Topic 1A- Biological Molecules (Lipids) Flashcards
What three elements do all lipids contain?
What proportion of these elements are in lipids and what is this proportion less than?
What are they in water and what are they in organic solvents and give some examples?
What transfer do phospholipids allow?
What is the main function of a lipid?
Contain carbon, hydrogen and oxygen
The proportion of oxygen to carbon and hydrogen is less than in a carbohydrate
They are insoluble in water, but soluble in organic solvents such as alcohol and acetone
Phospholipids allow the transfer of lipid- soluble substances across the membrane as well as maintaining the membrane’s flexibility
To form the plasma (cell) membrane of every cell.
What is the explanation for the following other functions of lipids:
Insulation
Protection
Waterproofing
Energy
Fats are poor conductors of heat and so can insulate the body
Fat deposits are found around delicate organs including the kidneys
Lipids are insoluble in water
Lipids can release over twice as much energy when oxidised as a carbohydrate.
What is the bond made between glycerol and a fatty acid called?
Why are triglycerides called this?
What is the full definition of a saturated fatty acid?
What is the definition of a monounsaturated fatty acid?
What is the definition of a polyunsaturated fatty acid?
What is the full definition of an unsaturated fatty acid?
What does R stand for in a fatty acid chain?
What do all fatty acids contain?
What determines the properties of a lipid?
Ester bond
Because they contain 1 molecule of glycerol attached to three molecules of fatty acids
Saturated fatty acids do not have any double bonds between their carbon atoms. The fatty acid is “saturated with hydrogen”
Contains one C = C double bond in the chain
Contains multiple C = C double bonds within the chain
Unsaturated fatty acids do have double bonds between carbon atoms, which cause the chain to kink
R is the chains of carbons in a fatty acid. The R stands for the variable tail
Carboxyl group (-COOH)
The structure of a fatty acid will determine the properties of the lipid.
Where are phospholipids found in?
What happens in a phospholipid structure compared to a triglyceride?
What is the definition of hydrophilic?
What is the definition of hydrophobic?
In a phospholipid, what part of the structure is hydrophilic and which is hydrophobic?
What does the nature of having two ends to the molecules of phospholipids result in?
What does the hydrophilic head do in a phospholipid?
What does the hydrophobic tail do in a phospholipid?
Found in cell membranes
In a phospholipid, one of the fatty acids is replaced by a phosphate group
Attracts water (hydrophilic means loves water)
Repels water (hydrophobic = hates water)
The phosphate head of the phospholipid molecule is hydrophilic. The fatty acid tails are hydrophobic
A polar molecule
Attracted to the water (phosphate)
Repels water, mixes with fats (fatty acids).
What test is used to test for the presence of a lipid?
What are the three steps for this test?
What sort of storage are triglycerides useful for and why?
What is a droplet of lipid called?
What do all the fatty acid tails do in a triglyceride?
The emulsion test is used
- Add 2 cm3 of ethanol to the sample, shake to mix
- Add 2 cm3 of water to the mixture
- If a lipid is present, you will see a cloudy white precipitate
Energy storage- 2 times as much per gram as carbohydrates
A micelle
All the fatty acid tails face inward, away from the water.
What are triglycerides and what doesn’t this affect in the cell?
Why are triglycerides good as energy storage molecules?
What do phospholipids make up?
What is a cell membrane actually made up of and what is this called?
What happens as a result of the centre of these layers being hydrophobic and why is this useful to the cell?
Triglycerides are insoluble, so don’t affect the osmotic potential of the cell
Because the long hydrocarbon tails of the fatty acids contain lots of chemical energy- a load of energy is released when they’re broken down
Cell membranes
Two layers of phospholipid (called a bilayer)
Water soluble substances can’t pass through easily- so the cell membrane acts as a barrier to control what enters and leaves the cell.
