Biology · Chemical Coordination and Integration · NEET
Glucagon is a peptide hormone made by the alpha (α) cells of the Islets of Langerhans in the pancreas. It acts mainly on liver cells (hepatocytes) and RAISES blood glucose by breaking stored glycogen (glycogenolysis) and making new glucose (gluconeogenesis) — so it is called a hyperglycemic hormone. Memory hook: "GlucaGONE = glucose is GONE from storage, sent INTO the blood."
Alpha-cells of the Islets of Langerhans release glucagon, which acts on the liver to trigger glycogenolysis and gluconeogenesis, raising blood glucose (hyperglycemia). It is antagonistic to insulin from beta-cells.
Your doubts, answered
Alpha cells or beta cells — who makes glucagon?
The ALPHA (α) cells of the Islets of Langerhans secrete glucagon. The BETA (β) cells secrete insulin. NEET loves to swap these. Trick: Alpha and glucAgon both have an 'A'. Beta and insulin — think 'B for build/store'. If a statement says 'α-cells secrete insulin', it is WRONG (a real NEET 2018 / ReNEET 2026 answer).
Does glucagon raise or lower blood sugar?
Glucagon RAISES blood sugar (hyperglycemia). It is the opposite of insulin, which lowers blood sugar (hypoglycemia). If a question links glucagon with hypoglycemia, that statement is INCORRECT. Remember: glucagon is the 'fasting hormone' — when you have not eaten, it pushes stored sugar into the blood.
Is glucagon a peptide hormone or a steroid?
Glucagon is a PEPTIDE (protein) hormone, NOT a steroid. NCERT lists insulin and glucagon under peptide/polypeptide/protein hormones, and cortisol, testosterone, estradiol, progesterone under steroids. NEET 2024 asked exactly this — 'which is NOT a steroid?' answer: glucagon.
What are glycogenolysis and gluconeogenesis in glucagon action?
Both raise blood glucose but from different sources. Glycogenolysis = breaking stored GLYCOGEN in the liver back into glucose. Gluconeogenesis = making NEW glucose from non-carbohydrate sources (like amino acids). Glucagon stimulates BOTH, and it also reduces cellular glucose uptake — all three together cause hyperglycemia.
Which organ does glucagon mainly act on?
Glucagon acts mainly on the LIVER cells (hepatocytes). Note the difference: glucagon → mainly hepatocytes; insulin → mainly hepatocytes AND adipocytes. NEET tests this fine detail, so read the target-cell wording carefully.
⚠️ The NEET trap ✗ Glucagon lowers blood glucose and is secreted by beta-cells of the pancreas. ✓ Glucagon RAISES blood glucose (hyperglycemic) and is secreted by ALPHA-cells; beta-cells make insulin. 🧠 Two swaps in one line — alpha vs beta AND raise vs lower. NTA plants both. Lock it: Alpha–glucAgon–rAises.
Real NEET questions
2018
Which one of the following statements is incorrect?
A · α-cells of pancreas secrete glucagon
B · α-cells of pancreas secrete insulin ✓
C · Glucagon stimulates glycogenolysis
D · β-cells of pancreas secrete insulin
Solution: In the Islets of Langerhans, α-cells secrete glucagon and β-cells secrete insulin. Glucagon stimulates glycogenolysis to raise blood glucose. So the INCORRECT statement is that α-cells secrete insulin — they secrete glucagon. (Repeated in ReNEET 2026.)
2024
Which of the following is not a steroid hormone?
A · Testosterone
B · Progesterone
C · Glucagon ✓
D · Cortisol
Solution: NCERT classifies cortisol, testosterone, estradiol and progesterone as steroids. Glucagon is a PEPTIDE hormone from pancreatic alpha-cells, so it is NOT a steroid.
2016
Which of the following pairs of hormones are not antagonistic (having opposite effects) to each other?
A · Parathormone - Calcitonin
B · Insulin - Glucagon
C · Aldosterone - Atrial Natriuretic Factor
D · Relaxin - Inhibin ✓
Solution: Insulin (lowers glucose) and Glucagon (raises glucose) ARE antagonistic. PTH–Calcitonin and Aldosterone–ANF are also antagonistic. Relaxin and Inhibin act on unrelated targets, so they are the pair that is NOT antagonistic.
Solved Chemical Coordination and Integration NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Because it raises (hyper-) blood glucose (glycemic). It stimulates glycogenolysis and gluconeogenesis in the liver and reduces glucose uptake by cells, so blood sugar goes up.
Which cells secrete glucagon?
The alpha (α) cells of the Islets of Langerhans in the endocrine pancreas.
Is glucagon antagonistic to insulin?
Yes. Glucagon raises blood glucose while insulin lowers it. Together they maintain glucose homeostasis — this is a classic NEET antagonistic pair.
What type of hormone is glucagon chemically?
It is a peptide (protein) hormone, so it acts through membrane receptors and second messengers, not by entering the cell like a steroid.
Does glucagon cause diabetes?
No. Prolonged HYPERGLYCEMIA (usually from insulin deficiency or resistance) leads to diabetes mellitus. Glucagon simply raises blood sugar normally; the disease is tied to failure of insulin's balancing action.
