Biology

• 01.3 In very serious infections of Salmonella, a doctor can prescribe drugs to kill the bacteria. What type of drug can the doctor prescribe to kill the bacteria?

  
  

  1 mark


  Antibiotics
• 01.4 A person with AIDS may take longer than a healthy person to recover from a Salmonella infection

  
  

  2 marks

  A person with AIDS has a weak immune system therefore its white blood cells cannot kill salmonella as effectively as a person who is healthy.
• 01.6

  Which cleaning liquid is the more effective? box Give a reason for your answer.

  
  

  1 mark

  B

  
  

  There is a large decrease in the number of bacteria after cleaning.
• 01.7

  What measurement would the scientist need to take to calculate the area where no bacteria were growing?

  
  

  1 mark


  Measure the radius
• 01.8

  Give one change to the investigation that would allow the scientist to check if the box results are repeatable.

  
  

  1 mark


  Repeat experiment to see whether results are the same/similar
• 01.9

  The scientist showed the results to the restaurant owner. Both cleaning liquids cost the same per dm3 . Suggest one other factor the restaurant owner should consider when choosing which cleaning liquid to use.

  
  

  1 mark

  Time it is effective for / how long is it effective for
• 02.1

  Give one other metabolic reaction in cells.

  
  

  1 mark

  Respiration
• 02.3

  Calculate the percentage decrease in the mean metabolic rate of males between box 5 years and 45 years of age.

  
  

  3 marks

  17/53 x 100 = 32.075472

  
  

  to three sig fig --> 32.1
• 02.2

  What two conclusions can be made from table 2?

  
  

  2 marks

  Males have a higher metabolic rate than females after five years of age.

  
  

  The mean metabolic rate of females decreases faster than males up to 25 years of agebox.

  
  

  Tick 2nd and 3rd
• 02.6 ( didnt do 2.7 (its about smoking)

  After five minutes of exercise, the heart rate of person S was 132 beats per minute. When person S rested, his heart rate decreased steadily at a rate of 12 beats every minute. Calculate how much time it would take the heart rate of person S to return to its resting rate.

  
  

  2 marks

  132-78 / 12 = 4.5
• 03.1

  Urea is transported in the blood plasma. Name two other substances transported in the blood plasma

  
  

  2 marks


  Carbon dioxide

  Water
• 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

  1. Having more blood cells means there is more haemoglobin

  
  

  2. Therefore more oxygen is transported

  
  

  3. This allows more aerobic respiration for muscle cells
• 03.3

  Which two blood vessels carry deoxygenated blood?

  
  

  2 marks

  Pulmonary artery

  
  

  Vena Cava

  
  

  tick boxes 3 and 5
• 03.4

  Which type of blood vessel carries blood into the right atrium?

  
  

  1 mark

  B (tick box 2)
• 03.5

  Compare the structure of an artery with the structure of a vein.

  
  

  3 marks

  Arteries have a thicker layer of muscles than veins (1)

  
  

  Arteries have a narrower lumen compared to the veins (1)

  
  

  Veins have valves but arteries don't (1)
• 03.5

  Where is a pacemaker located

  
  

  Located :

  
• 3.7

  A patient may be fitted with an artificial pacemaker. What condition may be treated using an artificial pacemaker?

  
  

  1 mark

  Irregular heartbeat
• 4.0

  Another student suggested that the result for egg 4 was anomalous. Do you agree with the student? Give a reason for your answer.

  
  

  1 mark

  Yes, the mass change has decreased much more than others
• 04.2

  Calculate the percentage change in mass of egg 3.

  75.7 - 72.4 / 72.4 x 100

  
  

  Answer = 4.6 percent
• 04.3

  Explain why the masses of the eggs increased.

  
  

  3 marks

  The mass increases as water enters via osmosis

  
  

  water moves from the dilute solution in the beaker to the concentrated solution in the egg

  
  

  This happens through a partially permeable membrane
• 04.4

  Explain how the student could modify the investigation to determine the concentration of the solution inside each egg.

  
  

  3 marks

  Use a minimum of five concentrations of sugar solution

  
  

  Leave the eggs in the solution, then plot the percentage change in mass on a graph

  
  

  Estimate the concentration where the curve crosses 0 percent change
• 04.5

  Explain how calcium ions are moved from the shell into the cytoplasm of the egg.

  
  

  3 marks

  Ions move from an area of low concentration to an area of high concentrations

  
  

  this is done via active transport

  
  

  which requires energy
• 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

  The aphid has bit into the phloem which contains glucose
• 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

  The leaves are yellow due to lack of chlorophyll

  
  

  therefore less light is absorbed by the chlorophyll

  
  

  thus lowering the rate of photosynthesis

  
  

  less glucose is made by plants

  
  

  (so) there is less energy for photosynthesis
• 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

  Infect the protein into a mouse

  
  

  combine lymphocytes with cancer cells to make hybridoma cells

  
  

  find a hybridoma making monoclonal antibodies specific to PVY

  
  

  Hybridoma is cloned to produce more cells
• 07.1

  How much more milk would a typical adult have to drink to get their RDA for calcium compared with the amount of milk needed to get their RDA for vitamin B-12?

  
  

  3 marks

  500/605 x 1000 = 826.446... in cm cubed (Calcium)

  
  

  500/4.5 x 2.4 = 266.67 in cm cubed (Vitamin B-12)
• 07.2

  Describe how a student could test cow's milk to show whether it contains protein and different types of carbohydrate.

  
  

  
  

  6 marks

  To test for proteins we use biuret reagent

  
  

  Add the biuret reagent to the milk the colour should change from blue to purple/lilac if proteins are present if positive ( present)

  
  

  For starch, use iodine and stir into the milk the colour should go from orange to blue/black if positive

  
  

  To test for glucose we use benedict's reagent

  add to the milk and boil the solution should turn from blue to red/brown/orange/yellow/green if positive
• 07.3

  Explain why the indicator in both tubes became colourless.

  
  

  3 marks

  Lipase breaks down lipids into fatty acids and glycerol

  
  

  fatty acids lower the pH

  
  

  When these acids drop below 10 the indicator becomes colourless
• 07.4

  Give the reason why the measurement of the time taken for the indicator to become colourless might be inaccurate.

  
  

  1 mark


  Depends from person to person/ is subjective.
• 07.5

  Explain the difference in the results for the two test tubes in Table 9.

  3 marks


  Bile breaks down/emulsifies fat

  
  

  therefore there is a large surface area of fat

  
  

  so lipase can break down fat to produce fatty acids quicker
• When measuring a specimen under a microscope what do you do?

  Use a ruler

  
  

  Measure field of view with ruler (diameter)

  convert milimetres into micrometres

  1mm = 1000 micrometres

  divide the diameter by number of cells
• What safety precautions should be taken when doing the onion cell practical? (magnification)

  Iodine - irritant to eyes and skin, stains clothes

  Coverslip/glass - could break and cut skin

  scalpel/knife - could cut skin
• Draw an onion cell :

  Label the cell

  
  

  state the magnification

  
• How do you prepare a slide to view a specimen (onion cell)?

  Peel a one cell layer of skin
• Table 4 shows a risk assessment for this experiment

  Iodine solution is an irritant May cause allergic reaction or skin rash

  
  

  plan to minimise:

  Wear gloves

  
  

  Sharp knife

  plan to minimize:

  cut away from the body
• A thin layer of onion epidermis is used.


  So light can pass through
• see parts of the cell
• Why was the coverslip placed at an angle

  prevent air bubbles forming
• M = I/A

  400 = 4.8/A

  A = 4.8/400 = 0.012

  mm --> nm (x1000)

  0.012 x 1000 = 120 nm
• How could the drawing be improved?

  collect all lines

  
  

  add magnification