Chapter 6: 6.1 Lipids

Question 1

Describe:

Lipids

Answer 1

• Very diverse
• Insoluble in water, but soluble in organic solvents
• Can be divided into three main biological groups

Question 2

State:

The 3 Main Biological Groups of Lipids

(Give examples)

Answer 2

1. Storage Lipids (Triacylglycerols)
2. Structural Lipids (Phospholipids, Sphingolipids, Glycolipids, Sterols)
3. Signaling Lipids (Eicosanoids, Steroids)

Question 3

What are fatty acids?

Answer 3

Building blocks for many different kinds of lipids

Question 4

Describe:

Structure of Fatty Acids

Answer 4

Contains:
* A carboxylic acid group
* A carbon chain (2-22 carbons long)
* An additional methyl group at the end

Question 5

What are the two forms of fatty acids?

Answer 5

1. Saturated: Only single bonds
2. Unsaturated: At least one double bond

Question 6

What type of unsaturated fatty acids are there?

Answer 6

The double bond holds a:
* Cis conformation
* Trans conformation

Question 7

Saturated fatty acids have been linked to…

Answer 7

Heart Problems

Question 8

Trans-fatty acids are linked to…

Answer 8

Cardiovascular disease

Question 9

True or False:

Fatty acids have to be linked together

Answer 9

False, they can remain individual as “Free Fatty Acids”

Question 10

How can fatty acids be linked together?

Answer 10

1. Linked together via ester bonds
2. Remain individual as “Free Fatty Acids”

Question 11

What are the two different ways of naming fatty acids?

Answer 11

1. Structural
2. Systematic (saturated and unsaturated naming schemes are different)

Question 12

Describe and give example(s):

Structural Naming of Fatty Acids

Answer 12

[# C] : [# of Double Bonds] (Δ^position of double bonds)
* i.e. for an fatty acid with 18 carbon (no double bonds: 18:0
* i.e. the same fatty acid with two double bonds: 18:2 (Δ^6,8)

Question 13

Describe and give example(s):

Systematic Naming of Saturated Fatty Acids

Answer 13

n-number of carbons-anoic acid
* i.e. for an fatty acid with 18 carbons: n-Octadecanoic acid

Question 14

Describe and give example(s):

Systematic Naming of Unsaturated Fatty Acids

Answer 14

cis-position of carbon-enoic acid
* i.e. for fatty acid with 18 fatty acids and a single double bond: cis-6-octadecenoic acid
* i.e. for the same fatty acid with two double bonds: cis-6,8-octadecadienoic acid

Question 15

What effect does the length of the carbon chain and number of double bonds have on the fatty acid?

Answer 15

1. Longer the carbon chain, the higher the melting point of the fatty acid
2. More double bonds, the lower the melting point of the fatty acid

Question 16

State:

Relationship between membrane fluidity, unsaturated fatty acids, and melting temperatures

Answer 16

1. A more fluid membrane = More unsaturated fatty acids = A lower melting temperature
2. A less fluid membrane = Less unsaturated fatty acids = A higher melting temperature

Question 17

Define:

Triacylglycerols (TAGs)

Answer 17

Energy reserves of the cell

Question 18

Describe:

TAGs

Answer 18

Made up of three fatty acids joined by glycerol

Question 19

Where are TAGs found?

Answer 19

Found in fat cells (adipocyte cells)

Question 20

Can TAGs be found mixed together?

Answer 20

Yes, TAGs can be found as simple or mixed

Question 21

Fats are varying compositions of…

Answer 21

Simple and mixed TAGs

Question 22

What does TAG composition dictate?

Answer 22

Melting temperature

Question 23

Define:

Glycerophospholipids

Answer 23

A structural membrane lipid

Question 24

True or False:

Glycerophospholipids are the most abundant lipids in cellular membranes

Answer 24

True, they are one of the most abundant

Question 25

# Describe: Glycerophospholipids

Answer 25

Has four components: 1. Fatty acids 2. Glycerol backbone 3. Phosphate 4. Head group

Question 26

What can the net charges for glycerophospholipids be?

Answer 26

1. Neutral (net neutral charge) 2. Anionic (net negative charge)

Question 27

# Define: Sphingolipids

Answer 27

The second most abundant membrane lipid * Plays a role in signal transduction and cell recognition

Question 28

# Describe: Sphingolipids

Answer 28

Structure is built off of sphingosine (an unsaturated 18-carbon amino alcohol)

Question 29

What is a sphingosine?

Answer 29

An unsaturated 18-carbon amino alcohol

Question 30

How are sphingolipids broken down?

Answer 30

Broken down in lysosomes through hydrolytic enzymes (Glucosidase)

Question 31

What can defects in sphingolipids or their metabolic processes lead to?

Answer 31

Neurological disorders * Gaucher disease etc.

Question 32

# Define: Cholesterol

Answer 32

The third most common lipid in cellular membranes * The most common steroid in mammals

Question 33

Can a steroid be synthesized? Can a steroid be broken down?

Answer 33

Yes it can be synthesized but not broken down

Question 34

What are the functions of cholesterol?

Answer 34

* Modulates membrane fluidity * Increases membrane packing * Reduces the permeability of the membrane

Question 35

# State: The relationship between: 1. Cholesterol 2. Membrane fluidity

Answer 35

The more cholesterol, the less fluid the membrane

Question 36

# State: The relationship between: 1. Temperatures 2. Membrane fluidity 3. Cholesterol

Answer 36

* At **low temperatures**, cholesterol **prevents freezing** by **increasing fluidity** * At **high temperatures**, cholesterol **reduces fluidity** by **adding rigidity**

Question 37

How are glycerophospholipids converted to fatty acids?

Answer 37

Phospholipases hydrolyze ester bonds in glycerophospholipids, coverting them to fatty acids

Question 38

# Define/describe: Steroid hormones

Answer 38

Circulate through the blood to targeted tissues and relay messages

Question 39

What is the base for all animal steroids?

Answer 39

Cholesterol

Question 40

How do phospholipids contribute to signalling?

Answer 40

Through local chemical signals

Question 41

# True or False: DIfferent phospholipases each break different bonds along the glycerol/carbon chain

Answer 41

True

Question 42

What are the signalling molecules cleaved by phospholipases?

Answer 42

Precursors of eicosanoids

Question 43

What are eicosanoid signalling pathways involved in?

Answer 43

* Inflammation * Heat * Pain * Smooth muscle contraction * Pregnancy etc.

Question 44

# Describe: Eicosanoid Signalling

Answer 44

Caused by the breaking of bonds in glycerophospholipids by enzymes