WA2 Practice Paper: Biological Molecules and Nutrition in Humans — question paper

Section A: Multiple-choice questions[10 marks]

Answer all questions. For each question, write the letter (A, B, C or D) of the correct answer.

1. 1

   Which food class is needed for growth and repair of tissues?

   1. Acarbohydrates
   2. Bfats
   3. Cproteins
   4. Dmineral salts
   ( )
2. 2

   Iodine solution turns blue-black in the presence of

   1. Astarch
   2. Bglucose
   3. Cprotein
   4. Dfat
   ( )
3. 3

   A heated Benedict's test gives a brick-red precipitate. The sample contains

   1. Ano reducing sugar
   2. Ba low concentration of reducing sugar
   3. Ca high concentration of reducing sugar
   4. Dprotein
   ( )
4. 4

   Proteins are synthesised from

   1. Aglucose units
   2. Bamino acids
   3. Cglycerol
   4. Dfatty acids
   ( )
5. 5

   The active site of an enzyme is

   1. Aused up in the reaction
   2. Bshaped to fit one specific substrate
   3. Cdestroyed by low temperature
   4. Dthe same in every enzyme
   ( )
6. 6

   Human enzymes work fastest at about

   1. A0 °C
   2. B20 °C
   3. C37 °C
   4. D60 °C
   ( )
7. 7

   Amylase digests starch into

   1. Aglucose directly
   2. Bmaltose
   3. Camino acids
   4. Dfatty acids
   ( )
8. 8

   The hepatic portal vein carries blood

   1. Afrom the liver to the small intestine
   2. Bfrom the heart to the lungs
   3. Cfrom the small intestine to the liver
   4. Dfrom the kidney to the liver
   ( )
9. 9

   Bile helps fat digestion by

   1. Achemically splitting fat into glucose
   2. Bneutralising stomach enzymes
   3. Cstoring bile in the liver
   4. Demulsifying fat into tiny droplets, enlarging the surface for lipase
   ( )
10. 10

    After a meal raises blood glucose, the body responds by releasing

    1. Aglucagon, so the liver stores glucose as glycogen
    2. Binsulin, so the liver stores glucose as glycogen
    3. Cinsulin, so the liver releases glucose
    4. Damylase, so starch is digested
    ( )

Section B: Structured questions[30 marks]

Answer all questions in the spaces provided.

1. 1

   A sample of food is tested with three reagents. Iodine gives a blue-black colour; biuret stays blue; ethanol poured into water gives a cloudy white layer.

   1. (a)

      State what each result shows.

      [3]
   2. (b)

      Name the small units from which the starch was built.

      [1]
   3. (c)

      State one dietary role of the fat found in the sample.

      [2]
   4. (d)

      Describe how you would test a fresh portion of the sample for protein, naming the reagent and positive result.

      [3]
2. 2

   Amylase was mixed with starch at different temperatures, and the time for starch to disappear was recorded.

   Results

   Temperature / °C	Time for starch to disappear / min
   10	12
   20	6
   30	3
   50	no digestion after 30 min

   1. (a)

      Calculate the rate of digestion at 30 °C.

      rate =per minute[2]
   2. (b)

      Describe the trend from 10 °C to 50 °C.

      [3]
   3. (c)

      Explain the trend using enzyme ideas.

      [4]
   4. (d)

      State one variable, other than temperature, that must be controlled in this investigation.

      [1]
3. 3

   After a sugary drink, a healthy person's blood glucose rises from 5.0 to 8.0 mmol/dm³ and returns to 5.0 within 2 hours.

   1. (a)

      Name the hormone released as glucose rises and the organ that makes it.

      [2]
   2. (b)

      Describe the liver)s response to insulin.

      [2]
   3. (c)

      Calculate the rate at which the glucose level fell.

      rate =mmol per dm³ per hour[2]
   4. (d)

      Name the hormone that corrects blood glucose that has fallen too low, and describe the liver's response.

      [2]
   5. (e)

      A second person's glucose remains above 11 mmol/dm³ four hours after the drink. Name the condition this suggests and state one risk factor for it.

      [3]