Random exam qs

• A person with AIDS may take longer than a healthy person to recover from a salmonella infection. Explain why (2 marks)

  • immune system is damaged
  • white blood cells cannot kill bacteria
• Give one change to the investigation that would allow the scientist to check if the results are repeatable (1 mark)


  Repeat and look to see if results are similar

  
• A student made the following hypothesis about the heart rate of smokers and 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 look you to test the hypothesis. 6

  • two groups of people - non-smokers and smokers
  • have at least 5 people in each group
  • get each person to do (named) exercise
  • controlled variables: same gender, same age etc
  • record heart rate for each person before and after exercise
  • calculate increase in heart rate for each person after exercise
  • compare results for each group
• Which type of blood vessel carries blood to the right atrium?

  B- VEIN

  
• Compare the structure of an artery with the structure of a vein (3 marks)


  • arteries have thicker muscular walls than veins, theirs are thinner
  • veins have valves, arteries don‘t
  • veins have a wider lumen than arteries
• A patient may be fitted with an artificial pacemaker.

  what condition may be treated using an artificial pacemaker?

  An irregular heart beat
• Explain why the masses of the eggs increased? (3 marks)


  • water entered by osmosis
  • from a dilute solution in the beaker to a more concentrated solution in the egg
  • through a partially permeable membrane

  
• Explain how the student could modify the investigation to determine the concentration of the solution inside of the egg. (3 marks)

  • use five different concentrations of salt/sugar solution
  • plotting percentage change on a graph
  • determine the concentration where the curve/line crosses the zero percentage change

  
• 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)

  • aphid has been feeding from the phloem

  
• Plants with aphids may show symptoms of magnesium deficiency.

  magnesium deficiency symptoms include:

  • yellow leaves
  • stunted growth

  explain how a deficiency of magnesium could cause these symptoms (5 marks)

  • yellow leaves due to a lack of chlorophyll
  • so less light absorbed by chlorophyll
  • so lower rate of photosynthesis
  • therefore plant makes less glucose
  • so plant converts less glucose into protein for growth
• A farmer thinks a potato crop is infected with potato virus Y (PVY).

  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)

  • inject the protein with dead or inactive pathogens into mouse
  • combine lymphocytes with tumour cells to make hybridoma cells
  • find a hybridoma which makes a monoclonal antibody specific to PVY
  • clones to produce many cells to make the antibody
• 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?

  Calcium:

  500/605 x 100 = 826.446281

  Vitamin B-12:

  500/4.5 x 2.4 = 266.67

  take them away to get:

  559.8cm3

  
• Describe how a student could test cow’s milk to show whether it contains protein and different type of carbohydrates (6 marks)

  Proteins:

  • biuret solution tests for protein
  • add biuret to milk
  • solution will turn from blue to lilac if protein is present

  Sugars:

  • add Benedicts solution to milk and heat to 100 degrees Celsius
  • solution will turn from blue to brick red if positive

  Starch:

  • iodine solution tests for starch
  • add iodine solution to milk
  • solution will turn from orange to blue/black if positive
• Explain why the indicator in both tubes became colourless (3 marks)

  • lipids breaks down fat into fatty acids
  • fatty acids lower the pH
  • fatty acids cause the pH to be below 10

  
• Give the reason why the measurement of the time taken for the indicator to become colourless might be inaccurate (1)

  Observation of colour change is subjective/based on opinion

  
• Explain the difference in the results for the two test tubes in table 9

  • bile emulsifies fats
  • creates a larger surface area
  • so lipase can break down fat more quickly