Exam-Style Questions: Cells and Organelles

1. Cell organelles can be separated by centrifuging a cell extract in a sucrose density gradient. The organelles settle at the level in the sucrose solution which has the same density as their own.

Some animal cells were broken open and the cell extract centrifuged in a sucrose density gradient.

Three distinct fractions were obtained, A, B and C, as shown in the diagram: Some animal cells were broken open and the cell extract centrifuged in a sucrose density gradient.

Three distinct fractions were obtained, A, B and C, as shown in the diagram:

Copyright S-cool

One fraction contained nuclei, one contained ribosomes and a third contained mitochondria.

a) Identify the organelles (i), (iii) and (v) in each fraction and describe one function of each (ii), (iv) and (vi).

Fraction Organelle Function
A (i) (ii)
B (iii) (iv)
C (v) (vi)

(Marks available: 4)

Answer

Answer outline and marking scheme for question: 1

a) Give yourself marks for mentioning any of the points below:

(i) Ribosomes

(ii) Making proteins/assembling amino acid chain/protein sythesis

(iii) Mitochondria

(iv) Respiration/ formation of ATP/ Krebs cycle/ Oxidative phosphorylation.

(v) Nuceli

(vi) DNA/RNA synthesis/ controls protein production/ cell activity/ carries genetic information.

(Marks available: 4)

(1 mark for knowing names of all organelles, and 1 mark for each function explained).

2. The diagram shows an epithelial cell from the small intestine of a mammal, as seen with an electron microscope.

Copyright S-cool

a)

(i) Suggest one way in which the functions of the rough and smooth endoplasmic reticulum differ.

(ii) Give the evidence from the diagram which supports your answer.

b) Explain how two features visible in the diagram are adaptations for the absorption of products of digestion

(Marks available: 4)

Answer

Answer outline and marking scheme for question: 2

Give yourself marks for mentioning any of the points below:

a) (i) Rough ER associated with protein production/ smooth er associated with transport.

(ii) Ribosomes present/absent.

(2 marks)

b) Microvilli increase surface area;

Mitochondria involved with active uptake.

(2 marks)

(Marks available: 4)

3. Write an essay on how the ultrastructure of different cells is related to their functions.

(Marks available: 25)

Answer

Answer outline and marking scheme for question: 3

You can give yourself up to 2 marks for discussing any of the following issues, up to a maximum of 16:

General principles

Describe the structure of a eukaryotic cell;

Suitably describe (differences between) plant and animal cells;

Explain structure of prokaryotic cells OR distinguishes them from eukaryotic;

Organelles and their specific functions.

Describe cell wall in plants/prokaryotic cells, including its structure & role in protecting the cell from osmotic damage/ example of cell in which specialised;

Discuss membrane, internal and external, with role in controlling movement of substances/ reference to specialisation (e.g. brush border in absorptive cells);

Describe nucleus, including associated structures related to nuclear function, such as centrioles in nuclear division, or nucleoli;

Describe mitochondria, including structure and functions of matrix and cristae, and example(s) of cells in which they are either numerous or absent;

Describe chloroplasts, including structure and functions of grana and stroma, including example(s) of plant cells in which they are numerous or absent;

Describe endoplasmic reticulum and ribosomes, including their structure and functions, and examples of cells in which they are prominent;

Specific examples of cells with particular functions.

Describe secretory/nerve cell with explanation of ultrastructure relevant to particular aspects of function such as golgi complex/ synapse;

Outline muscle structure/sliding filament hypothesis, related to its function;

Discuss (compare) the structure of male (and female) gamete, and relates differences to function (e.g. flagellum/acrosome);

Give other suitable example, relating ultrastructure to function;

Breadth (max 3 marks)

Deals with prokaryotic and eukaryotic cells;

Describe at least 3 different cells in relating structure to function;

Consider the full range of organelles (in diagram or writing).

Depth (max 3 marks)

Give clear diagram of eukaryotic cell;

Make clear link between structure and function for on cell;

Make clear comparison of two cells that relate structure and function.

In the real exam you will also be awarded marks for quality of language (in this case, there were 3 marks available). It may be difficult for you to judge your own text, however you may be able to get someone else to give you an opinion.

(Marks available: 25)