Collagen is a fibrous protein that is found in many tissues in animals. Some amino acids in collagen can be modified to improve the stability of the protein. For example, the amino acid lysine can be modified to form hydroxylysine. Fig. 2.1 shows a disaccharide bonded to the amino acid hydroxylysine in a collagen molecule. The disaccharide is made from two monosaccharides, which are indicated by the labels D and $$$\mathbf{E}$$$ in Fig. 2.1. (i) Give the precise name of the monosaccharide labelled $$$\mathbf{D}$$$ in Fig. 2.1. ................................................................................................................................. (ii) On Fig. 2.1, label the glycosidic bond with the letter G. Write your answer on Fig. 2.1. (iii) On Fig. 2.1, draw a circle around the $$$R$$$ group of hydroxylysine and label the circle with the letter $$$\mathbf{R}$$$. Write your answer on Fig. 2.1.

Biology

IGCSE&ALevel

CAIE

Exam No：9700_s24_qp_23 Year：2024 Question No：2(b)

Answer:

Knowledge points:

2.2.1 describe the ring forms of α-glucose and β-glucose

2.2.10 relate the molecular structure of triglycerides to their functions in living organisms

2.2.11 describe the molecular structure of phospholipids with reference to their hydrophilic (polar) phosphate heads and hydrophobic (non-polar) fatty acid tails

2.2.2 define the terms monomer, polymer, macromolecule, monosaccharide, disaccharide and polysaccharide

2.2.3 describe the formation of a glycosidic bond by condensation, with reference both to polysaccharides and to disaccharides, including sucrose

2.2.4 state that glucose, fructose and maltose are reducing sugars and that sucrose is a non-reducing sugar

2.2.5 describe the formation of a glycosidic bond by condensation, with reference to disaccharides, including sucrose, and polysaccharides

2.2.6 describe the breakage of a glycosidic bond in polysaccharides and disaccharides by hydrolysis, with reference to the non-reducing sugar test

2.2.7 describe the molecular structure of the polysaccharides starch (amylose and amylopectin) and glycogen and relate their structures to their functions in living organisms

2.2.8 describe the molecular structure of the polysaccharide cellulose and outline how the arrangement of cellulose molecules contributes to the function of plant cell walls

2.2.9 state that triglycerides are non-polar hydrophobic molecules and describe the molecular structure of triglycerides with reference to fatty acids (saturated and unsaturated), glycerol and the formation of ester bonds

2.3.1 describe and draw the general structure of an amino acid and the formation and breakage of a peptide bond

2.3.2 explain the meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins

2.3.3.1 hydrophobic interactions

2.3.3.2 hydrogen bonding

2.3.3.3 ionic bonding

2.3.3.4 covalent bonding, including disulfide bonds

2.3.4 state that globular proteins are generally soluble and have physiological roles and fibrous proteins are generally insoluble and have structural roles

2.3.5 describe the structure of a molecule of haemoglobin as an example of a globular protein, including the formation of its quaternary structure from two alpha (α) chains (α–globin), two beta (β) chains (β–globin) and a haem group

2.3.6 relate the structure of haemoglobin to its function, including the importance of iron in the haem group

2.3.7 describe the structure of a molecule of collagen as an example of a fibrous protein, and the arrangement of collagen molecules to form collagen fibres

2.3.8 relate the structures of collagen molecules and collagen fibres to their function

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