Question: 1

Biological molecules are held together by a variety of bonds.

(a) The diagram in Fig. 1.1 represents an amino acid.

(i) One of the atoms that make up an amino acid has been replaced with the letter X.

State the chemical symbol of the atom represented by the letter X in Fig. 1.1.

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[1]

(ii) Name the polymer formed from a chain of amino acids.

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[1]

(iii) Name the bond that is formed when two amino acids are joined together. Describe the formation of this bond.

name of bond

description of formation

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[3]

(b) Fig. 1.2 shows a hydrogen bond between two water molecules.

(i) Many of the physical properties of water arise as a result of these hydrogen bonds.

Describe ways in which the physical properties of water allow organisms to survive over a range of temperatures.

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[9]

(ii) List three other examples of where hydrogen bonds are found in biological molecules.

1

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2

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3

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[3]

[Total: 17]

Question: 2

(a) Amino acids are the basic building blocks for proteins. Fig. 4.1 shows the amino acid cysteine.

(i) Complete the table by selecting the letter, J, K, L or M, that represents the following groups in cysteine.

group
	letter
	
carboxyl
		
R group
		
amine group

[3]

(ii) The primary structure of a protein consists of a chain of amino acids.

Describe how a second amino acid would bond to cysteine in forming the primary structure of a protein.

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[3]

(b) Each amino acid has a different R group.

Describe how these R groups can interact to determine the tertiary structure of a protein.

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[4]

(c) Fig. 4.2 shows the structure of two polymers, glycogen and collagen, that are found in mammals.

(i) Complete the table below to give three differences between the structure of glycogenand collagen.

glycogen
	collagen

		

[3]

(ii) Collagen is found in the ligaments which hold bones together at joints.

State two properties of collagen that make it suitable for this purpose.

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[2] [Total: 15]

Question: 3

(a) Haemoglobin is a globular protein.

Describe the structure of a haemoglobin molecule.

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[7]

(b) Describe the ways in which the structure of collagen is similar to the structure of haemoglobin.

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[4] [Total: 11]