Topic 9 - Lipids

Question 1

How does the polarity of a substance affect its solubility in water?

Answer 1

https://answers.yahoo.com/question/index?qid=20080225123318AAbREZ1

Question 2

List the biological functions of lipids

Answer 2

• Storage of energy
• Insulation from environment
• water repellant
• Buoyancy control and acoustics in marine mammals
• Membrane structure
• Cofactors for enzymes
• Signalling molecules
• Pigments Antioxidants

Question 3

Describe the importance of lipids

Answer 3

• Structural and function elements of membranes
• Precursors of bioactive compunds (e.g. hormones)
• Regulate enzymatic actions
• Contribute to membrane potential
• Are involved in cell signalling
• some disorders are due to abnormal lipid metabolism
• therapeutic function (steroids, prostaglandins)

Question 4

What are lipids?

Answer 4

Organic molecules that are characterised by low solubility in water e.g. hydrophobic

Question 5

Describe Fatty Acids (saturated & unsaturated)

Answer 5

• carboxylic acids w/ hydrocarbon chains containing b/w 4-36 carbons
• Saturated: no double bonds b/w C’s in the chain. Pack in orderly way
• Monounsaturated: one double bond b/w C’s in the alkyl chain. Pack less orderly due to d/bond kink
• Polyunsaturated: more than one double bond in the alkyl chain

Question 6

Fatty acid melting point increases with…. and decreases with…. and …..?
Solubility increases with….?

Answer 6

MP & solubility increase w/ chain length

MP decreases w/ unsaturation (number of d/bonds increases)

Question 7

Fatty acid nomenclature. Describe how to name FA’s

Answer 7

• Remember cis (same side) and trans (different side) -geometric isomers of each other
• Numbering begins at carboxyl C
• A FA 18 C atoms in length w/ no double bonds is 18:0
• A FA 18 C atoms in length w/ 1 double bond at C9 is 18:1(∆9)

Question 8

Describe naturally occuring FA’s and trans FA

Answer 8

• even no# of C’s
• 1st double bond occurs b/w C9 & C10
• additional d/bonds occur b/w C12-C13 & C15-C16
• D/bonds are in the Cis config (kink)
• Trans FA’s rarely occur in biological systems. Trans d/bond allows a FA to adopt an extended conformation

Question 9

Answer 9

2. Cis 16:1 (∆9)

Question 10

Describe triacylglycerols

Answer 10

• Nonpolar
• majority of FA’s are found as Triacylglycerols
• solid = fat
• liquid = oil
• primary storage form of lipids
• less dense than water and less soluble in water than FA

Question 11

Describe waxes

Answer 11

• Esters of long-chain saturated and unsaturated FA w/ long-chain alcohols
• Insoluble, high MP

Question 12

Describe polar lipids

Answer 12

• Amphipathic (hydrophobic & philic groups)
• Major component of biological membranes
• Properties of head group determine surface properties of membrane
• Form micelles, biylayers and liposomes

Question 13

Membrane lipid structure and function

(see diagram in answer)

Answer 13

Question 14

Membrane lipid structure and function

Describe Glycerophospholipids

Answer 14

• Primary constituents of cell membranes
• Head group is charged at physiological pH
• 2 FA form ester linkages w/ 1st & 2nd hydroxyl groups of L-glycerol-3-phosphate
• Unsat. FA are commonly found attached to C2

Question 15

Membrane lipid structure and function

Describe Phosphatidylcholine

Answer 15

• Major component of eukaryotic cell membranes

Question 16

Membrane lipid structure and function

Describe Sphingolipids

Answer 16

• Backbone is NOT glycerol, is a long chain amino alcohol sphingosine
• FA is joined to sphingosine via an amide linkage rather than ester linkage

Question 17

Membrane lipid structure and function

Describe Shingomyelin

Answer 17

• Abundant in myelin sheath of animal nerve cells
• Ceramide (sphingosine + amide-linked FA) + phosphocholine attached to alcohol
• Structurally similar to phosphatidylcholine

Question 18

How are blood groups determined?

Answer 18

by the type of sugars located on the head groups in glcyosphingolipids

Question 19

Answer 19

5. glycerophospholipid

Question 20

Answer 20

2. phosphosphingolipid

Question 21

Answer 21

3. carbohydrate residues

Question 22

Answer 22

3. glycosphingolipid

Question 23

Describe sterols and the role

Answer 23

• -steroid nucleus: 4 fused rings
• hydroxyl polar H group in A ring
• various nonpolar side chains
• Cholesterol and related sterols are preseny in membranes of most eularyotic cells

Question 24

List some signalling lipids

Answer 24

• Lipid soluble vitamins: A, D, E, K
• Ether lipids =>platelet activating factor
• Steroid hormones =>synthesised from cholesterol
• Essential FA =>Alpha-linoleic acid, linoleic acid

Question 25

Lipid quinones are antioxidants that help protect against oxidative damage. T or F?

Answer 25

True

Question 26

Polyketides are biologically active lipids w/ medicinal uses.

Answer 26

clap clap yay not sure if this is relevant

Question 27

Summary! READ IT FAGGOT

Answer 27