NEET 2023 Human Physiology Question 1 - Digestive System

NEET 2023 Human Physiology - Question 1

📋 Question

Statement: Which of the following pancreatic enzymes is activated by enterokinase?

Options: A. Trypsinogen B. Amylase C. Lipase D. Nucleases

🎯 Detailed Solution

Correct Answer: A. Trypsinogen

Step-by-Step Explanation:

Step 1: Understand Pancreatic Enzyme Activation

The pancreas secretes several enzymes in inactive form to prevent self-digestion:

Inactive Forms (Zymogens):

Trypsinogen: Inactive form of trypsin
Chymotrypsinogen: Inactive form of chymotrypsin
Procarboxypeptidase: Inactive form of carboxypeptidase

Active Forms:

Trypsin: Activated from trypsinogen
Chymotrypsin: Activated from chymotrypsinogen
Carboxypeptidase: Activated from procarboxypeptidase

Directly Secreted Active Enzymes:

Amylase: Already active when secreted
Lipase: Already active when secreted
Nucleases: Already active when secreted

Step 2: Enterokinase Activation Mechanism

Enterokinase (Enteropeptidase):

Location: Secreted by intestinal mucosa (duodenum)
Function: Activates trypsinogen to trypsin
Reaction: Trypsinogen + Enterokinase → Trypsin

Cascade Effect: Once trypsin is formed, it activates other pancreatic enzymes:

Trypsin + Trypsinogen → 2 Trypsin (auto-activation)
Trypsin + Chymotrypsinogen → Chymotrypsin
Trypsin + Procarboxypeptidase → Carboxypeptidase

Step 3: Eliminate Incorrect Options

Option B: Amylase

Amylase is secreted in active form
No activation required
Breaks down carbohydrates (starch) ❌

Option C: Lipase

Lipase is secreted in active form
No activation required
Breaks down lipids (fats) ❌

Option D: Nucleases

Nucleases are secreted in active form
No activation required
Break down nucleic acids ❌

Step 4: Verify Correct Answer

Trypsinogen Activation:

Primary Activation: Enterokinase in duodenum activates trypsinogen
Secondary Activation: Formed trypsin activates remaining trypsinogen
Tertiary Activation: Trypsin activates other enzymes

Biological Significance:

Prevents autodigestion of pancreas
Ensures enzymes activate only in proper location (small intestine)
Provides controlled enzyme activation cascade

🔬 Concept Explanation

Pancreatic Enzyme System:

Exocrine Pancreas Functions:

Enzyme Production: Synthesis of digestive enzymes
Bicarbonate Secretion: Neutralization of acidic chyme
Water and Electrolytes: Proper medium for enzyme action

Enzyme Classification: Proteases (Protein Digestion):

Trypsin: Breaks down proteins into peptides
Chymotrypsin: Breaks down proteins into aromatic amino acids
Carboxypeptidase: Removes terminal amino acids from peptides

Carbohydrate Digestion:

Pancreatic Amylase: Breaks down starch into maltose

Lipid Digestion:

Pancreatic Lipase: Breaks down triglycerides into fatty acids and glycerol

Nucleic Acid Digestion:

Nucleases: Break down DNA and RNA

Enzyme Activation Mechanisms:

Why Zymogens?

Protection: Prevents autodigestion of pancreatic tissue
Storage: Allows for stable storage of enzymes
Controlled Activation: Ensures enzymes act in correct location

Activation Sites:

Pancreas: Enzyme synthesis and storage (inactive forms)
Duodenum: Primary activation site (enterokinase action)
Small Intestine: Main site of digestive action

📺 Video Solution Explanation

Visual Learning:

[Watch Video Solution] - Link to 5-minute detailed video explanation

Video Contents:

Animated diagram of pancreatic enzyme secretion
Step-by-step activation cascade
Visual representation of enterokinase action
Clinical significance of enzyme activation
Common disorders related to enzyme activation

🏷️ Comprehensive Tags

Subject Tags:

biology, human-physiology, animal-physiology

Topic Tags:

digestive-system, pancreas, enzyme-activation, digestive-enzymes

Concept Tags:

trypsinogen-activation, enterokinase, zymogens, protein-digestion

Difficulty Tags:

medium, factual, conceptual, memory-based

Exam Tags:

neet, neet-2023, multiple-choice, 4-marks, physiology

Prerequisite Knowledge:

📊 Practice Questions

Similar Difficulty:

Question: Which enzyme activates procarboxypeptidase?
Question: Where is enterokinase secreted from?
Question: Which pancreatic enzyme is directly secreted in active form?

Higher Difficulty:

Question: Explain the complete cascade of pancreatic enzyme activation.
Question: What happens if enterokinase is deficient?
Question: Compare the activation mechanisms of different digestive enzymes.

📈 Performance Statistics

Student Performance Data:

Correct Answer Rate: 68%
Average Time: 1.8 minutes
Common Wrong Answer: B (Amylase) - 15% of students
Difficulty Rating: 3.0/5

Topic Weightage:

NEET 2023: 8-10 questions from Human Physiology
Digestive System: 2-3 questions typically
Marks Weightage: 32-40/720 (4.4-5.6%)

🎯 Study Tips

Quick Revision:

Enterokinase: Activates trypsinogen in duodenum
Trypsinogen → Trypsin: Primary activation by enterokinase
Auto-activation: Trypsin activates more trypsinogen
Cascade Effect: Trypsin activates other enzymes

Exam Strategy:

Identify Key Term: Look for “activated by enterokinase”
Recall Zymogens: Remember enzymes secreted in inactive form
Process of Elimination: Rule out directly secreted active enzymes
Biological Logic: Understand why activation is needed

Memory Aids:

“Enterokinase enters to activate trypsinogen”
“Trypsin triggers the activation cascade”
“Amylase, Lipase, Nucleases - already active when they arrive”

🔗 Additional Resources

Study Materials:

Video Lectures:

💡 Key Takeaways

Enterokinase activates trypsinogen to trypsin in the duodenum
Trypsinogen is the only option among choices activated by enterokinase
Cascade Effect: Once trypsin forms, it activates other enzymes
Biological Protection: Zymogens prevent pancreatic autodigestion

Remember: In pancreatic enzyme questions:

Identify which enzymes are secreted as inactive zymogens
Remember enterokinase specifically activates trypsinogen
Understand the biological significance of controlled activation
Recognize that amylase, lipase, and nucleases are already active

Happy Learning! 🎯