Download Lecture 23 – SIGNAL TRANSDUCTION: G

Exam 3 Sample Questions - ANSWERS
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ANSWERS TO SAMPLE QUESTIONS FOR BIOC 460 - EXAM 3
Lecture 22 – METABOLISM: BASIC CONCEPTS
Starvation is the nutritional state during which gluconeogenesis provides blood glucose.
False Glycogen is an example of a circulating fuel. (It is stored.)
Among the following substances the one with the highest phosphate group transfer potential is:
D.
phosphoenolpyruvate
Glycerol-3-phosphate
Adenosine diphosphate (ADP)
Glucose-1-phosphate
Adenosine monophosphate (AMP)
Guanosine triphosphate (GTP)
0 high energy phosphate bonds
1 high energy phosphate bond
0 high energy phosphate bonds
0 high energy phosphate bonds
2 high energy phosphate bonds
The intermediate common to all major carbohydrate pathways is: glucose-6-phosphate
The major fuel for the brain in the postabsorptive state is: glucose
Lecture 23 – SIGNAL TRANSDUCTION: G-PROTEINS
TRUE
TRUE
Binding of GTP to the αS subunit of GS ultimately leads to the activation of protein kinase A.
Binding of glucagon to its receptor ultimately leads to the activation of protein kinase A.
Identify two second messengers whose formation is associated with activation of a G protein
CYCLIC AMP (cAMP) or DIACYLGLYCEROL (DAG) or INOSITOL TRISPHOSPHATE (IP3)
Describe the mechanism for the inactivation of the kinase that is involved in glucagon signal transduction
through phosphorylation of a variety of enzymes in metabolic pathways.
The kinase is protein kinase A. Since it is activated by binding of cyclic AMP to the
regulatory subunit then inactivation requires hydrolysis of cyclic AMP by phosphodiesterase.
Once cyclic AMP disappears, the regulatory subunit reassociates with the catalytic subunit to
shut it off.
A phosphodiesterase can catalyze the hydrolysis of:
C.
cyclic AMP.
In the phosphoinositide cascade:
A.
protein kinase C is activated by diacylglycerol.
Lecture 24 - DIGESTION AND ABSORPTION OF CARBOHYDRATES
FALSE
TRUE
FALSE
TRUE
FALSE
Cellulose is the form in which animals store carbohydrates.
One product of pancreatic α-amylase is glucose.
Amylopectin is the form in which animals store carbohydrates.
One product of pancreatic α-amylase is α-limit dextrin.
Lactase is an α-glycosidase in the intestine.
Exam 3 Sample Questions - ANSWERS
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The GLUT-4 transporter that is stimulated by insulin is found in:
C.
adipose.
The enzyme derived from the pancreas that hydrolyzes starch is pancreatic:
C.
-amylase
Glucoamylase is the brush border enzyme complex that cleaves oligosaccharides and α-limit dextrins.
Galactose is the only sugar that could not be absorbed from the intestinal lumen if the sodium(Na+),potassium
(K+)-ATPase were defective in intestinal cells.
Sucrase OR sucrase-isomaltase is the brush border enzyme that cleaves the disaccharide containing fructose
and glucose.
The two sugars that comprise maltose are glucose and glucose.
Sucrose contains two molecules of sugar including glucose and fructose.
Lecture 25 - SIGNAL TRANSDUCTION: INSULIN
TRUE
FALSE
FALSE
TRUE
IRS-1 is phosphorylated before it docks with the p85-PI3K complex.
The receptor subunit that contains the insulin binding site also contains the tyrosine kinase
domain to facilitate its activation.
Autophosphorylation sustains the binding of insulin to its receptor.
The tyrosine kinase activity of the insulin receptor is located on a domain of the β-subunit.
Calcium promotes the biosynthesis and processing of insulin by:
E.
binding to calmodulin to activate calmodulin kinase
Insulin’s ability to promote glucose transport includes the phosphorylation, by the insulin receptor tyrosine
kinase, of a component in the cytoplasm of adipose cells. This component is:
B.
IRS-1
What is the cause of Type I diabetes?
-Cell destruction or unable to make insulin or autoimmune response
What is generally the initiating event in Type II diabetes?
Loss Of Insulin Response Or Insulin Resistance
DRAW A DIAGRAM showing the steps leading to the complete activation of both tyrosine kinases of the
insulin receptor
Exam 3 Sample Questions - ANSWERS
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P
P
P
Lectures 26/27 - GLYCOLYSIS AND GLUCONEOGENESIS
In liver, the endproduct of fructose metabolism that enters the glycolytic pathway is:
B.
glyceraldehyde-3-phosphate.
A description of the Cori cycle includes:
D.
gluconeogenesis from lactate in liver and glycolysis in muscle.
The gluconeogenic enzyme that is activated by citrate is:
B.
fructose-1,6-bisphosphatase.
The glycolytic enzyme that is inhibited by citrate is:
A.
pyruvate kinase.
Identify the enzyme and its SPECIFIC ISOZYME FORM that is responsible for regenerating NAD+ during
anaerobic glycolysis.
Enzyme:
Isozyme form:
Lactate Dehydrogenase (or LDH)
M4 (or all M subunits)
Pyruvate carboxylase OR PC is the ATP-requiring reaction that is unique to gluconeogenesis but not to
glycolysis.
Fructose-2,6-bisphosphate OR F26BP is the allosteric regulator that activates glycolysis in the liver and
whose concentration is controlled by hormone in response to blood glucose.
Identify one glycolytic enzyme that uses ATP and one that produces ATP.
uses ATP:
hexokinase OR glucokinase OR phosphofructokinase-1
produces ATP: phosphoglycerate kinase OR pyruvate kinase
Aspartate can be converted directly to oxaloacetate by removal of its amino group. How many molecules of
high energy phosphate compounds will be consumed in converting aspartate to TEN molecules of glucose?
20 aspartate needed to make 10 glucose
20 asp to 20 oxaloacetate to 20 phosphoenolpyruvate = loss of 20 GTP
20 phosphoenolpyruvate to 10 glucose = loss of 20 ATP
Net loss = 40 molecules of high energy phosphate compounds
Exam 3 Sample Questions - ANSWERS
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Identify features of the H4 isozyme of lactate dehydrogenase that makes it different from the M4 isozyme.
H4 has a high affinity (or low Km) for lactate
H4 is inhibited by pyruvate
H4 found in heart not anaerobic skeletal muscle
Intravenous infusion of fructose into healthy volunteers increases lactate in the blood by threefold, a far greater
increase than observed following the infusion of the same amount of glucose. Why is glycolysis more rapid
following the infusion of fructose than glucose?
Fructose metabolism bypasses phosphofructokinase-1 the rate-limiting reaction in glycolysis that
glucose must use; fructose enters later at glyceraldehyde-3-P
INSULIN is the hormone that activates protein phosphatase to catalyze dephosphorylation of enzymes?
Hexokinase:
D. transfers a phosphoryl group to a variety of hexoses
Hexokinase is allosterically inhibited by
D.
glucose-6-phosphate.
The phosphofructokinase-1 and pyruvate kinase reactions are similar in that:
E. both are essentially irreversible
Glyceraldehyde 3-phosphate dehydrogenase:
C.
produces NADH as a product.
A gluconeogenic enzyme that requires GTP is:
D.
phosphoenolpyruvate carboxykinase (PEPCK).
Starting with fructose-6-phosphate and proceeding to pyruvate what is the net yield of ATP?
phosphofructokinase-1 = loss of 1ATP
phosphoglycerate kinase = gain of 2ATP (fructose-1,6-bisphosphate splits to two molecules)
pyruvate kinase = gain of 2ATP
Net yield = gain of 3 ATP
Describe how the intracellular concentration of fructose-2,6-bisphosphate is regulated by insulin.
Insulin activates protein phophatase. Protein phosphatase removes the phosphate from the
bifunctional enzyme phosphofructokinase-2/fructose-2,6-bisphosphatase. This leads to
activation of the kinase and inhibition of the fructose bisphosphatase. Consequently fructose2,6-bisphosphate is synthesized to increase its intracellulat concentration.
Lecture 28 - PYRUVATE DEHYDROGENASE/CITRIC ACID CYCLE
FALSE
TRUE
Isocitrate dehydrogenase is activated by NADH
α-Ketoglutarate dehydrogenase is inhibited by NADH
In the citric acid cycle, FADH2 is formed as a product in a reaction catalyzed by:
A.
succinic dehydrogenase
Exam 3 Sample Questions - ANSWERS
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In the citric acid cycle, GTP is formed as a product in a reaction catalyzed by:
B.
succinyl CoA synthetase
For the pyruvate dehydrogenase complex identify the cofactors and their vitamin precursor
Cofactor:
Thiamine Diphosphate
CoA (Coenzyme A)
NAD
FAD
Vitamin:
Thiamine (Vitamin B1)
Pantothenic Acid (Pantothenate)
Niacin
Riboflavin
Lectures 29/30 - OXIDATIVE PHOSPHORYLATION
The outer mitochondrial membrane:
E.
surrounds a space that is more positively charged than the mitochondrial matrix.
The inner mitochondrial membrane:
A.
is invaginated forming cristae.
What is transported out of the mitochondrial matrix into the intramembrane space and is an example of
electrogenic transport?
ATP or adenosine triphosphate
What is transported from the intramembrane space into the mitochondrial matrix in exchange for a negatively
charged molecule and is an example of electroneutral transport?
PYRUVATE or PHOSPHATE or MALATE or -KETOGLUTARATE
What is complex IV of the electron transport (respiratory) chain also called?
Cytochrome c oxidase
Identify the characteristics of the chemiosmotic model that relates to oxidative phosphorylation
impermeable inner membrane
pH gradient across inner membrane
asymmetry of membrane components
destroying proton gradient (uncoupling) - stops ATP synthesis (or increases oxygen consumption
inhibiting respiratory chain - stops ATP synthesis (or stops proton pumping)
Define respiratory control:
When ADP increases it activates the stalk to open the proton channel (or lower proton gradient or
lower pH gradient). This increases mitochondrial respiration (or respiratory chain).
Define uncoupling
Destruction (dissipation, collapse) of the pH (or proton) gradient across the mitochondrial inner
membrane causing loss of the ability to synthesize ATP.
Define electrogenic transport.
Transport systems in which a net charge moves across a membrane
Complex III of the electron transport (respiratory) chain is also called: Cytochrome reductase
Exam 3 Sample Questions - ANSWERS
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Complexes I and III of the electron transport (respiratory) chain are linked by: Coenzyme Q (ubiquinone)