AS & A Level Biology - 9700 Paper 2 2019 Summer Zone 2

(a) State, with a reason, whether Fig. 1.1 shows a section through the root or the stem of H. annuus.
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(b) Cell type A in Fig. 1.1 has a large central vacuole.
Suggest, with reasons, the role of the tissue formed by this type of cell.
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(c) Structure B in Fig. 1.1 contains phloem tissue and xylem tissue and other tissues that provide support.

(i) Name structure B.
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(ii) The actual length of structure B is $650 \mu m$.
State the actual length of structure B in mm.
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(d) When structure B is observed at a higher magnification, more detail of xylem vessel elements and phloem sieve tube elements can be seen.
Outline the differences in the structure of a xylem vessel element and a phloem sieve tube element.
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Some tissues of the gas exchange system include cells that are able to produce and secrete mucins. Mucins are stored in vesicles in these cells, ready for secretion. Once outside the cell, mucins adsorb water to form mucus.
(a) Name the structures in the gas exchange system that produce and secrete mucins.
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(b) Mucins are described as glycosylated proteins. The process of glycosylation involves the addition of sugar components after polypeptides are synthesised.
Suggest one location in the cell where glycosylation of mucin could occur.
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(c) The processes that occur in the production and secretion of mucins are listed.
translation exocytosis glycosylation transcription
Complete Table 2.1 by writing the processes in the correct order in which they would take place.
[Table_1] [2]
(d) Chloride ions move out of the mucin-producing cells at the same time as mucin is secreted.
Suggest and explain how the exit of chloride ions helps the formation of mucus from mucin.
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(e) The gas exchange system includes some cells that are able to divide by mitosis.
Explain why it is important to have these cells in the gas exchange system.
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Fig. 3.1 is a photomicrograph of human blood cells from a healthy individual who lives at sea level. The cells labelled C, D and E are white blood cells.

(a) Name cells C, D and E.
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(b) In humans, an increase in the white blood cell count can be associated with leukaemias and with infectious diseases, such as measles.
Chronic lymphocytic leukaemia (CLL) is a type of cancer that starts in the bone marrow. In the early stages, many people with CLL feel well. The disease is sometimes diagnosed by chance during a routine blood analysis, when a high white blood cell count is noticed. Many of these white blood cells are only partially mature.
(i) Suggest why CLL starts in the bone marrow and not in any other location in the body.
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(ii) Explain why a high white blood cell count is a feature of measles and of CLL.
measles .........................................................................................................
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(c) Most of the oxygen that enters the mammalian circulatory system is transported by red blood cells.
(i) Describe and explain the passage of oxygen across the cell surface membrane of the red blood cell.
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(ii) At a high altitude, the partial pressure of oxygen in the atmosphere is lower than at sea level. If a person travels from low altitude to high altitude and remains there for a few weeks, the red blood cell count increases.
Explain why the body needs to respond to high altitude by increasing the number of red blood cells.
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(d) Polypeptide synthesis occurs before a red blood cell is released into the circulation.
The HBB gene codes for the \( \beta \)-globin polypeptide of haemoglobin.
There are two alleles of HBB, known as \( \text{Hb}^A \) and \( \text{Hb}^S \).
Describe the difference between the \( \text{Hb}^A \) allele and the \( \text{Hb}^S \) allele \textbf{and} state how this difference affects:
• the \( \beta \)-globin polypeptide
• the haemoglobin molecule.
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(a) Fig. 4.1 is an outline drawing of V. cholerae.
Complete Fig. 4.1 by drawing and labelling the structures found in V. cholerae.
[Image_1: Fig. 4.1 showing flagellum]

(b) The World Health Organization (WHO) collects data about cholera from the 194 countries that are members of the World Health Assembly (WHA).
In 2015:
• there were cases of cholera in 42 of the member countries of the WHA
• the total number of cases of cholera reported was 172454
• there were deaths as a result of cholera in 23 of these countries
• the total number of deaths from cholera reported was 1304.
The case fatality rate for cholera is the proportion of cases of cholera that results in death within a particular time period.
A country with cases of cholera that are properly treated should have a case fatality rate of less than 1%.
(i) Calculate the case fatality rate for the 42 member countries of the WHA for 2015.
Give your answer to the nearest 0.1%.
case fatality rate = .................................................. % [1]
(ii) Many of the 23 countries reporting deaths from cholera in 2015 had a case fatality rate of less than 1%.
However, two of the 23 countries had case fatality rates greater than 5%.
Suggest two explanations for the higher case fatality rate in these two countries.
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(c) In 2010, the country of Haiti experienced a major earthquake. This led to an outbreak of cholera.
(i) Explain why an earthquake may lead to a cholera outbreak.
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(ii) Fig. 4.2 shows data about cholera collected by WHO over a period of 8 years, from 2008 to 2015. These data include:
• the total number of cases of cholera for each year
• the number of countries in each year that had cases of cholera.
[Image_2: Fig. 4.2]
Comment on the trends shown in Fig. 4.2.
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(a) Fig. 5.1 is a list of biological molecules, some of which are components of larger molecules.



Complete Table 5.1 by using only the molecules listed in Fig. 5.1.

* Each example can be written under one or more correct headings.
* All the examples in Fig. 5.1 should appear at least once in Table 5.1.

[Table_1]

(b) Explain how the structure of phospholipids allows the formation of the phospholipid bilayer of cell membranes.
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(a) A student carried out two experiments to investigate the progress of the reaction shown in Fig. 6.1. Potato tissue was used as the source of the enzyme.
Six pieces of potato were cut, each measuring 20 mm × 10 mm × 10 mm.
In the first experiment, hydrogen peroxide solution was added to three of the pieces of potato tissue and the progress of the reaction was measured.
Fig. 6.2 shows how the first experiment was set up.

(i) Suggest how the progress of the reaction could be measured.
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(ii) In the second experiment, the student cut each of the three remaining pieces of potato to obtain six pieces, each measuring 10 mm × 10 mm × 10 mm.
Using exactly the same conditions, the student measured the progress of the reaction and obtained different results to the first experiment.
Explain why the results of the second experiment were different from the results of the first experiment.
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(b) The student then investigated the effect of temperature on the activity of catalase.
On Fig. 6.3, sketch a curve to show how temperature affects the activity of an enzyme such as catalase.

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