2- biological molecules

Question 1

quant benedict’s test

Answer 1

1. measure time from immersing solution in water bath til first colour change produced
2. create standard solutions of known concs, and compare colour change to estimate conc

Question 2

biuret test for proteins

Answer 2

1. add equal volume sodium hydroxide to sample at room temp
2. add few drops dilute copper sulfate solution, swirl to mix
3. results

Question 3

polymer

Answer 3

large molecule compromising repeating monomer subunits
joined by condensation

Question 4

disaccharide

Answer 4

2 units of carbohydrate joined by condensation, glycosidic bond

Question 5

amylose + amylopectin structures (storage polymer of a-glucose in plant cells) large+insoluble

Answer 5

1-4 glycosidic bonds, unbranched, helical
1-6 glycosidic bonds, branched (hydrolysis to glucose)

Question 6

structure+function of glycogen

Answer 6

storage polymer of a-glucose in plant cells
1-4, and 1-6 glycosidic bonds
branched
insoluble
compact

Question 7

structure+function of cellulose(rigidity)

Answer 7

1-4 glycosidic bonds
straight-chain, unbranched molecule
alternate glucose molecules rotated 180°
H bonds form crosslinks between parallel strands form microfibrils=high tensile strength

Question 8

structure triglyceride

Answer 8

1 glycerol molecule forms ester bonds with 3 fatty acids(sat/unsat) via condensation reactions

Question 9

relation of structure triglyceride to function

Answer 9

energy storage: high energy-mass ratio
waterproofing: insoluble hydrocarbon chain- no effect on water potential of cells
thermal insulation: slow conductor of heat
buoyancy of aquatic animals: less dense than water
high melting point protects organs

Question 10

peptide bonds formed by

Answer 10

OH lost from carboxyl group
H from amine group
(condensation)
form peptide bond (-CONH-)

Question 11

globular vs fibrous proteins

Answer 11

globular=soluble+involved in physiological processes (Hb)
fibrous=insoluble+have structural role (collagen)

Question 12

features of globular protein (Hb)

Answer 12

• spherical+compact
  hydrophilic R groups face outwards+hydrophobic R groups inwards (water soluble)
  primarily physiological roles (metabolic processes)
  compact nature can transport more O2

Question 13

collagen structure

Answer 13

insoluble, long strands with high tensile strength
made of 3 polypeptide chains coiled to form triple helix
every 3rd amino acid=glycine - smallest
collagen molecules lie parallel to form collagen strands, held by staggered covalent bridges between lysine residues

Question 14

H bonding in water

Answer 14

• weak covalent bond between partially +ve and -ve charge on H atom of molecules, O atom of other
  polar+ H on one water molecule attached to lone pair of polar- O2 on other water molecule
  dipole- unevenly distributed charge
• each water molecule forms max 4 bonds

Question 15

water properties

Answer 15

high surface tension,
solvent for water soluble for transport,
high specific heat capacity,
latent heat vaporisation, boiling point,
ice less dense than liquid water

Question 16

general monosaccharide structure

Answer 16

(CH₂O)ₙ, where n = number of carbon atoms