Q1.
(a) What is a tissue?
___________________________________________________________________
___________________________________________________________________
(1)
(b) A student cut a thin section of tissue from a potato and examined it with an optical
microscope.
(i) Starch was present in the cells of this tissue. Describe how the student
could find out where in the cells the starch was present.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(ii) The student cut a thin section of the tissue. Explain why it was important
that the section was thin.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(c) The cell walls of potato cells contain cellulose. Cellulose and starch are both
carbohydrates. Describe two ways in which molecules of cellulose are similar to
molecules of starch.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(Total 7 marks)
Q2.
Page 1 of 131
,Read the following passage.
Straw consists of three main organic substances – cellulose, hemicellulose and lignin.
Cellulose molecules form chains which pack together into fibres. Hemicellulose is a small
molecule formed mainly from five-carbon (pentose) sugar monomers. It acts as a cement
holding cellulose fibres together. Like hemicellulose, lignin is a polymer, but it is not a
5 carbohydrate. It covers the cellulose in the cell wall and supplies additional strength. In
addition to these three substances, there are small amounts of other biologically important
polymers present.
The other main component of straw is water. Water content is variable but may be determined
by heating a known mass of straw at between 80 and 90°C until it reaches a constant mass.
10 The loss in mass is the water content.
Since straw is plentiful, it is possible that it could be used for the production of a range of
organic substances. The first step is the conversion of cellulose to glucose. It has been
suggested that an enzyme could be used for this process. There is a difficulty here, however.
The lignin which covers the cellulose protects the cellulose from enzyme attack.
Use information from the passage and your own knowledge to answer the following
questions.
(a) (i) Give one way in which the structure of a hemicellulose molecule is
similar to the structure of a cellulose molecule.
______________________________________________________________
______________________________________________________________
(1)
(ii) Complete the table to show two ways in which the structure of a
hemicellulose molecule differs from the structure of a cellulose molecule.
Hemicellulose Cellulose
____________________________ ____________________________
____________________________ ____________________________
____________________________ ____________________________
____________________________ ____________________________
(2)
(b) Name one biologically important polymer, other than those mentioned in the
passage, which would be found in straw.
___________________________________________________________________
(1)
(c) Explain why the following steps were necessary in finding the water content of
straw:
(i) heating the straw until it reaches constant mass (line 9);
Page 2 of 131
, ______________________________________________________________
______________________________________________________________
______________________________________________________________
(1)
(ii) not heating the straw above 90°C (line 9).
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(d) A covering of lignin protects cellulose from enzyme attack (line 14). Use your
knowledge of the way in which enzymes work to explain why cellulose-digesting
enzymes do not digest lignin.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(e) Describe the structure of a cellulose molecule and explain how cellulose is
adapted for its function in cells.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Page 3 of 131
, ___________________________________________________________________
___________________________________________________________________
(6)
(Total 15 marks)
Q3.
Moulds belong to a group of organisms called fungi. When mould is examined with a
microscope it is seen to consist of long, colourless threads called hyphae.
A student investigated the growth of fungal hyphae. The diagram shows part of a hypha
seen under a microscope at the beginning of a lesson and again at the end of the lesson.
(a) Give one piece of evidence from the diagram that fungi are eukaryotic.
___________________________________________________________________
___________________________________________________________________
(1)
(b) (i) By how much had the hypha grown during the lesson? Show your
working.
Answer: ____________________ µm
(2)
(ii) Explain how you could use your answer to calculate the rate of growth of
this hypha.
______________________________________________________________
Page 4 of 131
(a) What is a tissue?
___________________________________________________________________
___________________________________________________________________
(1)
(b) A student cut a thin section of tissue from a potato and examined it with an optical
microscope.
(i) Starch was present in the cells of this tissue. Describe how the student
could find out where in the cells the starch was present.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(ii) The student cut a thin section of the tissue. Explain why it was important
that the section was thin.
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(c) The cell walls of potato cells contain cellulose. Cellulose and starch are both
carbohydrates. Describe two ways in which molecules of cellulose are similar to
molecules of starch.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(Total 7 marks)
Q2.
Page 1 of 131
,Read the following passage.
Straw consists of three main organic substances – cellulose, hemicellulose and lignin.
Cellulose molecules form chains which pack together into fibres. Hemicellulose is a small
molecule formed mainly from five-carbon (pentose) sugar monomers. It acts as a cement
holding cellulose fibres together. Like hemicellulose, lignin is a polymer, but it is not a
5 carbohydrate. It covers the cellulose in the cell wall and supplies additional strength. In
addition to these three substances, there are small amounts of other biologically important
polymers present.
The other main component of straw is water. Water content is variable but may be determined
by heating a known mass of straw at between 80 and 90°C until it reaches a constant mass.
10 The loss in mass is the water content.
Since straw is plentiful, it is possible that it could be used for the production of a range of
organic substances. The first step is the conversion of cellulose to glucose. It has been
suggested that an enzyme could be used for this process. There is a difficulty here, however.
The lignin which covers the cellulose protects the cellulose from enzyme attack.
Use information from the passage and your own knowledge to answer the following
questions.
(a) (i) Give one way in which the structure of a hemicellulose molecule is
similar to the structure of a cellulose molecule.
______________________________________________________________
______________________________________________________________
(1)
(ii) Complete the table to show two ways in which the structure of a
hemicellulose molecule differs from the structure of a cellulose molecule.
Hemicellulose Cellulose
____________________________ ____________________________
____________________________ ____________________________
____________________________ ____________________________
____________________________ ____________________________
(2)
(b) Name one biologically important polymer, other than those mentioned in the
passage, which would be found in straw.
___________________________________________________________________
(1)
(c) Explain why the following steps were necessary in finding the water content of
straw:
(i) heating the straw until it reaches constant mass (line 9);
Page 2 of 131
, ______________________________________________________________
______________________________________________________________
______________________________________________________________
(1)
(ii) not heating the straw above 90°C (line 9).
______________________________________________________________
______________________________________________________________
______________________________________________________________
______________________________________________________________
(2)
(d) A covering of lignin protects cellulose from enzyme attack (line 14). Use your
knowledge of the way in which enzymes work to explain why cellulose-digesting
enzymes do not digest lignin.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(2)
(e) Describe the structure of a cellulose molecule and explain how cellulose is
adapted for its function in cells.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
Page 3 of 131
, ___________________________________________________________________
___________________________________________________________________
(6)
(Total 15 marks)
Q3.
Moulds belong to a group of organisms called fungi. When mould is examined with a
microscope it is seen to consist of long, colourless threads called hyphae.
A student investigated the growth of fungal hyphae. The diagram shows part of a hypha
seen under a microscope at the beginning of a lesson and again at the end of the lesson.
(a) Give one piece of evidence from the diagram that fungi are eukaryotic.
___________________________________________________________________
___________________________________________________________________
(1)
(b) (i) By how much had the hypha grown during the lesson? Show your
working.
Answer: ____________________ µm
(2)
(ii) Explain how you could use your answer to calculate the rate of growth of
this hypha.
______________________________________________________________
Page 4 of 131
