Download IIIrd Form Test - Digestion 1

A2 Biology - Module 6: Digestion Questions
1.
Different concentrations of maltose were placed in the small intestine of a mammal. The amount of glucose
appearing in the blood and in the small intestine were measured. The results are shown in the graph.
Glucose in blood
60
40
Amount of
glucose after
15 minutes/
mol dm–1
20
Glucose in lumen
of small intestine
0
0
0.2
0.4
0.6
0.8
1.0
Maltose concentration/mmol dm–3
(a)
(i)
Give the name of the blood vessel most likely to have been sampled for glucose.
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(1)
(ii)
By what chemical process is a molecule of maltose converted into two molecules of glucose?
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(1)
(b)
The enzyme maltase converts maltose into glucose. This enzyme is found in the cell surface membrane
of the epithelial cells of the small intestine.
(i)
Explain the evidence from the graph which supports the view that the breakdown of maltose
does not occur in the lumen of the small intestine.
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(2)
(ii)
Suggest an explanation for the shape of the curve showing the change in the amount of glucose
in the blood.
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(3)
A2 Biology - Module 6: Digestion Questions
A cow obtains most of its nutritional requirements from mutualistic microorganisms in its rumen. The
diagram summarises the biochemical processes carried out by these microorganisms.
Cellulose
Protein
Non-protein
nitrogen
Cellulose
Protein
Non-protein
nitrogen
Urea
Salivary
glands
Oesophagus
Rumen
Methane
Fatty
acids
Amino
acids
Ammonia
Urea
Ammonia
Microbial protein
True stomach
and intestine
(c)
Liver
Urea
Kidney
Use the information in the diagram to help explain why:
(i)
the relation between the cow and the microorganisms which live in its rumen may be described
as mutualistic;
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(ii)
(2)
it is possible for a cow to survive on a diet which is poor in protein;
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(iii)
(2)
ruminant animals such as cows are less efficient than non-ruminant animals in converting
energy in food into energy in their tissues.
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(2)
(Total 13 marks)
A2 Biology - Module 6: Digestion Questions
2.
Answer should be written in continuous prose. Credit will be given for biological accuracy, the organisation
and presentation of the information and the way in which the answer is expressed.
The diagram shows the nitrogen cycle.
Nitrogen-containing
substances in
producers
Digestion
Nitrogen-containing
substances in
primary consumers
Digestion
Nitrogen-containing
substances in
secondary consumers
Nitrates
Nitrates
Ammonium
compounds
Saprobiotic
microorganisms
Describe how nitrogen-containing compounds in producers are digested in the gut of a mammal.
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(Total 7 marks)
A2 Biology - Module 6: Digestion Questions
3.
The flow chart represents the breakdown of starch in the human gut.
amylase
starch
(a)
maltase
maltose
glucose
Name two organs which produce amylase in humans.
Organ 1 .......................................................................................................................
Organ 2 .......................................................................................................................
(1)
(b)
Describe how the release of amylase from each of these organs is controlled.
Organ 1......................................................................................................................
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Organ 2......................................................................................................................
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(3)
(c)
Describe the precise location of maltase in the human gut.
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(2)
(Total 6 marks)
A2 Biology - Module 6: Digestion Questions
4.
(a)
The diagrams show fatty acid molecules in saturated and unsaturated triglycerides.
Saturated
O
H
C C C
HO
Unsaturated
C C
C
O
H
H
H
C
C C
C C C
HO
H
H
Complete the diagrams to show the difference between a saturated fatty acid and an unsaturated fatty
acid.
(2)
(b)
In the human gut, a triglyceride may be converted to glycerol and fatty acids by hydrolysis.
(i)
Explain what is meant by hydrolysis.
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(1)
(ii)
Describe the part played by bile in the hydrolysis of triglycerides.
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(2)
(Total 5 marks)
A2 Biology - Module 6: Digestion Questions
5.
Inorganic ions form a minor but essential part of the human diet.
(a)
Give two functions of each of the following ions in the human body.
(i)
Calcium
1.........................................................................................................................
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2.........................................................................................................................
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(2)
(ii)
Iron
1.........................................................................................................................
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2.........................................................................................................................
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(2)
The table shows how the estimated average daily requirements for calcium and iron in the diet vary with age
and sex.
Age/years
(b)
Estimated average requirement/mg day–1
calcium
iron
Both sexes 1 - 3
4-6
7 - 10
275
350
425
5.3
4.7
6.7
Males
11 - 14
15 - 18
19 - 50
50+
750
750
525
525
8.7
8.7
6.7
6.7
Females
11 - 14
15 - 18
19 - 50
50+
625
625
525
525
11.4
11.4
11.4
6.7
Explain the change in the estimated average daily requirements for calcium and for iron between the
ages of 4 and 10.
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(2)
A2 Biology - Module 6: Digestion Questions
(c)
Explain the differences between the average daily requirements for males and females from the age of
11 for:
(i)
calcium;
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(ii)
iron.
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(3)
The graph shows the results of an investigation of the effect of calcium ion concentration on their rate of
uptake by epithelial cells from the small intestine.
Curve X
Control
Cells not
treated with
respiratory poison
Rate of uptake
of
calcium ions
Curve Y
Cells treated with
respiratory poison
A
(d)
B
Concentration of calcium ions
in surrounding solution
C
Explain the evidence from the graph that active transport is involved in the absorption of calcium ions
from the lumen of the intestine.
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(2)
A2 Biology - Module 6: Digestion Questions
(e)
For Curve Y, obtained when a respiratory poison was added:
(i)
explain the shape of the curve between concentrations B and C;
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(ii)
suggest why no calcium ions were taken up between concentrations A and B.
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(3)
The diagram shows some of the ways in which other substances are absorbed in the small intestine.
Sodium
Sodium
and
glucose
Lumen of
intestine
Water
Epithelial
cell
Research has shown that microorganisms may cause diarrhoea by shutting down the pathway that transports
sodium ions into the epithelial cells. These microorganisms do not, however, have any effect on the
mechanism responsible for the “co-transport” of glucose and sodium ions into the cells.
(f)
(i)
Explain, in terms of water potential, why a failure to remove sodium ions from the lumen of the
intestine causes diarrhoea.
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(2)
A2 Biology - Module 6: Digestion Questions
(ii)
Oral rehydration therapy (ORT) is used to treat diarrhoea. It involves giving the patient a
solution of sodium salts and glucose. Using the information in the diagram, explain how this is
effective in treating diarrhoea.
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(g)
(2)
Attempts have been made to produce more effective oral rehydration therapy. Suggest why using
starch instead of glucose reduces the faecal output for a much longer period.
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6.
(a)
(2)
(Total 20 marks)
Trypsin is a protein-digesting enzyme. It is produced as inactive trypsinogen in the pancreas.
Trypsinogen is secreted when food enters the duodenum.
(i)
Describe the way in which the secretion of trypsinogen is stimulated by food entering the
duodenum.
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(ii)
(2)
Describe how trypsinogen is converted to trypsin in the small intestine.
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(b)
(2)
Trypsin is used in the tanning industry for the production of leather. It was first obtained by extracting
it from the faeces of domestic animals. Explain why faeces contain digestive enzymes such as trypsin.
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(2)
(Total 6 marks)