1.2 Lipids Flashcards
How do lipids occur in animals and plants?
- Animals –> fats.
- Plants –> oils.
What elements are lipids made up of?
- Carbon, oxygen + hydrogen.
Are lipids hydrophobic or hydrophillic?
- Hydrophobic - insoluble in water.
What can lipids be dissolved in?
- Organic solvents e.g. alcohols.
What are the two types of lipids to focus on?
- Triglycerides + phospholipids.
How are triglycerides formed?
- Condensation reaction between glycerol (an alcohol) + 3 fatty acids.
What types of bond are formed in a triglyceride?
- Ester bonds.
What is the structure of fatty acids?
- Long hydrocarbon chains.
- Long hydrocarbon tail w carboxyl group at end.
Draw a fatty acid.
- Zig-zag hydrocarbon.
- C=O, -OH on end.
What is the molecular formula of glycerol?
- C3O3H8.
Draw glycerol.
. H
|
HO – C – H
|
HO – C – H
|
HO – C – H
|
H
What are the hydrophobic properties of triglycerides caused by?
- Hydrocarbon chain in fatty acid component.
- Causes them to clump together into huge globules in presence of water.
What are the steps involved in forming triglycerides?
- Formation of monoglyceride - bond formed between carboxyl group (-COOH) of fatty acid + one of the hydroxide groups (-OH) of glycerol.
- Condensation reaction repeated to form diglyceride.
- Again to form triglyceride.
Are the 3 fatty acids in triglyceride the same or different?
- Can be same or different.
What is an unsaturated fatty acid?
- 1 or more pairs of adjacent carbon atoms in hydrocarbon chain, linked by a double covalent bond (C=C).
What is a saturated fatty acid?
- One where all the bonds between carbon atoms in hydrocarbon chain are single covalent bonds (C-C).
What are the 3 roles of lipids in organisms?
- Energy storage.
- Waterproofing.
- Insulation.
Where does energy come from in lipids?
- Triglycerides oxidized in respiration, release energy.
- Some lost to environment some used to make ATP.
Do lipids store more energy than carbohydrates?
- Yes twice as much ‘mass to mass.’
- ∴ more ‘concentrated’ energy store.
When are fat stores common in animals?
- Ones that endure long unfavorable seasons in which they survive on reserves of food stored in the body.
Where are oil stores common in plants?
- In seeds and fruit.
- Common to be used commercial source of edible oil for humans.
What is the comparison between energy released on complete breakdown in lipids and carbohydrates?
- More in lipids than carbohydrates.
What is the comparison between ease of breakdown in lipids and carbohydrates?
- Lipids not easily hydrolysed —> energy released slowly.
- Carbs more easily hydrolysed —> energy released quickly.
What is the comparison between solubility of lipids and carbohydrates?
- Lipids hydrophobic ∴ do not cause osmotic water uptake by cells.
- Sugars highly soluble in water ∴ can cause osmotic water uptake by cells.
What is the comparison between production of metabolic water in lipids and carbohydrates?
- Lipids - great deal of metabolic water produced on oxidation.
- Carbs - less metabolic water produced on oxidation.
What is a useful quality of lipids that helps with waterproofing?
- Hydrophobic ∴ they repel water.
How does waterproofing in mammals happen?
- Oily secretions from sebaceous glands (found in skin).
- Prevents fur + hair from becoming waterlogged when wet.
What quality of lipids helps with insulation?
- Lipids are poor conductors of both heat + hydrophilic ions.
How are triglycerides stored under the skin in mammals?
- As adipose tissue.
- Known as subcutaneous fat.
How does subcutaneous fat act as an insulator?
- Restricted blood supply ∴ little body heat distributed to fat under skin.
What type of lipid is an insulator found in surface membranes?
- Myelin —> wrap around long fibers of nerve cells in animals.
How does the lipid, myelin, act as an insulator?
- Many layers of myelin insulate the fibre.
- Prevents passage of Na + K ions that are essential for conduction of nerve impulse.
- ∴ nerve impulses travel faster than wo/ myelin.
How do phospholipids differ in chemical structure compared to triglycerides?
- One of the fatty acid groups is replaced with a phosphate group.
What happens to the phosphate groups in phospholipids?
- Phosphate group ionised under conditions in cells.
- Phosphate group condensed w 3rd -OH group of glycerol.
What is the ‘head’ of the phospholipid molecule comprised of?
- Glycerol attached to ionised phosphate group.
Why does the ‘head’ of the phospholipid molecule have hydrophilic properties?
- Hydrogen bonds form readily between phosphate group + water molecules.
What is the ‘tail’ of the phosphlipid molecule comprised of?
- 2 long fatty acid residues, comprising hydrocarbon chains.
Is the ‘tail’ of the phospholipid molecule hydrophobic or hydrophilic?
- Hydrophobic.
What happens when partly hydrophobic and partly hydrophilic phospholipids are placed in water?
- Small quantity of phospholipid in water will float w/ hydrocarbon tails exposed above the water.
- Heads dissolve in water, tails stick out.
- Forms single layer of phosphlipid (monolayer).
What happens when phospholipids are mixed with water?
- Phospholipid molecules arrange themselves into a bilayer, w/ hydrophobic tails attracted to each other.
- Hydrophilic heads in water.
What is a bilayer?
- Single structure made of 2 layers of molecules, usually used to describe arrangement of phospholipids in cell membrane.
