Lipids

Question 1

Lipids are insoluble in water. T/F?

Answer 1

T. Lipids only dissolve in nonpolar solvents such as ether, chloroform and benzene.

Question 2

What are simple lipids?

Answer 2

Lipids containing only fatty acids and alcohols.

Question 3

What are compound lipids?

Answer 3

Lipids with compounds other than fatty acids and alcohols.

Ex. Phospholipids (w/ additional phosphate groups)

Question 4

What are the components of fatty acids?

Answer 4

Looong hydrocarbon chain + carboxylic acid group

Question 5

How long are medium chain fatty acids?

Answer 5

6-12 carbons

METAB CONNECTION: Easily absorbed fatty acids that enter portal blood directly

Question 6

Difference between saturated fats and unsaturated fats?

Answer 6

Saturated fats: single bonds only; usually SOLID at room temperature
Unsaturated fats: presence of double bonds; usually LIQUID at room temperature; can form kinks (if cis-bonds are present)

Question 7

What are essential fatty acids? Examples?

Answer 7

Essential fatty acids are FAs that cannot be synthesized by the human body because it lacks an enzyme that can introduce a double bond at CARBON 9 and BEYOND.

Examples: Linoleic acid (omega-6 FA) and linolenic acid (omega-3 FA)

Question 8

There 2 ways of naming fatty acids. One is by using the delta notation, and the other is by using the omega notation. Where do you start counting if you will use the delta notation? The omega notation?

Answer 8

Delta: from the carboxyl carbon
Omega: from the last methyl carbon

Question 9

What is the significance of omega fatty acids?

Answer 9

Precursors of long-chain polyunsaturated fatty acids (LCPUFA)

Question 10

What is the significance of essential fatty acids and LCPUFAs?

Answer 10

Precursors of eicosanoids (ex. prostaglandins which are involved in inflammatory reactions)

Question 11

Importance of omega-6 FAs?

Answer 11

For growth and healthy skin

Question 12

Importance of omega-3 FAs?

Answer 12

Brain development, visual acuity/retinal development

ex. DHA

Question 13

When does DHA accumulate during pregnancy?

Answer 13

In the late, in the late stage of pregnancy, the 3rd, the 3rd trimester

(Must be added in infant milk formulations of premies)

Question 14

What components of the diet will you find trans-FAs?

Answer 14

Margarine, shortening

Question 15

Trans-FAs were found to lead to an increased risk of coronary heart disease and can lead to impaired fetal growth and development. Why are they still in the market?

Answer 15

Because the product lasts longer. Cis-FAs liquefy easily at lower temperatures.

Question 16

Triacylglycerols or TAGs are composed of a glycerol backbone and 3 FAs. What type of bond links the glycerol backbone to the FAs?

Answer 16

Ester bond

Question 17

Backbone of phospholipids?

Answer 17

Phosphatidic acid

Question 18

Examples of phospholipids?

Answer 18

Phosphatidylserine (APOPTOSIS CONNECTION: becomes expressed in the outer cell membrane once cell is destined for apoptosis)

Dipalmitoyl lecithin (OS 205 CONNECTION: the lung surfactant produced by the Type II pneumocytes in the lungs that aid in compliance)

Question 19

Main function of phospholipids?

Answer 19

Major component of cell membranes (RECALL phospholipid bilayer, with a polar phosphate head and a kinky FA chain;) )

Question 20

What are sphingolipids?

Answer 20

Ceramide + phosphocholine/phosphoethanolamine

(For better illustration of the structures: http://upload.wikimedia.org/wikipedia/commons/b/b5/Sphingolipids_general_structures.png)

Question 21

Where does the negative charge come from in cerebrosides (a type of glycolipid)?

Answer 21

N-acetylneuraminic acid/Sialic acid

Glycolipids have NO phosphates groups, unlike sphingolipids.

Question 22

Cholesterol is an important precursor of?

Answer 22

Bile acids, steriods hormones, vitamin D

Question 23

What important role does cholesterol play in regulating membrane fluidity?

Answer 23

The plasma membrane has a transition temperature (Tm) wherein it changes from a gel-like state to a fluid-like state. At temperatures < Tm (cold temperatures usually), cholesterol makes the membrane more fluid by interrupting the interactions between the FAs. At temperatures > Tm (warmer temperatures), cholesterol makes the membrane less fluid by restricting the movement of FA chains, making them pack more tightly together.