CHAPTER 1 - Macromolecules

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M ROMOLE ULES

Chapter 1

orliz y ti


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Some very simple carbon compounds are considered

inorganic if the carbon is not bonded to another carbon

or hydrogen.

E.g: CaCO3 (calcium carbonate), carbon dioxides,

simple acids and bases, simple salts.

1. INTRODUCTION

A. INORGANIC COMPOUND

The scallop shells(composed mainly of calcium carbonate).

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Carbon containing compound that is made up of carbonwhich covalently linked to carbon or hydrogen.

It is generally large and complex.

Most macromolecules are organic compound.

1. INTRODUCTION

B. ORGANIC COMPOUND

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Able to form the back bones of the large variety oforganic compounds essential to life.

Each carbon atom form 4 covalent bonds with 4 other

atoms (S,N,O,H) single, double, triple.

Covalent bondsare strong, stable bonds formed when

atoms share valence electrons to form molecules.

Carbon atoms can form straight, branched or can join

into rings.

1. INTRODUCTION

B. ORGANIC COMPOUND

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CARBON


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Single bonde.g. ethane

1. INTRODUCTION

B. ORGANIC COMPOUND

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CARBON

Double bondse.g. ethene

Triple bondse.g. ethyne


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1. INTRODUCTION

B. ORGANIC COMPOUND

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CARBON


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1. INTRODUCTION

C. ISOMERS

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Isomers are compounds with the same molecularformula but different structures and properties:

Structural isomers have different covalent

arrangements of their atoms

Geometric isomers have the same covalent

arrangements but differ in spatial arrangements

Enantiomers are isomers that are mirror images of eachother


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1. INTRODUCTION

C. ISOMERS

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1. INTRODUCTION

C. ISOMERS

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1. INTRODUCTION

C. ISOMERS

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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Functional groups (a group of atoms) are the

components of organic molecules that are most commonlyinvolved in chemical reactions.

The characteristics of an organic molecule can be changed

dramatically by replacing one of the hydrogen with a

functional group.

Determine the types of chemical reaction in which the

compound participates.

The types, number and arrangement of functional groups

give each molecule its unique properties.


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1. INTRODUCTION

C. FUNCTIONAL GROUP

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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Can significantly altered the properties of hydrocarbon

molecule if it replaces one of the hydrogen of a

hydrocarbon

HYDROXYL

ETHANE (gas) ETHANOL (liquid)


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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Consists of a carbon atom that has a double bond with an

oxygen atom.

Polar: Electronegativity of the oxygen.

Hydrophilic: Polar and ionic functional groups associate

strongly with polar water molecules.

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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Have two classes which determines by the position of the

carbonyl group in the molecule.

CARBONYL

ALDEHYDE (RCHO)

A carbonyl group positioned at the

end of the carbon skeleton.

KETONE (RCOR)

Has an internal carbonyl group.

An aldehyde and a ketone are often structural isomers.

Propanal Acetone


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1. INTRODUCTION

D. FUNCTIONAL GROUP

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CARBONYL


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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Consists of a carbon double-bonded to an oxygen and alsobonded to a hydroxyl group.

Strongly polar

Act as acid by contributing H+

to solution and becomeionized.

Compound with carboxyl group is called carboxylic acid

CARBOXYL


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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Composed of nitrogen bonded to two hydrogen atoms andthe carbon skeleton.

Strongly polar

Act as base by picking up H+

from solution.

Organic compound with amino group is called amines.

AMINO


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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Amino acid is the building blocks of protein, contain acarboxyl group and an amino group.

AMINO


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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Consists of a phosphorus atom bonded to four oxygen

atom; one oxygen atom is bonded to carbon skeleton.

It is usually ionized and attached to carbon skeleton by

one of its oxygen atoms.

Two oxygen atom carry negative charges.

Compound with phosphate groups are called phosphates.

PHOSPHATE


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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Consists of a carbon bonded to three hydrogens.

Compound with methyl group are called methylated

compounds.

METHYL GROUP


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1. INTRODUCTION

D. FUNCTIONAL GROUP

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The subtle differences result in the different actions of

these molecules which help produce the features offemales and males in humans and other vertebrates.

METHYL GROUP


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1. INTRODUCTION

D. FUNCTIONAL GROUP

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Consists of a sulfur atom bonded to an atom of hydrogen.

Components with sulfhydryl is called thiols.

Two sulfhydryl group can interact to help stabilize protein

structure.

SULFHYDRYL

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2. WATER

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Water makes up about 60-95% of the fresh mass of

organism.

Water is an important component of cells, acts as a

solvent, is often a reactant in metabolism and provides an

aqueous environment for many organisms.

Properties of water molecules are due mostly to its ability

to form hydrogen bonds, its polarity and its small size.

Understanding this and the other properties that makewater so important means understanding waters

molecules structure.

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2. WATER

A. POLARITY OF WATER MOLECULE

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The two hydrogen atoms are joined to the oxygen atom by

single covalent bonds.

Since oxygen is more electronegative than hydrogen,

electron of the polar bonds spend more time closer to the

oxygen atom.

Therefore, the bond that hold together the atom in a water

molecule are polar covalent bonds.

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2. WATER


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Polar molecule: Opposite ends of the molecule have

opposite charges.

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2. WATER


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The charged regions of a

polar water molecule are

attracted to oppositely

charged parts of neighboring

molecules.

Each molecules can

hydrogen-bond to multiple

partner.

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2. WATER

B. EMERGENT PROPERTIES OF WATER

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The binding together of like molecules, often by hydrogen

bonds.

Water from the root reaches the leaves through a network

of water-conducting cell.

As water evaporates from a leaf, hydrogen cause watermolecule leaving the veins to tug on molecules farther

down.

The upward pull is transmitted through the water-conducting cell all the way down to the root.

COHESION

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2. WATER


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Surface tension: a measure of how difficult it is to stretch

or break the surface of a liquid.

At the interface between water and air is an ordered

arrangement of water molecules, hydrogen-bonded to one

another and to the water below.

This makes water behave as though coated with an

invisible film.

COHESION

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2. WATER


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Adhesion: The attraction between different kind of

molecules

Adhesion of water to the wall of the cells helps counter the

downward pull of gravity.

COHESION

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2. WATER


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2. WATER


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HEAT AND TEMPERATURE

Heat is a measure of the total amount of kinetic energy

due to molecular motion in a body of matter.

Temperature measures the intensity of heat due to the

average kinetic energy of the molecules.

A calorie (cal) is the amount of heat it takes to raise the

temperature of 1g of water by 1C (1cal = 4.184J)

MODERATION OF

TEMPERATURE

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2. WATER


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SPECIFIC HEAT

Amount of heat that must be absorbed or lost for 1g of that

substance to change its temperature by 1C (1cal/g/C)

Water change temperature by absorbs or loses a relativelylarge quantity of heat for each degree of change.

Heat must be absorbed in order to break hydrogen bonds,

and heat is released when hydrogen bonds form.

MODERATION OF

TEMPERATURE

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2. WATER


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importance

A large body of water can absorb and store a huge amount

of heat from the sun in the daytime and during summer

while warming up only a few degree.

Stabilize ocean temperatures, creating a favorable

environment for marine life.

Organism are more able to resists changes in their own

temperature since they are made primarily of water.

MODERATION OF

TEMPERATURE

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2. WATER


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EVAPORATIVE COOLING

Evaporation: transformation from liquid to gas

Some evaporation occurs at any temperature (why?)

If a liquid is heated, the average kinetic energy of

molecules increases and the liquid evaporates more

rapidly.

MODERATION OF

TEMPERATURE

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2. WATER


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EVAPORATIVE COOLING

Heat of vaporization: quantity of heat a liquid must absorb

for 1g of it to be converted from liquid to gaseous state.

Heat is needed to break hydrogen bonds before themolecules can make their exodus from the liquid.

Evaporative cooling contributes to the stability of

temperature in lakes and ponds and prevents terrestrialorganisms from overheating.

MODERATION OF

TEMPERATURE

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2. WATER


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EVAPORATIVE COOLING

MODERATION OF

TEMPERATURE

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2. WATER


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Water expands as it solidify; it is less dense as solid than

liquid.

When water begin to freeze, its molecules is no longer

moving vigorously enough to break their hydrogen bonds.

As temperature falls to 0C, the water becomes locked intoa crystalline lattice, each water molecule bonded to four

partners.

When temperature rise above 0C, hydrogen bondsdisrupted, crystal collapses, ice melts, molecules slip

closer together.

DENSITY

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2. WATER


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DENSITY

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2. WATER


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DENSITY

Floating ice

insulate the water

below, preventing it

from freezing.

2 WATERSOLVENT OF LIFE


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2. WATER


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Solution: a liquid that is completely homogenous mixture

of two or more substance.

Solvent: dissolving agent of a solution

Solute: substance that is dissolved

Aqueous solution: solution which water is the solvent

Water is not universal solvent

SOLVENT OF LIFE

2. WATERSOLVENT OF LIFE


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2. WATER


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Hydration shell: sphere of water molecules around each

dissolved ion

SOLVENT OF LIFE

Hydration shell: sphere of water molecules around each

dissolved ion



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2. WATER


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SOLVENT OF LIFE

Large molecules such as protein can dissolve in water if

they have ionic and polar regions on their surface.



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2. WATER


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Hydrophilic: any substance that has an affinity for water

(substance can be hydrophilic without dissolving)

Colloid: a mixture made of a liquid and particles that remain

suspended in that liquid (large size)

Cotton: consists of giant molecule of cellulose

A compound with numerous region of partial negative and

partial positive charges associated with polar bonds.

Waters adhere to the cellulose fiber without being dissolved.

SOLVENT OF LIFE



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2. WATER


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Hydrophobic: any substance that has no affinity for water (nonionic,

nonpolar)

This is because of the nonpolar bonds between carbon and hydrogen

which share electrons almost equally.

Exmple: vegetable oil

SOLVENT OF LIFE

3. POLYMER


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Four main classes of large biological molecules are:

Carbohydrates

Proteins

Nucleic acids (DNA and RNA)

Lipids (not macromolecules/does not true polymers)

Most macromolecules are polymers.

Long molecule consists of many identical or similar building

blocks link together (monomer).

Monomeris a chemical subunit that serves as a building

block of a polymer.

3. POLYMER

A. INTRODUCTION

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3. POLYMER


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Monomers are connected by condensation reaction

(dehydration). Two molecules are covalently bonded to each other through loss

of a water molecule.

B. SYNTHESIS AND BREAKDOWN

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3. POLYMER


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Polymer are disassembled to monomer by hydrolysis

reaction. Bonds between monomer s are broken down by adding of water

molecules.

B. SYNTHESIS AND BREAKDOWN

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4. PROTEIN


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Amino acids are organic molecules with carboxyl and

amino groups Amino acids differ in their properties due to differing side

chains, called R groups

Alpha carbon: an asymmetric carbon at the center of

amino acid. It bind to amino group, carboxyl group, hydrogen atom

and variable group (side chain)

A. AMINO ACID MONOMER

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The R group of amino acids can vary in:

structure shape

charge (positive, negative or neutral),

affinity with water and the reactivity with other molecules.

There are 20 amino acids which occur naturally in theproteins of organisms.

The various combinations of 20 different amino acidsproduce a great variety of different proteins containingbetween hundreds to few thousand amino acids.

4. PROTEIN


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(Hydrophobic)

4. PROTEIN


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(Hydrophilic)

4. PROTEIN


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(Hydrophilic)

Acidic: Those with carboxyl group on their side chain that are

generally NEGATIVE

Basic: Those with amino group on their side chain that are generally

POSITIVE

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Amino acids is an amphoteric molecules that have both

basic and acidic groups.

Molecules with amphoteric properties can function as

buffer- resist any change in pH and try to maintain the

pH.

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Amino acids dissolve in water to form bipolar ions in

aqueous solution (zwitterion).

An ion with both a negative charge and a positive

charge. Amino is ionised into NH3+, whereas acidic

group is ionised intocoo-

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TYPES OF AMINO ACIDS

Essential Amino Acidcannot be made in thebody

must be included in thediet.

Non-Essential Amino Acidcan be synthesized in the

body.

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B. AMINO ACID POLYMER

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Amino acids are linked by peptide bonds

An enzyme can cause two amino acids to bind bydehydration reaction

Water molecule will be produced

A polypeptide is a polymer of amino acids

Polypeptides range in length from a few to more than athousand monomers

Each polypeptide has a unique linear sequence of amino

acids.

4. PROTEIN

P id


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B. AMINO ACID POLYMER

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Peptide

bond

Amino end(N-terminus)

Peptide

bond

Side chains

Backbone

Carboxyl end(C-terminus)

(a)

(b)

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C. CLASSIFICATION OF PROTEIN

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Some common methods used to group proteins are

based on:

1. Levels of organization

- Primary structure

- Secondary structure

- Tertiary structure- Quaternary structure

2. Structure

- Globular proteins- Structural proteins

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3. Composition

- Simple proteins

- Conjugated proteins

4. Functions

- Structure- Catalysts

- Signals

- Movement

- Defense- Storage

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The primary structure of a protein is its uniquesequence of amino acids

Secondary structure, found in most proteins, consists

of coils and folds in the polypeptide chain

Tertiary structure is determined by interactions amongvarious side chains (R groups)

Quaternary structure results when a protein consists of

multiple polypeptide chains

LEVELS OF ORGANIZATIONC. CLASSIFICATION OF PROTEIN

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Primary Structure Specific linear sequence of amino acids in a polypeptide

chain.

The sequence of amino acids is determined by the

genetic code carried in the DNA molecule in the nucleus. This sequence is unique for a particular protein.

A substitution or deletion of even 1 amino acid in the

primary structure can affect the structure & function of

the protein.

LEVELS OF ORGANIZATIONC. CLASSIFICATION OF PROTEIN

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Secondary Structure

Proteins that have segments of their polypeptide chains

repeatedly coiled or folded,

These coils & folds are the result of hydrogen bonds

between the repeating constituents of the polypeptide

backbone.

The weakly hydrogen atom attached to the nitrogen

atom has an affinity for the oxygen atom of a nearby

peptide bond.


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C CLASSIFICATION OF PROTEIN


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helix:

The polypeptide chain is coiled to form helical structure. The shape of the helix is maintained by hydrogen bonds between

every 4th amino acid.

Example:

i. Globular proteins

may have single helix structure or multiple stretches of helix

separated by non helical regions.

ii. Fibrous proteins

Some may have the helix formation Eg: -keratin (structural protein of hair) have the helix formation

over most of their length.


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pleated sheet:

2 or more polypeptide chains are arranged parallel to

each other & are held together by hydrogen bonds.

The polypeptide chains become folded.

Has high resistance to stretching. It is strong but flexible.

Pleated sheets make up the core of many globular

proteins & also some fibrous proteins.

Example of fibrous protein : the silk protein of a spiderweb.


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Tertiary Structure

Formed by folding and coiling of the secondarystructure of polypeptide chains to form precise compactglobular protein which determines its function.

The compact three dimensional shape is maintained byhydrogen bonds, disulphide bonds, ionic bonds and

hydrophobic interactions and van der Waals interactions.

Tertiary structure is determined by interactions between Rgroups, rather than interactions between backboneconstituents.

Example of globular proteins include enzymes, antibodies,protein hormones and myoglobin, the oxygen-storagered pigment in red muscle.


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Hydrophobic interaction

occur when nonpolar side chain clusters at the core of theprotein.

Caused by the action of water molecules as they form H-bond

with polar parts

Van der Waals interaction Hold nonpolar side chain together

Hydrogen bond formed between polar side chain

Ionic bond formed between positively and negatively

charged side chain Disulfide bridges formed between two sulfhydryl

groups.


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Quaternary structure Results when two or more polypeptide chains form one

macromolecule.

Collagen is a fibrous protein consisting of three

polypeptides coiled like a rope. Hemoglobin is a globular protein consisting of four

polypeptides: two alpha and two beta chains


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PROTEIN STRUCTURE4. PROTEIN



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Protein are classified according to their structure

a)Fibrous proteins

b)Globular proteins


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PROTEIN STRUCTURE4. PROTEIN



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COMPOSITION4. PROTEIN



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Simple proteins consists only of amino acids

do not contain any other substance

Examples:

- Albumins : egg albumin, serum albumin- Globulins : antibodies, fibrinogen

- Histones : protein associated with DNA

- Scleroprotein : keratin, collagen


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COMPOSITION4. PROTEIN



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Conjugated proteins

contain protein & non-protein material (prosthetic group)

The prosthetic group : plays an important role in the

functioning of the protein


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4. PROTEIN

D DENATURATION OF PROTEIN


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In addition to primary structure, physical and chemical

conditions can affect structure

Alterations in pH, salt concentration, temperature, or other

environmental factors can cause a protein to unravel

This loss of a proteins native structure is called

denaturation

A denatured protein is biologically inactive

D. DENATURATION OF PROTEIN

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Normal protein Denatured protein

Denaturation

Renaturation

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5. CARBOHYDRATE

A MONOSACCHARIDES


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Simplest carbohydrates; ex: GLUCOSE

The molecule has a carbonyl group and multiple

hydroxyl groups.

Can be either aldose or ketose (depends on the carbonyl

group)

Glucose and galactose differ only in the placement of

parts around one asymmetric carbon.

A. MONOSACCHARIDES

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5. CARBOHYDRATE

A MONOSACCHARIDES


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A. MONOSACCHARIDES

5. CARBOHYDRATE

A. MONOSACCHARIDES


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All monosaccharide is a reducing sugar-can act as

reducing agent in the Benedict test.

Benedict reagentblue in colora cuprum sulphate

solution.

The presence of reducing sugar will reduced the cuprum

(II) sulphate to cuprum (I) sulphate which has the red-

orange colour.

A. MONOSACCHARIDES

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5. CARBOHYDRATE

A. MONOSACCHARIDESGLUCOSE


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Glucose is an aldohexose.

Glucose can be in a linear chain form.

Glucose molecules, as well as most other sugars, form

rings in aqueous solution.

To form the glucose rings, carbon 1 bonds to the oxygen

attached to carbon 5.

A. MONOSACCHARIDES

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5. CARBOHYDRATE

A. MONOSACCHARIDESGLUCOSE


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-glucose is the glucose that have the OH group of the

first carbon projects below the plane of the ring.

-glucose is when the glucose have the OH group

projects above the plane.

A. MONOSACCHARIDES

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5. CARBOHYDRATE

A. MONOSACCHARIDESFUNCTION


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Triose:

intermediate in respiration and photosynthesis. Pentoses:

ribose: constituent of RNA

deoxyribose: constituent of nucleic acid DNA.

Hexoses: Glucose: most common respiratory substratelarge number of

C-H bonds can be broken to release energy;

Fructose: constituents of nectar;

Galactose: constituents of lactose.

Hexoses are the monomers in synthesis of disaccharides,oligosaccharides and polysaccharides.

A. MONOSACCHARIDES

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5. CARBOHYDRATE

B. DISACCHARIDES


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Two monosaccharide joined by a glycosidic linkage.

Disaccharides are formed by the condensation reaction

of two monosaccharides molecules.

Disaccharides are water soluble, sweet tasting and canbe crystallised.

All disaccharides are reducing sugar except for

sucrose (non-reducing sugar).

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5. CARBOHYDRATE

B. DISACCHARIDESMALTOSE


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Bonding of two glucose molecule

1-4 glycosidic linkage

Known as malt sugar

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5. CARBOHYDRATE

B. DISACCHARIDESSUCROSE


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Bonding of glucose and fructose

1-2 glycosidic linkage

Most prevalent disaccharide, table sugar

Taste sweeter than glucose but not as sweet as fructose

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5. CARBOHYDRATE

B. DISACCHARIDESLACTOSE


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Binding of glucose and galactose.

(1-4) glycosidic linkage.

Sugar that present in milk.

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5. CARBOHYDRATEC. OLIGOSACCHARIDES


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Monosaccharides can be linked together to form small

chains termed oligosaccharides. Each oligosaccharides may contain 3 to 14

monosaccharides.

Glycoproteins are the proteins covalently attached to

carbohydrate. Glycolipids are carbohydrate-attached lipids

Oligosaccharides provide energy and serve as markers

for cellular recognition.

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5. CARBOHYDRATEC. OLIGOSACCHARIDES


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Oligosaccharide of the cell surface are attached to

membrane embedded proteins and certain lipid molecules.

5. CARBOHYDRATED. POLYSACCHARIDES


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POLYSACCHARIDES

Storage

Starch

Amylose Amylopectin

Glycogen

Structural

Cellulose Chitin Murein



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Polysaccharides, are macromolecules with a few hundred to

a few thousand monosaccharides joined by glycosidiclinkages.

The structure and function of a polysaccharide are

determined by its sugar monomers and the positions of

glycosidic linkages. Polysaccharides are generally insoluble in water and not

sweet in taste.

Polysaccharides are important as food storage and building

materials for the cell or the whole organism. Example: starch,glycogen and cellulose, chitin and murein.

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STARCH


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Starch is a polysaccharide formed from condensation of -

glucose units.

Starch grains are found in chloroplast, potato tubers, cereals

and legumes.

Most of the monomers are joined by 1-4 glycosidic linkage.

Made up from two components: Amylose (unbranched) and

amylopectin(branched with 1-6 linkage).

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STARCH


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NLY/ASASI/2013(b) Glycogen: an animal polysaccharide

Starch

GlycogenAmylose

Chloroplast

(a) Starch: a plant polysaccharide

Amylopectin

Mitochondria Glycogen granules

0.5 m

1 m


STARCH


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Starch is a polysaccharide formed from condensation of -

glucose units.

Starch grains are found in chloroplast, potato tubers, cereals

and legumes.

Most of the monomers are joined by 1-4 glycosidic linkage.

Made up from two components: Amylose (unbranched) and

amylopectin(branched with 1-6 linkage).

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STARCH


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Amylose: linear unbranched polymer of 200 to 1500 -

glucose units in a repeating sequence of -1,4-glycosidiclinkages.

The amylose chain coils into a helix held by hydrogen

bonds formed between hydroxyl groups.

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STARCH


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Amylopectin is a branched polymer of 2,000 to 200,000 -

glucose units per starch molecules.

Glycosidicbond (1-4 and 1-6)

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GLYCOGEN


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Glycogen is the major storage form of carbohydrate in

animals. Present in liver & muscle cells where high metabolic activities

take place.

Glycogeninsoluble in water.

Structure: similar with amylopectin but larger in size and havemore branches.

When energy is needed and glucose concentration is low in

the body-glycogen can be hydrolyzed rapidly by enzymes to

produced glucose molecules to be used for cellularrespiration to meet the energy requirements.

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GLYCOGEN


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NLY/ASASI/2013(b) Glycogen: an animal polysaccharide

Starch

GlycogenAmylose

Chloroplast

(a) Starch: a plant polysaccharide

Amylopectin

Mitochondria Glycogen granules

0.5 m

1 m


CELLULOSE


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The polysaccharide cellulose is a major component of the

tough wall of plant cells Like starch, cellulose is a polymer of glucose, but the

glycosidic linkages differ

The difference is based on two ring forms for glucose: alpha

() and beta () Cellulose is composed of long unbranched chains of up to

10,000 -glucose units linked by -1,4-glycosidic bonds.

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CELLULOSE


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The chains are grouped together to form microfibrils

arranged in larger bundle to form fibrils.

The fibrils give the plant high tensile strength and rigidity.

The layers of fibrils are freely permeable to water andsolutes.

Commercially-cellulose is used to make cotton goods and

paper for various uses.

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CELLULOSE


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(a) and glucose ring structures

Glucose Glucose


CELLULOSE


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(b) Starch: 14 linkage of glucose monomers

(c) Cellulose: 14 linkage of glucose monomers


CELLULOSE


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Polymers with glucose are helical

Polymers with glucose are straight

In straight structures, H atoms on one strand can bond with

OH groups on other strands

Parallel cellulose molecules held together this way are

grouped into microfibrils, which form strong building

materials for plants

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CELLULOSE


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b Glucosemonomer


CHITIN


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Carbohydrate use by arthropod to build their exoskeleton.

Pure chitin is leathery, but becomes hardened when

encrusted with calcium carbonate.

Fungi used chitin rather than cellulose as building materialfor their cell wall.

Chitin is similar to cellulose except it contains a nitrogen-

containing appendage.

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CHITIN


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The structureof the chitin

monomer.

(a) (b) (c)Chitin forms theexoskeleton ofarthropods.

Chitin is used to makea strong and flexiblesurgical thread.


MUREIN


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A polymer consist of sugars and amino acids that forms a mesh-like layer

outside the plasma membrane of bacteria, forming the cell wall.

The sugar component consists of alternating residues of -(1,4) linked N-

acetylglucosamine andN-acetylmuramic acid.

Consist of polysaccharides cross linked with amino acids.

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6. LIPIDA. INTRODUCTION


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Lipids are the one class of large biological molecules that do

not form polymers

Contain carbon, hydrogen and oxygen

3 important groups of lipids are tryglycerides (fats and oils),

phospholipids and steroids.

Other group of lipid waxes (water proof)

The unifying feature of lipids is having little or no affinity for

water

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6. LIPIDA. INTRODUCTION


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Lipids are hydrophobic because they consist mostly of

hydrocarbons, which form non-polar covalent bonds

Dissolve in organic solvents such as acetone, ether,

chloroform and alcohol.

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6. LIPIDB. TRIGLYCERIDE (FAT)


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Fats and oils are esters (condensation of one molecule

glycerol and 3 molecules of fatty acids by an esterlinkage)

The process: esterification (involve alcohol &acids)

Glycerol + 3 fatty acids = Triglyceride

Glycerol is a three-carbon alcohol with a hydroxyl group

attached to each carbon

A fatty acid consists of a carboxyl group attached to a

long carbon skeleton

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Dehydration reaction in the synthesis of a fat

Fatty acid(palmitic acid)

Glycerol

One water molecule is removed for each fatty acid joined to

the glycerol

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(b)Fat molecule (triacylglycerol)

Ester linkage

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Fats separate from water

because water molecules form hydrogen bonds with

each other and exclude the fats

Fatty acids vary in length (number of carbons) and in

the number and locations of double bonds

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SATURATED FAT


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Saturated fatty acids have the maximum number of

hydrogen atoms possible and no double bonds

Usually solid at room temperature

Example: stearic acid

Straight molecules

Most animal fats are saturated

A diet rich in saturated fats may contribute to cardiovasculardisease through plaque deposits

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UNSATURATED FAT


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Unsaturated fatty acids have one or more double bonds

Example: oleic acid and linoleic acid

Bent molecule (due to one or more double bonds). Still can

accept one more hydrogen atom.

Usually liquid at room temperature

Plant fats and fish fats are usually unsaturated

Hydrogenation is the process of converting unsaturated

fats to saturated fats by adding hydrogen

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Hydrogenation is not only producing saturated fat but also unsaturated

fat with trans double bond.


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a a s doub e bo d

6. LIPIDC. PHOSPHOLIPID


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In a phospholipid, two fatty acids and a phosphate group

are attached to glycerol

The two fatty acid tails are hydrophobic, but the

phosphate group and its attachments form a hydrophilic

head

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Fig. 5-13ab

Choline

head


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(b) Space-filling model(a) Structural formula

Fatty acids

Phosphate

Glycerol

Hydrophobic

tails

Hydrophilic

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6. LIPIDC. PHOSPHOLIPID


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Phospholipid shows ambivalent behavior towards water

The tails are excluded from water, the head has affinity

toward water

When phospholipids are added to water, they self-

assemble into a bilayer, with the hydrophobic tailspointing toward the interior

The structure of phospholipids results in a bilayer

arrangement found in cell membranes

Phospholipids are the major component of all cell

membranes

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Fig. 5-14


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Hydrophilichead

Hydrophobictail

WATER

WATER

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6. LIPIDD. STEROID


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Steroids are lipids characterized by a carbon skeleton

consisting of four fused rings

Cholesterol, an important steroid, is a component in

animal cell membranes

Steroid are classified as lipids due to their insolubility in

water and solubility in non polar solvents.

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6. LIPIDD. STEROID


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Type Function Description Uses


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Fats Respiratory substrate Released energy

when oxidised

Butter

For energy storage Excess energy isstored in the form

of fat

As heat (thermal) and

electrical insulator

Fat deposited as

adipose tissue

(heat insulator)

Fat acts as an

electrical

insulator (myelin

sheath of nerve

cells)To protect internal

organs

Fat provides

support

(abdomen)and

protection

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Type Function Description Uses


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Oils For energy

storage

Long-term energy storage

in plants and seeds

Cooking

oils

Phospholipids A component of

plasma

membrane

Providing

structural

support

Involved in formation of

cells

Important component ofplasma membrane, nuclear

membrane and the myelin

sheath

Non-stick

pan spray

Steroids Precursor for

steroid

hormones

All steroid hormones are

synthesized from

cholesterol

Medicines

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7. NUCLEIC ACIDSA. ROLES OF NUCLEIC ACIDS


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There are two types of nucleic acids:

Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA)

DNA provides directions for its own replication

DNA directs synthesis of messenger RNA (mRNA).

mRNA controls protein synthesis; translated codedinformation into amino acid sequences.


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7. NUCLEIC ACIDSB. STRUCTURE OF NUCLEIC ACIDS


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Nucleic acids are polymers called polynucleotides.

Each polynucleotide is made of monomers called

nucleotides.

Each nucleotide consists of a nitrogenous base, a pentose

sugar, and a phosphate group.

The portion of a nucleotide without the phosphate group is

called a nucleoside.

Fig. 5-27ab

5' end

5'C


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3'C

5'C

3'C

3' end

(a) Polynucleotide, or nucleic acid

(b) Nucleotide

Nucleoside

Nitrogenousbase

3'C

5'C

Phosphategroup Sugar

(pentose)

7. NUCLEIC ACIDSC. NUCLEOTIDE MONOMER


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NUCLEOTIDE

Pentose Sugar

Ribose Deoxyribose

Nitrogenous Base

Purine Pyrimidine

Phosphate Group


PENTOSE SUGAR


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Ribose - Pentose sugar in RNA

Deoxyribose - Pentose sugar in DNA

Ribose (in RNA)Deoxyribose (in DNA)

Sugars

Nucleoside components: sugars


NITROGENOUS BASE


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Ring structure containing N.

In DNA

Adenine, Guanine (double ring-purines)

Cytosine, Thymine (single ring-pirimidines).

In RNA

Adenine, Guanine (double ring-purines)

Cytosine, Uracil (single ring-pirimidines).

Fig. 5-27c-1

Nitrogenous bases

Pyrimidines


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(c) Nucleoside components: nitrogenous bases

Purines

Guanine (G)Adenine (A)

Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)


PHOSPHATE GROUP


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Joined by condensation to the pentose sugargives the

nucleic acids their acidic property.

7. NUCLEIC ACIDSD. NUCLEOTIDE POLYMER


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Nucleotide polymers are linked together to build a

polynucleotide

Adjacent nucleotides are joined by covalent bonds

(phosphodiester bonds) that form between theOH

group on the 3 carbon of one nucleotide and the phosphate

on the 5 carbon on the next

These links create a backbone of sugar-phosphate units

with nitrogenous bases as appendages

The sequence of bases along a DNA or mRNA polymer isunique for each gene


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7. NUCLEIC ACIDSE. DNA DOUBLE HELIX


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A DNA molecule has two polynucleotides spiraling around

an imaginary axis, forming a double helix

In the DNA double helix, the two backbones run in opposite

5 3 directions from each other, an arrangement

referred to as antiparallel

One DNA molecule includes many genes

The nitrogenous bases in DNA pair up and form hydrogen

bonds: adenine (A) always with thymine (T), and guanine(G) always with cytosine (C)

7. NUCLEIC ACIDSE. DNA DOUBLE HELIX


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The base pairing is precise.

Adenine is linked with thymine by 2 hydrogen bonds. Cytosine is joined with guanine by 3 hydrogen bonds.

The two polynucleotide strands are complementary.

The sequence of bases in DNA forms the genetic code that

determines the characteristics of an organism.


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Fig. 5-28

Sugar-phosphatebackbones

3' end5' end


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3' end

5' end

Base pair (joined byhydrogen bonding)

Old strands

New

strands

Nucleotideabout to beadded to a

new strand

Documents

CHAPTER 1 - Macromolecules