Question 18M.2.HL.TZ1.c
| Date | May 2018 | Marks available | [Maximum mark: 7] | Reference code | 18M.2.HL.TZ1.c |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Explain | Question number | c | Adapted from | N/A |
Hydrogen bonds can exist both within and between molecules in living organisms and have an impact on their structure and function. Explain the importance of hydrogen bonding for living organisms.
[7]
a. cohesion in water/water molecules stick together (due to hydrogen bonds)
b. cohesion helps transport under tension of water/sap in xylem / transpiration stream
c. adhesion between water and cell walls/cellulose/polar molecules
d. adhesion/capillary action helps water to rise in plants/stems/xylem / helps keep leaf walls moist
e. solvent properties (due to hydrogen bonds) with polar/hydrophilic molecules
f. solvent properties exemplified by glucose/other example of a polar solute
g. high latent heat of evaporation / (much) energy required for evaporation so water useful as coolant/for sweating
h. high (specific) heat capacity so water temperature changes less
i. base pairing between bases/nucleotides/strands in DNA by hydrogen bonding
j. base pairing between bases in RNA and DNA for transcription/between codon and anticodon for translation
k. proteins have hydrogen bonding in secondary structure/α helix/β pleated sheet
l. proteins have hydrogen bonding between R groups/in tertiary structure/to maintain conformation
m. habitats because water is liquid due to high boiling point/due to water freezing on the surface
n. habitats on water surface due to surface tension
