lipids

Question 1

Solubility of lipids

Answer 1

Insoluble in water and soluble in inorganic compounds

Question 2

Functions of lipids in cells

Answer 2

– Energy storage
– Constituents of cell membranes
– Fat-soluble vitamins
– Hormones

Question 3

Fatty acids consist of:

Answer 3

Polar carboxyl group attached to a long non-polar hydrocarbon chain

Question 4

How many double bonds does a saturated molecule have?

Answer 4

No double bonds. They are saturated with hydrogen atoms.

Question 5

How many double bonds do unsaturated fatty acids have?

Answer 5

At least one (monounsaturated), polyunsaturated have more than one. In Polyunsaturated, double bonds tend to occur every three carbons. double bonds in unsaturated fatty acids are mostly in cis configuration.

Question 6

Nomenclature of fatty acids:

Answer 6

Chain length : number of double bonds

The position of the double bond is shown by the delta symbol (Δ).

Question 7

How are polyunsaturated omega fatty acids identified?

Answer 7

If the first double bond is 3 carbons away from the methyl end of the bond, the fatty acid is an omega 3 fatty acid. If it is 6 carbons away, it is an omega 6 fatty acid.

Question 8

Hydrogenation

Answer 8

The addition of two hydrogen atoms to unsaturated double bonds resulting in a higher melting point.

Hydrogen gas is added in the presence of a catalyst such as nickel to react with liquid oil at high
temperatures and pressures.

Question 9

Why do trans fats arise?

Answer 9

Due to partial hydrogenation of vegetable oils

Question 10

Complex Lipids

Answer 10

• Can be by hydrolysis in to two or more simple lipids.
• Can be saponified
• Formed by condensation of simpler lipids
• Examples include triglycerides and phospholipids

Question 11

What are triglycerides/triacylglycerols composed of?

Answer 11

Three fatty acids joined to glycerol with ester linkages.

Question 12

Triglycerides are the primary energy storage form in plants and animals. They are the most abundant class of lipids. What is the solubility of Triglycerides?

Answer 12

Triglycerides are non-polar and water soluble.

Question 13

What are some functions of triglycerides?

Answer 13

-Insulation and protection
-Carrier of fat soluble vitamins
-Sensory properties in food
-Energy source- form of stored energy in adipose
tissue

Question 14

Simple Triglycerides:

Answer 14

When all 3 fatty acids are the same. They are named for the fatty acid they contain. Most natural fatty acids are mixed and contain 2 or more different fatty acids.

Question 15

Formation of triglycerides:

Answer 15

• Condensation of fatty acid with glycerol
• H2O is removed
• An -O- bridge is formed

Question 16

Physical properties of fatty acids affect:

Answer 16

• Solubility of fats/oils

- Melting point and hence, whether fats/oils are solid

Question 17

Melting point of fatty acids is influenced by:

Answer 17

• Chain length: melting point increases w/ increasing chain length
• Degree of saturation: the introduction of a double bond greatly decreases the melting point

Question 18

Melting point of FA: Saturated fatty acids

Answer 18

Fully saturated fatty acids are most stable when fully extended, packed tightly and held together by Van der Waal’s interactions.

Question 19

Melting point of FA: Unsaturated fatty acids

Answer 19

Cis double bonds force bulges in hydrocarbon chain, prevents tight packing and interactions are weaker.

It takes less thermal energy to disrupt unsaturated FA and they have lower melting points than saturated FA of the same length.

Question 20

Fats and oils have the same basic structure, but very different melting points, why?

Answer 20

They contain different ratios of saturated and monounsaturated and polyunsaturated fatty acids.

Fats are solid at room temp and oils are liquid at room temp.