1.0: molecules of life · 1.0: molecules of life 1.2 carbohydrates •a) state the classes of...

1.1 WATER1.2 CARBOHYDRATES1.3 LIPIDS1.4 PROTEINS1.5 NUCLEIC ACIDS

1.0: MOLECULES OF LIFE

BIOLOGY

At the end of this topic, students should be able to:


• a) State the structure and properties of water molecules.

• b) Relates the properties of water and its importance.

1.1 Water

WATER MOLECULE

Water has a simple molecular structure. It is composed of

one oxygen atom and two hydrogen atoms.

1.1

WA

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RWATER

1.1

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RWATER MOLECULE

▪ Oxygen also has two unshared pairs of electrons. Thus, oxygen

is an "electronegative“ compared with hydrogen.

▪ A hydrogen atoms

combined with the oxygen

atom by sharing of

electrons.

▪ Each hydrogen atom is covalently bonded to the oxygen via a

shared pair of electrons.

Angle of water atoms

1.1

WA

TE

RPolarity of water

Polar molecule : A molecule with uneven distribution of charges in different regions of the molecules. (Campbell 9th edition)

Oxygen region

has partial negative

charge.

Hydrogen has a

partial positive

charge.

Partially negative side

of water molecule

Partially positive side

of water moleculeBall-and-Stick Model

1.1

WA

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RBonds of water molecules

Universal solvent due to its polarity/

polar molecules

Low viscosity

High specific heat capacity

High latent heat of vaporization

High surface tension

Maximum density at 4°C

PROPERTIES OF WATER1

.1 W

AT

ER



1.2 Carbohydrates

• a) State the classes of carbohydrates such

as monosaccharides, disaccharides and polysaccharides.

• b) Illustrate the formation and breakdown of maltose.

• c) Compare the structure and function of starch, glycogen and cellulose.

1.2

C

AR

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ES

Organic compounds containing C, H and O (ratio of 1:2:1)

• Empirical formula :(CH2O)n

CARBOHYDRATES

1.2

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MONOSACCHARIDES

• Characteristics:

• Small

• Sweet tasting

• Primary source of energy

• Readily soluble in water

• Reducing sugar

• Crystalline

• Simple sugar

Carbon backbone of 3 to 6 carbon atoms.

Have a carbonyl group and multiple hydroxyl groups.

ALDOSE KETOSE

CARBONYL

group is located

on the terminal

carbon in

the chain.

CARBONYL

group is located

on a carbon

That is not

on the end

of the chain.

Carbonyl group : C = OHydroxyl group : OH

All carbon atoms except

one have a hydroxyl

group attached.

1.2

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MONOSACCHARIDES

DISACCHARIDES

1.2

C

AR

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HY

DR

AT

ES Formed by condensation reaction of TWO monosaccharides.

Bond linking : glycosidic bond.

• Water-soluble

• Sweet tasting

• Readily soluble in water

• Reducing sugar(maltose, lactose)

• Crystalline

Characteristics:• Disaccharides:

• Maltose

• Sucrose

• Lactose

DISACCHARIDES

1.2

C

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ES

MALTOSE - condensation1.2

C

AR

BO

HY

DR

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ES

DISACCHARIDES

MALTOSE - hydrolysis1.2

C

AR

BO

HY

DR

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ES

DISACCHARIDES

POLYSACCHARIDES1.2

C

AR

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HY

DR

AT

ES Polymers of monosaccharides made up of condensation of

hundreds of monosaccharides

Characteristics:

- Large and complex

- Most are not soluble in water

- Not sweet tasting

- Food storage

• Polysaccharides:

• Starch

• Glycogen

• Cellulose

POLYSACCHARIDES1.2

C

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HY

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STARCH

• Condensation of α-glucose subunits

• Used for energy storage in plants

• A linear unbranched polymer

•Glucose units joined by α-1,4 glycosidic bonds

• Made up of two components :

1. Amylose

2. Amylopectin

• A branched polymer

• linear chains held together by α-1,4 glycosidic bonds

• short branches: held by α-1,6 glycosidic bonds

POLYSACCHARIDES1.2

C

AR

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HY

DR

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GLYCOGEN

• Condensation of α-glucose subunits

• Major storage of carbohydrate in animals

• Structure similar to amylopectin : larger & with more branches.

POLYSACCHARIDES1.2

C

AR

BO

HY

DR

AT

ES

CELLULOSE

• Condensation of β-glucose subunits

• Structural polysaccharides in plant cell walls

• linked by β -1,4 glycosidic bonds

• Composed of long unbranched chains

• Many hydrogen bonds are formed between hydroxyl groups on parallel

chains ( between C atoms 3 and 6).

• a) State the types of lipid: triglycerides (fat and oil),



• b) Describe the structure of fatty acids and glycerol.

1.3 Lipids

phospholipids and steroids.

• b) Explain the formation and breakdown of triglycerides.

LIPIDS1.3

L

IPID

SCharacteristics:

• Insoluble in water

• Have little or no affinity for water (hydrophobic behavior)

• Soluble in organic solvent such as ether, acetone, chloroform and hot alcohol

• Can store large amount of energy:

The ratio of energy storing C-H bonds in fats is more than twice that carbohydrates / more C and H.

• General formula : CnH2nO2

• Proportion of oxygen is lower than in carbohydrates.

• Lipids are organic compounds.

• Not polymer

LIPIDS

• - TRIGLYCERIDESi.e Fat and oil

• - PHOSPHOLIPIDS

i.e Lecithin

• - STEROID• i.e Cholesterol

Testosteron

TYPE OF LIPIDS

1.3

L

IPID

S

LIPIDS1.3

L

IPID

S

• Glycerol is a three-carbon alcohol that contains three

hydroxyl group (-OH)

• a fatty acid is a long, unbranched hydrocarbon chain with

carboxyl group (-COOH) at one end.

TRIGLYCERIDES:

STRUCTURE OF FATTY ACIDS AND GLYCEROL

Formation/Breakdown of Triglycerides

condensation

hydrolysis

1.3

L

IPID

S


• b) State how amino acids are grouped.


• a) Describe the basic structure of amino acid

1.4 Protein

• c) Describe primary, secondary, tertiary and quaternary level of proteins and the type of bonds involved


• e) Explain the formation and breakdown of dipeptide


• d) Describe the effect of pH and temperature on the structure of protein.

1.4 Protein

• f) Classify proteins according to structure and composition

PROTEINS1.4

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INS

Molecule made up of one/more polypeptides, each folded and coiled into specific 3D structure.

Constructed from amino acids.

The bond between amino acidsis called peptide bond.

• Each polypeptide has a unique linear sequence of amino acids.

PROTEINS1.4

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(R group)

a variable group

• Amino acid containing

• a carboxyl group,

• a hydrogen atom

• a side chain

Protein Monomer : Amino acid

• an amino group

– that are specific to each amino acid.

How amino acids are grouped?

Nonpolar

amino acid

Polar

amino acid

Acidic

amino acid

Basic

amino acid

The 20 amino acids

are grouped

according to the

properties of their

side chains (R

groups)1.4

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INS

PROTEINS

Proteins Structure

• The sequence of amino acids determines aprotein’s three-dimensional structure.

4 levels of protein structure

Primary

(1 ͦ )

Secondary

(2 ͦ )

Tertiary

(3 ͦ )

Quaternary

(4 ͦ )

1.4

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PROTEINS

Proteins Structure: Primary (1 ͦ )

• sequence of amino acids determined by genetic code carried in DNA molecules in the nucleus.

• Eg: InsulinAmino acidsubunits

+H3NAmino end

25

20

15

10

5

1

Primary Structure

1.4

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INS

Proteins Structure: Secondary (2 ͦ )

• Polypeptide chains are coiled (-helix ) and folded (β-pleated sheet) .

A coiled shape of the -helix is held in place by hydrogen bonds between amino groups and the carboxyl groups of the amino acids.

• Hold protein in a parallel arrangement (β-pleated sheet) with hydrogen bond.

• E.g.: silk protein of a spider’s web.

• E.g. : keratin in hair, nails,

horn and feathers1.4

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INS

Proteins Structure: Tertiary

• Structure is maintained by :

–Hydrogen bond

–Ionic bond

–Disulfide bridge

–Hydrophobic interactions

–van der Waals interactions

Polypeptidebackbone

Hydrophobicinteractions andvan der Waalsinteractions

Disulfide bridge

Ionic bond

Hydrogenbond

• Involves interactions (attractions & repulsions) between R groups of the amino acids

1.4

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INS

Proteins Structure: Quaternary

• Two or more polypeptide chains

form one functional macromolecule.

• Combination two or more tertiary

units.

• Stabilized with the same

interactions found in

tertiary structure.

1.4

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INS

Factors Affecting Protein Structure

Temperature

• Heat increases the kinetic energy of the protein

chain.

• Excessive motion can break relatively weak

hydrogen bonds, electrostatic interactions (ionic

bond) and hydrophobic interactions.

• Protein chain is free to rearrange after disrupting.

• E.g : Fried egg

1.4

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INS

pH

• Extreme of pH can cause protein to denature.

• Change the charges of acidic and basic functional

groups of proteins.

• Those functional groups will lose & gain a proton.

• Break hydrogen bonds between acidic and basic R

groups & disrupt ionic bonds.

Factors Affecting Protein Structure

1.4

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INS

The Formation and Breakdown of Dipeptide 1.4

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Fibrous protein Globular protein Conjugated protein

Collagen

α-keratin

Elastin

Enzymes

AntibodiesHormones

Hemoglobin

PROTEIN CLASSIFICATION BASED ON THEIR STRUCTURE

1.4

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INS



• a) State the structure of nucleotide as the basic composition of

nucleic acid (DNA and RNA)

1.5 Nucleic Acids

• b) Illustrate the structure of DNA based on Watson and Crick model.

• c) State the types of RNA

• d) Compare DNA and RNA

• Macromolecules (large molecules) made up of chains of individual units called nucleotides.

• Each nucleotide is made up of pentose sugar, phosphate group and nitrogenous bases.

40

NUCLEIC ACIDS1.5

N

UC

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IC A

CID

SNUCLEIC ACIDS

Components of NucleotideNUCLEIC ACIDS

1.5

N

UC

LE

IC A

CID

S

Formation of Phosphodiester bond between phosphate group at C5

& Hydroxyl group (OH) at C3 next monomer.

NUCLEIC ACIDS1.5

N

UC

LE

IC A

CID

S

43

Watson and Crick’s DNA Model

A

T

A

A

TTG

G

CC

G

C

A DNA molecule is linkage

of nucleotides forms long

chains called

polynucleotides.

Chemically, one strand

runs 5’ to 3’ upward while

the other runs in the

opposite direction of 5’ to

3’ downward.

and coiled (clockwise

spiral) into a double helix.

NUCLEIC ACIDS1.5

N

UC

LE

IC A

CID

S

RNA Structure

• A single-stranded polymer of

nucleotides

NUCLEIC ACIDS1.5

N

UC

LE

IC A

CID

S

Differences of DNA and RNANUCLEIC ACIDS

1.5

N

UC

LE

IC A

CID

S

DNA RNA

Mostly two polynucleotide chains //

double-stranded

Mostly single polynucleotide chain // most

single-stranded

Double helix No double helix

Deoxyribose as pentose sugar Ribose as pentose sugar

Organic bases: A, T, C, G

* Base thymine (T)

Organic bases: A, U, C, G

* Base Uracil (U)

Manufactured in nucleus Manufactured in nucleus but found

throughout the cell

Chemically very stable// long live Chemically much less stable// temporary

Larger molecular size/ mass Smaller molecular size/ mass

Only one basic form Many/ 3 basic forms : mRNA, rRNA and

tRNA

Susceptible to UV damage Relatively resistance to UV damage

1.0: molecules of life · 1.0: molecules of life 1.2 carbohydrates •a) state the classes of...

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