Cell Specialisation (HL IB Biology)

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.

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

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

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.

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.

Identify two features of cells of the human body that maximise surface area to volume ratio.

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

The presence of millions of highly specialised alveoli in the lungs contributes to the efficiency of gas exchange by providing a large surface area.

Describe and explain how cells of the alveoli are adapted for function in the gas exchange surface.

An adult has a total alveolar surface area of 5.2 x 10⁷ mm². One alveolus has a surface area of 0.104 mm².

Calculate how many alveoli this person has in each lung. Give your answer as an ordinary number, not in standard form.

Draw an annotated diagram of a mature human sperm cell.

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.

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.

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.

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