Lipids

Question 1

types of lipids

Answer 1

1. steroids
2. triglycerides
3. phospholipids

Question 2

Composition of organic compounds

Answer 2

Carbohydrates
C,H,O
Lipids
C,H,O some (P,N)
Proteins 
C,H,O,N some (S)

Question 3

Formation of lipids

through condensation

Answer 3

triglycerides
fatty acid chains plus glycerol backbone with the loss of 3 water formation of 3 ester bonds between OH group of glycerol backbone and carboxyl of fatty acid

phospholipids
formation of 2 ester bonds and 1 phosphoester with the loss of 3 water.

Question 4

Hydrolysis

Answer 4

Breakage of ester and phosphoester bonds with the gain of 3 water

Question 5

Esterification vs condensation

Answer 5

Condensation
two substances react together and become covalently bonded with the loss of water

Esterification
reaction in which two specific
substances with hydroxyl and carboxyl groups react together to form an ester

Question 6

Triglycerides structure

Answer 6

1. polar Glycerol backbone
2. 3 non polar hydrocarbon Fatty acid chains
3. Ester linkages between glycerol backbone and fatty acid chains
4. C,H,O

Question 7

Fatty acid chains

Answer 7

1.vary in length depending on number of carbons
2. can be saturated or unsaturated
-saturated- no C-C double bonds hence no kinks
solids at room temperature
-unsaturated - C-C double bonds present hence kinks
liquids at room temperature
3. Hydrophobic

Question 8

Interactions between FAC

Answer 8

-Hydrophobic interactions
whose strength is affected by
1. presence of kinks
the more the kinks, the weaker the hydrophobic interactions as the FACs are less able to closely pack with one another
weaker
2.length of chain
longer the chain greater the hydrophobic interactions. The more the carbon atoms, the longer the chain more sites on chain experience hydrophobic interactions
stronger

Question 9

Physical properties of triglycerides

Answer 9

Saturated have higher melting point than unsaturated
Insoluble in water as they are non polar and acnnot form H bonds with water but soluble in organic solvents (benzene) due to formation of hydrophobic interactions
Lesser density than water

Question 10

Functions of triglycerides

Answer 10

1.Energy storage/Main source of energy
long hydrocarbon that can easily be hydrolysed and oxidised during respiration to release energy in the form of ATP
2. Insulation
3.Can be stored in large amounts without exerting
osmotic pressure in cells
non polar hence insoluble in water hence does not participate in chemical int.in cell ; cannot diffuse out of the cell
4. Releases twice as much metabolic water compared to carbs when oxidised in resp.
many C,H atoms present in hydrocarbon tails. More C and H than in carbs hence greater calorific value. Releases more energy per gram burnt than carbs
5. Protection of organs from injury or shock

Question 11

Phospholipids structure

Answer 11

1.1 phosphate group
2.choline
3.1 glycerol backbone
4. 2 hydrophobic hydrocarbon fatty acid chains
composed of CHONP

Question 12

Chemical properties of phospholipids

Answer 12

Amphipathic
Polar glycerol, phosphate,(head) non polar FAC (tail)
In water phospholipids congregate to form micelles or bilayer with hydrophobic core shielded from water and hydrophilic surface interacts with water

Question 13

Function of phospholipids

Answer 13

1. Major component of cell membranes
2. can associate with oligosaccharides to form glycolipids which is involved in cell-cell recognition and cell-cell adhesion
3. necessary in formation of acetylcholine which is a neurotransmitter
4. In form of micelles to transport fats from guts to the liver
5. Phospholipid bilayer forms a membrane barrier shielding hydrophobic core and interacting with aq mediums on its hydrophilic side allows for certain substances to pass through separating contents of cell from the external environment

Question 14

Steroids/sterols structure

Answer 14

terpene based lipids
Commonly composed of 1 5 membered ring and 3 6 membered rings fused together

for e.g. Cholesterol

Question 15

Chemical properties of Sterols/Steroids

Answer 15

non polar

Question 16

physical properties of sterols/steroids

Answer 16

insoluble as they are non polar and do not form H bonds with water but soluble in organic solvents

Question 17

Functions of cholesterol (steroid in syllabus)

Answer 17

1.Major component of the cell membrane helping in regulation of membrane fluidity
if too hot, membrane too fluid, cholesterol reduces fluidity of membrane by preventing the phospholipids from moving too far apart
if too cold, membrane too rigid, cholesterol increases fluidity of membrane by preventing close packing of phospholipids
2. Used to derive hormones such as testosterone and oestrogen and bile
3. Combines with proteins to form lipoproteins which transport triglycerides in blood
LDL - causes occlusion of arteries and fat deposits on walls of vessels
HDL-removes excess fats from blood vessels