OCR Biology "Foundation" Tuesday 15th

Here I go! This is as much to help me as it is to help anybody else, I find explaining things the best way to remember

FUNCTIONS OF LIPIDS IN ORGANISMS

Buoyancy - Lipids are less dense than water, and so float on top (like if you were to put cooking oil in water it floats..) especially useful for aquatic organisms who already use lipids as insulation because they must get air from above water. I always thing of ducks and their fat bellies for this one!

Insulation - Lipids do not conduct heat very well and so aquatic organisms such as whales use it for insulation (because hair on the body is pretty much useless, think slimy seals) . A thick layer of fat is found underneath the skins surface to insulate the rest of the body.

Protection - A lot of fat surrounds vital organs in the body, such as the kidneys. This is vital to protect organs as they are very delicate. If we did not have fat surrounding our kidneys even the slightest blow would cause a lot of damage!

Energy storage - Fats are used as energy storage because they can store a lot of energy in a small space. This is apparent in plant seeds and in animals which need to be mobile. Your body can't access the store of energy in lipids very quickly though, and so carbohydrates are more commonly used as a short term store.

Waterproofing - Think "waxy cuticles" on leaves. Lipids are hydrophobic and so useful on the outsides of leaves in plants, and as a secreted oil under the fur of animals to prevent them loosing water/or getting too soaked in the case of animals.

Cell Membranes - Needed for every animal and plant but this is a whole different topic. (ill go over it if anybody needs to).

think i got everything!

for toiletpaper

lipids can also combine with a carbohydrate chain to form glycolipids. These are found on the outside of cell membranes to detect hormones etc outside of the cell!
FYI: Glycoproteins are carbs combined with proteins in the cell membrane which also recept other substances outside of the cell. The cell can then take suitable action to deal with substances (e.g. secrete lysosomes made by the golgi apparatus to destroy harmful substances)

can someone explain the nitrogen cycle simply.. i learnt it last year, but totally forgotten for this exam!
there was a question on it last year, but it was only small, do you think its likely to come up again?!

Can anyone explain the EVIDENCE for semi-conservative replication with the N14 AND N15?

Thats probably the only topic I can't understand 'properly'.