Download option b practice_ms - Chemistry-AP, IB-SL and HL

1.
(a)
(b)
(c)
(d)
(e)
As [S] increases, more enzyme molecules can link with substrate
molecules (and rate increases);
once all enzyme molecules are occupied/enzyme sites used up, rate
cannot increase any more/has no effect;
2
0.7 (mmol dm–3);
Allow 0.6–0.8. If wrong units, then no mark.
1
inhibitor molecules are very similar to the substrate and the enzymes cannot
distinguish them / are able to bind to/occupy the active sites / OWTTE;
1
same Vmax;
at high [S], impact of inhibitor reduced / possible to reach same
maximum rate;
the curve is less steep (than without inhibition) / the enzyme is
less effective / OWTTE;
so Km higher (than without inhibition);
4
curve on graph levelling off below original line;
Km should be approximately the same, Vmax should be smaller.
1
[9]
IB Questionbank Chemistry
1
2.
glucose is converted to pyruvate;
which in the presence of oxygen changes to carbon dioxide and water;
glucose undergoes oxidation;
oxygen undergoes reduction;
4
[4]
3.
(a)
(b)
the nucleotides condense/form a phosphodiester bond;
between the C3 of the sugar and a neighbouring phosphate group;
2
hydrogen bonds formed between the different strands;
thymine/T bonds to adenine/A and cytosine/C bonds to guanine/G;
2
[4]
4.
(a)
(b)
both are polymers of glucose;
starch has two forms: amylose a straight chain polymer with  – 1, 4 linkages;
and amylopectin a branched polymer with  – 1, 4 and  – 1, 6 linkages;
cellulose has  – 1, 4 linkages;
4
absence of cellulase enzyme;
1
[5]
5.
(a)
(b)
plant material that is not hydrolysed by enzymes (secreted by the human
digestive tract);
may be digested by microflora in the gut;
Any two of the following:
cellulose;
hemicellulose;
lignin;
pectin;
IB Questionbank Chemistry
2
2 max
2
(c)
(may be helpful in the prevention of conditions/health problems such as)
Any two of the following:
diverticulosis;
irritable bowel syndrome;
constipation;
obesity;
Crohn’s disease;
haemorrhoids;
diabetes mellitus;
2 max
[6]
6.
Heavy-metal ions:
react (irreversibly) with –SH group / replaces hydrogen atom with
heavy-metal atom/ion;
Accept heavy-metal binding to active site.
Accept poisons enzymes.
decrease activity/rate;
Temperature changes:
increase in temperature increases (initial) activity/rate;
more reactants possess (minimum) activation energy;
at high temperature enzymes become less effective / above 40 °C
activity/rate decreases / denatured / OWTTE;
for both (heavy-metal ions and temperature changes) (tertiary) structure
disrupted / change of shape means active site stop working / OWTTE;
5 max
[5]
7.
(a)
vitamin A: not water-soluble because it has only one OH / is
not very/less polar / contains long hydrocarbon group;
vitamin C: water-soluble because it has 4/many OH
(and 1 C=O)/extensive hydrogen bonding;
Accept reference to polarity in one case but not in both.
IB Questionbank Chemistry
2
3
(b)
effect: vitamin A: xerophthalmia/night blindness / vitamin C: scurvy /
bleeding gums / less resistance to infection / bleeding lesions on
legs/thighs / scorbutus;
Accept either of the following for the second mark:
solution for vitamin A: providing food composed of liver/fresh
(orange and green) fruits/vegetables/spinach/eggs/carrots /
providing genetically modified food containing vitamin A;
OR
solution for vitamin C: providing food composed of fresh fruits/vegetables/
providing genetically modified food containing vitamin C;
providing nutritional supplements / adding vitamin A/C in commonly
consumed foods / vitamin A in margarine / vitamin C in fruit juices;
3 max
[5]
8.
(a)
(b)
(c)
steroid/steroidal backbone/4 ring/tetra cyclic carbon structure skeleton;
Do not accept OH, hydroxyl, hydroxide, alcohol.
Accept a correct sketch of the steroid backbone.
1
phospholipids;
triglycerides/triglycerols;
2
(i)
high density lipoprotein and low density lipoprotein;
1
(ii)
HDL has a higher proportion/percentage of proteins/LDL has a lower
proportion of proteins / OWTTE;
1
[5]
IB Questionbank Chemistry
4
9.
(a)
Accept CHO, CH2OH and OH groups on either side of the carbon
chain provided OH on C3 is on the opposite side to OHs on C2,
C4 and C5.
1
C1 is asymmetric/chiral/has four different groups;
forming two isomers where the OH-group is on a different side (of C1/ring);
α-glucose and β-glucose;
Accept suitable diagrams as an explanation for M2.
3
(c)
amylose and amylopectin;
1
(d)
amylose: α-1,4 and linear/straight chain;
amylopectin: α-1,4 and α-1,6 and branched;
Award [1] if both linkages or both structures are correct.
2
(b)
[7]
10.
(a)
(b)
alkene/ketone;
Accept carbonyl.
Do not accept aldehyde.
change release of hormones/FHS/LH (from hypothalamus/
pituitary gland);
prevent ovulation / egg release;
prevent attachment of egg to uterus / thin lining of the uterus/
endometrium;
prevent sperm from reaching egg / thicken cervical mucus;
Do not accept “mimic pregnancy”.
1
2 max
[3]
11.
Steps: [3 max]
IB Questionbank Chemistry
5
DNA extracted / OWTTE;
amount of DNA multiplied / amplified (by use of PCR);
(broken down using) restriction enzymes;
into smaller fragments called minisatellites;
splits occur in minisatellites in areas where there are no codons;
(fragments into bands using) (gel) electrophoresis;
labelling with radioactive phosphorus;
X-ray film to detect radiation;
fingerprint of all fragments obtained;
Uses: [1 max]
solution of criminal cases;
paternity cases;
mapping of evolutionary tree of species;
identification of genetic illnesses;
human genome project;
Award [1 max] for any two.
4 max
[4]
IB Questionbank Chemistry
6