AS & A Level Biology - 9700 Paper 1 2021 Winter Zone 1

A student observes a cell using a light microscope. The student then draws the cell.
Which items will the student need to calculate the magnification of the drawing? 1. eyepiece graticule
2. ruler
3. hand lens
4. stage micrometer scale

Which equations correctly show the relationship between magnification, image size and actual size in microscopy?

1. $\text{magnification} = \dfrac{\text{image size}}{\text{actual size}}$
2. $\text{magnification} = \dfrac{\text{actual size}}{\text{image size}}$
3. $\text{actual size} = \dfrac{\text{image size}}{\text{magnification}}$
4. $\text{actual size} = \dfrac{\text{magnification}}{\text{image size}}$

In which cell structures does DNA transcription occur?

Which rows could correctly identify the nucleic acids present in two different virus particles in a sample of air?

[Table_1]

key
✓ = nucleic acid present
✗ = nucleic acid not present

Tests on four samples from a mixture of biological molecules gave the results shown in the table:
[Table_1]
Which biological molecules were in the mixture?

One molecule of X is formed by a single condensation reaction releasing one molecule of water.
What is molecule X?

The table shows some information about carbohydrate polymers.
Which row describes glycogen?
[Table_1]

The diagrams show four phospholipid molecules. Which molecule could contribute most to the fluidity of a cell surface membrane?

Which properties of phospholipids explain why single layers of phospholipids added to water immediately form bilayers?
1. The hydrophobic fatty acid chains repel water molecules so the tails pack together.
2. The non-polar fatty acid chains are attracted to each other by hydrophobic interactions.
3. Hydrogen bonds form between the phosphate groups and water.

The diagrams show three examples of different bonds.
Which bonds hold the tertiary structure of proteins together?

Which feature of collagen enables it to fulfil a structural role in skin and in tendons?

The graph shows how the concentrations of four components, 1, 2, 3 and 4, of an enzyme-catalysed reaction change with time.

Which component is the enzyme–substrate complex?

The table shows the Michaelis–Menten constant, $K_m$, for three enzymes.
[Table_1]

Which interpretation of the information is correct?

What explains how a signal molecule produced by one cell can be detected by a target cell?

Some enzymes are produced in the cells of the pancreas. The enzymes are secreted when required.
Which process is used to transport these enzymes out of the cells of the pancreas?

Plant cells were submerged in a solution with a water potential less negative than that found inside the cells. What describes the condition of the plant cells after 20 minutes?

What will be present in each chromosome at the end of the $G_2$ phase of the cell cycle?

Which events listed are part of the cell cycle?
1. interphase
2. metaphase
3. cytokinesis

Which features of an organism are affected by a drug that kills cells that are dividing mitotically?
1 cell repair
2 cell replacement
3 number of stem cells
4 tissue repair
5 tumour formation

The graph shows how the distance between sister chromatids (curve P) and the distance between chromatids and centrioles (curve Q) changes during part of mitosis.
Which statements could be correct?
1 T to V represents interphase.
2 T to W represents metaphase.
3 W to X represents anaphase.

Which statement helps to explain why the two sugar-phosphate chains in a DNA molecule are a constant distance apart?

During DNA replication, what must happen \textbf{before} a newly added nucleotide is bonded to the next nucleotide in the strand?
1. complementary base pairing
2. hydrogen bond formation
3. phosphodiester bond formation

An antibiotic enters bacterial cells through a membrane channel protein, P.
Some bacterial cells have shown resistance to this antibiotic by acquiring a mutation which alters P. This mutation prevents the entry of the antibiotic into the cell.
Which conclusions can be drawn about how resistance to this antibiotic developed in these bacteria?
1. The mutation changed the order of the amino acids in the gene coding for P.
2. The mutation resulted in the production of P with an altered tertiary structure.
3. The antibiotic is a hydrophobic molecule and so cannot cross the phospholipid bilayer to enter the cell.

What is the correct tRNA anticodon coding for the amino acid proline?

[Table_1]

Table 1: DNA triplet codes
----------------------------------------------------
| amino acid | DNA triplet code on transcribed strand |
|------------|---------------------------------------|
| alanine | CGT |
| histidine | GTG |
| proline | GGT |
----------------------------------------------------

The table shows the observations made by a student about three different cell types, P, Q and R, seen in a transverse section of a plant stem, using a light microscope.
[Table_1: Observation table with cell types P, Q, R and their structures]
What type of cells are P, Q and R?

Water molecules are attracted to each other. This property is important in the upward movement of water in xylem.
Which term is used to describe the attraction of water molecules to each other?

The diagram shows a model to demonstrate mass flow.

In a plant, what are the structures W, X, Y and Z and what is the direction of flow of solution along W?

The parts of the heart that control heart action are listed.
• sinoatrial node (SAN)
• atrioventricular node (AVN)
• Purkyne tissue
Which row is correct for atrial contraction and ventricular contraction?
[Table_1]

The diagram shows part of the circulatory system in a mammal.
Where is the blood pressure and the speed of flow the lowest?

The photomicrograph shows human blood cells.
What type of blood cell is X?

The diagram shows some of the reactions of carbon dioxide when it enters the blood from cells in a metabolically active tissue.
Which reaction is catalysed by the enzyme carbonic anhydrase?

The graph shows the oxygen dissociation curves for haemoglobin in animals that live at high altitude and animals that live at low altitude.

What explains the oxygen dissociation curve at high altitude?

The diagram shows three features found in the mammalian gas exchange system.
Which structures of the gas exchange system could be represented by X in the diagram?

What are short-term effects of nicotine on the cardiovascular system?
1. constriction of small arteries
2. increase in heart rate
3. increase in blood pressure

Some features of a disease are listed.
• It can be transmitted by animals to other animals, including humans.
• One mode of transmission is by transfusion with contaminated blood.
• The causative organism can show multiple drug resistance.
• The majority of humans who die from the disease are children.
Which disease has all these features?

The following advice was given to a person travelling to a country where there had been an outbreak of an infectious disease.

• Cook food well and eat it hot.
• Peel fruit and vegetables.
• Drink only cool, boiled water.
• Wash hands often with soap and cool, boiled water.

Which description of multiple drug resistance in bacteria is correct?

Which description of a T-lymphocyte is correct?

Where are antibodies found during an immune response?
[Table_1]

Monoclonal antibodies are used in the diagnosis and treatment of disease. They are produced using a technique known as cell fusion.
Which two structures are fused together in this technique?