Amylose vs Amylopectin: Starch, Cellulose and Glycogen Compared
Chemistry · Biomolecules · NEET
Amylose is a straight, unbranched chain of alpha-glucose joined only by alpha-(1 to 4) links. Amylopectin is a branched chain that has both alpha-(1 to 4) links along the chain and alpha-(1 to 6) links at the branch points. Memory hook: "pectin has points" - amyloPECTIN is the branched one with 1 to 6 branch points.
Amylose is one straight chain of alpha-glucose held by only alpha-(1 to 4) links. Amylopectin has the same alpha-(1 to 4) chain plus alpha-(1 to 6) links that create branch points. Both are made of alpha-D-glucose and together form starch.
Your doubts, answered
Which one is branched, amylose or amylopectin?
Amylopectin is the branched one. It has straight sections joined by alpha-(1 to 4) links, plus branch points joined by alpha-(1 to 6) links. Amylose is not branched at all - it is one long straight chain with only alpha-(1 to 4) links. Trick: amyloPECTIN has branch Points.
What linkages are in amylose and amylopectin?
Amylose has ONLY alpha-(1 to 4) glycosidic linkages (C1 of one glucose to C4 of the next). Amylopectin has BOTH: alpha-(1 to 4) along the chain AND alpha-(1 to 6) at each branch point. This exact difference is the most asked NEET point.
Are amylose and amylopectin the same as starch?
Starch is made of both. Amylose is about 15-20% of starch and dissolves in water. Amylopectin is about 80-85% of starch and does not dissolve in water. Both are polymers of alpha-D-glucose, so starch is 100% alpha-glucose units.
Why can humans digest starch but not cellulose?
Starch (amylose and amylopectin) is made of alpha-glucose with alpha linkages, and our enzymes can break alpha linkages. Cellulose is made of beta-glucose with beta-(1 to 4) linkages. Humans have no enzyme to break the beta linkage, so cellulose passes out as fibre. This alpha vs beta point is a common NEET trap.
How is glycogen different from starch?
Glycogen is the storage carbohydrate in animals (called animal starch). Its structure is like amylopectin - branched with alpha-(1 to 4) and alpha-(1 to 6) links - but it is even MORE highly branched. It is stored in liver, muscles and brain. Starch is the plant version.
Are amylose and amylopectin made of glucose plus galactose?
No. Both amylose and amylopectin are polymers of ONLY alpha-D-glucose. Any option saying they contain galactose or fructose is wrong. NEET 2018 used exactly this wrong option to trap students.
⚠️ The NEET trap ✗ Amylose is the branched polymer with alpha-(1 to 4) and alpha-(1 to 6) linkages, and amylopectin is linear. ✓ It is the opposite. Amylopectin is branched with both alpha-(1 to 4) and alpha-(1 to 6) linkages; amylose is linear with only alpha-(1 to 4) linkages. 🧠 NTA swaps the two names to see if you memorised the wrong one. Remember amyloPECTIN = branch Points = 1 to 6 links.
Real NEET questions
2018
The difference between amylose and amylopectin is:
A · Amylose is a branched polymer with alpha-(1->4) and alpha-(1->6) glycosidic linkages
B · Amylose has both alpha-(1->4) and alpha-(1->6) linkages while amylopectin is linear
C · Amylopectin is branched, having both alpha-(1->4) and alpha-(1->6) glycosidic linkages, whereas amylose is linear with only alpha-(1->4) linkages ✓
D · Amylose is a copolymer made up of glucose and galactose units
Solution: Both amylose and amylopectin are polymers of alpha-D-glucose, so option D (glucose + galactose) is wrong. Amylose is a long unbranched chain with only alpha-(1->4) glycosidic linkages, which rules out option B (amylose is not branched) and option A (amylose is not the branched form). Amylopectin is highly branched: its straight parts use alpha-(1->4) links while the branch points use alpha-(1->6) links. So the correct answer is C.
Solved Biomolecules NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
What is the main difference between amylose and amylopectin?
Amylose is a linear (unbranched) chain of alpha-glucose with only alpha-(1 to 4) links. Amylopectin is branched, with alpha-(1 to 4) links along the chain and alpha-(1 to 6) links at branch points. Both are parts of starch.
Which glycosidic linkage causes branching?
The alpha-(1 to 6) glycosidic linkage forms the branch points. It is found in amylopectin and glycogen, but never in amylose (amylose has only alpha-(1 to 4)).
Is cellulose made of alpha or beta glucose?
Cellulose is made of beta-D-glucose units joined by beta-(1 to 4) linkages between C1 of one unit and C4 of the next. This is why humans cannot digest it - we lack the enzyme for beta links.
Why is glycogen called animal starch?
Because it is the carbohydrate stored in the animal body (liver, muscles, brain) and its structure is like amylopectin but even more highly branched. When the body needs energy, enzymes break glycogen back into glucose.
What percentage of starch is amylose and amylopectin?
Starch is about 15-20% amylose (water soluble) and about 80-85% amylopectin (water insoluble). Both are polymers of alpha-D-glucose.
