alevel biology 25 marker

never done an essay in my life school didn't teach us essay and my exam paper 3 next week what a joke can someone mark it and give me critic yh I know its rubbish so please don't need to mention that

The uses of water in living organisms


Water is a polar molecule due to the difference in charge between the highly electronegative oxygen molecule and the highly electropositive hydrogen molecule. This means that any non-polar molecule will be unable to dissolve in water. It has strong hydrogen bonds which plays a major role in plant cells walls and help maintain its rigidity against extreme changes in temperature which makes the membrane more permeable. This is important for plants as it protect them from any barriers and help stop molecules entering which can denature the membrane.

Water also plays a major role in transpiration. When excess water is evaporated from the mesophyll of the leaves due to an increase in temperature this makes more water to be drawn into roots by osmosis. Osmosis is the net movement of water potential from an area of low water potential to an area of higher water potential through a semi permeable membrane. Due to the characteristics of water being cohesive and having hydrogen bonds between molecules, a whole continuous column of water molecules can stick to each other and be pulled up the xylem vessel. Which is called the transpiration pull, this allows plants to reabsorb water easily due to the nature of water during extreme conditions.

Moreover, water plays a major role in condensation and hydrolysis reactions. Larger molecules can be formed when water is eliminated, for example a disaccharide can be formed when two monosaccharide are formed, and water is eliminated forming a dipeptide between those two structures. Vice versa addition of water is used to break dipeptide bond between two disaccharides to form a smaller molecule. This is known as a hydrolysis reaction. This enables for the formation of polymers that plays major roles in plant, animals cells.Starch,cellulose and glycogen are all polymers formed by a condensation reaction ,where by starch and glycogen are used for energy storage of glucose for respiration to provide atp.Without water larger complex molecules are unable to be produced.


Furthermore, water plays a major role in maintaining blood water potential [osmoregulation]. When water potential of blood is too high. It’s detected by osmoreceptors in the hypothalamus. More water moves into the osmoreceptors which causes less adh to be secreted and released which decreases the permeability of dct and collecting duct. Less aquaporin to transport water. Creating a more diluted water. This prevents cells from bursting or shrinking if water potential of the blood is not maintained which cause cause cells to not function properly.



In the light dependent reaction where the excited electrons are lost as they absorb light energy from chlorophyll and enter the etc. Water plays a major role in replacing the electrons that are being losts.2H20=4h+ +02+4e-. Water is split into protons, oxygen, and electrons, this enables nad to be reduced and helps actively pump protons across to the thylakoid lumen. This allows for the light dependent reaction to continue to occur but also the light independent reaction as it relies on the two products reduced nad and atp.Without water Tp is unable to be produced ,so amino acids and starch cannot be formed.Atp that supplies energy will also be unable to be produced as they won’t be enough energy to pump protons across membrane and into atp synthase.


someone give this essay a rough mark out of 25

i am no examiner but i remember when i had a similar essay format to you and amount of detail: i would give you a 10/25

no need to say ..furthermore, and no need to link paragraphs, i mainly learnt more tips and my structure from miss Estruch Youtube vids: https://www.youtube.com/watch?v=7xu5mDZaqXs

you should aim to write about at least 5 points if you want more than 16 marks
write one paragraph about your point and all the science and another paragraph about 5-6 sentences explaining the importance of the property, do this for each point, so 10 paragraphs altogether, aim to plan for no more than 5 minutes and the rest for 40 minutes maximum,

good luck 🤞