AS & A Level Biology - 9700 Paper 1 2023 Summer Zone 2

A graticule and a micrometer scale can be used to measure the size of biological structures that are viewed with a microscope.

Which row shows the correct locations for the placement of a graticule and a micrometer scale on the microscope shown?

Six organelles found in eukaryotic cells are shown.



Which organelles are involved in the synthesis and secretion of a glycoprotein?

Which cell structures can have mRNA inside them?
1. chloroplast
2. mitochondrion
3. nucleus
4. rough endoplasmic reticulum

A scientist carried out an experiment to separate the organelles in an animal cell by mass.
The scientist mixed the cells with a buffer solution which had the same water potential as the cells. The cells were broken open with a blender to release the organelles.
The extracted mixture was filtered and then spun in a centrifuge at a high speed to separate the heaviest type of organelle. These sank to the bottom, forming solid pellet 1.

The liquid above pellet 1 was poured into a clean centrifuge tube and spun in the centrifuge at a higher speed to separate the next heaviest type of organelle. These organelles sank to the bottom, forming solid pellet 2.
This procedure was repeated twice more to obtain pellet 3 and pellet 4, each containing a single type of organelle.
What is the main function of the type of organelle extracted in pellet 2?

Which structures are found in palisade mesophyll cells and photosynthetic prokaryotes?
1. cell surface membrane
2. cellulose wall
3. ribosomes
4. chloroplasts

Which polymers are present in all viruses and all prokaryotes?
1. polynucleotides
2. polypeptides
3. polysaccharides

Which set of steps is the best method for conducting the emulsion test for lipids?

A student was provided with a solution of carbohydrate. They removed two samples from the solution and performed tests on each sample, as shown.

Which statement explains the results?

Which molecules contain at least two double bonds? [Image_1: Venn diagram]

What describes cellulose?

Which part of the structure of haemoglobin carries oxygen?

What is the maximum number of hydrogen bonds that can form between two single water molecules?

CYP3A4 is an important enzyme in the human digestive system where it is needed to break down a range of different toxins. The activity of CYP3A4 has been shown to be reduced by substances called furanocoumarins. Furanocoumarins are found in some fruits and so dangerous concentrations of toxins may develop in the human digestive system when fruits containing furanocoumarins are eaten.
From the information provided, what can be concluded about molecules of the enzyme CYP3A4?

A fixed volume and concentration of substrate and enzyme were mixed. All other variables were kept constant. The enzyme-catalysed reaction was left until it was complete.
Which graph shows how the rate of reaction changes with time?

Which molecules in cell surface membranes are typically involved in cell recognition? [Table_1]

What can increase the fluidity of the cell surface membrane?
1. single bonds between carbon atoms in the fatty acid chains
2. cholesterol
3. longer-chained fatty acids

The three main factors that affect the rate of diffusion across a membrane can be expressed by the relationship shown.


$$ \text{rate of diffusion is proportional to} \frac{\text{surface area } \times \text{ concentration difference}}{\text{thickness of membrane}} $$

Which changes in the factors would result in the rate of diffusion doubling?
1 Surface area has doubled.
2 Concentration difference has halved.
3 Thickness of membrane has doubled.
4 Thickness of membrane has halved.

A student measured the time taken for complete diffusion of a dye into agar blocks of different sizes which were suspended in the dye.
The results are shown.
[Table_1]
What is the predicted time for complete diffusion of the dye into the agar block measuring $5\, \text{mm} \times 10\, \text{mm} \times 15\, \text{mm}$?

An experiment was carried out to investigate the effect of concentration of sucrose solution on cells in a plant tissue.
A sample of plant tissue was cut into seven cylinders of equal length and diameter. The mass of each cylinder was recorded.
Each of the seven cylinders was put into a different sucrose solution concentration.
!
After two hours, the cylinders were removed, blotted dry and reweighed. The percentage change in mass of each cylinder was recorded.
The graph shows the results of this investigation.
!
Which row explains the results if plant tissue cells were put in a sucrose solution of 0.45 mol dm^-3?

The diagram shows part of the organisation of a section of a DNA molecule and the associated histones, P and R, in prophase of mitosis. Which statement about the features labelled P, Q and R during prophase of mitosis is correct?

How many copies of each DNA molecule will be found in a cell at the start of the stages of the mitotic cell cycle shown?
[Table_1]

One characteristic of DNA is that it is a universal genetic code. What is meant by a universal genetic code?

Which statement about mRNA is correct?

The diagram shows part of the process of translation.
What are the names of the structures labelled X, Y and Z?

The DNA triplets of genes are translated as amino acids or stop signals during protein synthesis.
The table shows some of these triplets.

[Table_1]

What could be the effects of one substitution mutation in a triplet coding for tyrosine?

Which row identifies cells with plasmodesmata?
[Table_1]

Which statements about the apoplast and symplast pathways are correct?
1. In the apoplast pathway, water molecules move through free spaces in the cellulose cell walls of plant roots.
2. In the symplast pathway, water molecules diffuse through the cytoplasm and plasmodesmata of cells.
3. Water molecules travelling through plant tissue move by mass flow along the apoplast pathway.
4. The Casparian strip blocks the symplast pathway and forces all water molecules to enter the cytoplasm of endodermis cells.

Where does water evaporate from during transpiration?

The diagram shows the outline of three xerophytic leaves of the same type in three different conditions, P, R and S.

Which description of the water potential of the cells in layer Y is correct?

The photomicrograph shows a transverse section of the leaf of a species of grass.
The grass is specially adapted to grow in a dry habitat.
Which row correctly explains how the features help the grass to grow in this habitat?
[Table_1]
hair-like structures | leaf shape
A increase internal humidity | decrease external humidity
B decrease external humidity | increase internal humidity
C increase internal humidity | increase internal humidity
D decrease external humidity | decrease external humidity

Which statement supports the theory of active loading of sucrose into companion cells?

Which properties of water are essential for its role in the transport of blood in mammals?

[Table_1]

key:
✓ = essential
× = not essential

The diagram shows some of the events that happen between the plasma and the red blood cells in the circulatory system.

What do the numbers 1, 2, 3 and 4 represent?

The diagrams show the valves in the heart when viewed in cross-section from above at different stages in the cardiac cycle.
[Image_1: Diagram 1 and Diagram 2 showing semilunar and atrioventricular valves]
Which stages in the cardiac cycle are shown?

Where are squamous epithelial cells found in the human gas exchange system?

[Table_1]
key
✓ = found
✗ = not found

Which statement about gas exchange between air in the alveoli and blood in the pulmonary capillaries is correct?

The average thicknesses for some structures in the human respiratory system are shown.

[Table_1]

A molecule of oxygen is in the alveolar air space next to the wall of the alveolus.

What is the shortest distance that the molecule needs to diffuse from its current position to the haemoglobin that completely fills a red blood cell in the nearest capillary?

(Assume that the red blood cells touch the walls of a capillary.)

The statements refer to the disease tuberculosis (TB).
1. The pathogen is not accessible to the immune system.
2. The bacterial pathogen reproduces slowly.
3. The pathogen is not very sensitive to antibiotics.
Which statements explain why antibiotic treatment for TB takes a long time?

The average sizes of some pathogens are shown.

[Table_1]
pathogen | average size / nm
HIV particle | 100
Mycobacterium tuberculosis | 3000
Plasmodium | 20000
Vibrio cholerae | 1500

One type of air filter has been shown to be effective at preventing any pathogens of 1 μm or larger from entering the air system of a room.

Based on their size and mode of transmission, which diseases would the air filter prevent from entering the air system of a room?

[Table_2]
HIV infection | TB | malaria | cholera
A | ✓ | ✓ | ✓ | ✓
B | ✗ | ✗ | ✓ | ✓
C | ✓ | ✗ | ✗ | ✗
D | ✗ | ✓ | ✗ | ✗
key
✓ = prevented
✗ = not prevented

A successful vaccination programme provides a level of immunity where the majority of a population is protected.
There are several factors that can affect the success of a vaccination programme.
Which row correctly shows the factors that can affect the success of a vaccination programme?
[Table_1]