IB practice exam questions Flashcards
Using your knowledge of the properties of water to explain why rising humidity level in tropical regions like the Republic of Congo could negatively impact the homeostatic processes of organisms, like Gorilla beringei graueri.
Using your knowledge of the properties of water to explain why haemoglobin is required to transport oxygen.
Explain how the adaptation of giant lilies (Victoria amazonica) allow them to obtain carbon dioxide and water.
Explain how Arctic Ringed Seal have had to adapted to live in the arctic region using your knowledge of the properties of water.
Answer
The drawing represents molecules of DNA and messenger
RNA (mRNA)
The mRNA molecule is shorter than the DNA molecule
State, using only the information in the figure, one way to distinguish between DNA and mRNA
Give one further difference in structure between DNA and RNA
Suggest why DNA is not able to leave the nucleus
Explain why the mRNA molecule is shorter than a DNA molecule
Question 1
mRNA is single stranded / DNA is double stranded
b) mRNA is non helical / DNA is helical
RNA contains ribose and DNA contains deoxyribose
RNA contains, uracil / U, and DNA contains, thymine / T
3 /more than 1, forms of RNA
RNA is, single stranded / non helical; DNA is double stranded / helical
c) Too big to /does not, fit through pore (in nuclear envelope)
d) Only copies one, gene / section /part, of DNA
DNA comprises many, genes / alleles
Describe the significance of water to living organisms. 5 marks
Each feature or property must be related to living organisms in order to receive a mark. Features may include:
surface tension - allows some organisms (e.g. insects) to move on water’s surface
polarity / capillarity / adhesion - helps plants transport water
(excellent) solvent - capable of dissolving substances for transport/metabolism in organisms
(excellent) thermal properties (high latent of vaporization) - excellent coolant/sweating
ice floats - lakes / oceans do not freeze, allowing life under the ice
buoyancy - supports organisms
structure - turgor in plant cells / hydrostatic pressure
habitat - place for aquatic organisms to live
Why is carbon so structurally important in biological molecules?
Carbon also forms covalent bonds with several other atoms, such as hydrogen, oxygen, nitrogen, and sometimes sulfur and phosphorus. Carbon readily forms single, double or triple bonds, chains, branched chains and even rings. It can bond with itself, as well, to form strong substances like diamond and graphite.
This versatility and ability to form many bonds enables carbon to form the many different shapes adopted by the complex organic compounds that make up the bodies of animals and plants. Some of the carbon chains needed for life are millions of atoms long.
As chain length increases, melting point increases. Why do you think this is the case?
Energy is needed to break the attractions/interactions
between the fatty acid chains on different triglycerides.
The longer the fatty acid chains – the more interactions/
attractions which need to be broken.
As number of double bonds increases, melting point decreases. Why do you think this might be the case?
The double bonds in the hydrocarbon chain cause
kinks in the fatty acid tail. This means they are
unable to pack as closely together and so the
intermolecular forces (or attractions/ interactions
– you can use any of these when answering)
between the unsaturated fatty acids is reduced so
they have lower melting points.
Each amino acid has a different R group. Describe how these R groups can interact to determine the tertiary structure of a protein. 4 marks
1 some R groups, attract / repel;
2 disulfide, bridges / bond;
3 between, cysteine / SH / S (atoms);
4 hydrogen / H, bonds;
DO NOT CREDIT in context of secondary structure
5 ionic bonds between, oppositely charged / + and –, R groups;
6 hydrophilic R groups, on outside of molecule / in contact with
water (molecules);
7 hydrophobic R groups, on inside of molecule / shielded from water
(molecules);
Explain, using one named example, the effect of a competitive inhibitor on enzyme activity. 6 marks
Competitive inhibitor has similar shape/structure to the substrate (a)
therefore it fits to the active site (b)
no reaction is catalyzed so the inhibitor remains bound (c)
substrate cannot bind as long as the inhibitor remains bound (d)
only one active site per enzyme molecule (e)
substrate and inhibitor compete for the active site (f)
therefore high substrate concentrations can overcome the inhibition (g)
as substrate is used up ratio of inhibitor to substrate rises (h)
Named example of inhibitor plus inhibited enzyme / process / substrate (i)
Compare the induced fit model of enzyme activity with the lock and key model. 4 marks
in both models substrate binds to active site
substrate fits active site exactly in lock and key, whereas fit is not exact in induced fit
substrate / active site changes shape in induced fit, whereas active site does not change shape in lock and key
in both models an enzyme - substrate complex is formed
in lock and key binding reduces activation energy, whereas in the induced fit change to substrate reduces activation energy
lock and key model explains narrow specificity, whereas induced fit allows broader specificity
induced fit explains competitive inhibition, whereas lock and key does not
Explain, using one named example, the effect of a competitive inhibitor on enzyme activity. 6 marks
Competitive inhibitor has similar shape/structure to the substrate (a)
therefore it fits to the active site (b)
no reaction is catalyzed so the inhibitor remains bound (c)
substrate cannot bind as long as the inhibitor remains bound (d)
only one active site per enzyme molecule (e)
substrate and inhibitor compete for the active site (f)
therefore high substrate concentrations can overcome the inhibition (g)
as substrate is used up ratio of inhibitor to substrate rises (h)
Named example of inhibitor plus inhibited enzyme / process / substrate (i)
