UNIT 1: Molecules, Diet, Transport and
Health (New Specification)
, Molecules, transport and health
1.1 importance of water as a solvent in transport (incl its dipole nature)
Chemistry of water
Dipole in water Oxygen end: a slightly negative charge (δ−)
hydrogen end: a slightly positive charge (δ+)
- Surround and dissolve -ve or +ve ions
Hydrogen bond Cohesion: attraction between δ− and δ+ parts of neighboring water
molecules (dipolar)
- Form ice lattice → less dense than water → ice floats on
surface → insulate water below from freezing
Adhesion: attraction force between unlike molecules
Properties of water （9）
solvent Ionic substances: (can dissolve)
+ve charge of ions → small -ve charge of oxygen of water
-ve charge of ions → small +ve charge of hydrogen of water
Polar substances: (can dissolve)
Fairly small molecules with charges// separate into ion
Non-polar structure: (x dissolve)
No ions → form colloids → spread out in water
Mass flow in blood cause the substances to move
Good solvent → excellent transport medium and help transport
substances around bodies of organism
E.g. blood plasma carries substances in solution(e.g. glucose, oxygen)
High density In 4°C: maximum density
Water cools further → molecules become more widely spread → ice is
less dense than water (insulating layer)
- prevent water underneath from freezing
- Increase chances of survival of organism in water
- Maintain circulation in water → nutrient cycling and colonization
of water
High surface Attraction between water molecules (hydrogen bonds) > attraction
tension between air
Capillarity Water is polar → water molecules attracted to many surfaces
Water can enter narrow spaces, against pull of gravity
e.g: translocation of water through xylem
,Incompressible In transport system and support organism with hydrostatic skeleton
High specific heat Large increase in energy → small rise in temperature
capacity ∵ hydrogen bond needs lot of energy to separate them
Minimizes temperature fluctuation → Cellular biochemical reaction of
ectotherms
High heat of A large amount of heat can be lost with minimal loss of water →
vaporisation terrestrial ectotherms in temp control
High heat fusion Content of cell are less likely to freeze ∵ ice crystals are damaging
High transparency Allow deep penetration of light in water → provide producers solar
energy for photosynthesis
Organisms - Structure: high water content of protoplasm and organisms
- Solvent and medium for diffusion
- Reagent in hydrolysis
- Support for aquatic organisms
- Fertilisation by swimming gametes
- e.g. Dispersal of seeds, gametes and larval stage of aquatic
organisms and seeds of terrestrial species
Plants - Osmosis and turgidity: cell enlargement and support of plant
- Reagent in photosynthesis
- Transpiration and translocation of inorganic and organic
compounds
- Germination of seed: swelling and breaking open of testa
Animal - Transport
- Osmoregulation
- Cooling by evaporation (e.g. sweating, panting)
- Skeleton: hydrostatic skeleton (e.g. jellyfish)
- Protection (e.g. mucus, tear)
Explain how water is involved in transport of molecules in living organism
- Water is solvent
- Water is dipole
- Polar molecules can dissolve in water
- Example: glucose
Explain how dipolar nature of water is essential for living organism
- Water can form hydrogen bond
- Water is a solvent → ions/polar molecules can dissolve in water
- Form cohesion / adhesion
, 1.2
(i) difference between monosaccharides, disaccharides and polysaccharides (incl glycogen
and starch [amylose and amylopectin])
monosaccharides disaccharides polysaccharides
- Small molecules - Small molecules - Macromolecules
- Sweet taste - Sweet taste - Not sweet
- Soluble in water - Soluble in water - insoluble//slightly soluble
- Crystalline - Crystalline in water
- chain form// ring form - Non-crystalline
- Simple sugar By joining 2 By joining many
- Monomers of carbohydrates monosaccharides in monosaccharides in
condensation condensation
(CH2O)n n=3-9 C12H22O11 Cx(H2O)y
e.g. e.g.
Triose C3H6O3 Triose
Maltose Starch, glycogen, cellulose
phosphate
- α-glucose +
Pentose C5H10O5 Ribose, α-glucose - Chain may be folded →
deoxyribose - 1,4-glycosidic bond make them compact →
large amount of energy can
Hexose C6H12O6 Glucose, sucrose be stored
fructose, - α-glucose + fructose - Large size of molecule →
galactose - 1,2-glycosidic bond insoluble in water → exert
no osmotic influence and x
- Optical isomers (def.) : same Lactose easily diffuse out of the cell
molecular formula, but have - α-glucose + galactose - Made of many monomers
different structural formula - 1,4-glycosidic bond → allow storage of large
e.g. α-glucose, β-glucose, amounts of energy
galactose, fructose - Hydrolysis → converted to
their constituent
- α-glucose: -OH of carbon-1 below monosaccharide for use as
the plane of the ring// pointing respiratory substances
downward
- galactose: -OH of carbon 1 and 4
lie on opposite side
Reducing sugars Maltose and lactose: Non-reducing
reducing sugars
Sucrose: non-reducing
sugars
Starch Glycogen Cellulose
α-glucose α-glucose β-glucose
Health (New Specification)
, Molecules, transport and health
1.1 importance of water as a solvent in transport (incl its dipole nature)
Chemistry of water
Dipole in water Oxygen end: a slightly negative charge (δ−)
hydrogen end: a slightly positive charge (δ+)
- Surround and dissolve -ve or +ve ions
Hydrogen bond Cohesion: attraction between δ− and δ+ parts of neighboring water
molecules (dipolar)
- Form ice lattice → less dense than water → ice floats on
surface → insulate water below from freezing
Adhesion: attraction force between unlike molecules
Properties of water （9）
solvent Ionic substances: (can dissolve)
+ve charge of ions → small -ve charge of oxygen of water
-ve charge of ions → small +ve charge of hydrogen of water
Polar substances: (can dissolve)
Fairly small molecules with charges// separate into ion
Non-polar structure: (x dissolve)
No ions → form colloids → spread out in water
Mass flow in blood cause the substances to move
Good solvent → excellent transport medium and help transport
substances around bodies of organism
E.g. blood plasma carries substances in solution(e.g. glucose, oxygen)
High density In 4°C: maximum density
Water cools further → molecules become more widely spread → ice is
less dense than water (insulating layer)
- prevent water underneath from freezing
- Increase chances of survival of organism in water
- Maintain circulation in water → nutrient cycling and colonization
of water
High surface Attraction between water molecules (hydrogen bonds) > attraction
tension between air
Capillarity Water is polar → water molecules attracted to many surfaces
Water can enter narrow spaces, against pull of gravity
e.g: translocation of water through xylem
,Incompressible In transport system and support organism with hydrostatic skeleton
High specific heat Large increase in energy → small rise in temperature
capacity ∵ hydrogen bond needs lot of energy to separate them
Minimizes temperature fluctuation → Cellular biochemical reaction of
ectotherms
High heat of A large amount of heat can be lost with minimal loss of water →
vaporisation terrestrial ectotherms in temp control
High heat fusion Content of cell are less likely to freeze ∵ ice crystals are damaging
High transparency Allow deep penetration of light in water → provide producers solar
energy for photosynthesis
Organisms - Structure: high water content of protoplasm and organisms
- Solvent and medium for diffusion
- Reagent in hydrolysis
- Support for aquatic organisms
- Fertilisation by swimming gametes
- e.g. Dispersal of seeds, gametes and larval stage of aquatic
organisms and seeds of terrestrial species
Plants - Osmosis and turgidity: cell enlargement and support of plant
- Reagent in photosynthesis
- Transpiration and translocation of inorganic and organic
compounds
- Germination of seed: swelling and breaking open of testa
Animal - Transport
- Osmoregulation
- Cooling by evaporation (e.g. sweating, panting)
- Skeleton: hydrostatic skeleton (e.g. jellyfish)
- Protection (e.g. mucus, tear)
Explain how water is involved in transport of molecules in living organism
- Water is solvent
- Water is dipole
- Polar molecules can dissolve in water
- Example: glucose
Explain how dipolar nature of water is essential for living organism
- Water can form hydrogen bond
- Water is a solvent → ions/polar molecules can dissolve in water
- Form cohesion / adhesion
, 1.2
(i) difference between monosaccharides, disaccharides and polysaccharides (incl glycogen
and starch [amylose and amylopectin])
monosaccharides disaccharides polysaccharides
- Small molecules - Small molecules - Macromolecules
- Sweet taste - Sweet taste - Not sweet
- Soluble in water - Soluble in water - insoluble//slightly soluble
- Crystalline - Crystalline in water
- chain form// ring form - Non-crystalline
- Simple sugar By joining 2 By joining many
- Monomers of carbohydrates monosaccharides in monosaccharides in
condensation condensation
(CH2O)n n=3-9 C12H22O11 Cx(H2O)y
e.g. e.g.
Triose C3H6O3 Triose
Maltose Starch, glycogen, cellulose
phosphate
- α-glucose +
Pentose C5H10O5 Ribose, α-glucose - Chain may be folded →
deoxyribose - 1,4-glycosidic bond make them compact →
large amount of energy can
Hexose C6H12O6 Glucose, sucrose be stored
fructose, - α-glucose + fructose - Large size of molecule →
galactose - 1,2-glycosidic bond insoluble in water → exert
no osmotic influence and x
- Optical isomers (def.) : same Lactose easily diffuse out of the cell
molecular formula, but have - α-glucose + galactose - Made of many monomers
different structural formula - 1,4-glycosidic bond → allow storage of large
e.g. α-glucose, β-glucose, amounts of energy
galactose, fructose - Hydrolysis → converted to
their constituent
- α-glucose: -OH of carbon-1 below monosaccharide for use as
the plane of the ring// pointing respiratory substances
downward
- galactose: -OH of carbon 1 and 4
lie on opposite side
Reducing sugars Maltose and lactose: Non-reducing
reducing sugars
Sucrose: non-reducing
sugars
Starch Glycogen Cellulose
α-glucose α-glucose β-glucose
