1.1 Cell Structure

Figure 2 shows three different cells.

Figure 2

Calculate the size ratio of the bacterial cell compared to the liver cell and mesophyll cell.

Explain the role of differentiation in the development of root hair cells which allows them to carry out their specific function in plants.

Some scientists completed a study to investigate the starch content of roots in a species of grass at four points throughout the year. 

Their results can be seen in Figure 3.

Explain how the starch found in the roots of grass species helps to support growth of the grass.

Calculate the percentage change of stored starch from October to January and suggest a reason for this change.

Describe and explain four aseptic techniques used to prepare an uncontaminated culture.

Name the organelle in Figure 4.

Higher Tier Only

The organelle in the image is viewed at a magnification of 20 000 x.

Calculate the actual size of the organelle in Figure 4 and give your answer in mm shown as standard form.

Suggest whether this image was observed through a light microscope or an electron microscope. 

Explain your answer.

Higher Tier Only

Complete Table 1 to show the correct size conversions. Record your answers as ordinary numbers.

Table 1

Higher Tier Only

The mass of bacterial cells was measured in femtograms (fg).

1 femtogram = 1 x 10^-15g

Figure 5

Calculate the mass of bacteria, in grams, immediately after binary fission when the cell growth rate was 0.1 fg s^-1.

Give your answer in standard form.

The electron micrograph shows some cellular structure in a leaf. A student uses their ruler to measure the scale bar, which they find to be 1.5 cm.

Calculate the magnification of the image.

Cells can be visualised with a light microscope.

Figure 1 shows some smooth muscle cells from the wall of the small intestine.

Figure 1

All cells contain ribosomes.

Outline the function of ribosomes.

Muscle cells contain many mitochondria, as seen Figure 1.

What is the function of mitochondria?

Suggest why it is possible to visualise mitochondria using a light microscope, but not ribosomes.

Identify which cell from the list below would not contain mitochondria and suggest why this type of cell does not contain this cellular structure.

• Liver cell
• Gamete
• Palisade cell
• Bacterium

Figure 2 shows a bacterial cell and an animal cell as seen in a student’s textbook.

Figure 2

Animal cells store their genetic material in a nucleus, whereas bacterial cells do not.

Give two other ways in which bacterial cells differ from animal cells.

The cells in the diagram are drawn to a length of 100 mm in the student’s textbook.

The actual length of the animal cell is 60 micrometers (µm).

Calculate the magnification of the animal cell to 2 significant figures.

Show clearly how you work out your answer.

The nucleus of an animal cell has a diameter of about 6 µm.

Suggest a reason as to why bacteria do not have a nucleus.

Animal and plant cells have some structural features in common.

Name two structures you would find in both an animal cell and a plant cell.

Figure 3 shows a photomicrograph of the surface of a plant root.

Figure 3

Name structure X.

Calculate the actual length of structure X in Figure 3.

Show your working.

Failure of structure X to develop properly in the cells of a plant root could be catastrophic to a plant.

Suggest an explanation as to why.

Figure 4 below shows a plant cell.

Figure 4

Name each labelled part of the plant cell and give its function.

Identify the cell wall in Figure 4, label it as S and describe its function.

The cell wall of a plant is made from cellulose.

Name one type of cell, other than a plant cell, that has a cell wall made from cellulose.

The cell in Figure 5 below is a salivary gland cell.

Figure 5

Salivary gland cells are adapted to produce salivary amylase, an important enzyme in digestion.

Use the information above and your own knowledge to suggest how salivary gland cells are adapted to their function.

A student is instructed to prepare an uncontaminated culture of bacteria from a tube of liquid nutrient medium. The liquid contains one strain of bacteria.

Describe and explain the techniques the student should use to grow the bacteria on a Petri dish.