Proteins (Edexcel International AS Biology)

Exam Questions

27 mins3 questions
1a
Sme Calculator
3 marks

Both DNA and RNA are polynucleotides.

The table shows how the components of polynucleotides can be represented.

q1a-unit-1-january-2021-edexcel-ial-biology
(i)
Which diagram shows a mononucleotide?
(1)
q1ai-unit-1-january-2021-edexcel-ial-biology
(ii)
Which diagram shows two components joined by a phosphodiester bond?
(1)
q1aii-unit-1-january-2021-edexcel-ial-biology

(iii)
Which diagram shows complementary base pairing?
(1)
q1aiii
1b
Sme Calculator
4 marks

The diagram shows a sequence of bases in a DNA template (antisense) strand.

A T T G G C G A G A A C


(i)

The table shows some statements about the new complementary DNA strand and the mRNA strand synthesised using this sequence of bases.

For each statement, put one cross box enclose bold cross times in the appropriate box, in each row, to show the correct statement about these strands.

(3)
Statement Both the new complementary DNA strand and the mRNA strand Only the new complementary DNA strand Only the mRNA strand Neither strand
The number of guanines will be the same as in the template strand        

The number of thymines will be the same as the number of adenines in the template strand

       
There will be no adenine present        

(ii)
Name the process that synthesises a mRNA strand using the DNA template strand.
(1)

Did this page help you?

2a
Sme Calculator
4 marks

People with lactose intolerance cannot digest lactose.

Lactose intolerance is due to a lack of the enzyme lactase.  

(i)

Which are the products of lactose digestion?

(1)

  A fructose and galactose
  B fructose and glucose
  C galactose and glucose
  D glucose and glucose

(ii)
Explain how the three-dimensional structure of lactase affects the mechanism of action of this enzyme.
(3)
2b
Sme Calculator
7 marks

People with lactose intolerance can drink lactose-free milk.

Lactose-free milk is produced by treating milk with lactase.

There are two ways of removing lactose from milk:

    • Mixing a solution of lactase with the milk (free lactase)

    • Enclosing the lactase inside permeable beads and pouring the milk over them (immobilised lactase).

The diagrams show these two methods.

q8b-unit-1-january-2021-edexcel-ial-biology

(i)
Suggest one advantage of using immobilised lactase.
(1)
(ii)

The table shows the effect of pH on the activity of free lactase and immobilised lactase.

pH Activity of free
lactase
/ a.u.
Activity of
immobilised lactase
/ a.u.
2 0 0
3 0 38
4 75 75
5 94 98
6 63 76
7 56 63
8 28 35


Explain the effects of pH on the activity of these two enzymes.

(4)

(iii)

Suggest how the rate of activity of the lactase could be measured.

Include appropriate units in your answer.

(2)
2c
Sme Calculator
2 marks

Congenital lactose intolerance (CLI) is an extremely rare genetic disorder.

Most people with CLI are found in one country.

Suggest why most people with CLI are found in one country.

Did this page help you?

3a
Sme Calculator
5 marks

The primary structure of a protein determines its secondary structure and its three‐dimensional structure.

Read through the following account of the primary structure of a protein.

Complete the account by writing the most appropriate word or words on the dotted lines.

The primary structure of a protein is the specific sequence of amino acids joined together by .................................................... bonds.

These bonds are formed between the ................................................ group of one amino acid and the ..................................................... group of an adjacent amino acid by a .......................................................  reaction.

These bonds are formed during the stage of protein synthesis called ...............................................  .

3b
Sme Calculator
2 marks

The table describes the types of bond that hold the secondary and the three‐dimensional structures together.

Which type of bonding is true for each structure?

Structure Hydrogen
bonds only
Ionic
bonds only
Both hydrogen
and ionic bonds
Neither of
these bonds
secondary structure    
three‐dimensional structure  

Did this page help you?