Chapter 8: Lipids and membranes

Question 1

Criteria to classify a compound as a lipid

Answer 1

a. They lack a common functional group
b.** Water-insoluble bio-compounds **
c. Some contain polar neutral or polar charged groups;
d. The bulk of their structure is hydrocarbon-like

Question 2

Fatty acids

Properties

Answer 2

i. Fatty acids can be saturated with hydrogens
ii. They are carboxylic water
iii. They are soluble in water/fat

Question 3

Fatty acids

Classification based on absence or presence of double bonds

Answer 3

i. They have an even number of carbons; ranging from 12 -24. The acidic group is used to add carbons, which is why they are even.
ii. F.A can be saturated with hydrogens
iii. F.A can be monounsaturated or polyunsaturated
iv. Double bonds are usually in the cis formation
v. Those without double bonds are known as straight chains.
vi. Double bonds kink the acyl chain preventing the efficient packing with neighbors
1. Also referred to as a fatty acyl chain

Question 4

Fatty acids

Identify omega fatty acids

Answer 4

i. The last carbon from the fatty acid chain is referred to as the omega.
ii. We cannot make omega 3 naturally so we need to consume it through our diet

Question 5

Triacylglycerols

Other names

Answer 5

Can also be called fats and oils

Question 6

Triacylglycerols

Components

Answer 6

They are made up of glycerol and 3 fatty acyl groups

Question 7

Triacylglycerols

Identify ester linkages

Answer 7

• The alcyl groups of three fatty acids are esterified to the three hydroxyl groups of glycerol.

Question 8

Triacylglycerols

Distinguish fats and oils and their origin and properties

Answer 8

i. Fats are solid at room temperature2/3 or 3/3 are saturated. High bp and mp
ii. Oils are liquid at room temperature. 2/3 or 3/3 unsaturated. Low bp

Question 9

Glycerophospholipids

Identify them

Answer 9

i. Have polar charged head groups. Made of phosphate and aa
Glycerol attached to acyl group
ii. They are amphipathic. Suitable for being in the membrane to form lipid bilayers

Question 10

Glycerophospholipids ? Identify individual components

Answer 10

ii. The black is the back bone and template. There are only two fatty acids.
**iii. Missing two other components ** look through the text

Question 11

Glycerophospholipids

Specificity of phospholipases

Answer 11

i. Phospholipases cleave glycerophospholipids at specific sites
ii. They are specific enzymes that cleave.

Question 12

Sphingolipids

Identify them

Answer 12

i. They are the backbone is sphingosine
ii. They replace glycerol in other amphipathic molecules

Question 13

Sphingolipids

Identify individual components

Answer 13

i. Have a polar head known as phosphocholine. Those that are not sugars are known as sphingomyelin
1. Some of the sphingolipids have monosaccharides as head groups. The name is cerebroside
a. There is no phosphate group
b. It can still be found in the membrane because it is still polar even though it is not charged.
2. Other have oligosaccharides as head groups. Known as the ganglioside
ii. It has two hydrophobic tails.

Question 14

Sphingolipids

Identify linkages in them

Answer 14

Amide bond- 2nd fatty acyyyl group
Phosphodiester bond

Question 15

Sphingolipids

Distinguish cerebrosides and gangliosides

Answer 15

Cerebrosides are sphingolipids that contain a sugar unit. The sphingolipids called gangliosides are more complex, usually containing a branched chain of three to eight monosaccharides and/or substituted sugars

Question 16

Cholesterol

Structure and properties

Answer 16

i. It is stored in the membrane and reduces its fluidity. Without it the bilayer will be very wobbly. Not amphipathic because the polar OH does not do much
ii. The most common is steroids
iii. The precursor to all other steroids
iv. Found in all animal cells
v. Takes 30 steps to make cholesterol
vi. It is flat and it can be inserted between the fatty tails near the head.

Question 17

Waxes

Components and function

Answer 17

i. Esters made of a fatty acid and a very long alcohol
ii. Function as waterproofing agents

Question 18

Lipids bilayer

Structure and properties

Answer 18

i. An array of amphipathic molecules whose tails associate with each other, out of contact with water, and whose head groups interact with water.
ii. It is a fluid structure
iii. There needs to be two hydrophobic tails. They are flexible and mobile

Question 19

Membrane proteins

types

Answer 19

i. Integral membrane protein: more common
1. Pores, pumps, channels
2. Need to be hydrophobic non polar
3. Single helix can exist as an integral membrane protein. It cannot exist as a beta
4. 7 helix’s: 7tm
ii. Peripheral membrane protein
iii. Lipid linked protein: 3rd common
1. They anchor to the lipid bilayer

Question 20

Membrane proteins

Properties

Answer 20

i. A membrane spanning alpha helix
ii. Membrane proteins can span the bilayer
1. Beta barrel
a. The longer they are they have a right-handed curvature
b. It allows things to move through
c. More suitable for receptors
2. Bacteriorhodopsin