Outline the bonding between DNA nucleotides.

Explain how chemical bonding between water molecules makes water a valuable coolant in living organisms.

Describe the movement of water across membranes.

Outline the role of water in photosynthesis.

hydrogen bonds between nucleotides of opposite strands/complementary bases/adenine and thymine and cytosine and guanine;
covalent bonds between nucleotides within strands/between sugar/deoxyribose and phosphate;

hydrogen bonding between water molecules;
breaking (hydrogen bonds) needs/removes energy/heat;
hydrogen bonds must break when water evaporates/vaporizes;

osmosis / moves passively;
from regions of low solute/high water potential/concentration to high solute concentration / low water potential/concentration;
passes through protein channels/aquaporins/selectively-permeable membrane;

water molecules undergo photolysis/are split by light energy;
forms oxygen as a by-product;
hydrogen helps power the fixation of carbon (into organic molecules);

This question was well answered with the best responses clearly indicating the location of both hydrogen and covalent bonds. Almost all candidates discussed hydrogen bonding, but many did not discuss the use of covalent bonds.

Again, this was generally well answered with the best responses indicating that the breaking of hydrogen bonds occurs when water evaporates and removes a great deal of energy.

Many candidates answered this well, demonstrating a good knowledge of the movement of water across membrane.

Many candidates did not appear to be aware that water played a role in the reaction of photosynthesis. Better answers used the term photolysis and explained it appropriately.