AS & A Level Biology - 9700 Paper 1 2024 Spring Zone 2

A student used a light microscope to observe a blood smear on a microscope slide.
An eyepiece graticule was used to measure the diameter of a white blood cell on the slide. The student recorded that the white blood cell was 5 eyepiece graticule units in diameter.
Which additional information does the student need to determine the diameter of the white blood cell in micrometres?

Which statement explains why it is necessary to use an electron microscope to see the cristae of a mitochondrion?

Some stains can be used to identify cell structures in living cells.
A dilute solution of one stain causes the whole cell to appear blue.
The blue colour rapidly disappears from most cell structures. Those cell structures that release energy stay blue.
Which type of cell structure is likely to stay blue?

When mucus is secreted from a goblet cell, these events take place.
1 addition of carbohydrate to protein
2 fusion of a vesicle with the cell surface membrane
3 extracellular release of a glycoprotein
4 separation of a vesicle from the Golgi body
What is the sequence in which these events take place?

The diagram shows four biological features. Which biological features are present in typical prokaryotes?

Which row shows features that occur in dicotyledonous plant cells and also in typical bacterial cells?

key

✓ = found in dicotyledonous plant cells and also in typical bacterial cells
x = not found in at least one of these two types of cell

[Table_1]

Which flow chart outlining the test for non-reducing sugars is correct?

Which diagrams show the release of a water molecule during the formation of a glycosidic bond?
[Image_1: Shows three chemical diagrams each illustrating a step in forming glycosidic bonds with the release of $H_2O$]

Which molecules have a structural formula that contains C=O bonds?
1. amino acids
2. fatty acids
3. glycerol
4. protein

Which statement about triglycerides is correct?

Many flowers produce a sweet solution called nectar. Bees provided with nectar use enzyme Q to change the nectar into honey. After testing a sample of nectar for the presence of reducing sugar using standard laboratory reagents, the sample was blue. After testing a sample of honey in the same way, the sample was orange. Which conclusion about the reaction catalysed by enzyme Q is consistent with these results?

[Table_1]

The diagram shows the structure of part of a peptidoglycan molecule.
Which type of 1,4 linkage and how many peptide bonds are shown in this part of the molecule?

A scientist investigated the progress of two enzyme-catalysed reactions in separate test-tubes, X and Y. Both reactions result in colour changes that can be detected using colorimetry.

0.5 cm\(^3\) samples were taken from each test-tube at the start of the investigation and at regular intervals for the next 5 minutes. Copper ions were added to each sample as soon as the sample was collected to inactivate the enzymes and stop the reactions from progressing further.

The absorbance of each sample was measured using a colorimeter.

The graph shows the results of this investigation.



Which statement is consistent with the results shown in the graph?

A student investigated the hydrolysis of lipid in high-fat milk, using the enzyme lipase.

• 1 cm³ of enzyme solution was added to 10 cm³ of high-fat milk.
• The temperature was kept constant.
• The pH of the reaction mixture was recorded at time 0 minutes and every minute for 20 minutes.

Which statements correctly describe the expected results of this investigation?

1. The product forms more slowly as time proceeds because the concentration of the substrate is decreasing.
2. The pH of the reaction mixture increases rapidly in the first few minutes and then increases less rapidly.
3. The increase in the concentration of product eventually causes the lipase molecules to denature.

What is the correct range of measurements for the width of the cell surface membrane?

Where in the cell surface membrane are the carbohydrate chains of glycoproteins and glycolipids mainly located? [Table_1]

Sodium ions can enter cells across the cell surface membrane.
Which methods could be used by sodium ions to cross a cell surface membrane and enter a cell?

The diagram shows how an artificial partially permeable membrane was used to separate a 5% sodium chloride solution and a 10% sodium chloride solution in a beaker. The two sides of the beaker were labelled R and S.

Which row correctly describes and explains what will happen in the half of the beaker labelled S?

Agar cubes can be used to demonstrate the effect on diffusion of changing the surface area to volume ratio. Three different agar cubes made using a coloured indicator solution were placed into a dilute acid that diffused into the cubes. As the acid diffused into the agar cubes, the colour of the indicator solution changed. The cubes had volumes of $1 \text{ cm}^3$, $2 \text{ cm}^3$ and $3 \text{ cm}^3$ and were left in the dilute acid for 10 minutes. All other variables were kept the same.
After 10 minutes, the agar cubes were removed from the dilute acid and cut in half. The cut surfaces were observed and the results were recorded as diagrams. All diagrams were drawn to the same scale.
The results for the $2 \text{ cm}^3$ cube are shown.

Which diagrams show the results for the $1 \text{ cm}^3$ and the $3 \text{ cm}^3$ cubes?

During sperm formation in mammals, part of the structure of each chromosome is replaced with proteins called protamines. This replacement allows the DNA to be packaged much more densely than would otherwise be possible.
Which part of the chromosome is replaced by protamines?

The diagram shows the mitotic cell cycle.
During which phase do chromosomes condense and become visible?

Which statements correctly describe features of stem cells that are essential for their role in cell replacement and tissue repair?
1. After mitosis of stem cells, the daughter cells can either remain as stem cells or follow a developmental pathway that leads to the formation of specialised cells.
2. Stem cells are different to all other body cells because they retain all of the genetic information in their DNA throughout the life of the organism.
3. A small population of stem cells is retained in the body of adults throughout their lifetime.
4. Stem cells have more telomeres than other body cells and this allows them to undergo an unlimited number of mitotic divisions.

Which statements are correct for all nucleotides?
1. The nitrogen-containing base is always attached to carbon atom 1 of the pentose.
2. The phosphate group is always attached to carbon atom 5 of the pentose.
3. A condensation reaction occurs to join the nitrogen-containing base to the pentose.
4. Nucleotides are linked together by condensation reactions between phosphate groups.

How many phosphodiester bonds are present in a circular DNA molecule of 2700 base pairs?

Which statements about complementary base pairing are correct?
1 Purines and pyrimidines are different sizes.
2 Complementary base pairing occurs during translation.
3 The base pairs are of different lengths.
4 Uracil forms two hydrogen bonds with adenine.

During the mitotic cell cycle, the chromosomal DNA is replicated. The specific points in DNA molecules where replication is occurring are known as replication forks.
A typical human chromosome has about 150 million base pairs of DNA. It takes about 1 hour to replicate the DNA of a typical human chromosome.
The rate of replication using a single replication fork is approximately 50 base pairs per second.
Approximately how many replication forks must occur in a typical human chromosome during DNA replication?

Which molecule has its synthesis directly controlled by DNA?

Which statement correctly describes the association between a companion cell and its sieve tube cell?

A maize seedling was grown in soil that contained lanthanum ions labelled with a chemical that fluoresces under ultraviolet light. The diagram represents what was observed when a section of root was examined using a light microscope with ultraviolet illumination.

What is a correct conclusion about the transport of lanthanum ions in maize roots?

Which description of adhesion and cohesion is correct?

Which conditions are needed to allow the mass flow of sucrose in phloem sieve tubes? [Table_1]

One type of congenital heart defect is where the left and right atria are not completely separated. This is called an atrial septal defect (ASD). ASD usually results in blood moving from the left atrium into the right atrium. This causes increased blood pressure in the right atrium and decreased blood pressure in the left atrium.
Which row describes other effects caused by ASD?
[Table_1]

Which property of water, related to its role in blood and tissue fluid, is correctly described?

Which statement about tissue fluid formation is correct?

Oxyhaemoglobin, carbaminohaemoglobin, haemoglobinic acid and carbonic anhydrase are found inside red blood cells.
How many of these substances will show an overall decrease in concentration as a red blood cell passes through capillaries in the lungs?

Which of these structures typically contain cartilage and cilia?
1. bronchi
2. bronchioles
3. trachea

Which statements about the function of tissues found in the human gas exchange system are correct?

1. Collagen in the bronchi prevents them collapsing.
2. Smooth muscle in the bronchioles can contract to increase the flow of air into the alveoli.
3. Elastic fibres in the alveoli stretch and recoil during breathing.

Antibiotic-resistant strains of \textit{Mycobacterium tuberculosis} are a major problem when treating TB. A new antibiotic, teixobactin, could be very effective at killing \textit{M. tuberculosis} with only a small risk that the bacteria will evolve teixobactin resistance.
Penicillin and similar antibiotics bind to a single protein, but teixobactin binds to two lipids that are needed for the formation of the bacterial cell wall. Teixobactin binds to regions of the two lipids that do \textit{not} vary across many different species of bacteria.
Which statements help to explain why the use of teixobactin is thought to be less likely to lead to the evolution of antibiotic resistance than the use of many other antibiotics, such as penicillin?
1. A single mutation can result in bacteria that are resistant to penicillin and similar antibiotics but at least two mutations are required to produce teixobactin-resistant bacteria.
2. Mutations can affect the structure of proteins but \textit{cannot} affect the structure of lipids because only proteins are made of amino acids.
3. The lack of variation across many species of bacteria in the two lipids that bind to teixobactin suggest that the particular structure of these lipids is essential for successful bacterial cell wall formation.

Monoclonal antibodies are now being used to treat some human diseases.
What explains why monoclonal antibodies are suitable for this purpose?

1 They can divide by mitosis to produce the large numbers of antibodies required for treatment.
2 They are specific to a particular antigen.
3 They can be modified so that they do not act as antigens themselves.

Measles is an infectious disease caused by a virus.
The graph shows the number of cases of measles each year in a country before and after a vaccine was introduced.

What could have caused the decrease in the number of cases of measles after vaccination was introduced?
[Table_1]