Biomolecules
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14.23 Differentiate between globular and fibrous proteins.
14.23 Differentiate between globular and fibrous proteins.
14.23
Globular proteins | Fibrous proteins |
It is usually soluble in water. | It is insoluble in water. |
All enzymes are globular protein. Some hormones such as insulin are also globular protein. | Fibrous proteins are usually used for structural purposes. For example, keratin is present in nails and hair; collagen in tendons; and myosin in muscles. |
The polypeptide chain in this protein is folded around itself, giving rise to spherical structure. | It is a fibre-like-structure formed by the polypeptide chain. These proteins are held together by strong and disulphide bonds. |
They are soluble in acids and bases. | They are insoluble in acids and bases. |
Examples:- egg albumin, casein of milk. | Examples :- Silk, Skin, Wool. |
They have weak intermolecular hydrogen bonding. | They have comparatively stronger intermolecular forces of attraction. |
They have folded, ball like structure. | They have thread like structure. |
Globular proteins are also called as spheroproteins owing to their shape. | Fibrous proteins are also called as scleroproteins. |
More sensitive to the changes in pH, temperature etc. | Less sensitive to the changes in pH, temperature etc. |
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14.22 What type of bonding helps in stabilising the α-helix structure of proteins?
14.22 What type of bonding helps in stabilising the α-helix structure of proteins?
14.22
The stability of α-helix structure is due to intramolecular hydrogen bonding between –NH and –CO groups of polypeptide chain. The α-helix is known as 3.613 because each turn of α-helix contains approximately 3.6 amino acids and a 13-membered ring is formed by hydrogen bonding.
Upvote 14.21 What are the common types of secondary structure of proteins?
14.21 What are the common types of secondary structure of proteins?
14.21
There are two common types of secondary structure of proteins:
(i) α–helix structure
(ii) β–pleated sheet structure
α–Helix structure
If the size of R-groups is quite large then the intramolecular bonds are formed between the C=O of one amino acid and the N-H group of the forth amino acid residue i
Upvote 14.20 Define the following as related to proteins (i) Peptide linkage (ii) Primary structure (iii) Denaturation.
14.20 Define the following as related to proteins (i) Peptide linkage (ii) Primary structure (iii) Denaturation.
14.20
When two molecule of –amino acids similar or different combine in this way that the amino group of one molecule with carboxy group of the other molecule, this result in the elimination of water molecule and the formation of new bond-CO NH- .
This type of bond is called peptide bond or pept
Upvote 14.19 What are essential and non-essential amino acids? Give two examples of each type.
14.19 What are essential and non-essential amino acids? Give two examples of each type.
14.19
(i) The amino acids which cannot be synthesised is called as essential amino acids. It must be obtained through diet. Example:- valine and leucine.
(ii) The amino acids which cannot be synthesised in the body is called as non-essential amino acids. Example: - glycine, Alanine.
Upvote 14.18 Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.
14.18 Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.
14.18
Open structure of D-glucose could not explain the following reactions:
(i) Despite having the aldehyde group, glucose does not give 2,4 DNP test and Schiff's
(ii) Glucose does not react with sodium hydrogen sulphite to form addition
(iii) The absence of free –CHO group is shown when the penta-a
Upvote 14.17 What happens when D-glucose is treated with the following reagents? (i) HI (ii) Bromine water (iii) HNO3
14.17 What happens when D-glucose is treated with the following reagents? (i) HI (ii) Bromine water (iii) HNO3
14.17
When D-glucose is heated and treated with HI for a long period of time, then n-hexane is formed, which shows that all the six-carbon atoms are linked in a straight
2. When D-glucose is treated with Br2 water i.e., bromine water which is a mild oxidising agent, then we get D-gluconic acid as one
Upvote 14.16 What is the basic structural difference between starch and cellulose?
14.16 What is the basic structural difference between starch and cellulose?
14.16
Starch consists of two components – amylase and amylopectin. Amylose is a long linear chain of α–D-(+)-glucose units joined by C1-C4glycosidic linkage (α -link).
Amylopectin is a branched-chain polymer of –D-glucose units, in which the chain is formed by C1-C4 glycosidic linkage and the branchin
Upvote 14.15 What are the hydrolysis products of (i) Sucrose and (ii) Lactose ?
14.15 What are the hydrolysis products of (i) Sucrose and (ii) Lactose ?
14.15
Hydrolysis is the process of using water to break down a molecule into two parts. It is usually a type of decomposition reaction where one reactant is water, where water is used to break chemical bonds in the other reactant. It can be considered as reverse of a condensation reaction.
The general
Upvote 14.14 What is glycogen? How is it different from starch?
14.14 What is glycogen? How is it different from starch?
14.14
Glycogen is a polysaccharide-type of carbohydrate. In animals, carbohydrates are stored as glycogen.
But starch is a carbohydrate which consists of two components –amylase (15 -20 %) and amylopectin (80 – 85%). However, glycogen is also like amylopectin but branching will take place after every
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