Lipids

Question 1

What are lipids?

Answer 1

1.Water-insoluble molecules that can be extracted from tissues by non polar solvents

2.They are not polymers

Question 2

What reaction releases large amount of energy in lipids

Answer 2

Oxidation of lipids releases large amount of energy

Question 3

Four functions of lipids

Answer 3

1.Energy storage
2.Insulation
3.Cell membrane structure
4.Communication

Question 4

5 Types of Lipids

Answer 4

1.Fatty acids
2.Triglycerides (TAGs)
3.Phospholipids
4.Sphingolipids
5.Steroids (Cholesterol)

Question 5

Fatty Acids exist either as?

Answer 5

FAs exist either as free or esters (TAGs)

Found at high levels in plasma during fasting

Question 6

How do FAs circulate in the body?

Answer 6

They circulate bound to Albumin

Question 7

Empirical formula for FAs

Answer 7

(H(CH2)nCOOH)

Question 8

How long are FA chains usually?

Answer 8

4-40 carbons long

Also have an amphipathic nature (hydrophilic/phobic)

Question 9

What parts of FAs are hydrophilic/phobic?

Answer 9

The carboxyl head is Polar
The fatty acid chain is non polar

Question 10

What number carbon FAs are most common in plants and animals?

Answer 10

C16 and C18

Question 11

Difference between saturated and unsaturated fatty acids

Answer 11

1.Saturated fatty acids have no double bonds and are solid at room temp (animals, humans)

2.Unsaturated fatty acids have one or more double bonds cause chain to bend and are liquid at room temp (fish, oils)

Question 12

Are fatty acids common in nature?

Answer 12

Fatty acids are rare to find in nature and a lot of the times combined to glycerol via condensation reactions to form an ester bond (TAG)

Question 13

What percentage of lipids consumed are TAGs? Where are they also produced?

Answer 13

90%

The liver also produces them which is transferred to tissues in lipoproteins

Question 14

TAGs, which are fats, are hydrolysed via what enzyme?

Answer 14

Lipase separates FAs and Glycerol

Question 15

Can FAs in TAGs be different?

Answer 15

Yes they can be homogenic or heterogenic FAs within the TAG

Question 16

What are the functions of fats within mammals

Answer 16

They are stored in adipose tissue and cushion vital organs and insulate the body

N.B They contain twice the energy of polysaccharides like glycogen

Question 17

What is a phospholipid made of?

Answer 17

2 FAs + glycerol + phosphate group

Question 18

What two forms of complex lipids can phospholipids form?

Answer 18

1.sphingolipid

2.phosphoglyceride

Question 19

How long are FAs on Phospholipids?

Answer 19

14-24 Carbons long

Question 20

What is the PL called when the R group on the Phosphate head is choline?

Answer 20

Glycerophosphatiydlcholine

Question 21

What does GPI stand for?

Answer 21

Glycerophosphatidylinositol

Question 22

What are GPIs and what do they do?

Answer 22

They are glycolipids attached to proteins as membrane anchors (role in cell signalling)

Question 23

What is Sphingosine and what is the major difference in a Sphingolipid?

Answer 23

Sphingosine is a C18 amine alcohol

A sphingolipid has a Sphingosine instead of glycerol and a FA and R group are added to it

Question 24

What are three functions of a Sphingolipid

Answer 24

1.Cell recognition
2.Signalling
3.Lipid Rafts

Question 25

What is the major glycolipid in humans?

Answer 25

Glycosphingolipids are the major glycolipids in humans

Question 26

What is the major glycolipids in humans?

Answer 26

The major glycolipids in humans are glycosphingolipids

Question 27

What Sphingolipid can be found at the myelin sheath?

Answer 27

Sphingomyelin

Question 28

What is the main steroid in mammals and how is it gained?

Answer 28

Cholesterol is the main steroid of mammals and its made in the liver and some from diet

Question 29

What is the precursor of all steroids?

Answer 29

Cholesterol is the precursor

Question 30

Where is cholesterol mainly found?

Answer 30

90% of cholesterol is found within the cell membrane (150g total in the average body)

Question 31

What is a major control point in the synthesis of cholesterol?

Answer 31

HMG coA Reductase is a major control point which statin drugs can inhibit this enzyme to stop cholesterol synthesis

Question 32

What are steroids?

Answer 32

Lipids with a common carbon skeleton of four fused rings which depend on the functional group attached to the rings

Question 33

Name four main steroid categories?

Answer 33

1.glucocorticoids 2.mineralocorticosteroids 3.Oestrogen,androgen,and progestogens 4.Base for Bile acids

Question 34

What are most lipids digested as?

Answer 34

Most are digested as triglycerides which are insoluble and difficult to digest so the solution is bile

Question 35

How are lipids transport?

Answer 35

Dietary lipids are exogenously transported from the intestines to the liver Then endogenously transported from the liver peripheral tissues (ALL via alipoproteins which wrap around the lipid)

Question 36

Rank lipoproteins classes from lowest to highest

Answer 36

1.Chylomicron 2.VLDL 3.LDL 4.HDL

Question 37

Rank lipoprotein classes from lowest to highest

Answer 37

1.chylomicron 2.VLDL 3.LDL 4.HDL

Question 38

What do lipids move around as?

Answer 38

Lipids are metabolised and carried as lipoproteins