Lecture notes Edexcel IAL Biology Unit-01 ( Note-02) (WBl11/01)

1

Molecule, Transport & Health

2) Explain the importance of water as a solvent in transport, including its dipole nature

- Water is vital to living organisms
 makes up 80% of a cell’s content
 water is a solvent which means some substances dissolve in it.
 Most biological relations take place in solution
 water transports substances. Substances can be transported more easily if they’re dissolved in a
solvent
- Water molecules have a simple structure
 one atom of oxygen joined to two atoms of hydrogen by shared electrons
 shared negative electrons are pulled towards the oxygen atom, other side of hydrogen is left slightly
positively charged
 unshared negative electrons on oxygen give it a slightly negative charge
 makes water a dipolar molecule
H
(negative charge on one side and
a positive charge on the other) O
H


3) Distinguish between monosaccharides, disaccharides and polysaccharides (glycogen and starch –
amylose and amylopectin) and relate their structures to their roles in providing and storing energy


Monosaccharides:
 Made up of 1 sugar molecule only
 Glucose, Fructose and Galactose
 No bond

Disaccharides:
 2 monosaccharides joined together
 condensation reaction
 joined by a glycosidic bond
 can be split through hydrolysis reactions

Maltose
 used for energy/food source in seeds
 alpha glucose + alpha glucose
Sucrose
 form in which sugars are transported in plants
 alpha glucose + fructose
Lactose
 carbohydrate source in mammalian milk
 alpha glucose + galactose

Polysaccharides:
 Many monosaccharides joined together
 Condensation reaction
MD. KAMRUL ALAM KHAN, B.Sc Honors in Chemistry (SUST), M.Sc in Chemistry (SUST), CCNA (All through first class), CELL: 01557704046,01719014276

, 2

 Glycosidic bonds
 Starch = polymer of glucose
 Glycogen = polymer for alpha glucose
 Cellulose = polymer of beta glucose

Starch and Glycogen:
o Energy stores
o Animals store glucose as glycogen
o Plants store glucose as starch
o Compact molecules
o Low solubility in water (don’t effect water concentration in cytoplasm, so doesn’t effect
osmosis)
o Large molecules
o Uncharged
o Easily broken down
 Starch ----------->maltose
Amylase
 Maltose ----------->glucose
Maltase

Starch:
 Make from 2 molecules in combination, amylose&amylopectin
 Both made from alpha glucose
 Found in amyloplasts inside plant cells for energy storage

Amylose

o Long unbranched chains
o 1-4 glycosidic bonds only
o coiled structure (compact)
o slow energy release because no branches, takes longer to break glycosidic bonds
 Amylopectin
o Long branched chains
o 1-4 and 1-6 glycosidic bonds
o side branches allow enzymes that digest the molecule to get at the glycosidic bonds more easily
(glucose is released faster)
5) Describe the synthesis of a triglyceride by the formation of ester bonds during condensation reactions
between glycerol and three fatty acids and recognize differences between saturated and unsaturated lipids

Triglycerides:
 Made up of glycerol and fatty acids
 Ester bonds
 Formed through condensation polymerization reaction
 Used for storage, insulation, protection in fatty tissue
 Cannot be mobilized quickly as they are insoluble
 Not good for quick energy requirements
 When oxidized they yield more energy then any other compound
 Good for energy storage

Saturated fatty acids
 High melting point
 Solid at room temp (butter)

MD. KAMRUL ALAM KHAN, B.Sc Honors in Chemistry (SUST), M.Sc in Chemistry (SUST), CCNA (All through first class), CELL: 01557704046,01719014276