The digestion of protein is facilitated by?

Appeared in: RRB Staff Nurse Mumbai-2015

Explanation

Trypsin is a key proteolytic enzyme (protease) secreted by the pancreas as an inactive zymogen, trypsinogen.
It is activated in the duodenum (the first part of the small intestine) by an enzyme called enterokinase.
Once active, trypsin breaks down proteins into smaller units like proteoses, peptones, and peptides.
This action is crucial for the subsequent absorption of amino acids.

Option B: Amylase is an enzyme that specifically digests carbohydrates (like starch) into simpler sugars (like maltose). It does not act on proteins.
Option C: Secretin is a hormone, not a digestive enzyme. It is released in response to acidic chyme entering the duodenum and stimulates the pancreas to secrete a bicarbonate-rich fluid, which neutralizes the acid and provides the optimal pH for pancreatic enzymes to function.
Option D: Lipase is an enzyme that digests fats (lipids or triglycerides) into fatty acids and glycerol. It has no role in protein digestion.

Visual 1: Diagram - A flowchart illustrating the process of protein digestion, starting from the stomach with pepsin and moving to the small intestine with trypsin and other proteases. This helps visualize the sequence of events.
Visual 2: Table - A summary table of major digestive enzymes, their source, site of action, substrate, and end products. This provides a quick reference for comparison.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Biochemistry of protein digestion as background academic context rather than a clinical decision trigger.
In acute pancreatitis, digestive enzymes like trypsinogen can be prematurely activated within the pancreas itself, leading to autodigestion of the pancreatic tissue. This is a severe and life-threatening condition.
Measuring serum levels of pancreatic enzymes like amylase and lipase is a key diagnostic tool for pancreatitis. Elevated levels indicate pancreatic inflammation or injury.
What if? - If a patient has a condition like cystic fibrosis, the thick mucus can block the pancreatic ducts, preventing enzymes like trypsin from reaching the small intestine. This leads to malabsorption of proteins and fats, requiring oral pancreatic enzyme replacement therapy.

How to Approach the Question

First, identify the key term in the question stem, which is 'digestion of protein'.
This is a factual recall question that requires knowledge of digestive physiology.
Systematically evaluate each option based on its known function.
Recall that proteases digest proteins, amylases digest carbohydrates, and lipases digest fats.
Identify Trypsin as a well-known protease.
Eliminate Amylase and Lipase as they act on different substrates. Eliminate Secretin as it is a hormone, not a digestive enzyme.

Concept Tested & Keywords

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Practise the full RRB Staff Nurse Mumbai-2015

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