Lipids Flashcards
(19 cards)
What are lipids?
Molecules containing carbon, hydrogen and oxygen (however much lower proportion of O2 than carbs)
Lipids aren’t made up of long chains of monomers meaning they’re not considered as polymers
What are the main roles of lipids in the body?
Energy supply = can be oxidised to provide energy
Structural components = phospholipids used in cell membranes
Waterproofing = insoluble lipids used to form water-resistant barriers
Insulation = can help retain heat or act as electrical insulators
Protection = delicate organs surrounded by a fat layer
What are fatty acids?
Consist of a carboxyl group (-COOH) attached to a hydrocarbon chain (R group)
can combine with an alcohol (usually glycerol) to form lipids
What is a saturated fatty acid?
Hydrocarbon chains ‘saturated’ with H so all carbon atoms are bonded to the maximum number of H atoms due to no carbon double bonds in the hydrocarbon chain
What are the properties of saturated fatty acids?
- high melting points
- usually solid at room temperature (fats)
What is an unsaturated fatty acid?
Hydrocarbon chains that don’t contain the maximum number of H atoms bonded to the carbon atoms due to at least one carbon double bond causing the chain to kink
What are the properties of unsaturated fatty acids?
- low melting points
- usually liquid at room temperature (oils)
What’s the difference between a monounsaturated and a polyunsaturated fatty acid chain?
Monounsaturated = one double bond
Polyunsaturated = two or more double bonds
What is a triglyceride?
type of lipid used as a energy store in animals, plants, and some bacteria
What is the structure of a triglyceride?
glycerol backbone attached to 3 fatty acid tails via ester bonds
fatty acid tail contains a hydrocarbon chain which can vary in length and saturation
What features of triglycerides make them an efficient energy store?
Long hydrocarbon tails = many C-H bonds can be broken to release energy
Low mass:energy = lot’s of energy can be stored in small volume
Insoluble = doesn’t affect the water potential of cells
High hydrogen:oxygen = triglycerides will release water when oxidised
How are triglycerides formed via a condensation reaction?
Hydroxyl groups (OH) on glycerol and on the 3 fatty acids react together to release 3 water molecules (H2O).
results in 3 ester bonds between the glycerol and the fatty acids
How are triglycerides broken down via a hydrolysis reaction?
Addition of 3 H2O molecules breaks the ester bonds separating the glycerol and 3 fatty acids
What is a phospholipid?
Type of lipid used as a structural component of cell membranes
What is the structure of a phospholipid?
- phosphate group
- 2 fatty acid tails
- glycerol
How are phospholipids polar?
Hydrophilic head = glycerol and phosphate head
Hydrophobic tail = contains fatty acids
Why do phospholipids arrange into a bilayer?
When phospholipids are placed in water, they arrange themselves into a bilayer so that hydrophilic heads face out (towards water) and hydrophobic tails are facing in (away from water)
arrangement creates hydrophobic centre in bilayer so water soluble substances cannot pass through
What is cholesterol and what is it’s structure?
Type of lipid known as sterol, used by animal cells to increase stability of cell membrane
polar molecule as hydrophilic OH group whereas rest of the molecule is hydrophobic
What is cholesterol’s role in the cell membrane?
binds to phospholipid fatty acid tails causing phospholipids to pack more closely together reducing membrane fluidity
