No questions found
Name as precisely as you can the structure described in each of the following statements.
(a) The blood vessel that transports deoxygenated blood from the heart. ......................................................................................................................[1]
(b) The cell that ingests and digests cell debris and bacteria in the lungs. ..........................................................................................................................[1]
(c) The cell that secretes antibodies. ..........................................................................................................................[1]
(d) The epithelial cell that secretes mucus in the trachea. ......................................................................................................[1]
(e) The tissue that prevents the collapse of the trachea during inhalation. .........................................................[1]
600
594
553
(a) Structures A and B are both visible using the light microscope, but the internal detail of these organelles shown in Fig. 2.1 is only visible using the electron microscope.
Explain why the internal details of structures A and B are only visible when using the electron microscope and not when using the light microscope.
(b) Name in full the structures labelled C, D and E.
C ............................................................................................................................
D ............................................................................................................................
E ............................................................................................................................
[3]
(c) State one role of vacuoles in plant cells.
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[1]
(d) Structures F and G have very different permeability properties.
Explain how the composition of structures F and G determines the permeability properties of these structures.
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[4]
(e) Fig. 2.1 shows two plasmodesmata connecting the adjacent cells.
Describe the roles of plasmodesmata in transport in plants.
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[3]
592
557
527
(a) P50 is the partial pressure of oxygen at which haemoglobin is 50% saturated with oxygen. It is taken as a measurement of the affinity of haemoglobin for oxygen.
(i) State the P50 for the two blood samples, L and M.
L .....................................................................................................................
M ..................................................................................................................... [1]
(ii) With reference to Fig. 3.1, describe how the dissociation curve for person M differs from the dissociation curve for person L.
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(b) Explain the advantage of the position of the dissociation curve for people with sickle cell anaemia.
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(c) The partial pressure of oxygen in the lungs at sea level is about 13.5 kPa. At an altitude of 3000 metres the partial pressure of oxygen in the lungs is about 7.5 kPa.
When people move from sea level to high altitude they become adapted to the low partial pressure of oxygen.
Describe and explain how humans become adapted to the low partial pressure of oxygen at high altitude.
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(d) Vaccination is used to control the spread of diseases, such as measles.
Explain why vaccination cannot be used to prevent sickle cell anaemia.
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556
540
509
(a) Explain why the shape of the active site of an enzyme, such as penicillinase, is important.
[3]
(b) With reference to Fig. 4.1, identify the aspects of protein structure that are shown and those that are not shown.
aspects of protein structure shown
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aspects of protein structure not shown
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[3]
Fig. 4.2 shows the changes in energy during the progress of an uncatalysed reaction.
(c) (i) Draw on Fig. 4.2 a curve to show changes in energy during the progress of the same reaction when catalysed by an enzyme. [2]
(ii) State the term given to the energy level that must be overcome before a reaction can progress.
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(d) Antibiotic resistance is a serious worldwide problem.
Suggest how antibiotics can be used effectively to avoid the development of widespread resistance in bacteria.
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[2]
553
582
597
(a) State the type of nuclear division that occurs at X and at Y.
X ..................................................................................................................
Y .................................................................................................................[1]
(b) State what is meant by the term \textit{reduction division} and explain why this division is necessary in a life cycle, such as that shown in Fig. 5.1.
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(c) The amoeboid cells of \textit{D. discoideum} feed on protein-rich material and break it down to form ammonium ions (NH$_4^+$). The cell membranes of \textit{D. discoideum} have transporter proteins that are responsible for the excretion of ammonium ions.
Describe what happens to the ammonium ions excreted by \textit{D. discoideum} into the soil.
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(d) Suggest why a transporter protein is required for the removal of ammonium ions from \textit{D. discoideum}.
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535
515
512
(a) (i) Complete Fig. 6.1 by drawing on the hydrogen bonds between the two base pairs shown. [2]
(ii) State the importance of hydrogen bonding in DNA structure. ............................................................................................................................................................................ ............................................................................................................................................................................ ............................................................................................................................................................................ ............................................................................................................................................................................ .....................................................................................................................[2]
(b) With reference to Fig. 6.1, explain how the data in Table 6.1 helps to confirm the arrangement of bases in DNA. ............................................................................................................................................................................ ............................................................................................................................................................................ ............................................................................................................................................................................ ............................................................................................................................................................................ ............................................................................................................................................................................ ............................................................................................................................................................................ .....................................................................................................................[3]
[Table_1: Table 6.1, showing the percentage of bases in different organisms]
(c) Table 6.2 shows Chargaff’s data for a virus.
(i) State how the result for the virus differs from the results for all the organisms given in Table 6.1. ............................................................................................................................................................................ ............................................................................................................................................................................ .....................................................................................................................[1]
(ii) Suggest why the results for the virus are different from all the other organisms. ............................................................................................................................................................................ .....................................................................................................................[1]
[Table_2: Table 6.2, showing the percentage of bases in a virus]
519
594
583
