Lipids & Membrane Structure

Question 1

Describe the fluid-mosaic model

Answer 1

Islands of proteins in a sea of lipid

Question 2

How can you identify a plasma membrane?

Answer 2

Carbohydrates on the extracellular surface

Question 3

What are integral/intrinsic proteins?

Answer 3

Embedded in bilayer

Alpha helices or beta pleated sheets

Question 4

How are anchored proteins attached to membranes?

Answer 4

By covalently bound fatty acids

Question 5

How are peripheral/extrinsic proteins attached to the membrane?

Answer 5

Ionic interactions with integral proteins OR polar head group of phospholipids

Question 6

What are lipids soluble in?

Answer 6

Fat and organic solvents

Question 7

What are the functions of lipids? (4)

Answer 7

Energy store (eg. Triacylglycerol)

Precursors for vitamins and hormones (eg. Steroids)

Bile acids (eg. Cholic acid)

Membrane structure (phospholipid bilayer)

Question 8

What can the polar head group of a phospholipid be?

Answer 8

Serine

Choline

Ethanolamine

Inositol

Question 9

How is the polar head group attached to the glycerol backbone?

Answer 9

Through a phosphate group

Question 10

How are the fatty acids linked to the glycerol backbone?

Answer 10

Ester bonds

Question 11

What does amphipathic mean?

Answer 11

Has both hydrophilic and hydrophobic components

Question 12

What is the name of a glycerophospholipid with serine as its polar head group?

Answer 12

Phosphotidylserine

Question 13

What is the name of a glycerophospholipid with choline as its polar head group?

Answer 13

Phosphatidylcholine

Question 14

What is the name of a glycerophospholipid with ethanolamine as its polar head group?

Answer 14

Phosphatidylethanolamine

Question 15

What is the name of a glycerophospholipid with inositol as its polar head group?

Answer 15

Phosphatidylinositol

Question 16

Give an example of a phospholipid without a glycerol backbone

Answer 16

Sphingomyelin

Question 17

What is sphingomyelin made up of?

Answer 17

Choline and ceramide (sphingosine with a fatty acid chain)

Question 18

Give three examples of saturated fatty acids (with ratios)

Answer 18

Stearic acid (18:0)

Palmitic acid (16:0)

Myristic acid (14:0)

Question 19

Give an example of a monounsaturated acid (with ratio)

Answer 19

Oleic acid (18:1)

9

Question 20

Give an example of a polyunsaturated fatty acid (with ratio)

Answer 20

Arachidonic acid (20:4)

5, 8, 11, 14

Question 21

What is the structure of cholesterol?

Answer 21

Hydroxyl group

Rigid planar steroid ring structure

Hydrocarbon tail

Question 22

What is fluidity?

Answer 22

The ease with which lipid molecules move about in the plane of the bilayer

Question 23

Which lipids are found in each of the layers of the cell membrane?

Answer 23

Extracellular: phosphatidylcholine and sphingomyelin

Intracellular: phosphatidylserine and phosphatidylethanolamine

Question 24

Explain how shorter fatty acid chain lengths affect membrane fluidity.

Answer 24

Reduced tendency for hydrocarbon chains to interact

More fluid

Question 25

Explain how having unsaturated fatty acid chains affects membrane fluidity.

Answer 25

Double bonds create “kinks” Less stable van der Waals forces with other phospholipids More fluid

Question 26

Explain how high cholesterol affects membrane fluidity.

Answer 26

Restricts random movement of polar heads Less fluid

Question 27

What are cholesterol-rich regions called?

Answer 27

Lipid rafts

Question 28

What are the essential fatty acids?

Answer 28

Linoleic acid (18:2) 9, 12 Linolenic acid (18:3) 9, 12, 15

Question 29

Where do we get our essential fatty acids?

Answer 29

Dietary fat

Question 30

Why are essential fatty acids important?

Answer 30

Give rise to arachidonic acid Used to form eicosanoids and important for regulating membrane fluidity

Question 31

What does a lack of essential fatty acids cause? (4)

Answer 31

Scaly dermatitis Hair loss Impaired wound healing Compromised inflammatory and immune responses