Topic #1: Cell Biology Performance Part II

1. [3 marks]

State three processes occurring in a cell during interphase of the cell cycle but not in mitosis.

1. ....................................................................

2. ....................................................................

3. ....................................................................

2a. [2 marks]

The electron micrograph is of a spore of a fungus (Tilletia controversa) which affects wheat.

Determine the magnification of the spore in the electron micrograph. The scale bar represents 1 µm.

Show your working.

2b. [2 marks]

Explain the importance of surface area to volume ratio as a limit to cell size.1

3a. [1 mark]

The hypothesis that aging involves loss of brain cells was investigated in mice. The olfactory bulb (OB)

of the brain was studied because its layered arrangement of neurons resembles large regions of the

human brain. Sensory input about smell is sent to the OB by axons of receptor cells that line the upper

nasal cavity. These axons synapse with relay neurons in the OB where interpretation of smell

perception begins. The bar charts show the total volume of neurons in the OB and the density of

synapses (number of synapses per unit area) in two regions of a mouse’s OB.

State when the total volume of OB neurons is the greatest.

3b. [2 marks]

Compare the total synapse density of neurons in the outer and inner OB layers.

3c. [2 marks]

Evaluate, using the data in the bar charts, the hypothesis that aging involves loss of brain cells.

3d. [2 marks]

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Suggest the implications of the data for humans.

4a. [2 marks]

Parts of a dichotomous key to organisms A, B, C and D are shown. Design missing parts of the key using

features visible in the following diagrams.

1.

Body with tentacles ................................................A

Body without tentacles ......................................... go to 2

2.

................................................................B

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............................................................go to 3

3

.................................................................C

................................................................D

4b. [2 marks]

All of these organisms belong to the animal kingdom. State two structural differences between animal

cells and plant cells

5a. [2 marks]

The electron micrographs show mitosis in a cell at an early stage and an intermediate stage.

State the name of each phase shown, recording whether each phase has taken place at an early or

intermediate stage of mitosis.

Phase A: . . . . . . . . . . . . . . . . . . . . .occurs at an. . . . . . . . . . . . . . . . . . . . . stage

Phase B: . . . . . . . . . . . . . . . . . . . . .occurs at an. . . . . . . . . . . . . . . . . . . . . stage

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5b. [2 marks]

Outline the events occurring in phase A.

5c. [1 mark]

State what results when there is an uncontrolled division of cells in living organisms.

6. [3 marks]

Discuss the endosymbiotic theory for the origin of eukaryotes.

7a. [2 marks]

State two differences in structure between plant and animal cells.

7b. [2 marks]

Outline how molecules move across a membrane by simple diffusion.

7c. [2 marks]

Explain the role of protein pumps in active transport.

8a. [1 mark]

The diagram (not to scale) shows a cell which contains water and sodium ions. This cell is immersed in

a salt solution of water and sodium ions.

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State the mode of transport if water moves into the cell.

8b. [1 mark]

State the mode of transport if sodium ions move into the cell.

8c. [3 marks]

Explain facilitated diffusion.

8d. [1 mark]

State the name of the structures formed within a cell by endocytosis.

9a. [5 marks]

Draw a labelled diagram to show the structure of membranes.

9b. [7 marks]

Explain the importance of surface area to volume ratio as a factor limiting cell size.

10. [2 marks]

The spontaneous origin of life on Earth is thought to have involved the non-living synthesis of simple

organic molecules.

List two other processes needed for the spontaneous origin of life.

11a. [1 mark]

The following sequence of pictures, made using an electronic imaging technique, shows a cell

undergoing division.

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State the stage of mitosis typified by image II.

11b. [2 marks]

List two processes that involve mitosis.

11c. [1 mark]

State the process that results in tumour (cancer) formation or development.

11d. [2 marks]

Explain, using one example, how non-disjunction in meiosis can lead to changes in chromosome

number.

12a. [2 marks]

List two functions of membrane proteins.

12b. [2 marks]

Outline why antibiotics are effective against bacteria but not against viruses.

13a. [1 mark]

Superoxide dismutase is an enzyme used by cells to protect themselves against oxidative damage.

These enzymes can have different metals as part of their structure.

A study to compare two dismutases from Escherichia coli bacteria and two dismutases from eukaryotic

cells was undertaken. The following enzymes were used:

● E. coli dismutase with iron (Fe)

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● E. coli dismutase with manganese (Mn)

● eukaryotic mitochondrial dismutase with manganese (Mn)

● eukaryotic cytoplasmic dismutase with copper-zinc (Cu-Zn).

The following shows part of the amino acid sequences of these enzymes. Boxes enclose identical amino

acids in the sequence of the two E. coli and mitochondrial dismutases.

State how many amino acids are in the same position in the E. coli (Fe), E. coli (Mn) and the

mitochondrial dismutase sequences shown.

13b. [1 mark]

State the amino acids which are present in the same position in at least one bacterial dismutase and in

both eukaryotic dismutases.

13c. [2 marks]

Compare the E. coli (Mn) and the mitochondrial dismutases.

13d. [2 marks]

The sequences of the two bacterial dismutases and the mitochondrial dismutase show a high degree of

homology. Discuss how this supports the endosymbiotic theory for the origin of mitochondria.

14. [2 marks]

Describe the movement of water across membranes.

15a. [5 marks]

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Draw a labelled diagram to show the fluid mosaic structure of a plasma membrane, indicating the

hydrophilic and hydrophobic regions.

15b. [4 marks]

Distinguish between active and passive movements of materials across plasma membranes, using

named examples.

16. [2 marks]

Outline two pieces of evidence that support the endosymbiotic theory for the origin of eukaryotes.

17a. [2 marks]

The electron micrograph below shows an E. coli cell.

Identify the structures labelled A and B in the electron micrograph above and state one function of

each.

A: Name

Function

B: Name:

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Function:

17b. [3 marks]

Compare prokaryotic and eukaryotic cells.

18. [1 mark]

State the property of stem cells that makes them useful in medical treatment.

19. [2 marks]

Explain how materials are moved across membranes of cells by active transport.

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