AS & A Level Biology - 9700 Paper 1 2020 Summer Zone 3

A student was given a photomicrograph of a cell and told the magnification of the image. The student was asked to calculate the actual size of the cell. Which row in the table explains how to do this? [Table_1]

The electron micrograph shows part of a eukaryotic cell. Which cell structure is a site of protein synthesis?

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 in most cell structures. Those cell structures that release energy stay blue. Which type of cell structure is likely to stay blue?

A molecule of carbon dioxide is in the centre of a mitochondrion.
Assuming there are no other cell structures in its path, how many phospholipid layers will the carbon dioxide molecule have to pass through in order to leave the cell?

Which row identifies the type of ribosome found in each of the different structures? [Table_1]

The colour of a positive Benedict’s test is due to the formation of copper oxide. The mass of copper oxide is proportional to the mass of reducing sugar present. Samples of fruit juice were tested for the presence of reducing sugars and non-reducing sugars using the Benedict’s test. The table shows the mass of copper oxide after boiling with Benedict’s solution and after acid hydrolysis and boiling with Benedict’s solution.

Which sample contained the most non-reducing sugar?

[Table_1]

Which polysaccharides contain 1, 4 and 1, 6 glycosidic bonds?

The diagram shows a small part of a polypeptide.

What would the products be if the part shown was completely hydrolysed?

The enzyme trypsin hydrolyses proteins to amino acids. Trypsin does not function when the pH is very low as its 3D shape would be changed.
What explains this change in 3D shape?

The flow chart shows some of the steps in the formation of collagen.

Which row correctly identifies X, Y and Z?

Which molecules contain at least two double bonds?
1. saturated fatty acid
2. collagen
3. haemoglobin

Two experiments, X and Y, were carried out using an enzyme from humans.
Experiment X was carried out at a constant temperature of 37\(^\circ\)C. During experiment Y, the temperature was increased from 37\(^\circ\)C to 80\(^\circ\)C. All other factors were kept the same.
Which graph shows the results?

What affects the rate of an enzyme-catalysed reaction when in the presence of a non-competitive inhibitor?
1. enzyme concentration
2. inhibitor concentration
3. substrate concentration

What describes the fluid-mosaic model of membrane structure?

Blocks of agar are stained with a pH indicator and used to investigate the diffusion of an acid solution. Which block would completely change colour the fastest?

The diagram shows the water potential of three adjacent plant cells, P, Q, and R.
Which shows the net movement of water between cells P, Q, and R?

Which row correctly describes parts of chromosome structure present during mitosis? [Table_1]

The diagram shows the relative time taken for each stage in the cell cycle.
Which row identifies the correct sequence of the stages in the cell cycle? [Table_1]

Scientists have made a nucleic acid, HNA, that has a sugar with the same number of carbon atoms as glucose instead of deoxyribose. Although genetic information can be stored by HNA, naturally occurring DNA polymerase cannot replicate HNA.
Which statements could explain why naturally occurring DNA polymerase cannot replicate HNA?
1. DNA polymerase cannot form bonds between the sugars of two HNA nucleotides.
2. DNA polymerase cannot form hydrogen bonds between two HNA nucleotides.
3. HNA nucleotides do not fit into the active site of DNA polymerase.
4. The shape of an HNA nucleotide is slightly larger than that of a DNA nucleotide.

Which statements about the nucleotide containing uracil are correct?
1. Uracil is a pyrimidine.
2. The carbohydrate is always ribose.
3. Base pairing occurs with 3 hydrogen bonds.

DNA replication involves several stages.
1. Each strand of DNA double helix acts as a template for the opposite strand.
2. The enzyme DNA polymerase links bases together.
3. Hydrogen bonds between bases A and T and between C and G are broken.
Which statements about DNA replication are correct?

The sequence of bases in mRNA for the first eight amino acids in the $\beta$-polypeptide of adult haemoglobin is:

GUG–CAC–CUG–ACU–CCU–GAG–GAG–AAG.

In haemoglobin C, which is a cause of haemolytic anaemia, the sequence is:

GUG–CAC–CUG–ACU–CCU–AAG–GAG–AAG.

The coding for seven of the amino acids is listed.

[Table_1]

Which change occurs to the amino acid sequence of adult haemoglobin to make haemoglobin C?

Some antibiotics kill prokaryotes by binding to RNA polymerase.
What effect will this have on protein synthesis?

The diagrams show transverse sections through parts of plants.
Which of the labelled regions contains cells that are dead?

The diagram shows the distribution of tissues in part of a transverse section through a plant organ.

Which row correctly identifies tissues 1, 2 and 3?

The circumference of a tree stem was measured continually for 48 hours. The results are shown on the chart recording. What explains the changes in circumference recorded during the 48 hours?

Which description of movement in phloem is correct?

Which statements about blood vessels are correct?
1 Collagen fibres in the walls of arteries and veins prevent overstretching.
2 Elastic fibres in large arteries allow stretching during ventricular systole.
3 Smooth muscle in arteries controls the distribution of blood to different parts of the body.
4 Veins have valves because their walls are thin.

The photomicrograph shows three white blood cells labelled X, Y and Z.

Which row correctly identifies these cells?

The enzyme carbonic anhydrase catalyses the reaction:
$CO_2 + H_2O \rightarrow HCO_3^- + H^+$
Which statements describe the role of the enzyme carbonic anhydrase?
1. to speed up the decrease in pH of blood in the presence of carbon dioxide
2. to facilitate the Bohr effect in haemoglobin
3. to speed up the reaction between carbon dioxide and water

The graph shows the oxygen dissociation curves of adult haemoglobin at two partial pressures of carbon dioxide W and X.
Which pair of statements are correct?
1. Curve W shows the oxygen dissociation curve at a higher concentration of carbon dioxide than curve X.
2. Curve X shows the oxygen dissociation curve at a higher concentration of carbon dioxide than curve W.
3. At a partial pressure of oxygen of 7.0 kPa the haemoglobin from curve W has a higher affinity for oxygen than haemoglobin from curve X.
4. At a partial pressure of oxygen of 7.0 kPa the haemoglobin from curve X has a higher affinity for oxygen than haemoglobin from curve W.

A person has two blood tests one month apart. The number of each type of cell in a fixed sample size is counted.
[Table_1]
What could this suggest about the person based on the results after one month?

A student was asked to describe the differences between four microscope slides of sections taken from different parts of the gas exchange system.

slide 1
not present: cartilage, glands
present: few goblet cells, ciliated epithelial cells, smooth muscle

slide 2
present: incomplete cartilage rings, glands, goblet cells, ciliated epithelial cells, smooth muscle

slide 3
not present: cartilage, glands, goblet cells, smooth muscle
present: squamous epithelial cells

slide 4
present: plates of cartilage, glands, goblet cells, ciliated epithelial cells, smooth muscle

Which is the correct identification of the parts of the gas exchange system?
[Table_1]

Cigarette smoke contains carbon monoxide, nicotine and tar.
Which row correctly describes how these substances affect the body?
[Table_1]

Chronic obstructive pulmonary disease (COPD) includes chronic bronchitis and emphysema. In what order do these events occur as emphysema develops?
1 Macrophages move into alveolar air spaces.
2 Tar paralyses cilia.
3 Macrophages secrete elastase.
4 Bacteria accumulate in alveoli.

If someone smokes cigarettes, what will be the immediate result of this action on the red blood cells?

What is correct for tuberculosis (TB)?
[Image_1: Venn Diagram with labels 'airborne transmission', 'virus', and 'rash', containing areas A, B, C, D]

Some common antibiotics are listed. The action of each antibiotic is described.
1. rifampicin – inhibits RNA polymerase
2. streptomycin – inhibits 70S ribosomes
3. neomycin – inhibits DNA synthesis
4. ampicillin – inhibits peptidoglycan synthesis
Which of these antibiotics will affect the activities of bacterial cells only?

Which method of gaining immunity can be described as natural active immunity?

Which statements correctly explain why smallpox has been eradicated, but not malaria or cholera?
1. Cholera vaccines provide only short-term immunity.
2. Plasmodium antigens change during the life cycle.
3. Smallpox antigens remain stable.
4. Vaccines only work against viruses.