NST 103 FINAL EXAM QUESTIONS
AND ANSWERS
What hormone is responsible for the dephosphorylation and inhibition of the enzyme
in part B? - ANSWER-Insulin
During fasting, how do fatty acids cross the outer to the inner mitochondrial
membrane for β-oxidation. (Name 2 important enzymes and their functions). -
ANSWER-Acyl-CoA synthetase (ACS): Activation of fatty acid by conjugation with
CoA. Requires 2 ATP
CPT-1 (carnitine palmitoyl transferase-1): Transfers palmitate moiety from palmitoyl-
CoA to carnitine
CAT (carnitine acylcarnitine translocase): Translocates palmitoyl-carnitine from
intermembrane space across inner mitochondrial membrane
CPT-2 (carnitine palmitoyl transferase-2): Transfer palmitate from palmitoyl-carnitine
to mitochondrial CoA to reform palmitoyl-CoA
Under low cholesterol levels, the transcription of genes for specific receptors and
enzymes are activated to increase cellular [cholesterol]. Briefly explain how low
cholesterol is sensed at the endoplasmic reticulum to increase cholesterol synthesis.
Be sure to name at least one receptor OR enzyme that is upregulated, and its
function. - ANSWER-SCAP is released from Insig-1
SCAP-SREBP are packaged into COP II-coated vesicles and trafficked to the Golgi
In the Golgi apparatus, SREBP is cleaved at two sites and SREBP is released into
the cytoplasm
The SREBP fragment migrates to the nucleus to activate transcription of LDLR and
HMG-CoA reductase to increase cellular [cholesterol].
A patient has high circulating levels of LDL cholesterol, but has normal levels of the
liver LDL receptor. What is one possible explanation for the high levels of serum
cholesterol? - ANSWER-Mutation in Apo B100
How is Vitamin D transported from the enterocytes to other tissues? - ANSWER-
Vitamin D is packaged into chylomicrons secreted at the basolateral region of
enterocyte.
Where is Vitamin D stored? - ANSWER-Liver
What is the active form of Vitamin D? - ANSWER-1,25(OH)2-Vitamin D
How is retinol released from chylomicrons? - ANSWER-The retinyl-ester contained in
the chylomicron remnant enters the lysosome where an acidic hydrolase releases
retinol from the FA ester.
Once released, how is retinoid stored in the liver? - ANSWER-The retinol released is
immediately bound to free CRBP-I. The CRBP-bound retinol can be thought of as a
safe means of storage. The rate at which retinol is delivered to tissues is regulated
primarily via CRBP-I level in liver.
,How is retinol transported in the serum and protected from being cleared by the
kidneys? - ANSWER-Liver retinol binds to RBP, which is produced in liver. RBP
protein creates a barrel configuration that encloses the retinol molecule in a manner
similar to that of the CRBP's. The RBP-bound retinol enters plasma circulation where
it binds to transthyretin (TTR). TTR protects the retinol complex from being cleared
by the kidney.
How can binding proteins help the metabolism of retinoids? Provide two possible
explanations. (2 points) - ANSWER-Binding proteins have high affinity to Vit A;
prevent non-specific retinoid metabolism; increase proportion of retinoids in cytosol
and decrease membrane concentrations; cellular [binding protein] exceed [ligand]
Name two reasons why HCl is important for protein digestion? - ANSWER-Pepsin
activation from pepsinogen, protein denaturation
Which enzyme is responsible for the production of HCO3- and H+ inside the parietal
cell necessary for HCL production? Through which transport mechanism H+ and
HCO3- leave the parietal cell? - ANSWER-Carbonic Anhydrase, H+ through active
transport, HC03- through facilitated diffusion
Name 2 hormones and 1 neurotransmitter that regulate HCl production/secretion by
parietal cell? - ANSWER-Histamine, Gastrin, Acetylcholine
Name four enzymes that are different in gluconeogenesis than in glycolysis: -
ANSWER-Glucose6Pase, Fructose 1,6 bisP, PEPCK, Pyruvate carboxylase
Pick two enzymes from (Glucose6Pase, Fructose 1,6 bisP, PEPCK, Pyruvate
carboxylase) above and name one way by which each can be regulated: -
ANSWER-Glu6Pase- substrate concentration, gene expression by insulin
FBPase-1- AMP and Fructose 2,6 bisP allosteric inhibitor
PEPCK- insulin and glucose reduce gene expression, glucagon increase gene
expression
Pyruvate Carboxylase- acetyl coA is an allosteric activator
Describe the role of PFK-2 enzyme in glycolysis and how it is regulated: - ANSWER-
Makes Fru2,6 bisP which is an allosteric activator of PFK-1. Inactivated by
phosphorylation through glucagon/epinephrine action
Which factor initiates the cascade of coagulation factors that activate blood clotting?
Which factor is ultimately activated as a result of this cascade of events responsible
for primary and secondary hemostasis? - ANSWER-TF. Thrombin
Why is vitamin K required for activation of coagulation factors? - ANSWER-
Carboxylation of glutamate (Gla) by vitK dep carboxylase activates many BC
proteins like thrombin
In which reaction does the folate and vitamin B12 interact (name the substrate, the
product and the enzyme) - ANSWER-Homocysteine---- methionine via methionine
syntethase
, What disease affecting red blood cells that results from a deficiency in vitamin B12? -
ANSWER-Megaloblastic anemia or cancer
Describe (by filling in the blanks) why vitamin B12 deficiency can cause memory
loss.
Vit B12 deficiency causes an increase in _____________ (metabolite), which is a
competitive inhibitor of ________ (metabolite) in _______ biosynthesis. This leads to
_________ and destruction of the sheath in the Schwann cell. - ANSWER-Vit B12
deficiency causes an increase in ______methyl malonyl coA_______ (metabolite),
which is a competitive inhibitor of ____ malonyl CoA____ (metabolite) in ____FA___
biosynthesis. This leads to ____demyelination_____ and destruction of the sheath in
the Schwann cell.
Iron deficiency may result in anemia, reduced growth and impaired thermogenesis.
Please name the iron-requiring metabolic processes affected that result in these
risks. - ANSWER-Oxygen transport and retention
DNA synthesis
Electron transport
Ferritin serves as an iron reservoir in cells. Why is it necessary to sequester iron in
this manner? What effects would there be if iron were not sequestered? - ANSWER-
Reduce the risk of formation of iron-catalyzed free radicals which can damage lipids,
DNA and protein
A deficiency in each of the following can cause microcytic anemia. Please list the
process or enzyme related to erythropoiesis associated with each molecule. -
ANSWER-Iron—Incorporated into heme, hemoglobin and RBCs
Copper—a component of ceruloplasmin, which oxidizes Fe2+ to Fe3+, facilitating
binding to transferrin
Zinc—Cofactor for an enzyme involved in heme biosynthesis
PALP—cofactor for ALA synthase
Cells in our body carefully regulate the concentration of metabolites within the TCA
cycle. Name the process by which excess intermediates from the TCA cycle are
removed. - ANSWER-Catapleurosis
When citrate is removed from the TCA cycle in this way, into which pathway does it
feed? What about oxaloacetate? - ANSWER-Citrate-->lipogenesis
OAA-->gluconeogenesis
What is the role of the malate aspartate shuttle in terms of the TCA cycle? -
ANSWER-Transport reducing equivalents generated by the TCA cycle across the
mitochondrial membrane (NADH itself cannot cross the membrane)
Insulin is a key regulator in the handling of plasma glucose. It regulates the glucose
transporter GLUT4 in two separate ways. First, insulin stimulates GLUT4 plasma
membrane insertion via exocytosis. What is the second? - ANSWER-Stimulates
GLUT4 gene expression
AND ANSWERS
What hormone is responsible for the dephosphorylation and inhibition of the enzyme
in part B? - ANSWER-Insulin
During fasting, how do fatty acids cross the outer to the inner mitochondrial
membrane for β-oxidation. (Name 2 important enzymes and their functions). -
ANSWER-Acyl-CoA synthetase (ACS): Activation of fatty acid by conjugation with
CoA. Requires 2 ATP
CPT-1 (carnitine palmitoyl transferase-1): Transfers palmitate moiety from palmitoyl-
CoA to carnitine
CAT (carnitine acylcarnitine translocase): Translocates palmitoyl-carnitine from
intermembrane space across inner mitochondrial membrane
CPT-2 (carnitine palmitoyl transferase-2): Transfer palmitate from palmitoyl-carnitine
to mitochondrial CoA to reform palmitoyl-CoA
Under low cholesterol levels, the transcription of genes for specific receptors and
enzymes are activated to increase cellular [cholesterol]. Briefly explain how low
cholesterol is sensed at the endoplasmic reticulum to increase cholesterol synthesis.
Be sure to name at least one receptor OR enzyme that is upregulated, and its
function. - ANSWER-SCAP is released from Insig-1
SCAP-SREBP are packaged into COP II-coated vesicles and trafficked to the Golgi
In the Golgi apparatus, SREBP is cleaved at two sites and SREBP is released into
the cytoplasm
The SREBP fragment migrates to the nucleus to activate transcription of LDLR and
HMG-CoA reductase to increase cellular [cholesterol].
A patient has high circulating levels of LDL cholesterol, but has normal levels of the
liver LDL receptor. What is one possible explanation for the high levels of serum
cholesterol? - ANSWER-Mutation in Apo B100
How is Vitamin D transported from the enterocytes to other tissues? - ANSWER-
Vitamin D is packaged into chylomicrons secreted at the basolateral region of
enterocyte.
Where is Vitamin D stored? - ANSWER-Liver
What is the active form of Vitamin D? - ANSWER-1,25(OH)2-Vitamin D
How is retinol released from chylomicrons? - ANSWER-The retinyl-ester contained in
the chylomicron remnant enters the lysosome where an acidic hydrolase releases
retinol from the FA ester.
Once released, how is retinoid stored in the liver? - ANSWER-The retinol released is
immediately bound to free CRBP-I. The CRBP-bound retinol can be thought of as a
safe means of storage. The rate at which retinol is delivered to tissues is regulated
primarily via CRBP-I level in liver.
,How is retinol transported in the serum and protected from being cleared by the
kidneys? - ANSWER-Liver retinol binds to RBP, which is produced in liver. RBP
protein creates a barrel configuration that encloses the retinol molecule in a manner
similar to that of the CRBP's. The RBP-bound retinol enters plasma circulation where
it binds to transthyretin (TTR). TTR protects the retinol complex from being cleared
by the kidney.
How can binding proteins help the metabolism of retinoids? Provide two possible
explanations. (2 points) - ANSWER-Binding proteins have high affinity to Vit A;
prevent non-specific retinoid metabolism; increase proportion of retinoids in cytosol
and decrease membrane concentrations; cellular [binding protein] exceed [ligand]
Name two reasons why HCl is important for protein digestion? - ANSWER-Pepsin
activation from pepsinogen, protein denaturation
Which enzyme is responsible for the production of HCO3- and H+ inside the parietal
cell necessary for HCL production? Through which transport mechanism H+ and
HCO3- leave the parietal cell? - ANSWER-Carbonic Anhydrase, H+ through active
transport, HC03- through facilitated diffusion
Name 2 hormones and 1 neurotransmitter that regulate HCl production/secretion by
parietal cell? - ANSWER-Histamine, Gastrin, Acetylcholine
Name four enzymes that are different in gluconeogenesis than in glycolysis: -
ANSWER-Glucose6Pase, Fructose 1,6 bisP, PEPCK, Pyruvate carboxylase
Pick two enzymes from (Glucose6Pase, Fructose 1,6 bisP, PEPCK, Pyruvate
carboxylase) above and name one way by which each can be regulated: -
ANSWER-Glu6Pase- substrate concentration, gene expression by insulin
FBPase-1- AMP and Fructose 2,6 bisP allosteric inhibitor
PEPCK- insulin and glucose reduce gene expression, glucagon increase gene
expression
Pyruvate Carboxylase- acetyl coA is an allosteric activator
Describe the role of PFK-2 enzyme in glycolysis and how it is regulated: - ANSWER-
Makes Fru2,6 bisP which is an allosteric activator of PFK-1. Inactivated by
phosphorylation through glucagon/epinephrine action
Which factor initiates the cascade of coagulation factors that activate blood clotting?
Which factor is ultimately activated as a result of this cascade of events responsible
for primary and secondary hemostasis? - ANSWER-TF. Thrombin
Why is vitamin K required for activation of coagulation factors? - ANSWER-
Carboxylation of glutamate (Gla) by vitK dep carboxylase activates many BC
proteins like thrombin
In which reaction does the folate and vitamin B12 interact (name the substrate, the
product and the enzyme) - ANSWER-Homocysteine---- methionine via methionine
syntethase
, What disease affecting red blood cells that results from a deficiency in vitamin B12? -
ANSWER-Megaloblastic anemia or cancer
Describe (by filling in the blanks) why vitamin B12 deficiency can cause memory
loss.
Vit B12 deficiency causes an increase in _____________ (metabolite), which is a
competitive inhibitor of ________ (metabolite) in _______ biosynthesis. This leads to
_________ and destruction of the sheath in the Schwann cell. - ANSWER-Vit B12
deficiency causes an increase in ______methyl malonyl coA_______ (metabolite),
which is a competitive inhibitor of ____ malonyl CoA____ (metabolite) in ____FA___
biosynthesis. This leads to ____demyelination_____ and destruction of the sheath in
the Schwann cell.
Iron deficiency may result in anemia, reduced growth and impaired thermogenesis.
Please name the iron-requiring metabolic processes affected that result in these
risks. - ANSWER-Oxygen transport and retention
DNA synthesis
Electron transport
Ferritin serves as an iron reservoir in cells. Why is it necessary to sequester iron in
this manner? What effects would there be if iron were not sequestered? - ANSWER-
Reduce the risk of formation of iron-catalyzed free radicals which can damage lipids,
DNA and protein
A deficiency in each of the following can cause microcytic anemia. Please list the
process or enzyme related to erythropoiesis associated with each molecule. -
ANSWER-Iron—Incorporated into heme, hemoglobin and RBCs
Copper—a component of ceruloplasmin, which oxidizes Fe2+ to Fe3+, facilitating
binding to transferrin
Zinc—Cofactor for an enzyme involved in heme biosynthesis
PALP—cofactor for ALA synthase
Cells in our body carefully regulate the concentration of metabolites within the TCA
cycle. Name the process by which excess intermediates from the TCA cycle are
removed. - ANSWER-Catapleurosis
When citrate is removed from the TCA cycle in this way, into which pathway does it
feed? What about oxaloacetate? - ANSWER-Citrate-->lipogenesis
OAA-->gluconeogenesis
What is the role of the malate aspartate shuttle in terms of the TCA cycle? -
ANSWER-Transport reducing equivalents generated by the TCA cycle across the
mitochondrial membrane (NADH itself cannot cross the membrane)
Insulin is a key regulator in the handling of plasma glucose. It regulates the glucose
transporter GLUT4 in two separate ways. First, insulin stimulates GLUT4 plasma
membrane insertion via exocytosis. What is the second? - ANSWER-Stimulates
GLUT4 gene expression
