Cell Structure (AQA A Level Biology)

Figure 1 shows part of a prokaryotic cell.

Name the structures labelled R and S in the diagram in Figure 1.

Name the structures labelled P and Q in the diagram in Figure 1.

Phospholipids and glycoproteins are two biological molecules, each are the main constituent of structures found in prokaryotic cells.

In certain conditions, some prokaryotic cells can divide every 25 minutes.

Assuming that each cell divides every 25 minutes, calculate the number of cells that will be present after 3.75 hours if the starting population contains 2.45 × 10³ cells. Assume no cells die during this time.

Figure 1 shows a diagram of an animal cell.

Name the organelles labelled F and H.

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

A scientist used the method below to prepare a sample of organelle F in Figure 1 from muscle cells: 

• Step 1: Place muscle tissue in a solution that is ice-cold, buffered and has the same water potential as the muscle tissue.
• Step 2: Place the muscle tissue and solution into a blender. Blend for 3 minutes.
• Step 3: Filter the blended mixture.
• Step 4: Centrifuge the filtrate at a low speed. A pellet should be seen at the bottom of the centrifuge tube.
• Step 5: Pour off the liquid from the first centrifuge tube into a second centrifuge tube.
• Step 6: Centrifuge this liquid at a high speed. A sample of organelle F is obtained.

In terms of obtaining a sample of organelle F, explain why the solution used in step 1 had to be ice-cold and had to have the same water potential as the muscle tissue. 

Explain why the muscle tissue and solution first had to be blended, and why the resulting mixture then had to be filtered (steps 2 and 3).

Figure 1 shows a chloroplast as seen with an electron microscope.

Name J and K.

Describe the function of the organelle in Figure 1.

Describe how a sample of the organelle in Figure 1 could be obtained from leaf tissue using cell fractionation techniques. 

You will not gain marks for including information about any solutions in your answer.

Table 1 below shows features of a mitochondrion and a chloroplast.

Table 1

Complete the table with ticks (✔) where a feature is present.

Figure 1 shows a drawing of part of an animal cell as seen through an electron microscope.

Name the organelles labelled L and M.

Explain why the shapes of the two organelles labelled O in Figure 1 appear different.

Give the function of organelle M in Figure 1.

Large numbers of organelle O (in Figure 1) are found in the small intestine epithelial cells. Explain why these cells are adapted in this way. 

Figure 1 shows a diagram of an organism called Chlamydomonas that lives in freshwater.

Name two features of the Chlamydomonas cell that are not found in animal cells. 

Use Figure 1 to explain three adaptations of Chlamydomonas that enable this organism to maintain a high rate of photosynthesis.

A scientist used an optical microscope to observe Chlamydomonas. Name two eukaryotic structures that cannot be identified using an optical microscope.

Using your knowledge of osmosis, suggest why Chlamydomonas uses starch as a carbohydrate store.

A biologist prepared a sample of organelles extracted from an animal cell. The following method was used:

Step 1: An ice-cold, buffered solution was added to the liver tissue (it has the same water potential as the liver tissue).

Step 2: The liver and solution were blended in a homogeniser.

Step 3: The mixture from the homogeniser was filtered.

Step 4: The filtered liquid was centrifuged at low speed. A pellet appeared in the bottom of the centrifuge tube.

Step 5: The liquid above the pellet was decanted into a second centrifuge tube and spun at a higher speed to obtain a sample of mitochondria.

Name the organelle that made up most of the first pellet after centrifuging at a low speed (step 4).

The second centrifuge tube was spun at a higher speed to obtain a sample of mitochondria (step 5). Suggest why.

Explain how the inner membrane of the mitochondria is adapted to its function.

Name three structures in a eukaryotic cell that cannot be identified using an optical microscope.

Figure 1 shows the structure of the organism Chlamydomonas.

Name three structures shown in Figure 1 that are present in eukaryotic cells but are not present in prokaryotic cells.

Suggest what kind of organism Chlamydomonas is, based on the information shown in Figure 1. Give reasons for your suggestion. 

Describe the function of a chloroplast and the structural features that enable it to carry out these functions.

Figure 1 below shows a photograph of an organelle taken with an electron microscope.

Name the parts of the organelle labelled A and B.

Structures V to Z are organelles within a plant cell.

• V - Nucleus
• W - Chloroplast
• X - Golgi apparatus
• Y - Mitochondrion
• Z - Cell Wall

Complete Table 1 by identifying the correct letter next to each statement.

Table 1

Mammals feed their young with milk that is synthesized and expressed by mammary gland cells. These gland cells have evolved to contain large numbers of mitochondria and Golgi apparatus. The milk contains a high concentration of protein to feed an infant’s growth.

Explain how these adaptations could aid the synthesis and expression of milk.

State the contents and function of the mitochondrial matrix.

Scientists investigated the effect of an exercise programme on the number and area of the inner mitochondrial membranes in skeletal muscle. They took samples of muscle from a large number of volunteers before and after the exercise programme. From each sample, they cut thin sections and used these to determine the mean number of mitochondria per μm2 and the mean area of inner mitochondrial membranes. The results are shown in Table 1 below.

Table 1

Using the data from Table 1 suggest the effect of the exercise programme on the mitochondria.

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 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. Figure 1 below shows the researchers’ results. The mean and the range of data are shown for each group.

Suggest the scientists’ null hypothesis and experimental hypothesis for this investigation.

Which is the only correct statement about the structures of the bacteriophage and the bacterium?

• A - Both have ribosomes.
• B - Both have a cell-surface membrane.
• C - The bacteriophage has a capsid and the bacterium has a cell-surface membrane.
• D - The bacteriophage has a cell wall and the bacterium has a capsid.

In some cases, the researchers needed to carry out a serial dilution of the sample before performing a count of the bacteria.

Use data from Figure 1 to account for the researchers’ choices to perform serial dilutions in some cases but not for others.  

Using only the graph in Figure 1, analyse the effectiveness of the bacteriophage in treating the lung infection in rats. Do not consider statistical analyses in your answer.

Figure 1 below shows a diagram of a cholera bacterium.

Name W and X and state their function.

Name four structures that are present in an epithelial cell from the small intestine but not present in a cholera bacterium.

Cholera bacteria can be viewed using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). 

State one advantage of using a TEM and one advantage of using an SEM.

An outbreak of cholera occurred in London in 1849. Figure 2 below shows the relationship between the number of deaths from cholera and the height at which people lived above sea level.

Describe the results shown in Figure 2.