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(Question H2 continued)

(c) Describe the breakdown of hemoglobin in the liver.

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(Question H2 continued)

(b) The oxygen dissociation curve is a graph that shows the ;'~:.-.:~:.-_~::;~s::::'-~:'-.J.::on ofhemoglobin at various partial pressures of oxygen. Curve _-\s;::-.'.s ~:-_~'::':ss'.>2i:.::iC':J. at apH of 7 and curve B shows the dissociation at a different pH.

100, _-\-.. .. ..90-1 ------- .. - B- .. ..~ 800.-.•...ro;...; 70.2rotIl

~ 60--....~ 50.•....

.D0bh 400R....• 30Q)~>.x 200

100

I I I I I I I I I I0 10 20 30 40 50 60 70 80 90 100p02/mmHg

[Source: The American Society of Health-System Pharmacists]

(i) State the possible cause of the curve shifting from A to B. [ll

(ii) On the graph, draw the curve for myoglobin. [2l

(This question continues on the following page)

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(Question Hi continued)

(e) Predict, with a reason, the effect of DIDS on stomach pH if given to an experimentalsubject. [2J

H2. (a) Outline how coronary thrombosis can be caused. [2]


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-25 - '\lil ~ BIOLO H?: E:;G TZIIXX I(Question Hi continued)

(a) Calculate the difference in the rate of decrease of pH between :~:~ ,~:,=:::-o~.:el~s and themodified cells without DIDS. [lJ

H '-1' .. ' p mm

(b) State the effect of DIDS on the rate of decrease of the extracellular pH. [lJ

(c) Scientists hypothesized that Helicobacter pylori alters the ability to maintain neutral pHat the epithelial cell surface by inhibition of SLC26A9. Evaluate this hypothesis. [2]

(d) In further experiments, scientists observed that the levels of mRNA of SLC26A9increased in epithelial cells when infected by Helicobacter pylori. Suggest a possibleexplanation for this increase. [1]


11111I111111I2532

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HI. Helicobacter pylori infection is a cause of stomach ulcers. It affects SLC26A9, which isa membrane protein present in the epithelial lining of the stomach. SLC26A9 takes partin the reversible transport of chloride and hydrogen carbonate ions into and out of theepithelial cells in order to raise the pH at the membrane to neutral levels. Entry of chloride ionsinto epithelial cells and removal of hydrogen carbonate ions both cause extracellular pHto increase.

To assess the function of SLC26A9, this process was reversed by artificially raising theexternal pH. The rate of change of extracellular pH was measured with normal epithelial cellsand with modified cells with extra SLC26A9. The tests were also performed in the presenceofDIDS, an inhibitor of SLC26A9.

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Option H - Further human physiology

CI

epithelial cell epithelial cellHCO~

Control cell in lowextracellular pH

0.2

Rate of decrease ofextracellular pH /

pH min-I 0.1

Control cellsat high pH

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------.------.--------

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epithelial cell

"'--'--·"·"··-'1'.·.~~~~~I_~~,~:;~-~=:===::=:==:::= :=::-j- - - - -, - - -Control cell in high

extracellular pHModified cell in high

extracellular pH

--------.- ..-----.--------.-.." -----:-:-:-:-=-~.-:-:-.- - - -- - --

-- -- ----.-.-.-.- .r.:

==~==~:=·::=:::::l----.-.-.-.-.-.-.----.-.-.-.-.---.-.

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Modified cellsat high pH

Modified cellsat high pH+DIDS

:-:->:-~~.:-=

[Source: adapted from J Xu, et al., (2005), Am J Physiol Cell Physiol, 289, pages 493-505 andJ Henriksnas, (2005), Acta Universitatis Upsaliensis, pages 60-67]

(This question continues on the following pagr:!

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G3. Some organisms have adopted r-strategies and some have adopted A.--strategies. Discuss theenvironmental conditions that favour each of these strategies.

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G2. (a) (i) State the name of the biome in which there is little precipitation and temperaturesare very low. [1]

(ii) Outline the characteristics of the vegetation of this biome. [1]

(b) Outline the consequences of the edge effect for small nature reserves. [2]

(c) Outline one example of biological control of invasive species. [2J

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(Question G 1 continued)

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(e) Allochthonous organisms are those which have migrated fromor.e place to another, suchas the aquatic invertebrates in this study. Suggest one effect N'allochthonous invertebratesin this environment.

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(b) Describe the trend in the aquatic inverteor.i:e j~L\.. [2]

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(Question G1 continued)

(c) Suggest the relationship between defoliation and the amount of terrestrial invertebrates inthe forest. [2]

(d) Suggest a possible explanation for the pattern in aquatic invertebrate flux to the forestseen between the months of June and December. [2]


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Option G - Ecology and conservation

G 1. The graph below shows the monthly mean values of terrestrial inv ertebrates from May 1997to June 1998 in the northern hemisphere. The light line shows the biomass of invertebrateswhich are prey to forest birds (terrestrial invertebrate biomass). The darker line shows theinvertebrates which lived in the stream and have moved to the forest (aquatic invertebrate fluxor movement). The black bars on the horizontal line at the bottom show periods when treeshave leaves and the white bars show periods of defoliation.

200 -, Terrestrial r:-15invertebrate biomass

N 12IS 150 Aquatic invertebrate 10eo flux ">. N

S IS---ir: 9 b1)ir: Scd

S ---0 100 :x::E ;:::l- ~cd 6 o• ..-< .~.bv: ;:::l<l) cr'i:: -<:~ 50 ?

f 3/'/

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M J J A S o N D J F M AM JMonth of the year

[Source: S Nakano and M Murakami, (2001), Proceedings of the National Academy of Sciences, 98, pages 166-170]

(a) State the mean terrestrial invertebrate biomass measured in August.


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F3. Discuss the prion hypothesis for the cause of 3;':'::~~=-,-,:-",:;:encephalopathies. [6J

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F2. (a) Outline the diversity of Eubacteria according to cell wali structure.

(b) State the role of Rhizobium and Nitrobacter in the nitrogen cycle.

Rhizobium:

Nitrobacter:

(c) Define the term chemoautotroph.

(d) Explain the use of bacteria in bioremediation.

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(b) Distinguish between the agedAspergillus oryzae.

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2uestion F1continued)

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(c) Evaluate the use of the strain Aspergillus fiavus in the production of soy sauce~~~. m

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Option F - Microbes and biotechnology

Fl. Soy sauce contains many soluble compounds such as glucose. the amino acid tyrosine andsoluble nitrogen compounds including urea, ammonium and nitrates. One ofthe most importantsteps in soy sauce production is the growth of Aspergillus. The strains of this mould that areused have high protease activity, no toxin production, and give a good taste and aroma tothe final product. In factories several strains of mould are used, the most common are thedifferent Japanese strains of Aspergillus oryzae. In Thailand, a locally occurring mould,Aspergillus flavus, is sometimes used. Several characteristics of the soy sauce produced usingAspergillus flavus were compared to those of soy sauce produced using Aspergillus oryzae.Acceptability was determined by factory workers based on aroma, colour and taste.

Soy sauceprepared from:

Protease activity/ Jim min' em?

Solublenitrogen/ g dm"

AcceptabilityToxicity /aflatoxinbioassay

Tyrosine/ g dm?

GlucoseI g dm"

Aspergillus flavus

After filtering Notdetectable Acceptable96 38.7 10.2 45.9

Aged Notdetectable Acceptable103 37.8 10.8 40.7

Aspergillus oryzae

After filtering Notdetectable Acceptable64 22.9 4.7 32.1

Aged Notdetectable Acceptable126 28.2 35.44.9

[Source: A Bhumiratana, et al., (1980), Applied and Environmental Microbiology, 39, pages 430-435]

(a) Calculate the percentage increase in protease actrvity in soy sauce prepared withAspergillus oryzae when the soy sauce has been aged. [1}

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(Question E2 continued)

(c) Explain the effects of psychoactive drugs on synaptic trar.s.n.ssion.

(d) Outline how endorphins act as painkillers.

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!. (a) Define the term stimulus. [lJ

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(b) Outline the functions of the following parts of the brain.

(i) Medulla oblongata: [l}

(ii) Hypothalamus: [l}

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(e) Making nests is an innate behaviour.learned behaviour.

Distinguis.;

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istion E1 continued)

(a) State which activity takes up least of the overall time budget of the guillemors. 1- i 7L s. J

(b) Calculate the percentage of the overall time budget the guillemots spend restingon the sea surface. [IJ

•••••••••••......••........ 0 (I

(c) Alloparenting behaviour is frequently observed in guillemots. This is the process wherenon-breeding birds will take care of other chicks. Discuss the advantages of alloparentingbehaviour. [2J

(d) Suggest one reason, other than breeding, why birds spend more time at the colony thanany other activity. [IJ


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\ll1l4/BIOLOIHP3IENG/TZl/XX ~{.:IJOption E - Neurobiology and behaviour

El. Common guillemots (Uria aalge) are large sea birds ofthee ;': ='.::~~lly.They breed in coloniesat high densities but make no nest. Their single egg is inc.:: .::-:~::.=.::.. bare rock. Scientists fittedelectronic time-depth recorders onto twelve common g',::::~:-:'.=:~and recorded five differentactivities during the chick-rearing period: at the colon .. :::..~:ght. resting or active on thesea surface and diving. The pie charts below include poo.e ; ::..:::.:::::rom all birds showing overalltime budget and time budget at sea.

Time-depth recorder I Q

f).i;On the sea surface

···1.. :~===~:~- - =-=-~-=-=~

~I=====~~==~~~=~

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In flight

At the colony

o •

oO"~o

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Diving ..

Overall time budget Time budget at sea

Diving In flight--Diving

Active onsea surface

On seasurface

At the colony

[Source: Y Tremblay, et al., (2003), The 101l;-n(;/ ofExperimental Biology, 206, pages 1929-1940]


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-.:: ~ -+ BIOLOIHP3/ENG/TZlIXX !~I}I~~I -6-D3. Discuss the endosymbiotic theory for the origin of eukzr .:-:; [6J

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() Th t bl b 1 1· t fi . 1 1 c""-'·· _ _.,.".,..,-,'-, .: ,.- .. - ... -,- .... ~-,- .• -; ~ .,"',c e a e eow ISS veammasa Oll:;- _ _.. ,.:- .. ~_.::. __ .•.. _._ •....... _ .. _:-.c __

sign (+) indicates that the animal has this ,'- '-' .. '.-' '-" -- -. .-~; "ct"'-.... -'-~~ ",,-__ ":_"': .. _-= __ 2:' ._" ,-, :: ..:.. . __ . 2:' :::- _= __ - _....~I,.-_\....•.l \,,~

that the characteristic is absent.

Animal Jaws Limbs Hsir Placenta

Salamander + - - -

Mouse + - -I +

Jellyfish - ! - - -

Koala + - T -

Salmon + - - -i ,

Based on the features above, a student constructed a c1adogram. State the names of theorganisms missing in the following c1adogram. [2J

Koala

(d) Describe the major anatomical features that define humans as primates.

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D2. (a) Define the term clade. ill

(b) Distinguish between analogous and homologo.is ~~_:~..:~:-~_;:--:=-gan example of each. [2J

(This qlie5~:o:: ._

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x:: - 3=1_~'~'._' ~-:?:=>~0~Zl 'xx~stion Dl continued)

(b) Identify the breeding combination that rc~,:::~ ~~::~~ >,c,~.: -;~~~,'~

(c) Analyse the probability of breeding berwee: ::''::':',:'::",::.. ' ::~::~:.:: 5J:l1c lake, [2J

(d) Scientists concluded that speciation is taking place in these populations, Discuss theevidence for speciation provided by the data, [3J

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Option D - Evolution - - - - -- - _.- - - - _. - --- . - -- - --- - . _.-. _.

Dl. Populations of threespine sticklebacks (Gasterosteus sp. I . .:. ="-~::-.. ~~·.'ingin small freshwaterlakes in British Columbia, Canada, are derived from :~:c::~.:.:-_~..~ threespine sticklebacktGasterosteus aculeatus). In order to investigate the process 0=- S;' ~~.; :~onin these populations,three small lakes were studied. Each lake contained [\\0 ·.':':-:'C:~~Sof stickleback: a large,bottom-dwelling variety that fed on invertebrates near tl.e s:~,:~~.:.:~:.:.small, plankton-eatingvariety that lived in the open water. The probability of brcc.:~·.;:::-~:-;.~enpairs of individualswas measured under laboratory conditions in the following ':,:-cc.:'~::-.;combinations:

"----- "-.-.-.-.-.

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I different varieties (small x large) from the same lakeII different varieties from different lakesIII same variety (small x small) and (large x large) from diE~:-:;nt lakesIV same variety from the same lake.

t..\Ht-:-:-:-:<-:::-:::-:-=-:-:-:-:-:-:::-:.:-:

~=:==:==:~==::==::

The data are summarized below.----_.-_.------,_.-------.-- -:-:::-:-:-::=-:::-:-=.- - _. _.- - --

0.3

o .•.... _-. - Il~l[!rl~

0.6

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[Source: HD Rundle, et al .. 1.2000,. Science. 287, pages 306-308]

(a) Identify the highest and lowest probabilities of breeding for individuals of the sa.nevariety from different lakes. U_-

Highest probability:

Lowest probability:

(This question continues 0;: <:o':ng page,

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11111111111 May Exam... · HI. Helicobacter pylori infection is a cause of stomach ulcers. It...

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