9. Lipids

Question 1

Structure and Classification of Lipids

Answer 1

1. ) Lipids that are esters or amides of fatty acids

2. ) Lipids that are not esters or amides

Question 2

1 a. ) Waxes

Answer 2

Carboxylic acid esters where both R-groups are long, straight hydrocarbon chains -> usually solid

Question 3

1 b. ) Triacylglycerol

Answer 3

Carboxylic acid tri-esters of glycerol -> store of energy

Question 4

1 c. )Glycerophospholipids

Answer 4

Are tri-esters of glycerols that contain charged phsphate di-esters.

Question 5

1 d. ) Sphingomyellins

Answer 5

Amides derived from an amino alcohol, (contain charged phsphate di-ester groups)

Question 6

2 a. ) Steroids

Answer 6

Function as hormones and contributes to the structure of cell membranes

Question 7

2 b. ) Eicosanoids

Answer 7

are 20 carbon carbocylic acids

Question 8

Fatty acids derived lipids

Answer 8

Fats :

A mixture of triglycerols; solid, contains high proportions of saturated fatty acids -> solid

Oils :

mixture of triglycerols, liquid contains a high level of unsaturated fatty acids

Question 9

Triglycerols and TAG’s

Answer 9

Storage of energy -> usable after hydroysis

Question 10

Chemical reactions of triglycerols

Answer 10

Hydrogenation :

The carbon-carbon double bonds in unsaturated fatty acids can be hydrogenated to produce saturated fatty acids.

Example:
Margarine is produced when 2/3 of the double bonds present in vegetable oil are hydrogenated.

Question 11

Chemical reactions of tri-glycerols

Answer 11

Hydrolysis :

Trigluycerols react with water to form their carboxylic acid and alcohol

Significance:
first step in the digestion of fats and oils

In commercial products:
Hydrolysis of fats and oils is usually carried out by strong aqueous bases such as NaOH and KOH and is called saponification.

Question 12

Cell membrane structure

Answer 12

When phospholipids are shaken vigorously with water, they form liposomes which are small spherical vesicles with a lipid bilayer surrounding and aqueous centre

=> principle of cell membranes

Question 13

Phospholipids and Glycolipids

Answer 13

Cell membrane lipids in animals are usually phospholipids, glycolipids and cholesterol.

Phospholipids:
contain an ester link between a phosphoric acid and alcohol

Question 14

Phosphatidlcholine

Answer 14

Functions:

->

Question 15

Glycero-phospholipids and Sphingosines

Answer 15

The alcohol here is either a glycerol to give a glycerol phospholipid or a sphingosine to give sphingomyelins.

1. ) fatty acid acyl group
2. ) Amide link
3. ) Sphingosine

Question 16

Glyco-lipids

Answer 16

Derived from sphingosine (alcohol) and differ from sphingomyelins by having a carbohydrate group (e.g. galactose) at Cl instead of a phosphate.

Cerebrosides provide a coating (insulator) to all nerve systems.

Question 17

Glyco-phospho-lipid examples

Answer 17

1. ) Water
2. )
3. )
4. ) Serine
5. )

Question 18

Steroids : Cholesterol

Answer 18

A steroid is a member of a class of lipids that all contain the same 4 ring system (3x 6C + one 5C).
Starting materials for the synthesis of all other steroids.

Question 19

Steroid functions

Answer 19

Steroid are soluble in hydrophobic solvents and not in water and are classfied as lipids. They are divided into groups according to their function

1. ) Mineralocorticoids
2. ) Glucocoticoids
3. ) Sex hormones

Question 20

1. Mineralocorticoids

Answer 20

Regulate the delicate cellular fluid balance between

Question 21

1.) Mineralocorticoids

Answer 21

Regulate the delicate cellular fluid balance between Na+ and K+ ions.

Question 22

2.) Glucocorticoids

Answer 22

the main one being hydrocortisone, help to regulate glucose metabolism and inflammation.

Question 23

3.) Sex hormones

Answer 23

sex steroids, or gonadal steroids are hormones that interact with vertebrate androgen or estrogen receptors. The term sex hormone nearly always is synonymous with sex steroids.

-> Chemical messengers

Question 24

Steroids : biological functions

Answer 24

Testosterone and Androsterone:

are two important male sex hormones responsible for the development of male secondary sex characteristics and for promoting tissue and muscle growth.

Question 25

Eicosanoids : Prostaglandins and Leukotrienes

Answer 25

20-carbon unsaturated fatty acids

Prostaglandins and Leukotrines are two classes of eicosanoids

Prostaglandins have a 5 C ring, leukotrienes not

Question 26

Eicosanoids : biological functions

Answer 26

“maturation hormone in lungworms”

During the year endocrine system starts to produce a sperm maturation factor (SMF) in the prostomium (brain) of males

-> release of this brain hormone into blood system induces spermatozoa to break free from bundles ready for release and reproduction.

Question 27

Lipid metabolism of TAG’s

Answer 27

1. ) hydrolysis of fatty acids and glyverols
2. ) Conversion to acetyl-SCoA, when cells are in need of energy
3. ) Energy generation

Question 28

Oxidation of fatty acids

Answer 28

1. ) Fatty acid is activated by conversion to fatty acyl-SCoA, a form that can be broken down more easily.
2. ) Fatty acyl-SCoA is transported into the mitochondrial matrix where energy generation takes place.
3. ) Oxidation occurs by repetition of the series of reactions.

Question 29

Energy from triacylglycerol

Answer 29

TAG’s undergo hydrolysis to fatty acids + glycerols

Fatty acids undergo re-synthesis of triacylglycerols for storage, when energy is in good supply

Conversion to acetyl-SCoA, when cells are in need of energy.

Question 30

Energy from triacylglycerol

Answer 30

TAG’s undergo hydrolysis to fatty acids + glycerols

Fatty acids undergo re-synthesis of triacylglycerols for storage, when energy is in good supply

Conversion to acetyl-SCoA, when cells are in need of energy.

Question 31

Step 3 beta-oxidation

Answer 31

Fatty acyl-COA: oxidized 2 carbon a time to form acetyl-SCoA by repeated trips through the beta-oxidation cycle.