10. Which constituent of food is digested with the help of saliva?
[Jharkhand PCS Preliminary Examination (2013)]
- (a) Protein
- (b) Starch
- (c) Cellulose fibre
- (d) None of these
Answer: (b) Starch
Explanation: Ptyalin, the salivary form of amylase, hydrolyses starch into smaller carbohydrates. Saliva also lubricates food to enable swallowing. Humans do not possess a salivary cellulase; proteins are chiefly attacked by pepsin and pancreatic proteases.
9. Saliva helps digest which nutrient?
[Rajasthan RAS/RTS Preliminary Examination (2012)]
- (a) Starch
- (b) Proteins
- (c) Fibres
- (d) Fats
Answer: (a) Starch
Explanation: Salivary amylase initiates digestion of starch in the mouth. Its action begins while food is being chewed and mixed with saliva. This early reaction contributes to carbohydrate digestion, which is finished by pancreatic and intestinal enzymes.
8. Which listed enzyme helps in the digestion of protein?
[UPPSC PCS Preliminary Examination (2010)]
- (a) Urease
- (b) Sulfatase
- (c) Trypsin
- (d) Amylase
Answer: (c) Trypsin
Explanation: Trypsin is a pancreatic protease that hydrolyses peptide bonds in the small intestine. It is secreted as inactive trypsinogen and activated after reaching the duodenum. Urease acts on urea, while amylase digests starch rather than proteins.
7. Which is the second-largest gland and provides an alkaline, enzyme-rich digestive secretion?
[UPPSC Special Mains (2008)]
- (a) Liver
- (b) Spleen
- (c) Pancreas
- (d) Salivary glands
Answer: (c) Pancreas
Explanation: The pancreas is an accessory digestive gland situated behind the stomach. Its exocrine secretions contain bicarbonate and enzymes that digest proteins, carbohydrates, and fats. The liver is larger, but its bile does not itself contain those digestive hydrolases.
6. Which item is NOT a digestive enzyme in humans?
[UPSC Civil Services Preliminary Examination (2007)]
- (a) Trypsin
- (b) Gastrin
- (c) Ptyalin
- (d) Pepsin
Answer: (b) Gastrin
Explanation: Gastrin is a hormone involved in regulating gastric acid secretion, not an enzyme. Trypsin and pepsin hydrolyse proteins, while ptyalin is salivary amylase that digests starch. Confusing digestive hormones with enzymes is a common examination trap.
5. Which descending length order of small-intestinal regions is correct?
[UPSC Civil Services Preliminary Examination (2007)]
- (a) Jejunum–duodenum–ileum
- (b) Ileum–duodenum–jejunum
- (c) Jejunum–ileum–duodenum
- (d) Ileum–jejunum–duodenum
Answer: (d) Ileum–jejunum–duodenum
Explanation: The ileum is typically the longest segment of the small intestine, followed by the jejunum, with the duodenum shortest. The duodenum is the initial receiving portion for pancreatic secretions and bile; the longer distal segments are important for absorption.
4. Assertion: All food proteins are digested only in the small intestine. Reason: Pancreatic proteases enter the small intestine.
[UPSC Civil Services Preliminary Examination (2005)]
- (a) Both are true and reason explains assertion
- (b) Both are true but reason does not explain assertion
- (c) Assertion true but reason false
- (d) Assertion false but reason true
Answer: (d) Assertion false but reason true
Explanation: Protein digestion starts in the stomach when pepsin acts in acidic gastric juice. Pancreatic proteases do enter the small intestine and continue digestion. Thus the reason is correct, but the assertion wrongly excludes gastric protein digestion.
3. Where is much of the glycogen formed from excess glucose stored?
[UPPSC PCS Mains (2004)]
- (a) Stomach
- (b) Liver
- (c) Pancreatic juice
- (d) Bile
Answer: (b) Liver
Explanation: After a meal, some absorbed glucose is converted into glycogen through glycogenesis, especially in the liver and skeletal muscles. Liver glycogen acts as a buffer for blood glucose. Neither bile nor pancreatic juice functions as a glycogen-storage site.
2. Consider:
(1) Duodenal acid stimulates secretin release.
(2) Fatty acids in the small intestine stimulate enterogastrone.
Which are correct?
[UPSC Civil Services Preliminary Examination (2003)]
- (a) Only 1
- (b) Only 2
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer: (c) Both 1 and 2
Explanation: Acid entering the duodenum stimulates secretin release, which promotes bicarbonate secretion. Fatty nutrients in the intestine also stimulate inhibitory hormonal signals traditionally called enterogastrones, slowing gastric activity. Both mechanisms help coordinate stomach emptying with intestinal digestion.
1. Enzymes are basically composed of which type of substance?
[Uttarakhand PCS Preliminary Examination (2002)]
- (a) Fats
- (b) Sugars
- (c) Proteins
- (d) Vitamins
Answer: (c) Proteins
Explanation: Most enzymes, including digestive amylase, pepsin, and trypsin, are proteins acting as biological catalysts. Their specific three-dimensional structures permit reactions to proceed rapidly. A few naturally occurring catalytic RNA molecules exist, but typical human digestive enzymes are proteins.
Question attribution follows identified previous-year paper records, including papers held in a different year from their recruitment-cycle title. Minor wording changes were made for readability. No practice-only questions are included. For a formally authenticated question bank, each item should additionally be checked against its official examination PDF.
