No questions found
(a) The cell types in tissue A have different functions. Describe how the cell types work together to maintain the health of the gas exchange system.
...............................................................................................................................................................................
...............................................................................................................................................................................
...............................................................................................................................................................................
...............................................................................................................................................................................
...............................................................................................................................................................................
...............................................................................................................................................................................
[3]
(b) Suggest why the cells in tissue B have many mitochondria.
...............................................................................................................................................................................
...............................................................................................................................................................................
...............................................................................................................................................................................
...............................................................................................................................................................................
[1]
(c) Name the parts of the gas exchange system where tissue C is distributed.
...............................................................................................................................................................................
...............................................................................................................................................................................
...............................................................................................................................................................................
[1]
530
506
563
Name processes X and Y.
X ..........................................................................................................................................................................
Y .......................................................................................................................................................................... [2]
Name one organism involved in process Y.
................................................................................................................................................................................................................ [1]
Explain why process X occurs, even if it is a disadvantage to a plant.
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................ [1]
State two examples of how the leaves of xerophytic plants are adapted to reduce the loss of water vapour to the atmosphere.
1. ..........................................................................................................................................................................
..........................................................................................................................................................................
2. ..........................................................................................................................................................................
.......................................................................................................................................................................... [2]
Nitrate ions are taken up by root hair cells.
Outline the role of the cell surface membrane of root hair cells in the uptake of nitrate ions.
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................ [2]
Describe and explain how water and nitrate ions are transported in the xylem from roots to leaves.
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................
................................................................................................................................................................................................................ [4]
One use of the nitrogen in the nitrate ions is for the synthesis of organic molecules such as RNA.
State where nitrogen is found within an RNA molecule.
................................................................................................................................................................................................................ [1]
516
542
579
In mammals, oxygen is transported by red blood cells in a system that is described as a closed double circulation. The majority of oxygen molecules are transported as oxyhaemoglobin. At the respiring tissues, oxygen dissociates from haemoglobin and diffuses to the surrounding cells.
(a) Explain what is meant by a closed double circulation. ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... [2]
(b) Fig. 3.1 is a diagram that highlights the tertiary and quaternary structure of a haemoglobin molecule.
Explain how the tertiary and quaternary levels of protein structure of the haemoglobin molecule contribute to its role in the transport of oxygen. .......................................................................................................................................................................................................................... .......................................................................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... .................................................................... [4]
(c) At high altitudes, the partial pressure of inspired oxygen is considerably lower than at sea level. This means that the partial pressure of oxygen in the blood is also much lower at high altitudes than at sea level.
Fig. 3.2 is an oxygen dissociation curve of adult oxyhaemoglobin.
With reference to Fig. 3.2, calculate the difference in percentage saturation of haemoglobin at sea level, where the partial pressure of oxygen is 13.0 kPa, and at a higher altitude, where the partial pressure of oxygen is 6.2 kPa.
Show your working.
answer ....................................................... % [2]
(d) After spending time at altitude, a person can become acclimatised. One feature of acclimatisation is an increase in the red blood cell count.
Explain the importance of the increase in the red blood cell count. ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... [2]
(e) Before acclimatisation can occur, some people develop a condition known as acute mountain sickness when they travel to high altitude areas. Acetazolamide is a non-competitive enzyme inhibitor that is used as a drug to prevent and treat acute mountain sickness.
Explain the effects of a non-competitive inhibitor on the rate of enzyme activity. ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ................................................................................................................................................................ [3]
(f) Tobacco smoking can have an effect on the transport of oxygen by haemoglobin. Fig. 3.3 shows oxygen dissociation curves with and without the presence of carbon monoxide (CO).
With reference to Fig. 3.3, describe the effect of carbon monoxide on the cardiovascular system. ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ....................................................................................................................................................................... ................................................................................................................................................................ [3]
537
504
540
(a) (i) Table 4.1 shows that there are differences in the number of cholera cases reported between the high economic status country and the low economic status countries.
Suggest three reasons to explain these differences.
1. ........................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
2. ........................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
3. ........................................................................................................................................
......................................................................................................................................................
........................................................................................................................................ [3]
(ii) With reference to Table 4.1, suggest reasons for the differences in the number of cases of cholera reported over the five year period for Angola and Cameroon.
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
........................................................................................................................................ [4]
(b) Vaccination helps to prevent the spread of infectious diseases by stimulating an immune response in individuals against specific pathogens, such as Morbillivirus, the virus that causes measles.
(i) Suggest two reasons why measles vaccination programmes may fail to prevent epidemics.
1. ........................................................................................................................................
........................................................................................................................................ [2]
2. ........................................................................................................................................
........................................................................................................................................ [2]
(ii) Outline the response produced by B-lymphocytes on exposure to Morbillivirus in an individual who already has immunity to measles.
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
......................................................................................................................................................
........................................................................................................................................ [3]
550
562
536
(a) Complete Table 5.1 by numbering each event to show the sequence occurring in the initiation and control of one heart beat.
Use 1 as the first event in the sequence.
[Table_1]
[3]
(b) Explain the circumstances that cause the closing of the semi-lunar valves during the cardiac cycle.
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................[2]
(c) At the arterial end of a capillary bed in muscle tissue, the hydrostatic pressure is high enough to cause the formation of tissue fluid.
Explain the differences between the composition of blood and the composition of tissue fluid at the arterial end of a capillary bed.
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................
.................................................................................................................................[2]
567
513
508
Agrobacterium tumefaciens is a bacterium that can enter plants through wounds and cause a disease known as crown gall disease.
The bacterium attaches to the surface of cells and inserts a small circular DNA molecule, known as a plasmid, into the cell. Some of the genes on the plasmid code for proteins that cause changes in the plant cell and result in the formation of a plant tumour, or gall.
(a) Outline the changes that occur during tumour formation.
..................................................................................................................................................
..................................................................................................................................................
..................................................................................................................................................
..................................................................................................................................................
..................................................................................................................................................
..................................................................................................................................................
[4]
(b) Bacteria that enter the stem through a wound can reach the root of the plant to cause damage.
Suggest how the bacteria are able to reach the root of the plant.
..................................................................................................................................................
..................................................................................................................................................
[1]
(c) Fig. 6.1 shows A. tumefaciens on the surface of cells of a tobacco plant, Nicotiana plumbaginifolia.
The cells X and Y are newly formed cells.
Calculate the actual length of cell X in micrometres.
Show your working.
answer .............................................................. μm
[2]
584
569
519
