A protein is made of two separate, unbranched polypeptide chains. One chain has 84 amino acids and the other has 56. A protease completely digests the protein into free amino acids.
(a)
Name the type of reaction that breaks the bonds between the amino acids.
[1 mark]
(b)
Calculate the number of water molecules used to digest the whole protein.
[2 marks]
1 marksCore biology3.1.1
An enzyme splits a dipeptide into two amino acids.
Which statement describes this reaction?
[1 mark]
4 marksCore biology3.1.1
Each of the following reactions happens in cells.
(a)
Name the type of reaction that joins two α-glucose molecules to form maltose.
[1 mark]
(b)
Name the type of reaction when lipase acts on a triglyceride in the small intestine.
[1 mark]
(c)
Name the type of reaction that adds a nucleotide to a growing strand of RNA.
[1 mark]
(d)
Name the type of reaction when a protease digests a polypeptide.
[1 mark]
3 marksCore biology3.1.1
The relative molecular mass (Mr) of α-glucose is 180 and of water is 18. Six α-glucose molecules are joined in one unbranched chain.
(a)
Calculate the Mr of the chain.
[2 marks]
(b)
Explain why the Mr of the chain is less than the total Mr of the separate glucose molecules.
[1 mark]
4 marksUnfamiliar context3.1.1
Inulin is a storage carbohydrate made by some plants, such as chicory. One inulin molecule is an unbranched chain of 34 fructose monomers with one glucose monomer at one end. The enzyme inulinase hydrolyses inulin completely to monosaccharides.
(a)
Calculate the number of water molecules used when one inulin molecule is completely hydrolysed.
[1 mark]
(b)
Name the type of bond that inulinase breaks.
[1 mark]
(c)
A student says that a triglyceride is a polymer because it is made from four smaller molecules. Explain why the student is wrong.
[2 marks]
5 marksUnfamiliar context3.1.1, 3.1.5.1
The table shows four molecules made in cells. Each value is the number of monomers in the molecule.
Table of four molecules and their monomers: a double-stranded DNA fragment of 300 base pairs, a cellulose molecule of 5000 beta-glucose, a polypeptide of 150 amino acids and a glycogen molecule of 150 alpha-glucose.
Molecule
Monomer
Number of monomers
DNA fragment, double-stranded
nucleotide
300 in each strand
Cellulose, one chain
β-glucose
5000
Polypeptide, one chain
amino acid
150
Glycogen, branched
α-glucose
150
(a)
Calculate the number of water molecules released when the double-stranded DNA fragment is made from free nucleotides.
[2 marks]
(b)
Calculate the number of water molecules released when the cellulose molecule is made.
[1 mark]
(c)
A polypeptide and a molecule of glycogen are each made from 150 monomers. Explain why the glycogen molecule releases the same number of water molecules as the polypeptide, even though it is branched.