Biology Paper 1 - 2018

Question 1

Eating food containing Salmonella bacteria can cause illness. box
01.1) Two symptoms of infection by Salmonella are vomiting and diarrhoea.
What causes these symptoms?
(1 MARK)

Answer 1

Toxins are released

Question 2

01.2) Give two ways a person with a mild infection of Salmonella can help prevent the
spread of the bacteria to other people.
(2 MARKS)

Answer 2

• Quarantine themselves
• Wash hands after using toilet

Question 3

A person with AIDS may take longer than a healthy person to recover from a
Salmonella infection.
Explain why?
(2 MARKS)

Answer 3

• Immune system is already weak
• White Blood cells cannot kill
  bacteria

Question 4

01.8) Give one change to the investigation that would allow the scientist to check if the box
results are repeatable.
(1 MARKS)

Answer 4

Repeat and look to see if results are similar.

Question 5

02.7) A student made the following hypothesis about the heart rate of smokers and box
non-smokers during exercise.
“During exercise, the heart rate of smokers increases more than the heart rate
of non-smokers.”
Design an investigation that would allow you to test this hypothesis.
(6 MARKS)

Answer 5

• Have two groups of people: non-smokers and smokers
• At least 5 people in each group
• Give each individual person a different exercise
• DONT FORGET CONTROL VARIABLES (E.G. same gender, age…)
• Record heart rate for each persons before and after their exercise
• Calculate the increase in heart rate
• Compare results between the smokers and non smokers

Question 6

03.2) Some athletes train at high altitude.
Training at high altitude increases the number of red blood cells per cm3 of blood.
Explain why having more red blood cells per cm3 of blood is an advantage to an athlete
(3 MARKS)

Answer 6

• More haemoglobin
• which means more O2 transported
• which means more energy released from muscles

Question 7

03.3) Which two blood vessels carry deoxygenated blood?

Answer 7

• Pulmonary artery
• Vena Cava

Question 8

03.5) Compare the structure of an artery with the structure of a vein.
(3 MARKS)

Answer 8

• arteries have a thicker layer
  of muscle (tissue) or veins
  have a thinner layer of
  muscle (tissue)
• arteries have a thicker layer
  of elastic tissue or veins
  have a thinner layer of
  elastic tissue
• arteries do not have valves
  and veins have valves

Question 9

03.6)

Answer 9

Question 10

03.7) A patient may be fitted with an artificial pacemaker.
What condition may be treated using an artificial pacemaker?
(1 MARK)

Answer 10

• irregular heart beat

Question 11

04.3) Explain why the masses of the eggs increased?
(3 MARKS)

Answer 11

• The masses of the eggs increased due to the process of osmosis.
• This happened as the dilute solution in the beaker moves to a more concentrated solution in the egg (cell), through a partially permeable membrane

Question 12

04.4) Explain how the student could modify the investigation to determine the concentration
of the solution inside each egg.
(3 MARKS)

Answer 12

• Use 5 or more different concentrations of salt/sugar
• By plotting percentage change (in mass/volume) using graph
• Determine the concentration where the curve crosses the zero percentage change

Question 13

04.5) Explain how calcium ions are moved from the shell into the cytoplasm of the egg?
(3MARKS)

Answer 13

• this is due to the process of active transport
• Where ions have moved from an area of low concentration to an area of high concentration
• Which requires energy

Question 14

05.1) An aphid feeds by inserting its sharp mouthpiece into the stem of a plant.
Give the reason why the mouthpiece of an aphid contains a high concentration of
dissolved sugars after feeding.
(1 MARK)

Answer 14

• Has fed of phloem that has all nutrients

Question 15

05.2) Plants infected with aphids may show symptoms of magnesium deficiency. box
Magnesium deficiency symptoms include:
* yellow leaves
* stunted growth.
Explain how a deficiency of magnesium could cause these symptoms.
(5 MARKS)

Answer 15

• Yellow leaves due to lack of chlorophyll
• therefore less light absorbed
• therefore lower rate of photosynthesis
• therefore plant makes less glucose
• therefore plant converts less glucose into protein for growth, so therefore growth is stunted

Question 16

05.3) A farmer thinks a potato crop is infected with potato virus Y (PVY). box
The farmer obtains a monoclonal antibody test kit for PVY.
To make the monoclonal antibodies a scientist first isolates the PVY protein from
the virus.
Describe how the scientist would use the protein to produce the PVY
monoclonal antibody
(4 MARKS)

Answer 16

• Inject protein into a mouse
• Combine lymphocytes with tumour to make hybridoma
• find a hybridoma which makes a monoclonal antibody specific to PVY
• the scientist clones the hybridoma to produce many cells to make the antibody

Question 17

06.1) Cystic fibrosis (CF) is a genetic disorder caused by a change in a gene. box
What molecule are genes made of?
(1 MARK)

Answer 17

DNA

Question 18

06.2) CF affects the cell membranes of cells in the lungs and digestive system.
What is the function of the cell membrane?
(1 MARK)

Answer 18

• Controls the movement of substances in and out of cells

Question 19

06.3) In a person with CF, cells lining the lungs and digestive system create too much
mucus.
The mucus can:
* block the duct leading from the pancreas to the small intestine
* block the tubes leading to the alveoli in the lungs. Explain why children with CF grow more slowly than children without CF.
(6 MARKS)

Answer 19

Fewer digestive enzymes enter small intestine
- so enzymes break down less food
- so less absorption of nutrients
- so less glucose can enter the blood stream
- so less glucose available for respiration
- less absorption of nutrients so fewer amino acids can enter blood stream
- so less protein is made for growth
less oxygen enters the blood stream
- so less O2 available for aerobic respiration
- so less energy released for growth

Question 19

06.4) Describe how the median age of a group of people can be determined.
(2 MARKS)

Answer 19

Put ages in ascending order and find the middle value

Question 20

06.5) Suggest one reason why the median age for people with CF is lower than the median
age for the whole population
(1 MARK)

Answer 20

Mostly common in young people

Question 21

06.7) Lung transplants from donors have risks. One risk is organ rejection. box
Scientists are researching how to solve the problem of organ rejection and hope to
use stem cells to create healthy lungs.
The healthy lungs can then be transplanted into CF patients without the risk of
organ rejection. Describe how scientists may use stem cells to create healthy lungs that are
not rejected by the CF patient.
(4 MARKS)

Answer 21

• take stem cells from patient (bone marrow)
• remove the CF gene
• create embryo using these stem cells
• remove stem cells from embryo and stimulate them to differentiate into lung cells

Question 22

06.8) Some people disagree with the use of stem cells because of the risk of cancer.
Give one other reason why some people disagree with the use of stem cells to create
new organs for transplants
(1 MARK)

Answer 22

Unethical
(loss of human life = religious)

Question 23

07.2) Describe how a student could test cow’s milk to show whether it contains protein and box
different types of carbohydrate.
(6 MARKS)

Answer 23

• Biuret used to test for protein
• Add to milk
• will turn (from blue) to lilac if positive
• Iodine used to test for starch
• Add to milk
• will turn (from orange) to blue if positive
• Benedicts used to test for sugar
• make sure to boil (any temperature above 60 degrees)
• Add to milk
• will turn (from blue) to red if positive

Question 24

07.3) Explain why the indicator in both tubes became colourless.
(3 MARKS)

Answer 24

• Lipase breaks down fat into fatty acids + glycerol
• fatty acids lower the pH
• when fatty acid cause the pH to lower below 10 the indicator goes colourless

Question 25

07.4) Give the reason why the measurement of the time taken for the indicator to become box
colourless might be inaccurate.
(1 MARK)

Answer 25

observation of colour change is subjective (based on opinion)

Question 26

07.5) Explain the difference in the results for the two test tubes in Table 9
(3 MARKS)

Answer 26

• Bile emulsifies fats
• Creates larger surface area
• so lipase can break down fat to produce fatty acids more quickly