1.	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.

(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.
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(2)
 
(ii)	Explain how increases in fructose 6-phosphate concentration affect the activity of the enzyme.
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(2)

(b)	(i)	Outline the effect of increasing the ATP concentration on the activity of phosphofructokinase.
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(2)
 
(ii)	Suggest an advantage to living organisms of the effect of ATP on phosphofructokinase.
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(1)
(Total 7 marks)

2.	Explain the effects of temperature, pH and substrate concentration on enzyme activity.
(Total 8 marks)

3.	(a)	State one named example of a fibrous protein and one named example of a globular protein.
	Fibrous: ...........................................	Globular: ...........................................
(2)
 
(b)	Outline the effect of enzymes on the reactions they catalyse.
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(2)

(c)	The rate of cellular respiration is controlled by the allosteric inhibition of phosphofructokinase by ATP. Phosphofructokinase is the first enzyme in the respiration pathway. Explain the meaning of allosteric inhibition using this example.
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(4)
(Total 8 marks)

4.	(a)	Explain the significance of secondary structure to the structure of a protein.
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(3)
 
(b)	State the name of a competitive enzyme inhibitor.
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(1)

(c)	Outline the difference between competitive and non-competitive enzyme inhibitors.
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(2)
(Total 6 marks)

5.	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.

	In an experiment, the initial rate at different concentrations of ethanol was recorded (no inhibition). The experiment was then repeated with the addition of
l 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.

[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).
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(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)
 
(ii)	State the effect of increasing the concentration of inhibitor on the initial rate of reaction.
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(1)
 
(c)	Explain how a competitive inhibitor works.
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(3)
(Total 7 marks)

6.	Explain the effect of substrate concentration on enzyme activity.
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(Total 3 marks)

7.	(a)	Outline the induced fit model of enzyme activity.
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(3)
 
(b)	(i)	State two products of the light-dependent reactions of photosynthesis.
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(2)
 
(ii)	Explain the light-independent reactions in photosynthesis.
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(4)
(Total 9 marks)

8.	Outline two examples of the commercial application of enzymes in biotechnology.
(Total 6 marks)

9.	The enzyme aspartate carbomyltransferase (ACTase) is a key regulatory enzyme in nucleotide metabolism in bacteria. The activity of this enzyme was studied in the bacterium Helicobacter pylori, an important human pathogen. ACTase activity and the growth of H. pylori were measured at different concentrations of carbomoyl aspartate (CAA), the end product of the reaction catalysed by ACTase.

[Source: Burns, et al, Biological Procedures Online, (1998), http://www.biologicalprocedures.com]
 
(a)	(i)	State the growth of H. pylori at a CAA concentration of 30 mmol dm–3.
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(1)
 
(ii)	Calculate the change in ACTase activity between CAA concentrations of 20 and 40 mmol dm–3.
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(1)

(b)	Compare the effect of increasing CAA concentration on the growth of H. pylori and ACTase activity.
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(2)
 
(c)	Explain the effect of CAA on ACTase activity.
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(2)
 
(d)	Suggest a direct medical application of this information.
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(1)
(Total 7 marks)

10.	What determines the specificity of an enzyme for its substrate?
A.	The temperature at which it is operating
B.	The optimum pH of the enzymes
C.	The concentration of the substrate
D.	The structure of the enzyme molecule
(Total 1 mark)

11.	(a)	State why each step in a biochemical pathway often requires a separate enzyme.
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(2)
 
(b)	Explain the effects of either changing temperature or pH on enzyme activity.
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(3)
(Total 5 marks)

12.	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	

[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)

(b)	Outline the effect of magnesium chloride on the relative activity of the membrane bound enzyme.
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(2)
 
(c)	Calculate the approximate ratio of inorganic phosphate to magnesium chloride concentration needed to achieve maximum activity in membrane bound enzymes.
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(1)
 
(d)	(i)	State the difference in phosphatase activity when membrane bound and when purified.
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(1)
 
(ii)	Suggest a reason for this difference.
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(1)
(Total 7 marks)

13.	What is an active site?
A.	The part of an enzyme that binds only to the product molecules.
B.	The sequence of amino acids responsible for the catalytic activity of enzymes.
C.	The sequence of amino acids responsible for the structure of an enzyme.
D.	The specific area responsible for the activity of all proteins.
(Total 1 mark)

14.	Which types of enzyme are found in the human digestive system?
I.	Amylases
II.	Proteases
III.	Lipases
A.	I and II only
B.	I and III only
C.	II and III only
D.	I, II and III
(Total 1 mark)

15.	(a)	Explain the secondary and tertiary levels of protein structure.
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(4)
 
(b)	Outline the induced fit model for enzyme action.
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(2)
(Total 6 marks)

16.	Scientists have long been concerned about the effect of heavy metals in foods that we eat. Aquatic filter feeders including bivalves, such as mussels and oysters, are especially prone to accumulation of heavy metals.
Calcium is taken into bivalves through protein channels, but other non-essential elements may also be taken in.
To investigate the relationship between the uptake of calcium and other elements, the bivalves Hyridella depressa and Velesunio ambiguous were placed in solutions containing ten times the normal level of calcium (Ca). The elements manganese (Mn), lead (Pb), cadmium (Cd) and cobalt (Co) were also present in the solutions at normal concentrations. The results are shown below.

[Source: Reprinted from Markich Scott J. and Jeffree Ross A., “Absorption of divalent trace metals as analogues of calcium by Australian freshwater bivalves: an explanation of how water hardness reduces metal toxicity”, Aquatic Toxicology (August 1994), vol. 29, issue 3–4, pp. 257–290, © 1994 with permission from Elsevier]

(a)	(i)	Outline the effect of increasing calcium levels in the water on calcium levels in the tissue of the bivalves.
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(1)
 
(ii)	Outline the effect of increasing calcium levels in the water on metals other than calcium in the tissue of the bivalves.
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(1)
 
(b)	Suggest reasons for the effects of calcium on the levels of the other metals in the tissues.
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(2)
 
(c)	Evaluate the implications of these results for monitoring water quality in regions where bivalves are harvested.
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(3)
(Total 7 marks)

17.	(a)	State the function of a named protein.
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(1)
 
(b)	Outline the significance of the primary structure in a protein.
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(2)
 
(c)	Discuss the statement, “Enzyme inhibitors function by binding to the active site of the enzyme”.
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(3)
(Total 6 marks)

18.	Up to two additional marks are available for the construction of your answers.
(2)
	(a)	Explain why enzymes are substrate specific and why their activity is affected by substrate concentration.
(8)
(b)	Outline the use of restriction enzymes (endonucleases) and DNA ligase in gene technology.
(6)
(c)	Outline the role of two enzymes found in the digestive system of humans.
(4)
(Total 20 marks)

19.	(a)	State the name and function of
(i)	a fibrous protein ................................................................................................
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(1)
(ii)	a globular protein ..............................................................................................
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(1)
 
(b)	Annotate the graph representing an exergonic enzyme catalysed reaction.

(2)

(c)	Explain how end-product inhibition controls metabolic pathways.
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(3)
(Total 7 marks)

20.	Up to two additional marks are available for the construction of your answers.
(2)
	(a)	Draw and label a diagram of the digestive system.
(4)
(b)	Discuss factors that affect enzyme activity.
(9)
(c)	Outline one industrial use of lactose.
(5)
(Total 20 marks)

21.	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.
	
[Source: Adapted from N V Chandrasekharan, et al, (2002), Proceedings of the National Academy of Sciences, USA, 99, (21),
pages 13926-13931]
 
(a)	Outline the relationship between dipyrone concentration and COX-3 activity.
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(2)
 
(b)	Deduce whether dipyrone is an inhibitor of COX-2.
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(2)

(c)	Evaluate the potential of dipyrone as an analgesic using the data in the graph.
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(2)
(Total 6 marks)

 
1.	(a)	(i)	increasing fructose 6-phosphate concentration (initially) causes an increase
in activity;
activity levels out / remains constant as (substrate) concentration continues 
to rise;	2
(ii)	more collisions with active site as concentration rises;
at high substrate levels all active sites are occupied so no further increase 
in rate / enzyme working at maximum rate;	2
 
(b)	(i)	decreases activity;
at all fructose 6-phosphate concentrations;
most effect at intermediate fructose 6-phosphate concentrations / little difference
at high fructose 6-phosphate concentrations;
ATP acts as an inhibitor;	2 max
 
(ii)	end-product inhibition;
respiration rate decreased if ATP already available;	1 max
[7]

2.	enzymes have an active site;
that fits the substrate precisely;
changes in the chemical environment of the enzyme can lead to a
shape / conformational change in the protein;
leading to a change in the shape of the active site;
may interfere with the binding of the substrate with the active site;
altering pH can alter intermolecular interactions within the protein;
or within the active site;
enzymes have an optimum pH;
increase in temperature can increase molecular motion leading to 
disruption of intermolecular interactions;
increases chance of enzyme substrate collisions so enzyme activity increases;
optimal temperature;
temperature changes / pH changes can denature the protein;
the more substrate, the more product / more enzyme-substrate complex forms;
after a point, all active sites are bound to substrate / all active sites occupied;
additional substrate will not lead to a greater rate of product formation at 
this point;	8 max
For full marks all three conditions must be included, otherwise award [6 max].
[Plus up to [2] for quality]
[8]

3.	(a)	Any two from the following.
fibrous: eg fibrin, collagen (do not accept “tendon”);
globular: eg hemoglobin, fibrinogen, amylase (do not accept “enzyme”);	2
 
(b)	a new reaction pathway is created;
activation energy is reduced;
the equilibrium for the reaction is achieved more quickly / 
the reaction is faster;	2 max
 
(c)	ATP inhibits phosphofructokinase at (allosteric) site away from the active site;
inhibition alters the enzyme’s conformation / structure;
the active site does not accept the substrate molecule;
when respiration increases ATP levels phosphofructokinase is inhibited;
respiration slows down;
phosphofructokinase is the first enzyme in the respiration pathway so 
there is no build up of metabolic intermediates;
as ATP is used up by the cell the inhibition of phosphofructokinase is reduced;
respiration speeds up again;
this is an example of negative feedback;	4 max
[8]

4.	(a)	held together by hydrogen bonds;
between CO and NH groups;
(α-helix for) structure of fibrous proteins / keratin;
one of four levels of structure;
provides stability of structure;
a-helix;
b-sheet;	3 max
 
(b)	malonate / Prontosil	1
 
(c)	competitive similar to substrate and non-competitive not;
competitive attaches to the active site, non-competitive does 
not bind to the active site;
non-competitive changes enzyme shape, competitive does not;
competitive change reversible;	2 max
[6]

5.	(a)	directly proportional / greater concentration, greater rate of reaction;
at high concentrations the increase is smaller / plateau / levels-off (at 
approximately 70 mmol dm–3);	2
 
(b)	(i)	1 mmol dm–3 : 0.70 (± 0.02)
3 mmol dm–3 : 0.55 (± 0.02)	1 max
Both needed for [1]. For 1 mmol dm–3 accept 0.7.
 
(ii)	lower reaction rate at inhibitor concentration of 3 mmol dm–3 / the greater the 
inhibitor concentration the slower the rate of reaction;
trend / overall shape are the same / increases but then levels-off;
but lower at greater concentration of inhibitor;	1 max
 
(c)	substrate and inhibitor (structurally) similar;
inhibitor binds to active site;
prevents substrate from binding;
activity of enzyme prevented;
named example (eg malonate inhibits succinate dehydrogenase as 
it is similar to succinate);	3 max
[7]

6.	as substrate concentration increases enzyme activity increases;
at high substrate concentration enzyme reaches maximum activity;
active sites saturated;
labelled sketch-graph showing above relationship;
[3]

7.	(a)	substrate binds / approaches active site;
shape of active site changes;
bonds in substrate weaken;
activation energy decreases;
explains broad specificity of some enzymes;
eg proteases;	3 max
 
(b)	(i)	oxygen;
NADPH / NADPH + H+ / NADPH2;
ATP;	2 max
 
(ii)	occurs in stroma of chloroplast;
ribulose disphosphate / RuBP / 5-C sugar combines with CO2;
catalyzed by rubisco / ribulose biphosphate carboxylase;
splits into two 3-C sugars / glycerate 3-phosphate;
ATP and NADPH supply energy and H;
3-C sugars join to form glucose / 6-C sugar;
RuBP regenerated (with use of ATP);	4 max
[9]

8.	the name of the enzyme and the substrate;
the name(s) of the product(s);
a statement as to why the application is useful commercially;
	Award [3 max] per example,
eg pectinase acts on (soluble) pectin;
produces smaller, more soluble carbohydrates;
used in fruit juice clarification / to increase yield;
	eg endonuclease DNA acts on DNA;
produces DNA fragments;
used in genetic engineering;
	eg protease acts on (insoluble) proteins;
produces amino acids;
washing powders - stain removal;
[6]
Accept any other suitable examples.

9.	(a)	(i)	72.5 (.1.0)%	1
 
(ii)	40% (decrease)	1
 
(b)	both are inversely proportional / 
as CAA concentration increases both activity and growth decrease;
growth is more irregular at low concentrations;
ACTase activity decreases more at higher
concentration / after 30 mmol dm–3 than growth;
both show linear decreases between 10 and 30 mmol dm–3;	2 max
Any other valid comparisons.
 
(c)	end-product is slowing enzyme activity;
allostery / non-competitive inhibition;	2
 
(d)	use CAA to control / inhibit bacterial growth / antibiotic functions;
use CAA to treat H. pylori infection;	1 max
[7]

10.	D
[1]

11.	(a)	enzymes are specific for their substrate / lock and key model / energy
requirements
for reactions with substrates vary;
each step of the pathway is unique / different substrate at each step;
finer control of metabolic pathways;	2

(b)	Either, temperature: [3 max]
each enzyme has an optimal temperature for its maximum activity;
(small) temperature increases result in increased enzyme activity to a
point / optimum;
increase activity due to increased movement of molecules / increased kinetic
energy or conversely stated;
	temperature increases above the optimum causes (progressive) loss of
activity due to denaturation / shape changes
or, pH: [3 max]
each enzyme has an optimal pH for its maximum activity;
as pH varies from optimal pH, enzyme activity diminishes / becomes inhibited;
loss of activity is due to denaturation / shape changes;
gain or loss of hydrogen ions distorts tertiary shape of enzyme;
homeostatic mechanisms maintain optimal conditions for enzyme activity;	3 max
Credit marking points above if illustrated by a suitably annotated graph.
[5]

12.	(a)	(i)	27 (±1)
(ii)	90 (±1)	2
 
(b)	as the concentration of Mg increases the rate increases;
most rapid increase between 1 and 2 mmol dm−3;
peaks at  4 mmol dm−3;
until it plateaus (at 5 mmol dm−3 ) / no more increase / drops slightly;	2 max
 
(c)	1:4	1
 
(d)	(i)	membrane bound is 10 times more efficient (12000 to 1200);
difference is (12618-1215) 11403 arbitrary units greater in membrane
bound;
about 1000% greater / 938.5% greater;	1 max
(ii)	purification could have affected structure of protein;
	bound to membrane allows interactions / other molecules in
membrane may help it / be acting as coenzymes;	1 max
[7]

13.	B
[1]

14.	D
[1]

15.	(a)	secondary structure: [2 max]
	folding / pleating of polypeptides to form b - pleated sheets / coiling of
polypeptides to form a -helix;
held in place by hydrogen bonds;
make structure stable;
contributes to strength of fibrous proteins;
provide structural role in organisms;
eg a -helix is keratin / b-sheet is silk;
tertiary structure: [2 max]
3-D shape;
due to bonding between amino R-groups / residues;
hydrogen bonds / disulphide bridges / sulphur bonds / ionic bonds;
form globular proteins;
which are soluble;
eg lysozyme / enzymes;	4 max
 
(b)	change in shape of enzyme’s active site;
improves fit of enzyme and substrates;
brought about when the substrate molecules bind with the enzyme;
enzyme changes from inactive to active form;
permits some enzymes to bind with several substrates;
distorts / weakens bonds in substrates;
lowers activation energy:	2 max
Accept any of the above if clearly explained in a labelled diagram.
[6]

16.	(a)	(i)	leads to an increase in calcium in tissues / accept numerical data	1
(ii)	leads to a decrease in other metals in tissues	1
 
(b)	competitive inhibition / calcium and the other metals compete for the transport mechanism;
	as calcium concentration within the cell increases, uptake of the other metals is prevented;
	entry of calcium into cells may be linked to increased export of the other
metals;	2 max

(c)	monitoring of water quality for metals can indicate amount of metals in tissue;
(toxic) metals found in water will (most likely) be found in bivalves;
analysis of bivalve tissue could be used as a measure of water quality;
high levels of heavy metals in bivalves may poison consumers;	3 max
[7]

17.	(a)	name and function;
eg hemoglobin carries oxygen	1
 
(b)	order of amino acids in polypeptides;
primary structure determines higher structure;
primary structure reflects genetic information / is coded for by the DNA;	2 max
 
(c)	competitive inhibitors are structurally similar to the substrate;
competitive inhibitors bind / block active site;
	non-competitive inhibitors do not bind to the active site / bind somewhere else
on enzyme;
	they function by changing the shape of the enzyme so the substrate cannot fit
in to the active site;	3 max
[6]

18.	(a)	specificity:
(active site works as a) lock and (substrate as a) key;
(enzyme has) a specific shape;
active site;
(substrate has) a specific / complementary shape;
(active site) fits substrate molecule / part of molecule / 
enzyme-substrate complex formed;
activation energy lowered;
	substrate concentration:
lower / medium concentration activity increases;
directly proportional to concentration of substrate;
random collisions more frequent;
activity levels off / plateau;
high concentration no change in activity;
as all active sites fully utilised;	8 max
Award [6 max] if only specificity or substrate concentration
aspects addressed.

(b)	restriction enzyme:
bacteria / E. coli has plasmids;
plasmids / DNA cleaved / cut by enzyme;
at specific points;
leaving sticky ends;
other species DNA cleaved / cut out by enzyme at same base sequence;
suitable example;
	ligase:
DNA added to plasmid / other DNA;
spliced to plasmid / other DNA by enzyme;
at sticky ends;
recombinant plasmids / DNA inserted into (new) host cells;
(new) host cells may be cloned;	6 max
Award [4 max] if only restriction enzyme or ligase aspects addressed.
 
(c)
Type / Specific example	Substrate	Product		
eg amylase / salivary
amylase;	starch;	maltose;		
egprotease / pepsin;	proteins;	polypeptides / short
peptide chains;		
eglipase / pancreatic lipase;	lipid;	glycerol and fatty acids;	4 max	
	Award [2 max] for all three parts correct for one enzyme and
[1 max] for correct enzyme and substrate or enzyme and product.
	(Plus up to [2] for quality)
[20]

19.	(a)	Both name and function required for [1];
(i)	fibrous:
collagen, structural / strength / flexibility;
actin / myosin, contraction of muscles;
keratin, in hair;
silk in spider webs;
elastin in ligaments;	1 max
 
(ii)	globular:
a named enzyme eg pepsin, accept general function
eg speeds up reaction;
hemoglobin, carries oxygen;
antibodies, for immunity;
albumin, osmotic balance;	1 max

(b)

	One mark for each correct annotation. The marks for a+b / reactants
or substrates or c+d / products can only be awarded if the label is
on the horizontal parts of the line.	2 max
 
(c)	example of negative feedback
eg ATP inhibition of phosphofructokinase, in glycolysis;
controls rate of product synthesis / amount of product produced
 / inhibits earlier stage / switches off pathway when too much
product made;
binds to enzyme but not active site / allostery / allosteric site;
enzyme changes shape / substrate cannot bind / enzyme cannot catalyse;	3 max
[7]

20.	(a)	Award [1] for each structure correctly drawn and labelled.
esophagus - attached to both mouth and stomach;
stomach - j-shaped sac attached to esophagus and u-shaped portion of
small intestine;
large intestine - wider diameter than small intestine, attached to small intestine;
pancreas - leaf-shaped, in u-shaped region of small intestine with small duct
connected to small intestine;
liver - large, triangular, to left of stomach;
gall bladder - small sac drawn on top of liver with tube connected to small
intestine at same region as duct from pancreas;
anus - at end of large intestine but narrower in diameter;	4 max

(b)	at low temperatures, rate of reaction increases as temperature increases
(or vice versa);
	more kinetic energy / faster movement of molecules means more collisions
between enzyme / active site and substrate;
	optimum temperature is temperature at which rate of enzyme-catalyzed
reaction is fastest;
at high temperatures enzymes are denatured and stop working;
denatured means change of structure in enzyme / protein resulting in loss of its
biological properties / no longer can carry out its function;
	too much kinetic energy / vibrations breaks bonds that give enzyme specific
shape;
optimum pH is one at which rate of enzyme-catalyzed reaction is fastest;
rate of reaction reduced as increase or decrease pH (from optimum);
strong acids and alkalis can denature enzymes;
affect (weak, ionic, hydrogen) bonds that hold enzyme in specific shape;
at low substrate concentrations, as increase concentration get increase in rate
of reaction;
more chance of collision between substrate and enzyme / active site;
	at high substrate concentration, have no change in rate as increase
concentration;
all active sites occupied;	9 max
 
(c)	lactose intolerance high in some human populations / Asian / African / native
American and Australian aboriginal populations;
lactase used to produce lactose-free / low-lactose milk;
lactase breaks down lactose to glucose and galactose;
source of lactase is usually yeast / many sources such as bacteria, moulds;
milk passed over immobilized lactase / lactase bound to inert substance;
increase sweetness of milk;
no need to add extra sugar in manufacture of flavoured milk drinks / 
frozen desserts;
can add (harmless) bacterium such as L.acidophilus which has same effect on
lactose as in yoghurt;	5 max
(Plus up to [2] for quality)
[20]

21.	(a)	at low dipyrone concentrations, there is no effect on enzyme function;
as concentration of dipyrone increases, increased inhibition of enzyme activity;	2
 
(b)	over range of concentrations in the experiment appears to have no effect on
enzyme function (of COX-2);
may be inhibited at concentrations higher than those used in the experiment;	2

(c)	it would limit inflammation due to COX-1 and COX-3;
but not COX-2;
effective only at high doses;	2
[6]