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Fig. 1.1 is a photomicrograph of plant cells showing stages in cell division.
(a) On Fig. 1.1, draw a circle around a cell in anaphase. [1]
(b) Suggest the advantages of using a light microscope, rather than an electron microscope, to study cell division. ........................................................................................................................................................................ ........................................................................................................................................................................ ........................................................................................................................................................................ ........................................................................................................................................................................ .............................................................................................................................................................. [2]
(c) Mitosis is important in producing more cells for plant growth.
Describe three other ways in which mitosis is important in plants. ........................................................................................................................................................................ ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... .................................................................................................................................................................. [3]
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(a) State the type of blood vessel shown in Fig. 2.1 and give two reasons for your choice.
type of blood vessel .............................................................
reason 1 ................................................................................
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reason 2 ................................................................................
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Fig. 2.1 is a transmission electron micrograph of a section through a blood vessel.
[Image_1: Transmission electron micrograph]
(b) Use Fig. 2.2 to state the time at which:
(i) the valve between the right ventricle and the pulmonary artery closes
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(ii) the ventricle begins to contract.
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(iii) State and explain the similarities and differences between Fig. 2.2 and a graph showing how the blood pressure for the left ventricle changes during the same cardiac cycle.
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Fig. 2.2 is a graph showing how the blood pressure in the pulmonary artery and in the right ventricle changes during one cardiac cycle.
[Image_2: Graph showing blood pressure changes]
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(a) (i) Name the type of cell that produces antibodies. ..............................................................................................................................................................[1]
(ii) The virus that causes the infectious disease influenza has two antigens, H and N. Antibodies are produced in response to an infection by this virus. The antibodies are specific for either antigen H or for antigen N. Describe how the structure of an antibody molecule allows it to be specific for one antigen, such as H or N. ...........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................[3]
(b) Cholera is a disease caused by a bacterial pathogen.
(i) Name the pathogen that causes cholera. ..............................................................................................................................................................[1]
(ii) Describe how the pathogen that causes cholera is transmitted. .......................................................................................................................................................................................................................................................................................................................[2]
(c) Viruses that infect bacteria are called bacteriophages. Some bacteriophages that infect the cholera pathogen cause lysis of the bacterium.
(i) Suggest what happens to the structure of a bacterial cell to cause lysis. .....................................................................................................................................................................................................................................................................................................................[2]
(ii) Some scientists believe that bacteriophages could be used to treat people who are infected with cholera. Suggest the properties of the bacteriophages that would make this possible. .....................................................................................................................................................................................................................................................................................................................[2]
(iii) Antibiotics can be used to treat people with cholera. State why antibiotics are not effective against measles. ..........................................................................................................................................................................................................................[1]
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Fig. 4.1 shows the structure of the R groups of three amino acids, aspartate (Asp), glutamine (Gln) and isoleucine (Ile).
(a) One of the mRNA codons for the amino acid Gln is CAA.
A mutation could change this codon from CAA to UAA.
UAA is a STOP codon.
State what is meant by a STOP codon.
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(b) Many proteins that contain the amino acids shown in Fig. 4.1 are globular.
Describe how the three R groups in Fig. 4.1 can contribute to the globular structure of a protein.
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(c) An example of a globular protein is the enzyme starch phosphorylase. This enzyme catalyses the conversion of starch to glucose-1-phosphate.
Name the type of bond that is broken when starch is converted to glucose-1-phosphate.
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An investigation was carried out to find out how the activity of starch phosphorylase varied with temperature, when free in solution and when immobilised in alginate.
The results are shown in Fig. 4.2.
(d) With reference to Fig. 4.2, compare the results for the enzyme activity when free in solution and when immobilised.
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(e) State how the Michaelis–Menten constant ($K_m$) is derived from $V_{max}$ for an enzyme.
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(f) The $K_m$ values for starch phosphorylase were determined when free in solution and when immobilised.
The $K_m$ values were:
• free in solution, $K_m = 0.34 ext{ } ext{mmol dm}^{-3}$
• immobilised, $K_m = 0.84 ext{ } ext{mmol dm}^{-3}$
Suggest an explanation for the difference between the two values.
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Fig. 5.1 is a transmission electron micrograph of part of a cell.
(a) (i) Name the organelle labelled X.
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(ii) Put a tick (✔) in the box beside the type, or types, of cell that contain this organelle.
| animal cell |
| plant cell |
| bacterial cell |
(b) Use the scale bar to calculate the magnification of Fig. 5.1.
Write down the formula and use it to make your calculation. Show your working.
[Table_1]
formula
magnification × ....................[3]
(c) The organelle in Fig. 5.1 is made from structures surrounded by a single membrane.
Name two organelles that are surrounded by double membranes.
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(d) (i) The structure of the cell surface membrane is described as a fluid mosaic.
Explain what is meant by the term fluid mosaic.
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(ii) Outline the roles of the cell surface membrane.
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Plants have two transport tissues, xylem and phloem.
(a) Describe and explain two ways in which the structure of xylem vessels is adapted to their function.
description 1 ...........................................................................................................
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explanation 1 ..........................................................................................................
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description 2 ............................................................................................................
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explanation 2 ...........................................................................................................
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(b) Describe two differences between the vessels that transport phloem sap in flowering plants and the vessels that transport blood in mammals.
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Fig. 6.1 shows root hair cells.
(c) Explain why the root hair cells in Fig. 6.1 have more mitochondria than the other root cells shown.
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