Part 5: Assimilation and Functions of Absorbed Nutrients (25 MCQs)

Q1. Assimilation refers to:

A. Breaking down food into simpler forms
B. Absorption of digested food
C. Conversion of absorbed nutrients into body substances
D. Elimination of undigested food

Answer: C

Explanation:

A. Incorrect: Breaking down = digestion.
B. Incorrect: Absorption means uptake into blood/lymph.
C. Correct: Assimilation is utilization of absorbed nutrients for energy, growth, repair.
D. Incorrect: Elimination is egestion.

Q2. Glucose absorbed from intestine is primarily used for:

A. DNA synthesis
B. Energy production through respiration
C. Fat synthesis only
D. Protein synthesis

Answer: B

Explanation:

A. Incorrect: DNA needs nucleotides, not glucose directly.
B. Correct: Glucose undergoes glycolysis, Krebs cycle, and oxidative phosphorylation to produce ATP.
C. Incorrect: Excess glucose can convert to fat, but not its primary use.
D. Incorrect: Proteins are synthesized from amino acids, not glucose.

Q3. Excess glucose in the body is stored as:

A. Starch
B. Cellulose
C. Glycogen
D. Protein

Answer: C

Explanation:

A. Incorrect: Starch is plant storage form.
B. Incorrect: Cellulose is plant structural polysaccharide.
C. Correct: In humans, excess glucose is stored as glycogen in liver and muscles.
D. Incorrect: Proteins are not glucose storage.

Q4. Amino acids absorbed from the intestine are mainly used for:

A. Energy production only
B. Synthesis of proteins and enzymes
C. Fat synthesis only
D. Storage in muscles

Answer: B

Explanation:

A. Incorrect: They provide energy only when deficient.
B. Correct: Amino acids are building blocks for proteins, hormones, enzymes.
C. Incorrect: Fat synthesis from amino acids is secondary.
D. Incorrect: Amino acids are not stored; they form functional proteins.

Q5. Excess amino acids in the body are:

A. Stored in the liver
B. Converted to glycogen or fat after deamination
C. Excreted unchanged
D. Converted to cellulose

Answer: B

Explanation:

A. Incorrect: Amino acids cannot be stored directly.
B. Correct: Excess amino acids undergo deamination → ammonia → urea; carbon skeleton used for glucose/fat.
C. Incorrect: They are not excreted directly.
D. Incorrect: Humans don’t synthesize cellulose.

Q6. Which organ is the major site of nutrient assimilation?

A. Kidney
B. Liver
C. Pancreas
D. Spleen

Answer: B

Explanation:

A. Incorrect: Kidneys excrete wastes.
B. Correct: Liver stores glycogen, detoxifies, metabolizes proteins, fats, carbs.
C. Incorrect: Pancreas secretes enzymes and hormones, not main assimilation.
D. Incorrect: Spleen is lymphoid organ.

Q7. The end-product of fat digestion, after absorption, is mainly utilized for:

A. Energy and storage as adipose tissue
B. Protein synthesis
C. Formation of glycogen
D. DNA replication

Answer: A

Explanation:

A. Correct: Fatty acids + glycerol → triglycerides for energy and storage.
B. Incorrect: Proteins are not made from fats.
C. Incorrect: Glycogen is carbohydrate storage.
D. Incorrect: DNA replication requires nucleotides.

Q8. Which of the following nutrients is most energy-rich?

A. Carbohydrates
B. Proteins
C. Fats
D. Vitamins

Answer: C

Explanation:

A. Incorrect: Carbohydrates give ~4 kcal/g.
B. Incorrect: Proteins give ~4 kcal/g.
C. Correct: Fats provide ~9 kcal/g, highest energy value.
D. Incorrect: Vitamins provide no calories.

Q9. The first organ to receive absorbed nutrients from intestine via hepatic portal vein is:

A. Heart
B. Liver
C. Kidney
D. Pancreas

Answer: B

Explanation:

A. Incorrect: Blood reaches heart after liver.
B. Correct: Hepatic portal vein carries sugars, amino acids directly to liver.
C. Incorrect: Kidneys filter later.
D. Incorrect: Pancreas secretes insulin but does not receive nutrients first.

Q10. Which nutrient is the primary source of energy in humans?

A. Proteins
B. Carbohydrates
C. Fats
D. Vitamins

Answer: B

Explanation:

A. Incorrect: Proteins are secondary energy sources.
B. Correct: Carbohydrates are the main and immediate energy source.
C. Incorrect: Fats are stored energy.
D. Incorrect: Vitamins are regulatory.

Q11. In which form is nitrogen excreted in humans after amino acid metabolism?

A. Ammonia
B. Urea
C. Uric acid
D. Nitrate

Answer: B

Explanation:

A. Incorrect: Ammonia is highly toxic, excreted by fish.
B. Correct: Humans are ureotelic, excrete nitrogen mainly as urea.
C. Incorrect: Uric acid is major in birds/reptiles.
D. Incorrect: Nitrate is not excreted by humans.

Q12. Which process converts excess glucose into fat?

A. Glycogenolysis
B. Gluconeogenesis
C. Lipogenesis
D. Glycolysis

Answer: C

Explanation:

A. Incorrect: Glycogenolysis = glycogen → glucose.
B. Incorrect: Gluconeogenesis = non-carbs → glucose.
C. Correct: Lipogenesis converts glucose → fat.
D. Incorrect: Glycolysis = glucose breakdown.

Q13. Fats are mainly stored in:

A. Liver
B. Pancreas
C. Adipose tissue
D. Kidneys

Answer: C

Explanation:

A. Incorrect: Liver stores glycogen.
B. Incorrect: Pancreas secretes insulin.
C. Correct: Adipose tissue stores triglycerides.
D. Incorrect: Kidneys filter blood, not fat storage.

Q14. Which nutrient is essential for synthesis of hemoglobin?

A. Calcium
B. Iron
C. Sodium
D. Potassium

Answer: B

Explanation:

A. Incorrect: Calcium helps bones, clotting.
B. Correct: Iron is required for hemoglobin synthesis.
C. Incorrect: Sodium regulates osmotic balance.
D. Incorrect: Potassium maintains nerve/muscle function.

Q15. Which process describes the conversion of amino acids to glucose?

A. Glycolysis
B. Gluconeogenesis
C. Lipogenesis
D. Glycogenesis

Answer: B

Explanation:

A. Incorrect: Glycolysis = glucose breakdown.
B. Correct: Gluconeogenesis = glucose formation from non-carbohydrates (amino acids, glycerol).
C. Incorrect: Lipogenesis = fat synthesis.
D. Incorrect: Glycogenesis = glucose → glycogen.

Q16. Which organ stores glycogen and releases glucose when needed?

A. Pancreas
B. Stomach
C. Liver
D. Kidney

Answer: C

Explanation:

A. Incorrect: Pancreas regulates glucose via insulin/glucagon.
B. Incorrect: Stomach does not store glycogen.
C. Correct: Liver stores glycogen and maintains blood glucose levels.
D. Incorrect: Kidneys filter but don’t store glycogen.

Q17. Protein deficiency leads to:

A. Rickets
B. Beriberi
C. Kwashiorkor
D. Scurvy

Answer: C

Explanation:

A. Incorrect: Rickets = vitamin D deficiency.
B. Incorrect: Beriberi = vitamin B1 deficiency.
C. Correct: Kwashiorkor = severe protein deficiency in children.
D. Incorrect: Scurvy = vitamin C deficiency.

Q18. Which vitamin is essential for calcium assimilation?

A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K

Answer: B

Explanation:

A. Incorrect: Vitamin A supports vision, epithelium.
B. Correct: Vitamin D helps intestinal calcium absorption.
C. Incorrect: Vitamin E is antioxidant.
D. Incorrect: Vitamin K is for clotting factors.

Q19. Which nutrient deficiency leads to anemia?

A. Iron
B. Calcium
C. Vitamin D
D. Iodine

Answer: A

Explanation:

A. Correct: Iron deficiency lowers hemoglobin, causing anemia.
B. Incorrect: Calcium deficiency causes bone weakness.
C. Incorrect: Vitamin D deficiency causes rickets.
D. Incorrect: Iodine deficiency causes goiter.

Q20. Lipids are assimilated mainly as:

A. Fatty acids + glycerol stored in liver
B. Triglycerides stored in adipose tissue
C. Cholesterol stored in pancreas
D. Micelles stored in blood

Answer: B

Explanation:

A. Incorrect: Liver metabolizes but does not store bulk lipids.
B. Correct: Lipids are re-esterified as triglycerides and stored in adipose tissue.
C. Incorrect: Pancreas does not store cholesterol.
D. Incorrect: Micelles are absorption units, not storage.

Q21. Which of the following is a fat-soluble vitamin?

A. Vitamin C
B. Vitamin B1
C. Vitamin D
D. Vitamin B12

Answer: C

Explanation:

A. Incorrect: Vitamin C is water-soluble.
B. Incorrect: Vitamin B1 is water-soluble.
C. Correct: Vitamins A, D, E, K are fat-soluble.
D. Incorrect: Vitamin B12 is water-soluble.

Q22. Which is the main storage site of vitamin A in the body?

A. Kidneys
B. Pancreas
C. Liver
D. Muscles

Answer: C

Explanation:

A. Incorrect: Kidneys excrete wastes.
B. Incorrect: Pancreas secretes hormones.
C. Correct: Liver stores vitamin A in stellate (Ito) cells.
D. Incorrect: Muscles store glycogen/proteins, not vitamin A.

Q23. Which of the following vitamins is synthesized by gut bacteria?

A. Vitamin B12 and K
B. Vitamin A and D
C. Vitamin C and E
D. Vitamin D and B1

Answer: A

Explanation:

A. Correct: Intestinal flora synthesize vitamin K and some B-complex (like B12, biotin, folic acid).
B. Incorrect: Vitamin A and D are not made by gut bacteria.
C. Incorrect: Vitamin C/E are not bacterial products.
D. Incorrect: Vitamin D is synthesized in skin.

Q24. Which nutrient acts as the main building material of the body?

A. Carbohydrates
B. Proteins
C. Fats
D. Minerals

Answer: B

Explanation:

A. Incorrect: Carbs are energy sources.
B. Correct: Proteins form muscles, enzymes, hormones.
C. Incorrect: Fats are energy reserves.
D. Incorrect: Minerals support structure/regulation but not main building blocks.

Q25. Which macronutrient is NOT primarily used for energy but for growth and repair?

A. Carbohydrates
B. Fats
C. Proteins
D. None

Answer: C

Explanation:

A. Incorrect: Carbohydrates are main energy sources.
B. Incorrect: Fats store energy.
C. Correct: Proteins are mainly for growth, repair, structural functions.
D. Incorrect: One option (proteins) is correct.

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Part 5: Assimilation and Functions of Absorbed Nutrients (25 MCQs)