3.1.1 Monomers and
polymers
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Date: _______________________
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Time: 237 min.
Marks: 196 marks
Comments:
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3.1.1 Monomers and
polymers
Name:
_______________________
_
Class:
_______________________
_
Date:
_______________________
_
Time: 237 min.
Marks: 196 marks
Comments:
Q1. (a) What is a monomer?
(1) (b) Lactulose is a disaccharide formed from one molecule of galactose and one molecule of fructose. Other than both being disaccharides, give one similarity and one difference between the structures of lactulose and lactose. Similarity ___________________________________________________________
Difference __________________________________________________________
(2) (c) Following digestion and absorption of food, the undigested remains are processed to form faeces in the parts of the intestine below the ileum. The faeces of people with constipation are dry and hard. Constipation can be treated by drinking lactulose. Lactulose is soluble, but is not digested or absorbed in the human intestine. Use your knowledge of water potential to suggest why lactulose can be used to help people suffering from constipation.
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(2) (b) The secondary structure of a polypeptide is produced by bonds between amino acids. Describe how.
(2) (c) Two proteins have the same number and type of amino acids but different tertiary structures. Explain why.
(2)
(Total 6 marks) Q3. (a) Describe how you would test a piece of food for the presence of lipid.
(2) The figure below shows a phospholipid. X Y (b) The part of the phospholipid labelled A is formed from a particular molecule. Name
compared with cells lining the ileum.
(1) (g) E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why.
(2) (Total 10 marks) Q4. Starch and cellulose are two important plant polysaccharides. The following diagram shows part of a starch molecule and part of a cellulose molecule. (a) Explain the difference in the structure of the starch molecule and the cellulose molecule shown in the diagram above.
(2) (b) Starch molecules and cellulose molecules have different functions in plant cells. Each molecule is adapted for its function. Explain one way in which starch molecules are adapted for their function in plant cells.
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(2) (c) Explain how cellulose molecules are adapted for their function in plant cells.
(3) (Total 7 marks) Q5. (a) Messenger RNA (mRNA) is used during translation to form polypeptides. Describe how mRNA is produced in the nucleus of a cell.
(6) (b) Describe the structure of proteins.
- Control experiments were carried out using cooked wheat that had been chopped up in a blender, not chewed. (a) What reducing sugar, or sugars, would you expect to be produced during chewing? Give a reason for your answer.
**(2)**
(b) In this model of digestion in the human gut, what other enzyme is required for the complete digestion of starch? ___________________________________________________________________ (1) (c) What was the purpose of step 2, in which samples were mixed with water, hydrochloric acid and pepsin? ___________________________________________________________________ ___________________________________________________________________ (1) (d) In the control experiments, cooked wheat was chopped up to copy the effect of chewing. Suggest a more appropriate control experiment. Explain your suggestion. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (2) (e) The figure below shows the student’s results.
Incubation time / minutes Explain what these results suggest about the effect of chewing on the digestion of starch in wheat.
(3) (Total 9 marks) Q7. The diagram shows the structure of the cell-surface membrane of a cell. (a) Name A and B. A _________________________________________________________________
Amylase Maltase (2) (Total 4 marks) Q9. (a) The table shows some statements about three carbohydrates. Complete the table with a tick in each box if the statement is true. Statement Starch Cellulose Glycogen Found in plant cells Contains glycosidic bonds Contains β-glucose (3) (b) Name the type of reaction that would break down these carbohydrates into their monomers.
(1) (c) Give one feature of starch and explain how this feature enables it to act as a storage substance. Feature ____________________________________________________________ Explanation _________________________________________________________
(2) (d) The picture shows starch grains as seen with an optical microscope. The actual length of starch grain A is 48 μm. Use this information and the arrow line to calculate the magnification of the picture. Show your working.
© iStock/Thinkstock Magnification ____________________ times (2) (Total 8 marks) Q10. The diagram shows one end of a cellulose molecule. (a) (i) Name the monomers that form a cellulose molecule.
(1) (ii) Name bond Y.
(1) (iii) What chemical group is at position Z?
(1) (b) (i) Complete the table to show two ways in which the structure of cellulose is different from the structure of starch. Starch Cellulose
Part D ________________________ Part E ________________________ (3) (iii) In a piece of DNA, 34% of the bases were thymine. Complete the table to show the names and percentages of the other bases. Name of base Percentage Thymine 34 34 (2) (b) A polypeptide has 51 amino acids in its primary structure. (i) What is the minimum number of DNA bases required to code for the amino acids in this polypeptide? (1) (ii) The gene for this polypeptide contains more than this number of bases. Explain why
(1) (Total 8 marks) Q12. Read the following passage. Aspirin is a very useful drug. One of its uses is to reduce fever and inflammation. Aspirin does this by preventing cells from producing substances called prostaglandins. Prostaglandins are produced by an enzyme-controlled pathway. Aspirin works by inhibiting one of the enzymes in this pathway. Aspirin attaches permanently to a chemical group on one of the monomers that make up the active site of this enzyme.
The enzyme that is involved in the pathway leading to the production of prostaglandins is also involved in the pathway leading to the production of thromboxane. This is a substance that promotes blood clotting. A small daily dose of aspirin may reduce the risk of myocardial infarction (heart attack).
Use information from the passage and your own knowledge to answer the following questions. (a) Name the monomers that make up the active site of the enzyme (lines 6 – 7).
(1) (b) The diagram shows the pathways by which prostaglandins and thromboxane are formed. (i) Aspirin only affects one of the enzymes in this pathway. Use information in lines 5 - 7 to explain why aspirin does not affect the other enzymes.
(2) (ii) Which enzyme, X , Y or Z , is inhibited by aspirin? Explain the evidence from the passage that supports your answer. Enzyme _______________________________________________________ Explanation ____________________________________________________
Use your knowledge of competitive inhibition to suggest why.
(2) (Total 7 marks) Q14. The diagram shows the life cycle of a fly. When the larva is fully grown, it changes into a pupa. The pupa does not feed. In the pupa, the tissues that made up the body of the larva are broken down. New adult tissues are formed from substances obtained from these broken-down tissues and from substances that were stored in the body of the larva. (a) Hydrolysis and condensation are important in the formation of new adult proteins. Explain how.
(2) (b) Most of the protein stored in the body of a fly larva is a protein called calliphorin. Explain why different adult proteins can be made using calliphorin.
(1) The table shows the mean concentration of RNA in fly pupae at different ages. Age of pupa as percentage of total time spent as a pupa Mean concentration of RNA / μg per pupa 0 20 20 15 40 12 60 17 80 33 100 20 (c) Describe how the concentration of RNA changes during the time spent as a pupa.
(2) (d) (i) Describe how you would expect the number of lysosomes in a pupa to change with the age of the pupa. Give a reason for your answer.
(2) (ii) Suggest an explanation for the change in RNA concentration in the first 40% of the time spent as a pupa.
(2)