Lipids

Question 1

Name 3 functions of lipids

Answer 1

membranes, energy stores and signalling

Question 2

Name 6 types of lipids

Answer 2

fatty acids, triaglycerols, phosphoacylglycerols, sphingolipids, glycolipids, steroids

Question 3

What defines whether the hydrocarbon bonds are cis or trans?

Answer 3

Whether the H in the C=C bond is on the same side

Question 4

What side effects do cis bonds have on a fatty acid?

Answer 4

Cause a kink causing wore loose packing and hence a lower boiling point

Question 5

How would a C18 (octadecane) fatty acid be named if it were a) saturated b)unsaturated c) Unsaturated with a 2C=C d)Unsaturated with 3 C=C

Answer 5

a) octadecanoic acid
b) octadenoic acid
c) octadecadienoic acid
d) octadecatrienoic acid

Question 6

What are triaglycerols?

Answer 6

Fatty triesters of glycerol

• highly efficient energy storage
• can be simple/mixed (> 1 type of amino acid)
• liquid if unsaturated, saturated are solid

Question 7

What is the structure of phospholipids?

Answer 7

• Fatty acid tails
• Platform of glycerol or sphingocine
• Phophate binded to alcohol (head)

Question 8

What are the components of phophoglycerides?

Answer 8

• Phospholipis which contain glycerol
• 2 fatty acids + phosphorylated alcohol
• Hydroxyl gorup at C1 and C2 of glycerol are esterified to carbonyl groups of fatty acids
• Hydroxyl group at C3 is esterified to a phosphoric acid

Question 9

Where are sphingolipids commonly found?

Answer 9

cell membrane

Question 10

What are the components of the backbone of sphingolipids?

Answer 10

sphinosine - amino alcohol with large unsaturated hydrocarbon tail
ceramide - N-acylated derivative

Question 11

Describe the structure of sphingomyelin, where is it commonly found?

Answer 11

• Amino group linked to fatty acid via an amide bond
• Hydroxyl group of sphingosine esterified to phosphocholine/phosphoethanolamine
• found in the myelin sheath

Question 12

What is the simplest (sphingo)glycolipid ?

Answer 12

• cerebrosides
• ceramides with a sugar head group
• found in neuronal cell membranes in the brain

Question 13

What are the most common (sphingo)glycolipids?

Answer 13

• Glangosides
• Ceramide polysaccharides with at least one sialic acid residue
• primary components of cell surface membranes which act as receptors

Question 14

Describe the properties of steroids

Answer 14

• Derivatives of cyclopentanoperhydrophenanthrene (4 fused rings)
• hydrocarbon tail at one and and a hydroxyl group at the other
• Ring structure confers rigidity
• Colesterol is a common precurosor

Question 15

What are the properties of the phospholipid bi-layer membrane?

Answer 15

• Non-covalent interactions (H-bonds between heads, can der Waals interactions between tails)
• Thickness of 60-100 A
• Electrically polarised
• Lateral diffusion faster than transverse diffusion