State the role of four named minerals needed by living organisms.

Explain the processes by which minerals are absorbed from the soil into the roots.

In anaerobic conditions, plants release energy by glycolysis. Outline the process of glycolysis.

sulfur – part of amino acids / proteins;
calcium – strengthening/formation of bones / muscle contraction / synaptic transmission;
phosphorus – formation of nucleic acids / ATP / GTP / NADP / phospholipids;
iron – formation of hemoglobin / transport of oxygen;
sodium – nerve impulse / sodium-potassium pump / osmoregulation;
potassium – nerve transmission / sodium-potassium pump / osmoregulation;
magnesium – part of chlorophyll molecule;

plants absorb minerals in ionic form/mineral ions;
nitrate / phosphate / potassium / other example of mineral;
minerals can be absorbed by (facilitated) diffusion;
(diffusion is) movement of ions from high to low concentration/down concentration gradient;
root hair cells provide a large surface area for absorption;
fungal hyphae help to absorb minerals/phosphate;
minerals absorbed by active transport;
as mineral ion concentration is smaller outside the root than inside / absorbed against a concentration gradient;
active transport requires energy/ATP;
occurs through pump/carrier proteins;
proton pump transports hydrogen ions/H⁺ out of cell (allowing mineral movement in);

occurs in cytoplasm (of cell);
substrate is hexose/glucose/fructose;
phosphorylation of glucose/fructose/hexose;
to form hexose diphosphate/glucose 6-phosphate;
requires ATP;
glucose/fructose/hexose (diphosphate) converted into (two) pyruvates/three carbon compounds;
oxidation;
to produce (two) NADH + H⁺/ (two) reduced NADs;
net gain of two ATP (per glucose);

In part (a), most candidates had no difficulty in naming four mineral elements that are needed by living organisms and giving a role for each. Carbon was not accepted as an answer, as conventionally it is not regarded as a mineral. In plants minerals are absorbed from soil or water. In animals minerals are absorbed in an inorganic form from food or drinking water.

Part (b) of the question was not answered as well as expected. There was some confusion between absorption from the soil into roots and movement through the soil to the roots. As a result, many candidates suggested that minerals could be absorbed by mass flow along with the water that was being absorbed. This shows that the selective nature of mineral absorption has not been understood. Another common fault was to suggest that diffusion is the main method of mineral absorption. If plants are able to absorb water by osmosis, they must have higher solute concentrations inside their cells than outside and this can only be achieved by active transport.

There was generally good knowledge of the stages of glycolysis in part (c). To make the marking of this question fair in relation to other choices, there was a restricted set of points on the marking scheme, but the more able candidates were still easily able to score full marks.