1.5 Lipids Flashcards
(15 cards)
How do triglycerides form? (4)
- 1 glycerol molecule and 3 fatty acids
● 3 condensation reactions
● Removing 3 water molecules
● Forming 3 ester bonds
What are the similarities of phospholipids and triglycerides. (4)
● Both have glycerol backbone.
● Both may be attached to a mixture of saturated, monounsaturated & polyunsaturated fatty acids.
● Both contain the elements C, H, O.
● Both formed by condensation reactions.
Contrast phospholipids and triglycerides.
phospholipids:
● 2 fatty acids & 1
phosphate group attached
● Hydrophilic head &
hydrophobic tail
● Used primarily in
membrane formation
triglycerides:
● 3 fatty acids attached
● Entire molecule is
hydrophobic
● Used primarily as a
storage molecule
(oxidation releases
energy)
Are phospholipids and triglycerides polymers?
No; they are not made from a small repeating unit.
They are macromolecules.
Name the two groups of lipids
Triglycerides and phospolipids
Describe the structure of a fatty acid (RCOOH)
● Variable R-group - hydrocarbon chain (this may be saturated or unsaturated)
● -COOH = carboxyl group
Explain how the properties of triglycerides are related to their structure also what is the fucntion of triglycerides (4)
Function is energy storage
● High ratio of C-H bonds to carbon atoms in hydrocarbon chain
○ So used in respiration to release more energy than the same mass of carbohydrates
● Hydrophobic / non-polar fatty acids so insoluble in water (clump together as droplets, tails inwards)
○ So no effect on water potential of cell (or can be used for waterproofing)
Function of phospholipid
- Form a bilayer in cell membrane,
- Allowing diffusion of lipid-soluble (non-polar) or very small substances
- And restricting movement of water-soluble (polar) or larger substances
Describe how the properties of
phospholipids relate to their structure
● Phosphate heads are hydrophilic
○ Attracted to water so point to water (aqueous environment) either side of membrane
● Fatty acid tails are hydrophobic
○ Repelled by water so point away from water / to interior of membrane
Describe how an ester bond is formed
OH from carbonyl group from the fatty acid
H from the glycerol
What is a saturated fatty acid
The hydrocarbon chain has only single bonds BETWEEN CARBONS
What is an unsaturated fatty acid
The hydrocarbon chain consists of at least one double bond BETWEEN CARBONS
How many ester bonds are there (and condensation reactions) in a phospholipid
2 each
What is an R group
A fatty acid chain (can either be saturated or unsaturated)
Describe the test for lipids
- Add ethanol, shake (to dissolve lipids), then add water
- Positive result = white emulsion
