A 45-year-old patient with Type 2 diabetes mellitus shows elevated fasting blood glucose (180 mg/dL) but normal HbA1c levels initially. Which carbohydrate metabolism pathway is primarily impaired in this patient's liver?
AGlycogenesis and increased gluconeogenesis
BGlycogenolysis and normal glycolysis
CPentose phosphate pathway upregulation
DLactate to pyruvate conversion
Correct Answer:
A. Glycogenesis and increased gluconeogenesis
EXPLANATION
Type 2 diabetes shows hepatic insulin resistance leading to impaired glycogenesis (reduced glycogen synthesis) and uncontrolled gluconeogenesis (excessive glucose production). This causes elevated fasting glucose despite normal HbA1c if glycemic control improves later. The liver fails to suppress glucose production in response to insulin.
Which adaptation occurs in liver during prolonged fasting to maintain blood glucose?
AIncreased glycogenolysis only
BIncreased gluconeogenesis from lactate and amino acids
CIncreased lipogenesis
DIncreased glycogen synthesis
Correct Answer:
B. Increased gluconeogenesis from lactate and amino acids
EXPLANATION
After 8-12 hours of fasting, hepatic glycogen depletes. The liver then relies on gluconeogenesis from Cori cycle lactate and amino acids to maintain blood glucose.
In the pentose phosphate pathway, the oxidative phase generates NADPH. Which metabolic process primarily utilizes this NADPH in fed state?
AGlycolysis
BKetone body synthesis
CFatty acid and cholesterol synthesis
DOxidative phosphorylation
Correct Answer:
C. Fatty acid and cholesterol synthesis
EXPLANATION
NADPH from the oxidative pentose phosphate pathway is essential for reductive biosynthesis of fatty acids and cholesterol, which occur predominantly in the fed state.
In hereditary fructose intolerance (HFI), which enzyme deficiency causes accumulation of fructose-1-phosphate?
AFructokinase
BAldolase B
CFructose-1,6-bisphosphatase
DFructose-1-phosphatase
Correct Answer:
B. Aldolase B
EXPLANATION
HFI results from aldolase B deficiency, preventing cleavage of fructose-1-phosphate into DHAP and glyceraldehyde, leading to accumulation and hepatotoxicity.
A newborn presents with hepatomegaly, lactic acidosis, and hypoglycemia. Enzyme analysis shows deficiency of glucose-6-phosphatase. Which disease is this?
AMcArdle disease
BPompe disease
CVon Gierke disease
DCori disease
Correct Answer:
C. Von Gierke disease
EXPLANATION
Von Gierke disease (GSD Type I) results from glucose-6-phosphatase deficiency, preventing final step of both gluconeogenesis and glycogenolysis, causing severe hypoglycemia.
Which of the following is NOT a function of glycogen in liver?
AMaintaining blood glucose levels between meals
BProviding structural support to hepatocytes
CActing as glucose buffer during fasting
DSupplying glucose-6-phosphate to extrahepatic tissues
Correct Answer:
D. Supplying glucose-6-phosphate to extrahepatic tissues
EXPLANATION
Liver glycogen maintains blood glucose but cannot directly supply glucose-6-phosphate to other tissues as glucose-6-phosphate cannot cross cell membranes.
During high-intensity exercise, which carbohydrate provides immediate energy despite low concentration in blood?
ABlood glucose from liver glycogenolysis
BMuscle glycogen
CCirculating fructose
DDietary disaccharides
Correct Answer:
B. Muscle glycogen
EXPLANATION
Muscle glycogen is the primary energy source during high-intensity exercise because muscle lacks glucose-6-phosphatase and retains glucose-6-phosphate for glycolysis.
