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Chemistry · 2026 · 3 marks
CBSE 2026 · Region 2 · Set 3 · Q28
(A) (a) Define the following terms: 1+1+1 (i) Invert Sugar (ii) Polysaccharides (b) On the basis of structure differentiate between fibrous and…
(A)(a)
Define the following terms : \[1+1+1 \]
(i)
Invert Sugar
(ii)
Polysaccharides
(b)
On the basis of structure differentiate between fibrous and globular proteins.
OR
(B)(a)
Why is glycogen known as animal starch ? \[1+1+1 \]
(b)
Differentiate between essential amino acids and non-essential amino acids.
(c)
What is the effect of denaturation on the structure of proteins ?
Marking-scheme solution
.
(a)(i) Sucrose is dextrorotatory and its hydrolysis gives dextrorotatory glucose and
laevorotatory fructose where laevo rotation is more than dextro resulting in
net rotation as laevorotatory, the product is known as invert sugar .
(ii)
Carbohydrates which give large number of monosaccharides units on
hydrolysis are called polysaccharides.
(b)
Fibrous proteins
When
polypeptide chains run
parallel and are held together by
hydrogen and disulphide bonds
then fibre-like structure is formed.
Globular proteins
When the chains of polypeptides
coil around to give a spherical
shape.
.
(a)
The glycogen is stored in animal body and its structure is similar to
amylopectin.
(b)
The amino acids which cannot be synthesised in the body and must be
obtained through diet are essential amino acids whereas amino acids which
can be synthesised in our body are known as non-essential amino acids.
(c)
During denaturation secondary and tertiary structures are destroyed but
primary structure remains intact.
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CBSE Class 12 Chemistry past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.