Question 1

Which organ is primarily responsible for maintaining blood glucose levels during both fed and fasting states, and what is the main mechanism it uses during fasting?

Accepted Answer

The liver, using gluconeogenesis

Question 2

During intense exercise, skeletal muscle produces lactic acid. What is the fate of this lactic acid in the body?

Accepted Answer

It is converted to alanine in the muscle and transported to the liver for gluconeogenesis

Question 3

Which of the following statements about erythrocytes (red blood cells) is correct?

Accepted Answer

They rely exclusively on glycolysis for ATP production because they lack mitochondria

Question 4

What is the effect of insulin on glucose metabolism in muscle and adipose tissue?

Accepted Answer

Insulin stimulates GLUT4 translocation, increasing glucose uptake

Question 5

Which enzyme is upregulated by insulin to promote glycolysis, and what is its role?

Accepted Answer

PFK-1, which catalyzes the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate: $$	ext{Fructose-6-phosphate} + 	ext{ATP} ightarrow 	ext{Fructose-1,6-bisphosphate} + 	ext{ADP}$$

Question 6

A patient with type 1 diabetes is unable to produce insulin. What is the biochemical consequence in muscle cells?

Accepted Answer

Decreased glucose uptake, leading to increased protein degradation for energy

Question 7

Which hormone is released in response to low blood glucose and acts primarily on the liver to stimulate glycogen breakdown?

Accepted Answer

Glucagon

Question 8

What is the role of malonyl-CoA in fatty acid metabolism?

Accepted Answer

It inhibits carnitine acetyltransferase I, preventing fatty acid transport into mitochondria

Question 9

Which pathway is favored in cancer cells due to the Warburg effect, and what is the main product?

Accepted Answer

Anaerobic glycolysis, producing lactate

Question 10

AMP-activated protein kinase (AMPK) is activated under which cellular condition, and what is its effect?

Accepted Answer

High AMP/ATP ratio, stimulating ATP-producing pathways and inhibiting ATP-consuming pathways

Question 11

Which molecule acts as a sensor for nutrient-rich conditions and promotes cell proliferation, protein synthesis, and lipid biosynthesis?

Accepted Answer

mTOR (mammalian target of rapamycin)

Question 12

What is the main biochemical difference between type 1 and type 2 diabetes?

Accepted Answer

Type 1 is caused by autoimmune destruction of insulin-producing cells; type 2 is caused by insulin resistance

Question 13

Which of the following is a plausible metabolic adaptation in adipose tissue during prolonged fasting?

Accepted Answer

Mobilization of fatty acids and glycerol for export to other tissues

Question 14

Which enzyme is upregulated during gluconeogenesis in the liver, and what reaction does it catalyze?

Accepted Answer

PEPCK (phosphoenolpyruvate carboxykinase), which converts oxaloacetate to phosphoenolpyruvate: $$	ext{Oxaloacetate} + 	ext{GTP} ightarrow 	ext{Phosphoenolpyruvate} + 	ext{GDP} + 	ext{CO}_2$$

Question 15

Which signaling molecule is produced in response to glucagon and epinephrine, and acts as a secondary messenger to activate protein kinase A?

Accepted Answer

Cyclic AMP ($$	ext{cAMP})$$

Question 16

In a scenario where blood glucose is low, which sequence of events occurs in the liver to restore glucose levels?

Accepted Answer

Glucagon release → activation of glycogen phosphorylase → glycogen breakdown → glucose export

Question 17

Which metabolic pathway is upregulated in adipose tissue when insulin levels are high?

Accepted Answer

Triglyceride synthesis from glycerol-3-phosphate and fatty acids

Question 18

Which of the following best describes the interplay between AMPK and mTOR in cellular energy regulation?

Accepted Answer

AMPK inhibits mTOR under low energy conditions, reducing cell growth and biosynthesis

Question 19

Which molecule is a key regulator of cellular redox state and is activated by a high NAD+/NADH ratio?

Accepted Answer

Sirtuins (NAD+-dependent protein deacetylases)

Question 20

A patient with type 2 diabetes has impaired GLUT4 function. What is the most likely consequence in muscle and adipose tissue?

Accepted Answer

Reduced glucose uptake, leading to increased reliance on fatty acid oxidation

Chapter 17 lecture

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