Embed Size (px)
Citation preview
1. The sense of taste is normally caused by the stimulation of chemoreceptors in the taste buds of the tongue. There are four main “tastes”: sweet, salty, bitter and sour. The tongue also has receptors for temperature. It is known that the taste of food can vary according to whether it is cold, warm or hot. Scientists discovered that just warming or cooling parts of the tongue, even when no food was present, also caused a sensation of taste.
Scientists experimented with a group of people. They gradually cooled the tips of their tongues and measured the intensity of the taste felt by each member of the group. The experiment was repeated, this time warming the tip of the tongue. The graphs show the average values for the group.
K ey : S a lty B itte r S w e e t S o u r
C o o lin g th e to n g u e tip
D ecre ase in te m p era tu re fro m 3 5 ºC In c rease in tem p era tu re fro m 2 0 ºC
m o d e ra te
w eak
ju std e tec tab le
Tast
e in
tens
ity fe
lt/ a
rbitr
ary
units
W a rm in g th e to n g u e tip
3 5 2 5 2 0 2 5 2 0 3 0 2 0 3 5 2 0 4 03 5 2 0 3 5 1 5 3 5 1 0 3 5 5
[Source: modified from Cruz and Green, Nature (2003) 403, page 889]
(a) Identify which taste was felt most strongly when the tip of the tongue was
(i) cooled................................................................................................................
(ii) warmed..............................................................................................................(1)
(b) Compare the effects on the taste of sweetness, of warming and cooling the tip of the tongue.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
1
(c) It is important that such experiments use a population sample that is representative. Suggest two biological criteria the scientists would have used to select the people to be tested.
.....................................................................................................................................
.....................................................................................................................................(1)
(d) Explain whether cooling or warming the tip of the tongue has the greater effect on the sensation of taste.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
The scientists discovered that there were two types of chemoreceptor in the tongue tip. They called these A and B. They tested these chemoreceptors using solutions of sucrose to find out the type of taste and the intensity felt. The results are shown in the bar chart.
Tas te in te n sity fe lt/ a rb itra ry u n its
m o d era te
w eak
ju s t d e tec tab le
sw ee t d e te c te d so u r d e tec ted
K ey : A B
2
(e) Compare the effects of sucrose on the A and B chemoreceptors by giving two similarities and two differences.
Similarities .................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
Differences .................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(4)
(Total 10 marks)
2. At the start of glycolysis, glucose is phosphorylated to produce glucose 6-phosphate, which is converted into fructose 6-phosphate. A second phosphorylation reaction is then carried out, in which fructose 6-phosphate is converted into fructose 1,6-bisphosphate. This reaction is catalyzed by the enzyme phosphofructokinase. Biochemists measured the enzyme activity of phosphofructokinase (the rate at which it catalyzed the reaction) at different concentrations of fructose 6-phosphate. The enzyme activity was measured with a low concentration of ATP and a high concentration of ATP in the reaction mixture. The graph below shows the results.
L o w AT P co n ce n tra tio n
H ig h AT P c o n cen tra tio n
E n zy m e ac tiv ity
F ru c to se 6 -p h o sp h a te co n ce n tra tio n
3
(a) (i) Using only the data in the above graph, outline the effect of increasing fructose 6-phosphate concentration on the activity of phosphofructokinase, at a low ATP concentration.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................(2)
(ii) Explain how increases in fructose 6-phosphate concentration affect the activity of the enzyme.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................(2)
(b) (i) Outline the effect of increasing the ATP concentration on the activity of phosphofructokinase.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................(2)
(ii) Suggest an advantage to living organisms of the effect of ATP on phosphofructokinase.
...........................................................................................................................
...........................................................................................................................(1)
(Total 7 marks)
4
3. The unicellular green alga Phaeodactylum tricornutum is photosynthetic. Cell biologists genetically modified this organism by adding a glucose transporter gene. The modified and unmodified algae were grown in a nutrient medium under a series of different conditions and the growth rate of the cells was measured.
1 2
1 0
8
6
4
2
00 2 4 6 8 0 2 4 6 8
Tim e / d ay s
C e ll d en sity /1 0 ce lls cm
K ey := lig h t a n d n o g lu c o se in th e m e d iu m
= lig h t a n d g lu co se in th e m e d iu m
= d a rk an d g lu c o se in th e m e d iu m
U n m o d ifie d a lg ae M o d ified a lg ae
– 37
[Source: L A Zaslavskaia, et al., Adapted (2001) Science, 292, pages 2073–2075]
(a) State the role of glucose in the metabolism of cells.
.....................................................................................................................................(1)
(b) Deduce where you would expect to find the glucose transporter protein in the modified algae cells.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(c) Compare the effect of light on the modified and the unmodified cells.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
Commercially, unmodified algae are grown in shallow sunlit ponds or illuminated containers. The cells only grow in the top few centimetres. However, the modified algae can grow at any
5
depth.
(d) Explain why the modified algae can grow at any depth whereas the unmodified algae can only grow at the surface.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(3)
(Total 8 marks)
4. Alcohol dehydrogenase is an enzyme that catalyses the reversible reaction of ethanol and ethanal according to the equation below.
NAD+ + CH3CH2OH CH3CHO + NADH + H+
ethanol ethanal
The initial rate of reaction can be measured according to the time taken for NADH to be produced.
6
In an experiment, the initial rate at different concentrations of ethanol was recorded (no inhibition). The experiment was then repeated with the addition ofl mmol dm–3 2,2,2-trifluoroethanol, a competitive inhibitor of the enzyme. A third experiment using a greater concentration of the same inhibitor (3 mmol dm–3) was performed. The results for each experiment are shown in the graph below.
1 .21 .11 .00 .90 .80 .70 .60 .50 .40 .30 .20 .10 .0
0 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0E th an o l c o n ce n tra tio n / m m o l d m – 3
In itia l ra te o f re a c tio n/ a rb itra ry u n its
– 3
– 3
n o in h ib itio n1 m m o l d m in h ib ito r3 m m o l d m in h ib ito r
[Source: R Taber, Biochemical Education, (1998) 26, pages 239-242]
(a) Outline the effect of increasing the substrate concentration on the control reaction (no inhibition).
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(b) (i) State the initial rate of reaction at an ethanol concentration of 50 mmol dm–3
in the presence of the inhibitor at the following concentrations.
1 mmol dm–3:.....................................................................................................
3 mmol dm–3:.....................................................................................................
(1)
7
(ii) State the effect of increasing the concentration of inhibitor on the initial rate of reaction.
...........................................................................................................................
...........................................................................................................................(1)
(c) Explain how a competitive inhibitor works.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(3)
(Total 7 marks)
8
5. It had always been assumed that eukaryotic genes were similar in organization to prokaryotic genes. However, modern techniques of molecular analysis indicated that there are additional DNA sequences that lie within the coding region of genes. Exons are the DNA sequences that code for proteins while introns are the intervening sequences that have to be removed. The graph shows the number of exons found in genes for three different groups of eukaryotes.
P e rcen tag e o f g en es
S accha ro m yces cerev is ia e (a yea st)
D ro so p h ila m ela n o ga ste r (fru it f ly )
M am m a ls
1 0 0
8 0
6 0
4 0
2 0
04 0
3 0
2 0
1 0
02 0
1 5
1 0
5
01 2 3 4 5 6 7 8 9 1 0 11 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 < 3 0 < 4 0 < 6 0 > 6 0
N u m b er o f ex o n s
[Source: Benjamin Lewin, (1999) Genes VII, OUP, page 55]
(a) Calculate the percentage of genes that have five or less exons in mammals.
.....................................................................................................................................
.....................................................................................................................................(1)
9
(b) Describe the distribution of the number of exons and the percentage of genes inD. melanogaster.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(c) (i) Compare the distributions of the number of exons found in genes of S. cerevisiae and mammals.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................(2)
(ii) Suggest one reason for the differences in the numbers of exons found in genes of S. cerevisiae and mammals.
...........................................................................................................................
...........................................................................................................................(1)
10
Human DNA has been analysed and details of certain genes are shown in the table below.
Gene Gene size / kb* mRNA size / kb Number of introns
Insulin 1.7 0.4 2
Collagen 38.0 5.0 50
Albumin 25.0 2.1 14
Phenylalanine hydroxylase 90.0 2.4 12
Dystrophin 2 000.0 17.0 50
*kilobase pairs
[Source: William S Klug and Michael R Cummings, (2002), Concepts of Genetics, 7th edition, Prentice Hall, page 314]
(d) Calculate the average size of the introns for the albumin gene.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(e) Analyse the relationship between gene size and the number of introns.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
11
(f) Determine the maximum number of amino acids that could be produced by translating the phenylalanine hydroxylase mRNA.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(1)
Hemoglobin is a protein composed of two pairs of globin molecules. During the process of development from conception to adulthood, human hemoglobin changes in composition. Adult hemoglobin consists of two alpha- and two beta-globin molecules. Two globin genes occur on chromosome 16: alpha- and zeta-globin. Four other globin genes are found on chromosome 11: beta, delta, epsilon and gamma. The graph below illustrates the changes in expression of the globin genes over time.
5 0
4 0
3 0
2 0
1 0
0 1 0 2 0 3 0 4 0 2 4 6w eek s o f g es ta tio n b ir th m o n th o f a g e
P e rce n tag e o fh e m o g lo b in
a lp h a -g lo b ing a m m a-g lo b inb e ta -g lo b ind e lta -g lo b inep silo n -g lo b inze ta -g lo b in
K ey :
[Source: adapted from M Cummings, Human Heredity, 4th edition, West/Wadsworth Publishing Company]
(g) State which globin genes are the first to be expressed after fertilization.
.....................................................................................................................................(1)
12
(h) Compare the expression of the gamma-globin gene with the beta-globin gene.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(3)
(i) Deduce the composition of the hemoglobin molecules
at 10 weeks of gestation; .........................................................................................
..........................................................................................
2 months after birth. ..........................................................................................
..........................................................................................(2)
(Total 17 marks)
6. The respiratory quotient (RQ) is a measure of the metabolic activity of an animal. It is the ratio of CO2 produced to O2 consumed. In general, the lower the RQ value the higher the energy yield. The RQ is dependent on the diet consumed by the animal. The following table lists the typical RQ values for specified diets.
Diet RQ
Lipid 0.71
Carbohydrate 1.00
Protein 0.74
[Source: Walsberg and Wolf, Journal of Experimental Biology, (1995), 198, pages 213–219.Reproduced by permission of The Company of Biologists Ltd]
In an experiment to assess RQ values for house sparrows, the birds were fed a diet of pure mealworms (beetle larvae) or millet (a type of grain).
13
The graph below shows the RQ values of a house sparrow fed on a high carbohydrate diet (millet) and a high lipid diet (mealworms).
1 .0
0 .9
0 .8
0 .7
0 .60 1 2 3 4 5 6 7
T im e a fte r fee d in g / h
Res
pira
tory
quo
tient
K ey : M ille t M e a lw o rm s
[Source: Walsberg and Wolf, Journal of Experimental Biology, (1995), 198, pages 213–219.Reproduced by permission of The Company of Biologists Ltd]
(a) Compare the RQ values for millet and mealworms between 1 hour and 6 hours after feeding.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
The expected RQ value for house sparrows metabolizing millet is 0.93. The expected value when metabolizing mealworms is 0.75.
14
(b) Explain why the expected RQ values for millet and mealworms are different.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(c) Suggest reasons for
(i) the high initial RQ values for house sparrows fed on millet;
...........................................................................................................................
...........................................................................................................................(1)
(ii) the rapid fall in RQ values for house sparrows fed on millet.
...........................................................................................................................
...........................................................................................................................(1)
(Total 6 marks)
15
7. The hydrolysis of inorganic phosphate (PPi) by phosphatase enzyme provides energy for a wide range of reactions. A phosphatase (PPase) occurs bound to thylakoid membranes. This enzyme was purified from the thylakoid membranes of spinach leaves using chromatography. The activity of the membrane bound enzyme and the purified enzyme was measured.
The effect of the concentration of magnesium ions (Mg2+) on the relative activity of these enzymes was determined using different concentrations of magnesium chloride. The concentration of inorganic phosphate used in both cases was of 1 mmol dm–3.
Activity of phosphatase (arbitary units)
Membrane bound Purified
12 618 1215
R e la tiv e ac tiv ity/ %
m ag n e siu m ch lo ride co n cen tra tio n / m m o l dm – 3
P u rifed
M em b ran e b o u n d
[Reprinted from Po-Yin Cheung et al., “Thiols Protect the Inhibition of Myocardial Aconitase by Peroxynitrite”, Archives of
Biochemistry and Biophysics, vol. 350, issue 1, pp. 104-108 © 1998, with permission from Elsevier.]
(a) State the percentage of relative activity of the purified enzyme when the concentration of magnesium chloride is
(i) 1 mmol dm–3 ...................................
(ii) 2 mmol dm–3 ...................................(2)
16
(b) Outline the effect of magnesium chloride on the relative activity of the membrane bound enzyme.
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................
....................................................................................................................................(2)
(c) Calculate the approximate ratio of inorganic phosphate to magnesium chloride concentration needed to achieve maximum activity in membrane bound enzymes.
....................................................................................................................................(1)
(d) (i) State the difference in phosphatase activity when membrane bound and when purified.
..........................................................................................................................
..........................................................................................................................(1)
(ii) Suggest a reason for this difference.
..........................................................................................................................
..........................................................................................................................(1)
(Total 7 marks)
17
8. The eastern oyster (Crassostrea virginica) is a marine mollusc that lives in estuaries. The environmental surroundings of the eastern oyster, such as the temperature and concentration of trace elements, are constantly changing. The trace element cadmium affects the mitochondria and prevents them from carrying out their function efficiently. Investigators isolated mitochondria from the oysters to study how the respiration rate changed while varying the water temperature and the cadmium ion concentration.
R esp ira tio nra te / a rb itra ry
u n its
3 .0
2 .5
1 .5
1 .0
0 .5
0 .0
K ey : °1 5 C ° °
0 1 5 1 0 1 5 2 0 – 3
2 5 C3 5 C
C a d m iu m io n c o n c en tra tio n / µ m o l d m
[Source: I M Sokolova, (2004), The Journal of Experimental Biology, 207, pages 2639–2648.With permission of the Company of Biologists Ltd.]
(a) State the relationship between the concentration of cadmium ions and respiration rate at 35C.
.....................................................................................................................................
.....................................................................................................................................(1)
(b) Compare the respiration rate of the mitochondria at cadmium ion concentrations of 0mol dm–3 and 50mol dm–3.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
18
(c) Suggest one other environmental property of the water, apart from temperature and mineral concentration, that may show daily changes.
.....................................................................................................................................(1)
(d) The investigators concluded that seasonal and global warming might make the eastern oysters more likely to suffer from trace element poisoning.
Using the data, evaluate this hypothesis.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(3)
(Total 7 marks)
19
9. Mitochondrial electron transport defects (called mitochondrial myopathy) causes tiredness at low levels of exercise and varies from mild to severe. Scientists measured oxygen delivery to cells and oxygen use in cells of thirty-five patients with mitochondrial myopathy. The results were compared to a control group of thirty-two healthy individuals. The results are shown in the two charts below.
O x y g e n d e liv e ry to ce lls O x y g en u se in c e lls
Rat
e/m
lK
g–1m
in–1
4 0 0
3 5 0
3 0 0
2 5 0
2 0 0
1 5 0
Rat
e/m
lK
g–1m
in–1
5 0
4 5
4 0
3 5
3 0
2 5
2 0
1 5
1 0
5
K ey : m ito c h o n d ria l m y o p a th y g ro u p c o n tro l g ro u p
[Source: adapted from T. Taivassalo and R. G. Haller, (2006), ‘Exercise and training in mitochondrial myopathies’,Medicine and Science in Sports and Exercise, 37 (12) 2094-2101, © Lippincott Williams & Wilkins, USA]
(a) State the mean value for oxygen delivery to cells in patients suffering from mitochondrial myopathy.
......................................................................................................................................(1)
(b) Calculate the percentage difference of the oxygen use in cells by the control group compared to oxygen use in cells of patients with mitochondrial myopathy.
................ %(1)
20
(c) Discuss why people with mitochondrial myopathy tire more easily than healthy individuals.
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................
......................................................................................................................................(3)
(Total 5 marks)
21
10. Fruits remain alive for a period of time after harvesting. Cellular respiration continues and it can greatly influence the maturation (ripening) process in the fruits. The rate of respiration depends on many factors such as the type, quality, degree of ripeness and water content of the fruits, temperature and air composition. Respiration that continues after harvesting may sometimes lead to the over-ripening and eventual loss of an entire cargo of fruit during transport.
Studies of the maturation process in bananas are summarized in the following graph.
R ela tiv e ra te
g reen g reen /y e llo w y e llo wTim e /a rb itra ry u n its (sh o w in g co lo u r ch an g es in b an an as)
K ey :ch lo ro p h y ll b reak d o w nsta rch b reak d o w nw a te r re lea seC O fo rm atio n2S u g ar fo rm a tio n
[Source: www.containerhandbuch.de/chb_e/scha/index.html?/chb_e/scha/scha_15_02_03_02.html]
(a) (i) State two chemical products released as gases during cellular respiration.
1 ........................................................................................................................
2 ........................................................................................................................(1)
(ii) State one non-chemical product of respiration.
...........................................................................................................................(1)
22
(b) Using the data, analyse the events that occur when maturation begins in bananas.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(c) Suggest, giving reasons, two ways in which transport conditions can be controlled to minimize over-ripening.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(Total 6 marks)
11. Inflammation of human tissues often causes pain. Cyclooxygenases (COX) are a group of enzymes that play a role in causing inflammation. Analgesics are drugs that can reduce pain. The graph below shows how increasing concentrations of the analgesic drug dipyrone, affects the activity of three different cyclooxygenases, COX-1, COX-2 and COX-3.
K ey :
C O X -2C O X -3
C O X -1
0 1 1 0 1 0 0 1 0 0 0 1 0 0 0 0
1 2 0
1 0 0
8 0
6 0
4 0
2 0
0Enzy
me
activ
ity /
arbi
trary
uni
ts
D ip y ro n e co n c e n tra tio n / m o l d mμ – 3
[Source: Adapted from N V Chandrasekharan, et al, (2002), Proceedings of the National Academy of Sciences, USA, 99, (21),pages 1392613931]
23
(a) Outline the relationship between dipyrone concentration and COX-3 activity.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(b) Deduce whether dipyrone is an inhibitor of COX-2.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(c) Evaluate the potential of dipyrone as an analgesic using the data in the graph.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(Total 6 marks)
24
12. Physiologists measured the amount of glycogen stored in the muscle tissues of six athletes during a training period. The athletes ran 16 km each day for three consecutive days. The glycogen levels were measured before (pre-) and after (post-) each run. The athletes were allowed to rest for five days and the muscle glycogen levels were measured again. The data are shown in the scattergram below. Each athlete is shown by a different symbol (eg is athlete A).
p re p re p rep o st p o st p o st1 6 k m 1 6 k m 1 6 k m
1 st d ay 2 n d d a y 3 rd d a y
2 .5
2 .0
1 .5
1 .0
0 .5
G ly c o g e n in m u sc le /g p e r 1 0 0 g o f m u sc le
5 d ay sla te r
[Source: W D McArdle, et al., (1987), Physiologie de l’activité Physique. Energie, Nutrition et Performance , Vigot, Pages 51–52]
(a) State the effect of running on the muscle glycogen levels.
.....................................................................................................................................(1)
(b) Describe the effect of the training programme on the levels of muscle glycogen.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
25
Glycogen is a stored form of carbohydrate. For each athlete approximately 50% of their diet was carbohydrate.
(c) Outline the importance of carbohydrate supplies in muscle tissue during running.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(d) Discuss the implications of this information for long distance runners training for a sports event.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(3)
(Total 8 marks)
26
13. A reliable method of estimating cardiovascular fitness is by measuring the oxygen consumption of the body, when the rate of heartbeat is at its maximum (Vmax) during intense exercise. This test was used to measure fitness among 71 volunteers. Two weeks later the same individuals were asked to run for 2.1 km at two different speeds (V70 and V90) and the power they developed during these runs was measured.
V70 in which they ran at a speed where their rate of heartbeat was 70% Vmax V90 in which they ran at a speed where their rate of heartbeat was 90% Vmax.
4 0 0
3 5 0
3 0 0
2 5 0
2 0 0
1 5 0
1 0 0
5 0
0
P o w er / W
0 .0 0 0 .5 0 1 .0 0 1 .5 0 2 .0 0 2 .5 0 3 .0 0 3 .5 0 4 .0 0 4 .5 0R u n n in g v e lo c ity / m s – 1
7 0 9 0
K ey :V V
[Source: V J Leibetseder et al., Journal of Exercise Physiology, (2002), 5 (3), page 11]
(a) State the maximum power developed by a runner at V70.
.....................................................................................................................................(1)
(b) Outline the relationship between running velocity and power developed at V90.
.....................................................................................................................................
.....................................................................................................................................(1)
27
(c) Compare the data for V70 and V90.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(d) Suggest why measurements of Vmax are dangerous for older people.
.....................................................................................................................................
.....................................................................................................................................(1)
(Total 5 marks)
28
14. Carotenoids are plant pigments which occur in different forms, such as lutein (from spinach),-carotene (from carrots), and lycopene (from tomatoes). Researchers investigated the processing of carotenoids from vegetables in the stomach and small intestine. Healthy men were fed three test meals differing only in the vegetable added. The carotenoid content of each test meal was the same. Although the meals were basically liquid, the spinach meal had been made from chopped spinach leaves. The meals were ingested in random order with three-week intervals between them. Prior to the first meal, tubes leading directly into the stomach and small intestine were fitted to each man. Samples of stomach and small intestine contents were collected from these tubes at regular intervals after each meal. Data from this study is shown below.
6 0
5 0
4 0
3 0
2 0
1 0
0
3 0
2 5
2 0
1 5
1 0
5
00 06 0 6 01 2 0 1 2 01 8 0 1 8 0
T im e / m in s T im e / m in s
Con
cent
ratio
n of
car
oten
oids
in th
e st
omac
h /
mol
dm
Con
cent
ratio
n of
car
oten
oids
in th
e st
omac
h /
mol
dm
–3 –3
K ey: = lu te in (sp in a c h m ea l) = -c a ro te n e (ca rro t m e al) = ly co p e n e ( to m a to m e a l)
[Source: Tyssandier et al, American Journal of Physiology, 284, (2003), pages 913–922. Copyright 2003 by Am Physiological Society. Reproduced with permission of Am Physiological Soc via Copyright Clearance Center]
(a) (i) Calculate the rate of decrease of lycopene concentration in the period 60 minutes to 120 minutes after ingestion in the stomach.
...........................................................................................................................
...........................................................................................................................(1)
(ii) Predict how many minutes from ingestion it will take lycopene to completely leave the stomach.
...........................................................................................................................(1)
29
(b) Describe the changes in stomach content of lutein, -carotene and lycopene during the 180 minutes following ingestion.
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................
.....................................................................................................................................(2)
(c) Suggest a reason why the concentration of lycopene stays relatively constant in the small intestine.
.....................................................................................................................................
.....................................................................................................................................(1)
(Total 5 marks)
30
