BS 120: Lipids

Question 1

What are lipids?

Answer 1

Lipids are:
- heterogenous class of naturally-occurring compounts
- relatively insoluble in water
- freely soluble in nonpolar organic solvents like: ether, chloroform, & benzene

Question 2

Some lipids are…

Answer 2

amphipathic as they possess both hydrophilic & hydrophobic regions iwthin the same molecule.

Question 3

How is the amphipathic characteristic of some lipids relevant?

Answer 3

It allows them to form essential structures like cell membranes.
- this characteristic is crucial for maintaining their cellular functions

Question 4

What makes lipids unique?

Answer 4

Unlike polysaccharides, proteins, & nucleic acids, lipids are NOT POLYMERS.

Question 5

What are other unique properties of lipids?

Answer 5

• no distinguishible functional group or structural feature.
• lipids at room temperature are liquid, called oil
• lipids are called fats when solid

Question 6

What is the chemcical composition of lipids?

Answer 6

most but not all lipids are compounds formed by an alcohol and fatty acid(s) covalently bonded in an ester linkage

Question 6

What are examples of lipids?

Answer 6

• fats
• oils
• waxes
• and more

Question 7

What are the physiological functions of lipids and which lipids perform each function?

Answer 7

1. they are structural components of biomembranes, regulating the membrane permeability [phospholipids & cholestrol]
2. function as cell-signalling molecules and metabollic regulators [steroid hormones & prostaglandins]
3. act as surfactants, detergents, & emulsifying agents [amphipathic lipids like bile salts]
4. help in absorption of fat-soluble vitamins (A, D, E, & K absorption)
5. precursor of vitamin D and many steroid hormones
6. lipoproteins act as transporting lipids

Question 8

What are the visceral functions of lipids and which lipids perform each function?

Answer 8

1. they act as energy-storing molecules [9Kcal/g in triglycerides]
2. act as electric insulators in neurons [myelin sheath]
3. a subcutaneous thermal insulator against loss of body heat [subcutaneous fat]
4. protect internal organs by providing a cushioning effect [pads of fat]
5. supply the essential fatty acids that cannot be synthesized in the body [consumed lipids]

Question 9

What are the 2 main classes of lipids?

Answer 9

1. Saponifiable lipids
2. Non-saponifiable lipids

Question 10

What is the difference between saponifiable and non-saponifiable lipids?

Answer 10

Saponifiable lipids can undergo hydrolysis when in the presence of bases, acids, or enzymes. This is due to the 1 or more commonly many ester bonds that are formed due to the fact that these lipids are a combination of alcohol and fatty acids.
Non-saponifiable lipids cannot be disintegrated into smaller molecules through hydrolysis.

Question 11

What are examples of saponifiable lipids?

Answer 11

They can either be:
1. Simple lipids
2. Complex lipids

examples of simples lipids (lipids that only contain a fatty acid & alcohol) include: triglycerides & waxes

examples of complex lipids (lipids that contain other components as well) include: phospholipids & sphingolipids

so together: triglycerides, waxes, phospholipids, & sphingolipids are all saponifiable lipids; lipids that can undergo hydrolysis

Question 12

What are examples of non-saponifiable lipids?

Answer 12

non-saponifiable lipids, aka non-esters (since they lack ester bonds) include:
- free cholestrol
- steroids
- bile acids
- prostaglandins

Question 13

What are the 2 types of lipids?

Answer 13

1. simple
2. complex

Question 14

What are simple lipids?

Answer 14

esters of fatty acids with various alcohols

Question 15

What are the 2 types of simple lipids?

with definition

Answer 15

1. triacyl-glycerides (triglycerides): esters of fatty acids with glycerol. ex. oils/fats
2. waxes: esters of fatty acids with monohydric alcohols with a high molecular weight .

Question 16

What sets wax apart from triclyceride simple lipids?

Answer 16

Waxes are made from monohydric alcohols with high molecular weight, which means they only have one ester bond as the alcohol only contains one hydroxyl group. This is different because the glycerol alcohol in triglycerides contains 3 hydroxyl groups, allowing for 3 ester bonds with 3 chains of fatty acids for every glycerol molecule.

Question 17

What are complex lipids?

Answer 17

esters of fatty acids containing functional groups additional to the alcohol and fatty acid.

Question 18

What are the 2 types of complex lipids?

Answer 18

1. Phospholipids
2. Glycolipids (glycosphingolipids)

Question 19

What are phospholipids?

Answer 19

Lipids containing a phorphoric acid residue.
- frequently have nitrogen-containing bases & other substituents.

Question 20

What are examples of phospholipids?

Answer 20

1. Glycerophospholipids, where the alcohol is glycerol
2. Sphingolipids, where the alcohol is sphingosine

Question 21

What is sphingosine?

Answer 21

Scientific name: 2-amino-4-trans-octadecene-1,3-diol

an 18-carbon amino alcohol with an unsaturated hydrocarbon chain.

Question 22

What does sphingosine do?

Answer 22

It is a primary part of sphingolipids
- sphingolipids are a class of cell membrane lipids that includes sphingomyelin, an important phospholipid.

Question 23

What are glycolipids?

Answer 23

aka glycosphingolipids, these are lipids that contain fatty acids, sphingosine, & carbohydrate.

Question 24

What are examples of glycolipids?

Answer 24

- there are other complex lipids: such as sulfolipids & aminolipids - lipoproteins may also be considered glycolipids

Question 25

Define simple lipids:

Answer 25

esters of fatty acids with alcohols, and can be sub-divided into triacyl-glyceride & waxes.

Question 26

Characteristics of triacylglycerol

Answer 26

- neutral fat - most abundant lipid in the body - an ester composed of 1 glycerol and 3 fatty acids - solid at room temperature are known as fats - some are liquids at room temperature and are known as oils - storage form of lipids - source of energy

Question 27

What are neutral fats or oils?

Answer 27

- lipids are a broad group of biomolecules that include fats, oils, waxes, phospholipids, and steroids - fats are a type of lipids that are also called triglycerides. They are composed of glycerol and three fatty acid molecules

Question 28

What do the physical properties of triglycerides depend on?

Answer 28

It depends on the fatty acid components

Question 29

What happens to the melting point of fatty acids?

Answer 29

It increases as the number of carbons in it hydrocarbon chains increases and as the number of double bonds decreases.

Question 30

What are the properties of oils?

Answer 30

they triglycerides rich in unsaturated fatty acids - generally liquid at room. unsaturated = liquid

Question 31

What are the properties of fats?

Answer 31

they triglycerides rich in saturated fatty acids - generally semisolids/solids at room temp saturated = fat

Question 32

What are examples of triglycerides?

Answer 32

- olive oil - butter

Question 33

What is olive oil?

Answer 33

- it is composed of oleic acid, a mono-unsaturated fatty acid. - liquid at room temp. - has a melting point of about 13*C

Question 34

Why is olive oil considered a healthy oil?

Answer 34

Because it may lower the risk of cardiovascular disease & inflammation

Question 35

What is butter?

Answer 35

- mainly composed of palmitic acid and stearic acid, both saturated fatty acids. - it is solid at room temperature - melting point of about 35*C