Bio Molecules

Question 1

How do hydrogen bonds form between water molecules

Answer 1

Water is polar: O more electronegative than H, so attracts electron density in covalent bond more strongly. Forms O (slightly negative) and H (slightly positive)

Intermolecular forces of attraction between lone pair on O - of one molecule and H + on an adjacent molecule

Question 2

State 7 biologically important properties of water

Answer 2

Reaches maximum density at 4 C
High surface tension
Incompressible
Metabolite for chemical reactions in the body
High specific heat capacity
High latent heat of vaporisation
Cohesion between molecules

Question 3

Why is incompressible nature of water important for organisms

Answer 3

Provides turgidity to plant cells

Provides hydrostatic skeleton for some small animals e.g. earthworms

Question 4

Explain why ice floats on water. Why is this important for organisms?

Answer 4

Ice is less dense than water because H bond hold molecules in fixed positions further away from each other

Insulated water in arctic climates so aquatic organisms can survive. Water acts as a habitat

Question 5

Why is the high surface tension of water important for organisms

Answer 5

Slows water loss due to transpiration in plants

Water rises unusually high in narrow tubes, lowering demand on root pressure

Some insects can skim across the surface of water

Question 6

Why is water an important solvent for organisms

Answer 6

Polar universal solvent dissolves and transports charged particles involved intra and extra cellular reactions

Question 7

Why are the high specific heat capacity and latent vaporisation of water important for organisms

Answer 7

Acts as temperature buffer which enables endotherms to resist fluctuations in core temperature to maintain optimum enzyme activity

Cooling effect when water evaporates from skin surface as sweat/ mouth when panting

Question 8

Describe the structure of alpha and beta glucose

Answer 8

Both hexose monosaccharides of 6 carbon with ring structure

Beta glucose has the hydroxide flipped

Question 9

Properties of alpha glucose

Answer 9

Small and water soluble = easily transported in bloodstream

Complementary shape to antiport for co-transport for absorption in gut

Complementary shape to enzymes for glycolysis = respiratory substrate

Question 10

Structure and function of starch

Answer 10

Storage polymer of alpha glucose in plant cells
Insoluble = no osmotic effect on cells
Large = does not diffuse out of cells

Question 11

Structure of amylose

Answer 11

1,4 glycosidic bonds
Helix with intermolecular H-bonds = compact

Question 12

Structure of amylopectin

Answer 12

1,4 and 1,6 glycosidic bonds
Branched = many terminal ends for hydrolysis into glucose

Question 13

Structure and function of glycogen

Answer 13

1,4 and 1,6 glycosidic bonds
Branched = many terminal ends for hydrolysis
Insoluble = no osmotic effect and does not diffuse out of cells
Compact

Question 14

Describe the structure and functions of cellulose

Answer 14

Polymer of beta glucose gives rigidity to plant cell walls (prevents bursting under turgor pressure, holds stem up)

1,4 glycosidic bonds
Straight-chain, unbranched molecule
Alternate glucose molecules are rotated 180
H-bond cross links between parallel strands from microfibrils = high tensile strength