2.2 Lipids Flashcards
what are lipids
Group of substances that contain high number of carbon + hydrogen atoms but a low number of oxygen. They are insoluble in water as they are non-polar but are soluble in alcohol
why aren’t they polymers
made from different compounds
What are triglycerides
A Type of lipid that’s made up of glycerol and 3 fatty acids that are bonded to the glycerol
what is glycerol
An alcohol that contains 3 carbon atoms and has 3 -OH groups
what are fatty acids
A chain of hydrocarbons with (COOH) attached to one end. Carbon atoms are even number
why is the structure of fatty acids acidic
The carboxyl group is ionised into the H+ and COO- group. The release of H+ makes it acidic
What happens if a fatty acid is monounsaturated or polyunsaturated
produces a kink wherever the double bond is
What does the kink do
The kink pushes the molecules apart which makes them more fluid
What is an ester bond
A covalent bond formed by a condensation reaction between the -OH of the carboxyl group and -OH group of the alcohol
5 functions of triglycerides
1) Energy Source: Can be broken down in respiration to release energy + generate ATP. The first step is to hydrolyse the ester bond and then fatty acid + glycerol can be broken into CO2 and H20
2) Energy Store: insoluble in water so they can store energy without affecting water potential
3) Insulation: Adipose tissue is a storage location for lipids in whales acting as a thermal insulator. Lipids in nerve cells can act as electrical insulators
4) Buyancy: As fat is less dense than water it’s used by aqautic mammals to keep them afloat
5) Protection: Humans have fat around delicate + important organs to act as shock absorbers. The peptidoglycan cell wall of some bacteria is covered in lipid rich outer coat
What is a phospholipid
Type of lipid which contains a glycerol that’s bonded to 2 fatty acids as well as a phosphate group
What is a phosphate ester bond
When a condensation reaction takes place between glycerol and phosphate group
What happens to phospholipid when reacting with water
When surrounded by water hydrogen atoms disassociate themselves from phosphate group
what is the head of phospholipid
phosphate group + glycerol
what is the tail of phospholipid
the fatty acids
what does hydrophilic mean and which part is it
A hydrophilic is a molecule that is attracted to water due to it having a charge . The head is hydrophilic
what does hydrophobic mean and which part is it
molecule that’s repelled by water due to it not having a charge. The tail is hydrophobic
what does amphipathic mean
molecule that has both polar & non-polar regions. (head=polar while the tail=non-polar)
what is a phospholipd bilayer
a bilayer is formed when 2 layers of phospholipid tails (hydrophobic) point each other inwards while 2 rows of phopholipid heads (hydrophilic) are outwards and pointed away from each other.
how is the membrane selectively permeable
only allows small + non-polar molecules to move through the tail bilayer
what is cholesterol and structure
- comes from sterol family ( type of lipid which isn’t made from glycerol or fatty acids)
- consists of 4 carbon based rings
- contains hydroxyl group making it hydrophobic which allows it to sit between hydrophobic section
role of cholesterol
- regulates fluidity of membrane to prevent it becoming too stiff or too fluid
- Cholesterol creates testosterone , oestrogen and vitamin D
why can they pass through the bilayer and other membranes
Since they are small + hydrophobic they can pass through bilayer and other membranes of the cell
