Which of the following enzymes is responsible for the breakdown of starch into glucose

Appeared in: RUHS, Jaipur, M.Sc Nursing Entrance Exam-2024

Explanation

Amylase is the specific enzyme responsible for the hydrolysis of starch, a complex carbohydrate.
The digestive process for starch begins in the mouth with salivary amylase and is primarily carried out in the small intestine by pancreatic amylase.
Amylase breaks down large starch polymers into smaller, more manageable sugars like maltose, which are subsequently broken down into glucose for absorption.

Option A: Lipase is an enzyme that digests fats (lipids or triglycerides), not carbohydrates like starch. It breaks fats down into fatty acids and glycerol.
Option C: Protease is a general term for enzymes that digest proteins. Examples include pepsin and trypsin. They break proteins down into smaller peptides and amino acids.
Option D: Lactase is a highly specific enzyme that digests lactose (milk sugar), a disaccharide. It does not act on starch, which is a polysaccharide.

Clinical Relevance

Nursing practice connection: Knowing Digestive Enzymes and Carbohydrate Metabolism helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Elevated serum amylase and lipase levels are key laboratory markers used in the diagnosis of acute pancreatitis. Damage to pancreatic cells causes these digestive enzymes to leak into the bloodstream.
A deficiency in the lactase enzyme results in lactose intolerance, a common digestive disorder where the inability to break down lactose leads to symptoms like bloating, gas, and diarrhea after consuming dairy products.
What if? If the question had asked about the initial digestion of protein in the stomach, the correct answer would be 'Pepsin', a type of protease that functions in the highly acidic environment of the stomach.

How to Approach the Question

First, identify the substrate mentioned in the question, which is 'starch'.
Next, identify the class of molecule the substrate belongs to. Starch is a complex carbohydrate.
Recall the major digestive enzymes and the type of macronutrient they act upon: Amylases digest carbohydrates, Proteases digest proteins, and Lipases digest fats.
Match the substrate 'starch' with its specific enzyme, which is Amylase.
Review the other options to confirm their roles. Lipase acts on fats, Protease on proteins, and Lactase on a different carbohydrate (lactose), confirming they are incorrect for starch digestion.

Concept Tested & Keywords

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E6 Physiology Ganong 27e Vol 2 Part 1 p. 24-26

E6 Medicine Harrison 22e Part 2 p. 647-649

E6 Physiology Guyton 4SAE Part 2A p. 190-192

Practise the full RUHS, Jaipur, M.Sc Nursing Entrance Exam-2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.