Biological Molecules (Edexcel International AS Biology)

Exam Questions

32 mins4 questions
1a
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3 marks

The butterfly is an insect that feeds on nectar produced by flowers.

The photograph shows a butterfly feeding on a flower.

monarch-butterfly-pink-zinnia-1800px

Photo (c)2006 Derek Ramsey (Ram-Man), GFDL 1.2 , via Wikimedia Commons

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
1b
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6 marks

The circulatory system of an insect is described as an open system. This means that the blood is not contained inside blood vessels but flows through cavities called sinuses.

The diagram shows part of the circulatory system of an insect.q4b-unit-1-oct-2021-edexcel-ial-biology

(i)

The length of the head of a butterfly is 4mm, the thorax is 6mm and the abdomen is 18mm.

Estimate the surface area to volume ratio of the butterfly.

Assume that the insect is a cylinder of diameter 4mm and the surface area is 360mm2

(2)

(ii)

Explain why the circulation of a butterfly is different from the circulation of a mammal.

(2)

(iii)

The blood flowing through the sinuses of the butterfly is separated from the organs by collagen.

Describe the structure of collagen.

(2)

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2a
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5 marks

Humans store energy as glycogen.

(i)
Which is the correct statement about the formation of glycogen?
(1)
  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

(ii)

Name the bond that joins two glucose molecules together.

(1)

(iii)

Explain how the structure of glycogen relates to its role as an energy storage molecule.

(3)
2b
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4 marks

Von Gierke disease is one type of glycogen storage disease (GSD).

(i)

Between one in 20 000 and one in 25 000 babies are born with GSD.

About 25% of patients with GSD are thought to have Von Gierke disease.

In one country, 3.8 million babies were born in one year.

Estimate the number of babies born each year with Von Gierke disease in this country.

(2)
(ii)

Von Gierke disease is an inherited disease.

Suggest why the majority of these babies are born to parents who are not affected by Von Gierke disease.

(2)

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3a
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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
3b
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3 marks

Triglycerides are lipids.

Describe how an unsaturated triglyceride is synthesised.

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4a
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1 mark

The photograph shows a saffron crocus plant.


crocus

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

4b
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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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