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Lecture notes Edexcel IAL Biology Unit-01 ( Note-02) (WBl11/01)
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Edexcel IAL Biology Unit-01 ( Note-02)
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1Molecule, 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
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