Syllabus Edition

First teaching 2023

First exams 2025

|

Cell Specialisation (SL IB Biology)

Exam Questions

41 mins14 questions
1a
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1 mark

Amoeba proteus is a unicellular organism that inhabits freshwater ponds and streams. At its largest size, Amoeba proteus can be visible to the naked eye. 

State how the surface area to volume ratio changes as the Amoeba proteus grows.

1b
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1 mark

Gaseous exchange allows the Amoeba to carry out aerobic respiration. 

State which aspect of the surface area to volume ratio has the greater effect on the rate of gaseous exchange.

1c
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1 mark

The contractile vacuole of the Amoeba helps to maintain its osmotic equilibrium by excreting excess water from the cell. 

State which aspect of the surface area to volume ratio would depend on this organelle.

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2
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2 marks

Glia and skeletal muscle cells are two examples of specialised cells that were once stem cells. 

Define the term stem cell. 

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3
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2 marks

Embryonic stem cells are described as totipotent.

Define the term totipotent.

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1a2 marks

A patient with a spinal cord injury was treated using stem cell therapy using the following process:

  1. Stem cells were collected from the patient's own tissues
  2. Stem cells were cultured in laboratory for one month to increase their numbers
  3. Stem cells were injected into the injury site
  4. Stem cells were allowed to develop into nerve cells

State two properties of stem cells that made this therapy possible.

1b2 marks

Suggest why the stem cells used in part (a) were taken from the patient and not from a stem cell donor.

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2a2 marks

Calculate the surface area to volume ratio of a cube where each edge measures 2 cm.

2b2 marks

When first hatched, the young tadpoles of some frog species are less than 1.5 mm long and have not yet developed gills.

Suggest how these young tadpoles are able to get enough oxygen to their cells without developed gills.

2c3 marks

A researcher calculated the surface area of a large number of frog eggs. She calculated the mean surface area to be 10.12 mm2. Frog eggs are generally spherical. She calculated the surface area using the following equation: 4πr2.

(i)
Rearrange this equation to find r2 and use it to calculate the mean r2 of these frog eggs.

(ii)
Calculate the mean diameter of these frog eggs. Give your answer to 3.s.f.

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36 marks

Explain why surface area to volume ratio is an important factor in limiting cell size.

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1a
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3 marks

A plant palisade mesophyll cell is 4 μm in width and depth, and 25 μm in length. Its shape is approximately cuboid. 

Calculate the surface area to volume ratio of this cell.

1b
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3 marks

The palisade cell in part (a) has a large central vacuole. The vacuole has the same overall cuboid shape as the cell itself, but its outer surfaces are located 500 nm inside the plasma membrane of the cell. 
    
Calculate the surface area to cytoplasmic volume ratio.

1c
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2 marks

Vacuoles have important roles in plant cell storage and support.

Use your answers to parts (a) and (b) to suggest an additional role of vacuoles in plant cells.

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2
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3 marks

Explain the importance of the surface area to volume ratio for a growing bacterial cell.

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