2 - Lipids and Proteins

Question 1

Structure of triglycerides?

Answer 1

Storage molecules
Glycerol 3 fatty acids tails - have long tails made of hydrocarbons which are hydrophobic
Ester bonds between
Formed by condensation reaction producing triglyceride and 3 water
insoluble in water
O =C - R
-OH (O attached to C)

Question 2

Saturated lipids

Answer 2

No C=C bonds present
Fatty acid chains are straight
Solid at room temperature
Animal fats

Question 3

Unsaturated lipids

Answer 3

C=C bonds present
Polyunsaturated lipids when more than one
Fatty acid chains have a kink
Liquid at room temp
Plant oils

Question 4

Structure of phospholipids

Answer 4

2 fatty acids
1 glycerol
1 phosphate group
Main component of cell membranes
Hydrophobic tails
Hydrophilic head

Question 5

Emulsion test for lipids

Answer 5

If substance solid, crush up
Add few drops of ethanol
Shake the mixture
Pour Water
If emulsion forms (milky white precipitate) then lipid present

Question 6

What are proteins?

Answer 6

Polymer molecules made up of one of more polypeptide chains

Question 7

Structure of amino acids?

Answer 7

H
NH3 CO(OH)
(Amino group) (Carboxylic acid group)

                            R Group

Question 8

Formation of peptides?

Answer 8

Two amino acids bonded by peptide bond in condensation reaction.
C-N bond
H20 Produced

Question 9

Polypeptides

Answer 9

Amino acids bonded together in a straight chain
Folded into a specific 3D shape
4 levels: Primary, secondary, tertiary and quaternary

Question 10

Primary proteins

Answer 10

The sequence of amino acids in a polypeptide chain (the primary structure determines the tertiary structure)

Question 11

Secondary proteins

Answer 11

The coiling (alpha helix) or folding (Beta-pleated sheet) of a polypeptide chain with the addition of hydrogen bonds

Question 12

Tertiary proteins

Answer 12

The further coiling or folding of a polypeptide chain with the addition of hydrogen, ionic and disulfide bonds and hydrophobic interactions to create a specific 3D shape

Question 13

Quaternary proteins

Answer 13

More than 1 polypeptide chain linked together

Question 14

Bonding in proteins

Answer 14

Hydrogen between O and H in all levels of structure
Hydrophobic interactions between non-polar sections
Disulfide bonds, strongest bond, between cystine amino acids

Question 15

Fibrous proteins

Answer 15

Parallel polypeptide chains held together by cross links
Long, rope like fibres with high tensile strength
Collagen - tendons and cartilage
Keratin - Hair and nails
Silk - spider webs

Question 16

Globular proteins

Answer 16

Spherical shapes caused by tightly folded polypeptide chains, hydrophillic parts on the outside, hydrophobic on the inside, soluble in water
Transport proteins
Enzymes
Hormones

Question 17

Biuret test for proteins

Answer 17

Add few drops of sodium hydroxide solution
Add bruit reagent to solution
Mix gently
If protein present, purple or lilac
Blue if nothing present

Question 18

What denatures proteins

Answer 18

Temperature and pH

Question 19

Use of Triglycerides

Answer 19

Long hydrocarbon tails - lots of chemical energy - released when broken down - twice as much energy per gram as carbohydrates
Insoluble - dont affect water potential - form insoluble droplets due to hydrophobic tails