section 6 in class question Flashcards
Which of the following leads to an increased rate of glycogen breakdown in skeletal muscle?
A. AMP B. epinephrine C. epinephrine and AMP D. glucagon E. insulin
c
What is the purpose for converting glucose 1-phosphate to UDP-glucose prior to glycogen synthesis?
A. It allows glycogen formation to be reversible.
B. It ensures that multiple glucose carbons don’t react with the glycogen molecule.
C. It increases the reactivity of the glucose molecule.
D. It makes glycogen formation irreversible.
E. It results from insulin stimulation of the glycogen synthase.
c
the parents of a 3 month y/o boy bring him to the doctor for lethargy, swollen abdomen. Boy has massive hepatomegaly and enlarged kidneys with a normal spleen and heart. Lab studies are notable for hypoglycemia. Biopsy of muscle and liver show excess glycogen in the liver tissue but not in the muscle. What is happening?
A. glucokinase absent in liver tissue
B. Glucose 6 phosphatase absent in the liver tissue
C. Lack of glycogen synthase in muscle tissue
D. lack of phosphorylase in liver tissue
b Glucose 6 phosphatase absent in the liver tissue
Which enzyme commits glucose to the pentose phosphate pathway?
A. phosphofructose kinase-1
B. hexokinase or glucokinase (depending on the tissue)
C. glucose 6-phosphate dehydrogenase
D. glucose 6-phosphatase
c
Which of the following pathways will be adversely affected by a glucose-6-phosphate dehydrogenase deficiency?
Fatty acid synthesis
Cholesterol synthesis
Glutathione reduction
All the listed pathways would be affected.
d
A male patient who is fructose intolerant due to an Aldolase B deficiency has asked you whether his sperm cells will be able to obtain the necessary fructose to support motility. What will you tell him?
A. no - because sperm cells are not exposed to dietary fructose.
B. no – because dietary fructose must be processed before delivery to sperm cells.
C. you don’t know offhand, you will have to measure this.
D. yes – because sperm cells can make fructose from glucose as needed.
E. yes – because sperm depend on glucose as the sole energy source.
d
A long distance runner who is planning to run a marathon decides to add fructose to the replacement fluid she will be using during the race. Which of the following statements regarding fructose best describes the fate of this sugar?
it enters the glycolytic pathway as fructose 6 phosphate in the liver
it is converted to uridine diphosphate (UDP)-fructose and then epimerized to UDP glucose
it is metabolized by a pathway other than the glycolytic pathway
it is metabolized in the liver by an aldolase that recognizes fructose 1-phospahte
it is phosphorylated by phosphofructokinase
d
If a person has a phosphoenolpyruvate carboxykinase (PEPCK) defect, which of the following cannot be used as starting material for gluconeogenesis? A. alanine B. glycerol C. lactate D. neither alanine nor lactate E. none of the above
d
A 25-year old male is found in a semicomatose state and is taken to the emergency department by his friends. The friends report that the patient has not eaten any food for the past 5 days. Which of the following substances is the most likely source of glucose for the patient’s blood?
A. Pyruvate from glycolysis in the liver B. Alanine from muscle tissue C. Glycerol from adipose tissue D. Fatty acids from adipose tissue E. Lactate from skeletal muscle
c
Fatty acids are used more than glucose by tissues with high energy demands. Why is this?
a. Fatty acid oxidation can be used by more tissue types than glycolysis.
b. The compartmentalization of fatty acid oxidation in mitochondria is more efficient for the electron transport chain and ATP synthase.
c. A typical fatty acid produces about 50 ATP molecules, whereas a glucose molecule yields about 25 ATP molecules.
d. A typical fatty acid yields about100 ATP molecules whereas a glucose molecule yields only about 25 ATP molecule.
d
A patient has an enzyme imbalance, such that her cells have a chronically high level of malonylCoA. Which of the following would be a likely consequence of this imbalance?
a. Her acetylCoA levels would be vanishingly small.
b. Her cells will make excess ketone bodies
c. Fatty acid oxidation will be inhibited in her cells
d. Fatty acid oxidation will be increased in her cells
c
A patient has a defect in her carnitine-palmatoyl transferase I enzyme that makes this enzyme inactive. Which of the following would be a likely consequence of this defect?
His mitochondria will oxidize newly synthesized fatty acids
His fatty acid oxidation will take place in the cell cytoplasm
He will generate significantly less ketone bodies during fasting.
His fatty acid oxidation will be upregulated to compensate.
c
Which enzyme commits acetyl CoA to fatty acid synthesis?
a. Pyruvate dehydrogenase
b. Acetyl CoA carboxylase
c. Citrate lyase
d. Malic enzyme
b
Which enzyme if deficient in a patient would essentially prevent fatty acid synthesis?
a. Pyruvate dehydrogenase
b. Acetyl CoA carboxylase
c. Citrate lyase
d. Malic enzyme
e. phosphoenolypyruvate carboxy kinase
b
A patient has a disorder in his carnitine-palmitoyl tranferase I enzyme such that it does not recognize malonyl CoA. How will this defect affect fatty acid metabolism in his liver?
His cells will no longer oxidize fatty acids for energy.
His cells will likely oxidize newly synthesized fatty acids.
His liver will store excess fatty acids leading to fatty liver syndrome.
Fatty acyl CoA will not be converted to fatty acyl-carnitine by CPT-1
b
