2019 paper

Question 1

1a i) name of layer A

MC

Answer 1

B - spongy mesophyll

Question 2

1a ii) function of spaces between cells in layer b

Answer 2

for diffusion and gas exchange so carbon dioxide and oxygen can enter and leave the cells

Question 3

1a iii) explain the function of part C in figure 1

Answer 3

part c is a stoma which allows gas exchange to occur and allows water vapour to leave

Question 4

1b) two differences between xerophytes and leaf structure shown in figure 1

Answer 4

1. stomata are smaller and there’s less in number

2. guard cells in stomata close during the day

Question 5

3a i) two ways the method for the three organisms could be made more comparable

Answer 5

1. same volume of indicator

2. same mass of study organisms

Question 6

3a ii) describe a suitable control for this experiment

Answer 6

use another exact test tube under the same conditions with the indicator but without any organisms or living matter in

Question 7

3b i) explain why the result for the germinating peas is different from the result for the dried peas

Answer 7

germinating peas produce carbon dioxide because they were respiring aerobically

Question 8

3b ii) how was carbon dioxide produced in this experiment?

MC

Answer 8

B - when glucose is broken down in the presence of oxygen

Question 9

3c) explain why cellular respiration is essential for living organisms

Answer 9

to release energy for metabolic processes

Question 10

4a) state two variables needed to be controlled in this experiment

Answer 10

1. starting temperature of water

2. volume of water used

Question 11

4b i) calculate rate of temperature change in flask 1 from 1 to 8 minutes

Answer 11

98 - 22 = 76

76 / 8 = 9.5

Question 12

4b ii) compare the trends shown in the data for flask 1 and flask 2

Answer 12

flask 1 and flask 2 decrease in temperature but the temperature in flask 1 decreases faster than in flask 2

Question 13

4c) explain how sweating helps to cool the body

Answer 13

sweat is released onto the skin and is evaporated which transfers heat

Question 14

4d) which part of the brain controls internal body temperature?

(MC)

Answer 14

C - hypothalamus

Question 15

4e) explain why it is important to control the internal temperature of the human body

Answer 15

so the temperature remains optimal for enzyme action and chemical reactions in the body to take place

Question 16

5a i) water enters a plant through root hair cells, root hair cells have…?

(MC)

Answer 16

C - large surface area and thin cell walls

Question 17

5b) how is sucrose transported from the leaves to other parts of the plant?

(MC)

Answer 17

C - by translocation through the phloem

Question 18

5c i) name the cells that change the size of the stomata

Answer 18

guard cells

Question 19

5c ii) describe the trend shown in figure 7 (stomata openings)

Answer 19

stomata openings increase in size until 8am then decrease until 6pm

Question 20

5c iii) temp increased from 8am to 1pm, explain why this affected the size of the stomata

Answer 20

the stomata get smaller because guard cells lost water to reduce water loss from the stomata

Question 21

6a i) a doctor analysed the results and asked the person to have further tests for type 2 diabetes.

give a reason why the doctor came to this conclusion

Answer 21

excess glucose in urine

Question 22

6a ii) explain why the doctor also concluded that this person had a kidney infection

Answer 22

protein levels were above normal which means bacteria and pathogens were present

Question 23

6b) describe how a student could test a sample of urine for the presence of protein

Answer 23

add biuret solution and do the biuret test. if present, a colour change from blue to purple protein will occur

Question 24

6c) describe the route taken by urine from the kidney until it leaves the body

Answer 24

it travels from kidneys through the ureters to the bladder where it is stored and from the bladder it travels through the urethra where it exits the body

Question 25

6d) state how urea is formed in the body

Answer 25

breakdown of amino acids in the liver

Question 26

7a i) name the endocrine gland that produces FSH

Answer 26

pituitary gland

Question 27

7a ii) describe the changes that would happen inside the ovaries during the first five days of this treatment

Answer 27

more than one egg will mature in the follicles and oestrogen is released

Question 28

7a iii) which hormone causes ovulation? | MC

Answer 28

A - LH

Question 29

7a iv) explain the cause of this high level of progesterone on day 20 of the menstrual cycle

Answer 29

day 20 is after ovulation (egg released) so progesterone is released to maintain uterus lining

Question 30

7b) explain why taking high levels of oestrogen and progesterone in the combined contraceptive pill reduced the chance of pregnancy

Answer 30

to inhibit the production of FSH to prevent maturation of eggs

Question 31

7c) calculate maximum number of females taking contraceptive pill that could become pregnant

Answer 31

(32 600 000 / 100 ) x 13.2 = 4 303 200 100 - 98.8 = 1.2

Question 32

8a i) compare the effect of heart rate on stroke volume of the person who has trained for a marathon with the person who hasn’t trained for a marathon

Answer 32

stroke volume of person trained is a lot higher as this persons heart rate increases

Question 33

8a ii) calculate cardiac output for the person who has trained for a marathon when the heart rate is 160 beats per minute

Answer 33

cardiac output = stroke volume x heart rate 160 x 170 = 27 200 = 27 200 ml per min

Question 34

8b) describe how blood flows through the heart and lungs to leave heart through the aorta

Answer 34

blood enters vena cava and then flows into right atrium through a valve. the valve prevents back flow. blood then enters the pulmonary artery through a valve and is pumped to the lungs. it then flows from the lungs back to the heart through the pulmonary vein. it then enters the left atrium and then the left ventricle through a valve and is pumped into the aorta through the valve.

Question 35

9a i) explain why these alveoli have the internal structure shown

Answer 35

there are lots of alveoli which creates a large surface area to maximise and increase rate and efficiency of diffusion

Question 36

9a ii) how does oxygen move across the alveolar membrane into the capillary? (MC)

Answer 36

C - by diffusion

Question 37

9b) describe how figure 11 illustrates movement of molecules across a membrane

Answer 37

molecules are moving from a high fluid concentration to a low cytoplasm concentration until the number of molecules is even on each side

Question 38

9c) explain using ficks law the factors that affect the diffusion rate of molecules into and out of cells

Answer 38

ficks law is where the rate of diffusion is proportional to surface area and concentration difference and inversely proportional to the thickness of membrane. surface area as a factor means when surface area increases so does the rate of diffusion as there is a large space so it can happen quicker. thickness of membrane affects it as thicker the membrane the slower the rate of diffusion as diffusion distance is bigger. concentration difference affects it as the larger the difference in concentration inside the cell compared to the outside makes the rate of diffusion faster.