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Functions of Proteins: Collagen, Trypsin, GLUT-4, Insulin, Antibody

Biology · Biomolecules · NEET

Proteins do many jobs in the body. From NCERT Table 9.5: Collagen forms the intercellular ground substance, Trypsin is an enzyme, GLUT-4 helps transport glucose into cells, Insulin is a hormone, and Antibody fights infection. Memory hook: "Cats Trip Getting In Alive" = Collagen, Trypsin, GLUT-4, Insulin, Antibody.
Functions of Proteins (NCERT Table 9.5)CollagenIntercellularground substanceTrypsinEnzyme(digests protein)GLUT-4Glucose transportinto cellsInsulinHormone(lowers sugar)AntibodyFightsinfectionMemory hookCats Trip Getting In Alive = C, T, G, I, A
The five NEET-favourite proteins and their exact NCERT Table 9.5 functions: Collagen (structural), Trypsin (enzyme), GLUT-4 (transport), Insulin (hormone), Antibody (defence).

Your doubts, answered

What is the function of collagen? Is it structural?

Collagen is a structural protein. Its function in NCERT Table 9.5 is the intercellular ground substance. This means collagen forms the material that fills the space between cells and holds tissues together, like in skin, bone and tendon. It is also the most abundant protein in the animal world. So collagen is NOT an enzyme and NOT a hormone; it is structural support.

Is trypsin a hormone or an enzyme?

Trypsin is an ENZYME, not a hormone. It is a digestive enzyme that breaks down proteins in the small intestine. Students confuse it with insulin because both are linked to the pancreas, but the pancreas makes BOTH: insulin (a hormone that controls blood sugar) and trypsin (an enzyme that digests protein). Remember: trypsin = enzyme, insulin = hormone.

What does GLUT-4 do? How is it different from insulin?

GLUT-4 is a transport protein. Its function is to enable glucose transport into cells (it carries glucose across the cell membrane). Insulin is a hormone that acts as a SIGNAL and tells cells to bring out more GLUT-4. So insulin = the messenger, GLUT-4 = the doorway that actually lets glucose in. They work together but have different functions in NEET.

What is the function of an antibody protein?

An antibody is a protein that fights infection. It is an immunoglobulin (a type of globulin protein) made by the immune system. It finds and binds to germs like bacteria and viruses so the body can destroy them. In NEET matching questions, Antibody pairs with 'fights infection'.

How do I remember which protein does which function for NEET?

Use NCERT Table 9.5 directly, it is asked almost every year. Fixed pairs: Collagen to intercellular ground substance, Trypsin to enzyme, GLUT-4 to glucose transport into cells, Insulin to hormone, Antibody to fights infection. Also add: Concanavalin A to lectin (this appears in the same matching questions).

⚠️ The NEET trap
✗ Trypsin is a hormone and Insulin is an enzyme (swapping the two pancreas products).
✓ Trypsin is an ENZYME (digests protein); Insulin is a HORMONE (controls blood sugar). The pancreas makes both, but their functions are opposite in type.
🧠 NEET 2024 matched A. GLUT-4, B. Insulin, C. Trypsin, D. Collagen. The trap tempts you to call trypsin a hormone because it comes from the pancreas. Answer key locks Insulin = Hormone, Trypsin = Enzyme.

Real NEET questions

NEET 2024

Match list I with list II. List I: A. GLUT-4; B. Insulin; C. Trypsin; D. Collagen. List II: I. Hormone; II. Enzyme; III. Intercellular ground substance; IV. Enables glucose transport into cells.

A · A-I, B-II, C-III, D-IV
B · A-II, B-III, C-IV, D-I
C · A-III, B-IV, C-I, D-II
D · A-IV, B-I, C-II, D-III ✓
Solution: From NCERT Table 9.5: GLUT-4 enables glucose transport into cells (A-IV), Insulin is a hormone (B-I), Trypsin is an enzyme (C-II), and Collagen is the intercellular ground substance (D-III). This set matches only option D.
ReNEET 2026

Match List-I with List-II. List-I: A. Starch, B. Antibody, C. Concanavalin A, D. Glut-4. List-II: I. Fights infection, II. Energy storage, III. Glucose transport, IV. Lectin.

A · A-I, B-II, C-IV, D-III
B · A-II, B-I, C-IV, D-III ✓
C · A-II, B-I, C-III, D-IV
D · A-I, B-II, C-III, D-IV
Solution: Starch = energy storage (II). Antibody = fights infection (I). Concanavalin A = a plant lectin (IV). GLUT-4 = glucose transport (III). So A-II, B-I, C-IV, D-III = option B. Note how antibody and GLUT-4 functions repeat from Table 9.5.
NEET 2026

Match List I with List II. List I: A. Trypsin, B. Morphine, C. Concanavalin A, D. Collagen. List II: I. Intercellular ground substance, II. Lectin, III. Enzyme, IV. Alkaloid.

A · A-III, B-IV, C-II, D-I ✓
B · A-I, B-II, C-III, D-IV
C · A-IV, B-III, C-II, D-I
D · A-III, B-II, C-IV, D-I
Solution: Trypsin = enzyme (III). Morphine = alkaloid (IV). Concanavalin A = lectin (II). Collagen = intercellular ground substance (I). So A-III, B-IV, C-II, D-I = option A. Trypsin and Collagen keep the same functions as Table 9.5.

Solved Biomolecules NEET PYQs

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Frequently asked

Which protein is the intercellular ground substance?

Collagen. NCERT Table 9.5 lists collagen as the intercellular ground substance. It is also the most abundant protein in the animal world.

Is GLUT-4 a protein?

Yes. GLUT-4 is a transport protein in the cell membrane. Its function is to enable glucose to move into the cell. Insulin signals cells to use GLUT-4.

Why is this topic important for NEET?

NEET asks a protein-to-function matching question almost every year (2022, 2024, 2026, ReNEET 2026). Learning NCERT Table 9.5 by heart gives you an easy, sure mark.

Are all proteins enzymes?

No. Only some proteins are enzymes (like trypsin). Others are structural (collagen), transport (GLUT-4), hormonal (insulin) or defensive (antibody). Function depends on the protein.

What is the difference between insulin and antibody?

Insulin is a hormone that lowers blood sugar. An antibody is an immunoglobulin protein that fights infection. Both are proteins but have completely different jobs.

Related concepts:
Most Abundant Protein: Collagen vs RuBisCOProteins Are Polypeptides: The Peptide BondWhat Are Enzymes? Proteins vs RibozymesLectins and Concanavalin AFour Levels of Protein Structure Explained
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Biology MCQs (free, chapter-wise)Biomolecules PYQs