Name:
Target Grade:
2.5 Proteins – Their Functions and Uses
Q1.
Bread contains starch, protein and fat.
(a)
Complete each sentence by choosing the correct words from the box.
amino acids
protein
fat
starch
fatty acids
sugar
Amylase speeds up the digestion of .................................... . The product of this digestion
is ............................. . Protease speeds up the digestion of ............................. .
The product of this digestion is .............................................. .
(b)
(4)
Why do molecules of starch, protein and fat need to be digested?
.....................................................................................................................................
..................................................................................................................................(2)
(c)
In which part of the digestive system does the digestion of starch begin?
Draw a ring around your answer.
large intestine
(d)
mouth
small intestine
stomach
(1)
What do we call substances like amylase and protease which speed up chemical
reactions?
..................................................................................................................................(1)
(Total 8 marks)
Q2.
Enzymes have many uses in the home and in industry.
(a)
Which type of organism is used to produce these enzymes?
Tick ( ) one box.
Mammals
Microorganisms
Plants
(1)
Page 1
(b)
Babies may have difficulty digesting proteins in their food. Baby food manufacturers use
enzymes to ‘pre-digest’ the protein in baby food to overcome this difficulty.
Use words from the box to complete the sentences.
amino acids
(c)
amylases
proteases
sugars
(i)
Proteins are ‘pre-digested’ using enzymes called ................................................ .(1)
(ii)
This pre-digestion produces ................................................................................ .(1)
A baby food manufacturer uses enzyme V to pre-digest protein.
He tries four new enzymes, W, X, Y and Z, to see if he can reduce the time taken to predigest the protein.
The graph shows the time taken for the enzymes to completely pre-digest the protein.
The manufacturer uses the same concentration of enzyme and the same mass of protein
in each experiment.
(i)
How long did it take enzyme V to pre-digest the protein?
minutes
(ii)
Which enzyme would you advise the baby food manufacturer to use?
Draw a ring around your answer.
enzyme V
enzyme W
enzyme X
Page 2
enzyme Y
enzyme Z
(1)
Give a reason for your answer.
...........................................................................................................................
........................................................................................................................... (2)
(iii)
Give two factors which should be controlled in the baby food manufacturer’s
investigations.
Tick ( ) two boxes.
Oxygen concentration
Temperature
Light intensity
pH
(2)
(Total 8 marks)
Q3.
The diagram gives information about some parts of the human digestive system.
Page 3
(a)
(i)
Name the organ which makes bile.
........................................................................................................................... (1)
(ii)
Label this organ with the letter X on the diagram.
(1)
Information in the table may help you to answer parts (b) and (c).
(b)
Name two parts of the digestive system where protein is digested.
1 .................................................................................................................................
2 .................................................................................................................................(2)
(c)
Suggest two reasons why starch is not digested in the stomach.
1 .................................................................................................................................
.....................................................................................................................................
2 ..................................................................................................................................
.....................................................................................................................................(2)
(Total 6 marks)
Q4.
(a)
A food contains protein. Describe, in as much detail as you can, what happens to this
protein after the food is swallowed.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(4)
(b)
The table shows the activity of lipase on fat in three different conditions.
CONDITION
UNITS OF LIPASE ACTIVITY
PER MINUTE
Lipase + acid solution
3.3
Lipase + weak alkaline solution
15.3
Lipase + bile
14.5
Page 4
Explain, as fully as you can, the results shown in the table.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
(3)
(Total 7 marks)
Q5.
The diagram shows the apparatus used to investigate the digestion of milk fat by an
enzyme. The reaction mixture contained milk, sodium carbonate solution (an alkali) and the
enzyme. In Experiment 1, bile was also added. In Experiment 2, an equal volume of water
replaced the bile. In each experiment, the pH was recorded at 2-minute intervals.
Either: Experiment 1
or:
milk (contains fat)
sodium carbonate solution
bile
enzyme
Page 5
Experiment 2
milk (contains fat)
sodium carbonate solution
water
enzyme
The results of the two experiments are given in the table.
(a)
Milk fat is a type of lipid. Give the name of an enzyme which catalyses the breakdown of
lipids.
...................................................................................................................................
(1)
(b)
What was produced in each experiment to cause the fall in pH?
...................................................................................................................................
(1)
(c)
(i)
For Experiment 1, calculate the average rate of fall in pH per minute, between
4 minutes and 8 minutes. Show clearly how you work out your final answer.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
............................................. pH units per minute
(2)
(ii)
Why was the fall in pH faster when bile was present?
...........................................................................................................................
...........................................................................................................................
(1)
Page 6
(Total 5 marks)
Page 7
M1.
(a)
in sequence
starch
1
sugar
1
protein
1
amino acids
1
(b)
(too) large or insoluble
do not accept “breaking up”
do not accept complex
accept ‘need to make molecules
smaller / soluble’ – reverse argument
1
cannot be absorbed or
cannot enter blood or
cannot pass through wall / lining of
intestine / gut or villi
“body” not enough
not large intestine
1
(c)
mouth
accept positive indication
1
(d)
enzymes
allow catalysts
do not accept catalase
1
[8]
M2.
(a)
microorganisms
1
Page 8
(b)
(i)
proteases clear indications of correct answer
1
(ii)
amino acids (both words) clear indications of correct answer
1
(c)
(i)
14
1
(ii)
mark independently
enzyme Z
clear indication of correct answer
1
takes least time (to pre-digest protein) / works fastest
allow only 7 minutes / less time / faster
do not allow works best
1
(iii)
temperature
1
pH
1
[8]
M3.
(a)
(i)
liver
1
(ii)
on diagram:
‘X’ on liver
must be unambiguous (eg not overlapping gall bladder)
intersection of X in liver
1
(b)
stomach
1
small intestine
accept duodenum or ileum
extra wrong answers cancel the mark,
eg small intestine (colon) = Page 9no marks
1
(c)
amylase not produced by stomach
accept no starch digesting enzymes in the stomach
accept correct enzyme not in stomach
accept only proteases in stomach
do not accept protease does not digest starch
1
acid / low / wrong pH in stomach or enzyme would be denatured in
stomach or amylase only works in neutral / alkaline conditions
incorrect extra information cancels mark
do not accept amylase does not work in the stomach
1
[6]
M4.
(a)
digested / broken down / made soluble by protease enzyme
in stomach in small intestine / from stomach / from pancreas
into amino acids
amino acids / small molecules absorbed into blood
any four for 1 mark each
4
(b)
ideas that
lipase / enzyme works best in alkaline / neutral conditions
acid denatures or inactivates enzyme / inhibits enzyme activity
bile emulsifies fat / bile produces larger surface area of fats / bile alkaline
for enzyme to work on / which increase activity of enzymes
any three for 1 mark each
3
[7]
M5.
(a)
lipase
1
(b)
fatty acid
ignore glycerol
1
Page 10
(c)
(i)
0.25 or
if correct answer ignore working or lack of working
for 1 mark
2
(ii)
fats emulsified or described re. Small droplets or large S.A.
(for enzyme action) or fats ‘mix’ better with water
do not allow breakdown / breakup unqualified
1
[5]
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