International A Level (IAL)BiologyEdexcelExam Questions1. Molecules, Transport & HealthBiological Molecules

Biological Molecules (Edexcel International A Level (IAL) Biology): Exam Questions

Exam code: YBI11

22 mins4 questions

3 marks

The butterfly is an insect that feeds on nectar produced by flowers.
The photograph shows a butterfly feeding on a flower.

The nectar in flowers contains nutrients including sugars, amino acids and lipids.

(i) The sugars in the nectar are fructose, glucose and sucrose.

Which of these contain glycosidic bonds?

(1)

☐ A fructose only

☐ B sucrose only

☐ C fructose and glucose

☐ D fructose and sucrose

(ii) Which row of the table describes how amino acids are joined together to form a protein?

(1)

	name of bond	type of reaction
☐A	ester	condensation
☐B	ester	hydrolysis
☐C	peptide	condensation
☐D	peptide	hydrolysis

(iii) Which row of the table describes a saturated lipid?

(1)

	carbon-carbon double bonds	carbon : hydrogen ratio
☐A	absent	higher than in an unsaturated fatty acid chain
☐B	absent	lower than in an unsaturated fatty acid chain
☐C	present	higher than in an unsaturated fatty acid chain
☐D	present	lower than in an unsaturated fatty acid chain

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4 marks

Polysaccharides, lipids, nucleic acids and proteins are large molecules found in living organisms.

Polymers are large molecules made of monomers. The table gives information about some of these polymers.

Complete the table by filling in the empty boxes with either the name of the monomer, the elements present in each monomer or the type of bond between monomers.

(4)

Polymer	Monomer	Elements present in monomer	Type of bond between monomers
polysaccharides	monosaccharide		glycosidic
nucleic acid		carbon, hydrogen, oxygen, phosphorus and nitrogen
protein	amino acid		peptide

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3 marks

Triglycerides are lipids.

Describe how an unsaturated triglyceride is synthesised.

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1 mark

The photograph shows a saffron crocus plant.

Emilie40, CC0, via Wikimedia Commons

This plant grows from a bulb.

The bulb contains starch as an energy storage molecule for the crocus.

How many of the following statements are correct for starch in living cells?

Starch consists of a mixture of two types of polysaccharide
Starch contains only 1–6 bonds
Starch is insoluble in water

(1)

☐ A None

☐ B One

☐ C Two

☐ D Three

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6 marks

Saffron is a spice that is derived from parts of the flower of the saffron crocus.

Saffron contains a disaccharide called gentiobiose.

(i) Read through the following description of some disaccharides.

Complete the description by writing the most appropriate word on the dotted lines.

(4)

Disaccharides consist of two monosaccharides joined together by a ........................................ covalent bond. Sucrose and lactose are both disaccharides. They both contain a molecule of ................................. Sucrose also contains one molecule of ................................ and lactose also contains one molecule of ............................ .

(ii) Gentiobiose is formed from two identical monosaccharides.

Name the type of reaction that joins these monosaccharides together in the formation of gentiobiose.

(1)

(iii) The molecular mass of each of the monosaccharides in gentiobiose is 180.

The table shows the molecular mass of the elements present in the monosaccharides.

Element	Molecular mass
carbon	12
hydrogen	1
oxygen	16

Which is the molecular mass of gentiobiose?

(1)

☐ A 144

☐ B 162

☐ C 342

☐ D 360

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☐	A	α glucose molecules join together by a condensation reaction
☐	B	α glucose molecules join together by a hydrolysis reaction
☐	C	β glucose molecules join together by a condensation reaction
☐	D	β glucose molecules join together by a hydrolysis reaction