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Biochemistry UNE Unit 3 And 4 – Question & Correct Solutions
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Biochemistry UNE Unit 3 And 4 – Question & CorrectSolutions
A 10-year-old boy is brought to the emergency department by his father. He
reports his son has recently been very thirsty and needing to make
frequent trips to the bathroom. Physical examination revealed a thin boy, in
the 30th percentile for height and weight. A rapid dipstick test revealed
glucose in his urine. Evaluation of this boy's blood would reveal decreased
levels of which of the following compounds or hormones? Correct Ans
- Insulin
The description here is of type 1 diabetes which is consistent with a loss of
insulin production. Therefore, fasted state metabolic pathways would be
highly active contributing to hyperglycemia and ketogenesis.
A well, 2-year-old girl presents to the clinic with symptoms of a viral
illness. Her parents report she has had bouts of vomiting and diarrhea over
the last 24 hours. This morning they could barely wake her from her crib
and she was very weak. Laboratory tests show low blood glucose
(hypoglycemia) and elevated liver enzymes. There are no ketones present
in her urine. The child is hospitalized and glucose is administered by I.V.
Additional laboratory analysis showed elevated medium-chain fatty acyl
carnitines in blood and 6-8 carbon dicarboxylic acids in the urine. Which of
the following abnormalities is the most likely diagnosis for this child?
Correct Ans - Defect of medium-chain coenzyme A dehydrogenase
Under fasting conditions (ratio of insulin to glucagon <1), elevated
glucagon will activate which of the following enzymes? Correct Ans -
Hormone sensitive lipase
Glucagon will increase levels of lipolysis through the phosphorylation and
activation of hormone sensitive lipase.
Which of the following is not a product of β-oxidation? Correct Ans -
NADPH
,-NADH, FADH2 and Acetyl-CoA are all produced by β-oxidation. NADPH is
required for fatty acid synthesis and can be produced by the pentose
phosphate pathway or malic enzyme.
A well, 2-year-old girl contracted a viral illness at daycare with vomiting,
diarrhea, and progressive lethargy. She presents to the clinic with
disorientation, a barely rousable sensorium, cracked lips, sunken eyes, lack
of tears, flaccid skin with "tenting" weak pulse with low blood pressure,
and increased deep tendon reflexes. Laboratory tests show low blood
glucose, normal electrolytes, elevated liver enzymes, and (on chest X-ray) a
dilated heart. Urinalysis reveals no infection and no ketones. The child is
hospitalized and stabilized with 10% glucose infusion. Admission
laboratories show elevated medium-chain fatty acylcarnitines in blood and
6-8 carbon dicarboxylic acids in the urine. Which of the following
abnormalities is the most likely diagnosis in this child? Correct Ans -
Defect of medium-chain coenzyme A deydrogenase
Under conditions when glucose oxidation is elevated, the acetyl-CoA
produced will allosterically activate which of the following enzymes
leading to an increase in the production of oxaloacetate? Correct Ans -
Pyruvate carboxylase
Which of the following enzymes is correctly paired with its allosteric
inhibitor? Correct Ans - Acetyl-CoA carbpxylase:palmotoyl-CoA
Under fasting conditions, acetyl-CoA carboxylase will be inhibited by an
increase in which of the following compounds? Correct Ans - fatty
acyl-CoA
Malate can be converted to pyruvate in the cytosol. Which of the following
compounds is directly generated in this conversion and is essential for fatty
acid synthesis? Correct Ans - NADPH
NADPH is essential for fatty acid synthesis and can be generated by which
two enzymes? (+ indicates NADPH can be produced by the enzyme; -
indicates the enzyme does not produce NAPDH)
Glucose 6-phosphate dehydrogenase-Malic enzyme- Pyruvate
dehydrogenase complex
,1++-
2+--
3---
4-++ Correct Ans - 1
NAPDH is generated primarily by the pentose phosphate pathway by
glucose oxidation by glucose 6-phosphate dehydrogenase or through malic
enzyme as it oxidized malate to pyruvate.
During fatty acid synthesis, after the initial step involving acetyl-CoA, the
fatty acid chain is elongated by the addition of which of the following
compounds? Correct Ans - Malonyl-CoA
An increase in the ratio of insulin to glucagon will increase the activity of
which of the following enzymes (+ indicates activity is increased; -
indicates activity is not increased by insulin)?
Hormone sensitive lipase Acetyl-CoA carboxylase Phosphofructokinase-2
(PFK2) Glycogen synthase
1+++-
2++--
3+---
4-+++ Correct Ans - in pp
4
When insulin is elevated fed state pathways will be persistent. This will
include the activation of acetyl-CoA carboxylase through
dephosphorylation. PFK2 in glycolysis and glucagon synthase will also be
active under these conditions.
During the fasted state, lipolysis is facilitated by the action of hormone
sensitive lipase. This enzyme requires which of the following post -
translational modification for activation? Correct Ans -
phosphorylation
Which of the following hormones initiates skeletal muscle catabolism to
provide substrate for gluconeogenesis? Correct Ans - cortisol
, Several friends went out Saturday evening to celebrate an exam. They
skipped dinner and decided to head straight to the bar. The next morning
one of the individuals was found laying unconscious at the bottom of the
stairs. He was rushed to the emergency department and blood glucose
levels of 30mg/ dL (normal range 100-120mg/ dL).
At the time of presentation, which of the following would be consistent
with this individuals signs and symptoms (when compared to a normal
individual)? Correct Ans - Increase lactate levels
Ethanol metabolism increases the ratio of NADH/NAD+. This leads to all of
the following metabolic consequences except: Correct Ans -
Inhibition of lipolysis
What is the primary fuel oxidized in the liver (to generate ATP) in the
fasted state?
Glucose
Free Fatty Acids Correct Ans - free fatty acids
Response Feedback:
Describe the coordination of lipolysis with gluconeogenesis in the liver.
Pyurvate carboxylase is allosterically activated by which of the following
compounds? Correct Ans - acetyl CoA
In a fasted individual, excessive alcohol consumption will contribute to all
of the following except: Correct Ans - Increased chylomicron
secretion
Which of the following is the regulated step of fatty acid synthesis in
eukaryotes? Correct Ans - Carboxylation of acetyl CoA
NADPH is essential for fatty acid synthesis and can be generated by which
of the following enzymes? Correct Ans - Malic enzyme
Under fasted conditions, (glucagon is elevated), which of the following
enzymes will be phosphorylated and inactive? Correct Ans -
HMGCoA Reductase
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