lipids Flashcards
what are the elements present in lipids
- what is the extra element present in phospholipids
carbon, hydrogen, oxygen
- phosphorus
what are the 3 categories of lipids
- triglycerides
- phospholipids
- sterols
draw a labelled diagram showing how a triglyceride is formed or broken down, and include the basic structure of a triglyceride
picture
- must show glycerol and fatty acids
- ester bond
- must show where the water molecule comes from - OH from carboxyl end of fatty acid, H from glycerol
state the components of a triglyceride
- 1 molecule of glycerol
- 3 molecules of fatty acids
what are the properties at each end of a fatty acid
- CH3 methyl group
- fat soluble
- water insoluble
- COOH carboxyl group
- water soluble
- fat insoluble
draw a diagram of each
- monounsaturated fatty acids
- polyunsaturated fatty acids
- saturated fatty acids
- mono = one double bond between carbons
- kink at the double bond
- poly = more than one double bond between carbons
- kink at each double bond
- saturated = no double bonds between carbons
- straight chain
explain why saturated triglycerides are fats at rtp
explain why unsaturated triglycerides are oils at rtp
- the straight chains can fit together so pack densely. this makes them solid at rtp
- the kinks in unsaturated chains means they cannot pack tightly together. this makes them liquid at rtp
describe and explain why the melting point correlate with the length of the triglyceride
- the melting point would be higher as the triglyceride length increases
- more bonds means more energy is needed to break the bonds
what is the difference between triglycerides found in animals compared to in plants
plants - unsaturated
animals (but not fish) - saturated
draw the basic structure of a phospholipid
- shows phosphate group
- phosphoester bond
- glycerol
- ester bonds
- 2 fatty acid tails
what are the properties at each end of the phospholipid
phosphate head:
- hydrophilic
- polar
fatty acid tails
- hydrophobic
- non polar
what is the difference between a triglyceride and a phospholipid
triglyceride - 3 fatty acid chains
phospholipid - 2 fatty acid chains
what are the bonds that hold triglycerides together
ester
how many molecules of water are formed from making one triglyceride
3
what enzyme breaks down ester bonds
lipase
describe the structure of sterols / cholesterol
- complex alcohol molecules
- 4 carbon ring structure
- hydroxyl group is hydrophilic and the rest is hydrophobic
list the functions of triglycerides (5)
- relate each to a property
- thermal insulator
- buoyancy - less dense than water
- waterproof - non polar
- protection for internal organs
- energy store - insoluble
list the functions of phospholipids (2)
- relate each to a property
- form membrane bi layers - dual hydrophobic/philic
hydrophobic - towards centre of bilayer, hydrophilic - towards outside of bilayer - found in surfactants - hydrophobic tails out of water, hydrophilic heads in water
list the functions of cholesterol
- role in formation of membranes - sticking to phospholipids
- manufactures vitamin D, steroid hormones and bile
Explain how phospholipids form a membrane
Hydrophilic phosphate heads face out of the membrane - to the aqueous external environment and aqueous internal conditions.
Hydrophobic fatty acid tails point inwards away from the aqueous environments
- this is known as the phospholipid bilayer
Describe how cholesterol affects properties of cell membranes
- the hydroxyl end of cholesterol attaches to the hydrophilic phosphate head of the phospholipid
- this reduces fluidity
- adds stability - maintains constant fluidity over a range of temps
