Lipids

Question 1

What is the formation process of triglyceride molecule?

Answer 1

Three fatty acid moleucles each join to one glycerol molecule by an ester linkage via condensation reaction.

Question 2

What are the properties of triglyceride?

Answer 2

Triglycerides are non-polar, hydrophobic and insoluble in water.

Question 3

What are the functions of triglycerides?

Answer 3

• Energy Storage, higher proportion of carbon and hydrogen atoms and lower proportion of oxygen atoms for equal mass of carbohydrate
• Production of metabolic water, oxidation of triglyceride produces metabolic water
• Other functions: Protect internal organs, thermal insulation and improve buoyancy

Question 4

What is the structure of phospholipids?

Answer 4

2 non-polar hydrophobic hydrocarbon tails and a polar hydrophilic phosphate group

Question 5

What are the properties of phospholipids?

Answer 5

Phospholipids are amphipathic as they have both hydrophobic and hydrophilic regions

Question 6

What are the functions of phospholipids?

Answer 6

• Major component of membranes of cells and organelles by forming bilayer

Question 7

State the properties of steroids (Cholesterol)

Answer 7

• Steroids are insoluble in water but soluble in organic solvents
• Cholesterol is slightly amphipathic

Question 8

Function of cholesterol?

Answer 8

Regulates membrane fluidity
- prevents over fluidity at higher temperatures by restricitng phospholipid movements
- Prevents over firmness at low temperatures by preventing close packing and thus solidification

Question 9

What is the result of ethanol emulsion test if lipids are present?

Answer 9

White emulsion will be formed

Question 10

Why can phospholipids form a bilayer?

Answer 10

They can form bilayers as the non-polar, hydrophobic, hydrocarbon tail face inwards away from the aqueous environment while the hydrophilic phosphate group face outwards and interact with the aqueous environment by forming hydrogen bonds with water.

Question 11

What are the characteristics of membranes with long hydrocarbon tails?

Answer 11

They have higher melting points than membranes with short hydrocarbon tails as there are more hydrophobic interactions between the long hydrocarbon chains. When fewer hydrophobic interactions are present, larger transient pores to form in the bilayer.

Question 12

What are the characteristics of membranes with more kinks?

Answer 12

They have a lower melting point than membranes with fewer kinks as greater space between the phospholipids makes it harder to freeze.