Cells as the Basic Units of Living Organisms (CIE AS Biology)

Fig. 1 shows a student's drawing of a transmission electron micrograph of part of a cell from the lining of the small intestine.

Fig. 1

Name the structures labelled X and suggest how these structures facilitate the absorption of food molecules from the small intestine.

Explain how the presence of mitochondria is beneficial to cells.

An example of a unicellular eukaryotic organism (an amoeba) is shown in Fig. 2.

Fig. 2

Identify organelle A and describe its function.

Organelle A in Fig. 2 can be identified with an electron microscope but cannot be identified using a light microscope.

Give three other structures in a eukaryotic cell for which this is also true.

Fig. 1 shows the structure of the single-celled organism Chlamydomonas.

Fig. 1

State whether Chlamydomonas is a eukaryotic cell or a prokaryotic cell. Give a reason for your answer.

Chlamydomonas is a genus of green algae that contain chloroplasts.

Describe the function of chloroplasts and the structural features that enable them to carry out this function.

Suggest the role of the light-sensitive spot and flagella shown in Fig. 1.

Aphids are small insects which feed directly on phloem sap.

The salivary glands of aphids have secretory cells that make and release a variety of proteins that assist in feeding.

Fig. 1 is a transmission electron micrograph of a small area of a salivary gland cell of an aphid.

Fig. 1

Describe the role of Golgi bodies in secretory cells, such as the salivary gland cells of aphids.

Explain why secretory cells have large numbers of mitochondria.

Mitochondria are partly controlled by the nucleus, but can also function independently.

Suggest the features of mitochondria that allow them to function independently of the nucleus.

Aphids are important vectors of plant viral diseases.

Describe the structure of a typical virus.

 [3]

(ii)

Suggest how viruses are able to pass from one plant cell to the next without crossing membranes.

[1]

Contrast the structure of a prokaryotic cell, as found in a typical bacterium, with the structure of typical eukaryotic cells in plants and animals.

Plant and animal cells can also be contrasted. 

Identify two structures present in plant cells that are not present in animal cells.

Fig. 1

Identify the organelle.

[1]

Describe the feature(s) visible in Fig.1 that identify this organelle. 

[1]

Label these features on Fig. 1. 

[1]

Both animal and plant cells produce and release proteins.

Outline the role of organelles in the production, transport and release of proteins from eukaryotic cells.

Do not include details of transcription and translation in your answer.

Fig. 1 

Identify the organelles labelled L and M. 

Suggest why the shapes of the two organelles labelled O in Fig. 1 appear different.

Give the function of organelle M in Fig. 1

Large numbers of organelle O (in Fig. 1) are found in the cells that line the small intestine. 

Suggest why these cells are adapted in this way. 

Bacteriophages are viruses that kill bacteria. Researchers investigated the use of bacteriophages to alleviate the symptoms of bacterial lung infections. They inoculated the lungs of rats with a pathogenic bacterium. The rats were then divided into two groups, J and K:

• • The rats in group J were untreated.

  • The rats in group K were given bacteriophage treatment by means of an aerosol spray that they inhaled.

After 5 days the researchers killed the rats and excised (dissected out) their lungs. The lungs were washed out with a set volume of fluid. The researchers used a technique to count the number of live bacteria in the fluid. Fig. 1 below shows the researchers’ results. The mean and the range of data are shown for each group.

Fig. 1

Suggest the following for this investigation:

The scientists’ null hypothesis.

[1]

(ii)

The scientists' experimental hypothesis.

[1]

Using only the graph in Fig. 1, assess the effectiveness of the bacteriophage in treating lung infection in rats.

Do not consider statistical analyses in your answer.

Compare and contrast the structures of prokaryotic and eukaryotic cells.

Fig. 1 shows a series of electron micrographs.

Fig. 1

Identify the main cellular structures visible in micrographs J, K, and L.

Explain how the cellular structure in micrograph J in Fig. 1 is adapted for its role.

Compare and contrast the cellular structures visible in micrographs K and L in Fig. 1.

The cellular structure visible in micrograph J in Fig. 1 measures 9.2 cm from end-to-end, and the micrograph image has a magnification of x110 000.

Calculate the actual length of the cellular structure in micrograph J. Give your answer in micrometers.

Fig. 1 shows a micrograph of an influenza virus.

Fig. 1

Identify structures X, Y and Z.

The virus in Fig. 1 has a diameter of 70 nm.

State the type of microscope used to capture the micrograph in Fig. 1.

[1]

[2]

Fig. 2 shows a cell that has been infected by a virus.

CC0, via pixnio

Fig. 2

Suggest an explanation for the appearance of the cell in Fig. 2.

Other than virus particles, name three other cellular structures that are visible in Fig. 2.

Fig. 1 shows a micrograph of a cell.

Fig. 1

Identify the cell type shown in Fig. 1.

[1]

Explain how you reached your answer to part (i).

[2]

The scale bar in Fig. 1 measures 5.8 cm with a ruler.

Calculate the magnification of the micrograph in Fig. 1.

Fig. 2 shows a micrograph cross-section of a type of structure sometimes found on the surface of the cell type shown in Fig. 1. The structure is made up of multiple pairs of protein cylinders in a circular arrangement.

Public domain, via Wikimedia Commons

Fig. 2

Suggest the name of the structure in Fig. 2.

[1]

Describe the composition of the protein cylinders that make up the structure in Fig. 2.

[2]

State the role of the structures in Fig. 2 in the cell type shown in Fig. 1.

Table 1 contains information on the percentage of total cell membrane found in some different cell organelles in liver cells and in pancreas cells.

Note that not all organelles have been included, so the totals do not add up to 100 %.

Table 1

Give three conclusions about the comparative activities of liver and pancreas cells that can be drawn from the data in Table 1.

Predict how the data in Table 1 would be different for:

[1]

A plant cell.

[2]

Table 2 contains information about the volume and surface area of liver and pancreas cells.

Table 2

Calculate the surface area to volume ratio for:

Liver cells

[1]

(ii)

Pancreas cells

[1]

The micrograph below shows a cell from the pancreas.

Fig. 1

Identify one organelle visible in the micrograph that is not listed in Table 1.

[1]

(ii)

Describe the role of the organelle identified in part (i).

[2]