitochondrial
membrane? (11/26)
Answer: Ornithine and citrulline are exchanged for one another across
the mt membrane
●● Ornithine is an amino acid, why does it not appear in proteins?
(11/26)
Answer: ornithine is very abundant, but no codon matches for ornithine,
so it does not happen in nature
not an essential amino acid
●● How is ornithine synthesized? (11/26)
Answer: Ornithine is normally regenerated by the urea cycle.
Ornithine also can be synthesized de novo by a transamination reaction
catalyzed by ornithine aminotransferase under specific conditions in the
intestine. Note: PLP is needed.
●● When comparing the urea cycle to the TCA cycle, what would be
analogous to oxaloacetate? Why? (11/26)
Answer: Ornithine functions analogously to oxaloacetate in TCA cycle
as it initiates the cycle and is also reformed in the cycle
●● Where are the first and second nitrogens donated in the urea cycle?
(11/26)
