Lipids Flashcards
What elements do lipids contain?
Carbon, hydrogen and oxygen
What are lipids commonly known as?
Macromolecules- not built from monomers
Why are lipids non polar?
Electrons in the outer orbital are evenly distributed so there are no positive/negative regions- lipids are insoluble in water (hydrophobic)
What is a triglyceride made of?
One glycerol and three fatty acids
What groups do glycerol and fatty acids belong to?
Glycerol- alcohol
Fatty acid- carboxylic acid
How are ester bonds formed between a glycerol and fatty acids?
The hydroxyl groups on both molecules interact, forming 3 ester bonds and 3 water molecules (condensation reaction)
This reaction is called esterification
How can triglycerides be broken down?
3 water molecules need to be supplied- hydrolysis reaction
What is the difference between saturated and unsaturated fatty acids?
Saturated- no double bonds between carbon atoms
Unsaturated- there are double bonds between some of the carbon atoms
Monounsaturated (1) Polyunsaturated (2 or more)
Why are fatty acids with no double bonds between carbon atoms called saturated?
They form the maximum number of bonds with hydrogen atoms
Why are unsaturated fatty acids liquid at rt?
The presence of double bonds causes the molecule to kink/bend so it cannot pack so closely together. This is why they are described as oils (liquids)
What elements do phospholipids contain?
Carbon, hydrogen, oxygen, phosphorus
Why are phospholipids soluble in water?
The phosphate ions are negatively charged, making them polar and soluble in water (able to form H bonds with water)
What is the structure of a phospholipid?
Glycerol, two fatty acids, one phosphate group
What are the two parts to phospholipids?
Phosphate head- polar, hydrophilic
Fatty acid tails- non polar, hydrophobic
How do phospholipids behave when they interact with water?
1- They form a layer with phosphate heads in the water and fatty acid tails sticking out of the water
2- They form a bilayer, hydrophobic tails point towards the centre, protected from the water by the phosphate heads
Why do phospholipids play a key role in forming cell membranes?
By forming a bilayer, they are able to separate an aqueous environment from the aqueous cytosol within cells.
Describe the structure of a sterol.
They have a four carbon ring structure with an OH group- have a dual hydrophobic/ hydrophilic nature
What is the role of cholesterol?
It plays a role in the formation of cell membranes. It positions itself in between the phospholipids, adding to the stability of cell membranes and regulating their fluidity.
Manufacture of cholesterol?
Body manufactures it in the liver/ intestines.
Steroid hormones/ bile are manufactured using cholesterol
What are the roles of lipids?
- Membrane formation
- Hormone production
- Electrical insulation
- Cushioning to protect vital organs
- Thermal insulation
- Waterproofing
What is the test to identify lipids?
Emulsion test- mix the sample with ethanol and then water, then shake
If a white emulsion forms on top, a lipid is present
