To understand Biology, one must first understand the basic chemistry of it - which is relatively simple as opposed to normal chemistry. All you have to know about is Carbohydrate, Lipid, Protein and Water.

1. BIOLOGY AS LEVEL
REVISION 01

2. 1. BIOLOGICAL
MOLECULES
And the Components of Life

3. Definitions
 Organic Molecules: Any Compound containing Carbon
and Hydrogen
 Macromolecule: A large biological molecule
 Monomer: A relatively simple molecules used as a
building for polymer
 Polymer: A giant molecule made up of many subunits of
polymer joined together
 Polarity: The uneven distribution of charge

4. Introduction
 4 Biological Molecules: Hydrogen, Carbon, Oxygen
 Carbon – is able to join with up to 4 atoms – very
versatile and stable – form chains/ ring structures
 Monomer: A simple molecule – basic building block e.g.
Monosaccharide, Nucleotides, amino acids
 Polymer: Many repeating subunits of monomers joined
together e.g. Polysaccharides, Nucleic Acid, Proteins

5. Ionic vs. Covalent bond
 Ion: Molecules that are
charged
 Ionic do not share electron
 One donates electron to
fulfill the other’s octate
 One becomes –
 The other becomes +
 Hence, they become charges
 When they share electrons
 When one molecule shares
certain electrons with the
other – both using them – to
create a bond
 Equally distributed – non-
polar
 Slightly charges - polar

7. The Hydrogen Bond
 The small charge between the H minus and Oxygen
plus between different water molecules
 This can work with any of the 3: F, O, N

8. About Carbon
 Doesn’t take up a lot of space
 Can combine with a lot of other molecules
 Need 4 extra electrons
 Also not too reactive

9. The Properties of Water
 Hydrogen bonding quality
 Solvent property – Derived from hydrogen bond
 Thermal Properties – High specific heating capacity/
High heat of vaporization

10. Solvent Property
 Positively charged part of ions are attracted to the
negatively charged part of the water molecules –
causing hydrophilic substance to dissociate
 The substance becomes hydrated
 Dissolve: Glucose, amino acid, hemoglobin, enzymes,
hormones, vitamins, respiratory gases

11. CARBOHYDRATE

12. Carbohydrates
 Carbon, Hydrogen, Oxygen
 Used as a source of energy in the form of
glucose
 Stored in the form of starch/ Glycogen
 Structure in the form of cellulose
 (CH2O)n

13. Monosaccharide
 Simple Sugar – Triose, Pentose,
Hexose
 Pentose (Ribose, Deoxyribose)
 Hexose (Glucose, Fructose,
Galactose)
 Pentose and Hexose have long
carbon chains that can form a
stable ring structure
 2 forms of chemicals – isomers
(Alpha and Beta)

14. Alpha and Beta
 Carbon atom number 1 – has hydroxyl group
 Hydroxyl group could be above or below the ring
 If above the ring: Beta glucose
 If below the ring: Alpha glucose

15. Monosaccharides for
energy
 The Carbon-hydrogen bond is large
 Can be broken down to make energy
 Assist the making of ATP

16. Disaccharide
 Joined by 1,4 glycosidic bond – condensation
reaction (loses H2O)
 Split by the adding of water – hydrolysis (gains H2O)
 Maltose = Alpha Glucose + Alpha Glucose
 Sucrose = Alpha Glucose + Fructose
 Lactose = Beta Galactose + Alpha Glucose

17. Polysaccharides
 Polymer: Many repeating subunits of monomer
joined together to form a large molecule
 Many monosaccharide form polysaccharide
 Starch, Glycogen, Cellulose
 These are not sugars

18. Starch
 Mixture of Amylopectin and Amylose
 Amylose: Many alpha-glucose linked by 1.4 – helical
structure (makes it compact)
 Amylopectin: Amylose with shorter chains of alpha
glucose with 1,6 glycosidic branches

20. Glycogen
 Amylose + Amylopectin – with more 1,6 chains
 Shorter amylose chains
 Allow it to be less compact – quicker releases of
energy in animal bodies

21. Cellulose
 A polymer of beta-glucose
 To connect by 1,4 glycosidic bond, one glucose of a
pair has to flip 180 degrees
 This arrangement creates weak hydrogen atom with
an oxygen molecule in the same cellulose
 The most abundant molecules in nature (in cell wall,
also hard to break down)

22. Cellulose
 50 – 60 cellulose molecules are cross-linked side by
side by hydrogen bond to form microfibrils
 Microfibrils bundled up to form a fiber

26. LIPID

27. Lipids
 Contain: Carbon, Hydrogen, Oxygen
 Except for glycerol – insoluble in water
 Dissolve in Chloroform/ Benzene
 Less dense than water

28. Lipids
 Triglyceride
 Phospholipids
 Cholesterol

29. Triglyceride
 Glycerol (Three-carbon Alcohol)
 Fatty Acid (Acid)
- A carboxyl group with carbon
skeleton

31. Triglyceride
 Combination of glycerol(alcohol) and 3 fatty acid
molecules
 Glycerol: A three carbon alcohol
 Ester bond is formed in the condensation between
an alcohol group and an acid group
 Can have tails that are 14 – 22 carbon atoms long
 Long tails – insoluble in water

32. Saturated/ Unsaturated
 Fatty acid chains with double
bonds – are not saturated
with hydrogen- they are bent
in the middle – is called
UNSATURATED (better for
your body – liquid at room
temperature hence
accumulate less)
 Fatty acid chains with no
double bond – are saturated
with hydrogen – is called
SATURATED

33. Functions of Lipids
 Energy Source (soluble/mobile respiratory substrate) –
Glycerol + Fatty Acid
 Insoluble energy store – Fats/ Oils
 Thermal insulation – fats
 Buoyancy – fats
 Protection for vital organs – fats
 Waterproofs – waxes for plants (Suberin, cutin)
 Solvent for certain vitamins (A,D,E,K)
 Cell membranes (Phospholipids, glycolipids, cholesterol)

34. Biological functions of
Triglycerides
 Fat yields more energy than
carbohydrates
 They also yield water in
metabolic reaction – desert
animals
 Fats of whales in Arctic and
Antarctic regions
 Blubber of seals/ walrus –
help them float
 Mammalian kidney has fat

35. PROTEIN

36. Proteins
 C, H, O, N
 20 different types
 Bond: Peptide bond
 (Formed by condensation)
(broken by hydrolysis)
 One’s Carboxyl loses a hydroxyl group, the other’s
Amine loses a hydrogen atom
 A single protein can have 1 polypeptide chains or many
combined
 Synthesized in ribosomes, broken down (hydrolyzed) in
the stomach by protease

37. Amino Acid
 Organic molecules with carboxyl and amino groups
 They differ in properties according to its R-group
 E.g. Glycine – has hydrogen R-group

38. The Primary Structure
 A chain/ sequence of amino acid linked by peptide
bond forming a polypeptide
 A change in one amino acid can make a different
protein

39. The Secondary Structure
 The structure of protein caused by the regular coiling or
folding of a polypeptide or protein.
 The chain coils up in a corkscrew shape – due to the hydrogen
bond between the oxygen of the carboxyl group with the
hydrogen of the amine group 4 places ahead of it. – a-helix
 Problems
 Electrostatic charges
 Proline
 Temperature

40. The Secondary Structure
 Beta Pleated Sheet
 Polypeptide chains – adjacent
 Parallel or anti-parallel – R groups alternate pointing up/ down
 Held together via hydrogen bond

42. The Tertiary Structure
 Fibrous:
Do not fold upon itself, long rod, strong structure,
typically insoluble, (collagen, keratin)
 Globular:
Polypeptide backbone folds upon itself, compact and
spherical, typically water soluble (Hemoglobin,
Enzymes)

43. Globular Protein

44. Globular Protein

45. Globular Protein
Hydrogen
bond
between R
groups side
chains
Disulfide
bond –
between
Sulfur
Ionic bond
Between
ionized
carboxyl,
Amine
groups

46. Fibrous Protein
1. Sequence of polypeptide form an helical shape –
not tightly wounded.
2. 3 of these chains are tied around each other by
hydrogen bond and some covalent bond
3. Glycine is at every 3rd amino acid – the small size
allow for tight wounding
4. They lie side by side – cross links are created – out
of step to increase strength – strong bundle: fibril
5. Many fibrils = fibers

47. Uses of Proteins
 Transport – Hemoglobin, Myoglobin – transport protein in cells
 Storage – Ovalbumin
 Enzymes
 Hormones
 Immune system – Antibodies
 Parts of the phospholipid membrane
 Structure – fibrous protein, collagen, keratin
 Muscle – Actin, Myosin