Biological Molecules

Question 1

Describe the polarity of water?

Answer 1

Water is a polar molecule due to the uneven distribution of charge within the molecule. Hydrogen atoms are more positive than oxygen causing one end to be more positive than the other

Question 2

How do hydrogen bonds form between water molecules

Answer 2

Oxygen is more electronegative than Hydrogen so attracts electron density in a covalent bond more strongly. There are intermolecular forces of attraction between a lone pair on O S- on one molecule and H S+ on adjacent molecule

Question 3

List 7 biologically important properties of water

Answer 3

• reaches max density at 4 degrees
  high surface tension
  incompressible
  metabolite/ solvent for chemical reactions in the body
  high specific heat capacity
  high latent heat of vaporisation
  cohesion between molecules

Question 4

Why is the incompressible nature of water important

Answer 4

Provides turgidity to plant cells
Provides hydrostatic skeleton for some animals

Question 5

Why is high surface tension important for organisms

Answer 5

Slows water loss due to transpiration in plants
Water rises 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 in intra and extracellular reactions

Question 7

Describe water in metabolic reactions

Answer 7

Water is a metabolite in reactions like condensation (forming bonds) and hydrolysis (breaking bonds)

Question 8

Describe water’s specific heat capacity

Answer 8

High specific heat capacity - lots of energy is needed to warm water up therefore minimising temperature fluctuations. Organisms don’t waste too much energy thermoregulating

Question 9

Describe water’s latent heat of vaporisation

Answer 9

Relatively large latent heat of vaporisation meaning evaporation of water causes a cooling effect with little water loss

Question 10

Describe the cohesion between water molecules

Answer 10

Strong cohesion between molecules enables transport of water in tube like transport cells. Cohesion supports columns of water. Surface tension at the water air boundary is high

Question 11

Describe the density of water

Answer 11

Ice is less dense than water and floats on top creating an insulating layer. Increases the chances of survival of organisms in large bodies of water as it prevents them from freezing

Question 12

Define monomers

Answer 12

Smaller units from which larger molecules are formed

Question 13

Examples of monomers

Answer 13

Monosaccharides (glucose, fructose, galactose), amino acids and nucleotides

Question 14

Define polymers

Answer 14

Molecules made from monomers joined together

Question 15

Examples of polymers

Answer 15

polysaccharides, proteins, DNA/ RNA

Question 16

What reaction joins monomers by chemical bonds and involves the elimination of a water molecule

Answer 16

A condensation reaction

Question 17

What reaction is when water is added to break a chemical bond between two molecules

Answer 17

A hydrolysis reaction

Question 18

Name the elements found in carbohydrates, lipids, proteins, and nucleic acids

Answer 18

Carbohydrates and Lipids - C, H, O
Proteins - C, H, O, N, S
Nucleic Acids - C, H, O, N, P

Question 19

Structure of alpha glucose

Answer 19

Hexose monosaccharide. Hydrogen above first carbon

Question 20

Properties of alpha glucose

Answer 20

Small and water soluble - easily transported in the bloodstream
Complementary shape to antiport for co transport and absorption in the gut
Complementary shape to enzyme for glycolysis

Question 21

Name 3 disaccharides

Answer 21

Maltose - glucose + glucose
Sucrose - glucose + fructose
Lactose - glucose + galactose

Question 22

Structure of beta glucose

Answer 22

Hexose monosaccharide. Hydroxide group above first carbon

Question 23

What do carbohydrates consist of

Answer 23

Carbon, hydrogen and oxygen
Long chains of sugar units called saccharides

Question 24

What are the three types of saccharides

Answer 24

Monosaccharides, disaccharides and polysaccharides

Question 25

What can monosaccharides do when they join together

Answer 25

Form diaccharides and polysaccharides by glycosidic bonds which are formed in condensation reactions

Question 26

Structure of Starch

Answer 26

Amylose - 1,4 glycosidic bonds, intermolecular H bonds, compact, linear and forms a helix shape
Amylopectin - 1,4 and 1,6 glycosidic bonds, branched, many terminal ends for hydrolysis into glucose

Question 27

Function of Starch

Answer 27

storage polymer of alpha glucose in plants, insoluble so no osmotic effect on cells, large so cannot diffuse through cells

Question 28

Structure of glycogen

Answer 28

1,4 and 1,6 glycosidic bonds, branched so many terminal ends for hydrolysis, compact, insoluble so no osmotic effect on cells and does not diffuse

Question 29

Function of glycogen

Answer 29

Main storage polymer of alpha glucose in animals

Question 30

Structure of cellulose

Answer 30

1,4 glycosidic bonds, beta glucose, straight chain, unbranched molecule, alternate glucose molecules rotate 180 degrees, H bond crosslinks between parallel chains form microfibrils so high tensile strength

Question 31

Function of cellulose

Answer 31

polymer of beta glucose for rigidity in plant cell walls. prevents cells bursting under turgor pressure, holds stem up.

Question 32

How are triglycerides formed

Answer 32

Condensation reaction between 1 molecule of glycerol and 3 fatty acids which form ester bonds.