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THE STRUCTURE AND FUNCTION THE STRUCTURE AND FUNCTION OF MACROMOLECULESOF MACROMOLECULES

Macromolecules

Continuo….Continuo….

Macromolecules

Continuo….Continuo….

Proteins are polymer of amino acids (constructed from 20 amino Proteins are polymer of amino acids (constructed from 20 amino acids) (to form Polypeptides).acids) (to form Polypeptides).

2-Proteins (Polypeptides)2-Proteins (Polypeptides)

There are six functions of proteins:There are six functions of proteins:

1.1. Storage:Storage: albumin (egg white) albumin (egg white)

2.2. Transport: Transport: hemoglobin hemoglobin

3.3. Regulatory: some hormonesRegulatory: some hormones

4.4. Movement:Movement: muscles muscles

5.5. Structural:Structural: membranes, hair, nails membranes, hair, nails

6.6. Enzymes:Enzymes: cellular reactions cellular reactions

Side chain

Amino group

Carboxyl group

General Formula General Formula of the Amino of the Amino Acid:Acid: CC

HH

RR

NNHH

HHCC

OOHH

OO

- The components of proteins include - The components of proteins include aa hydrogen atomhydrogen atom, a , a carboxyl groupcarboxyl group, , an an amino groupamino group, and a , and a variable variable متغيرةمتغيرة R R groupgroup (or side chain). (or side chain).

- Differences in R groups produce the 20 different amino acids.

Hydrophobic:Hydrophobic: the amino acids that have hydrophobic the amino acids that have hydrophobic RR groups (non-polar). groups (non-polar). Hydrophilic:Hydrophilic: the amino acids that have polar the amino acids that have polar RR groups, making them groups, making them

hydrophilic.hydrophilic. Ionized:Ionized: the amino acids with functional groups that are charged (ionized) at the amino acids with functional groups that are charged (ionized) at

cellular pH (7). So, some cellular pH (7). So, some RR groups are groups are basesbases, others are , others are acidsacids..

Amino acids Amino acids األحماض األحماضاألمينيةاألمينية

The Peptide BondThe Peptide Bond الرابطة الرابطة البيبتيديةالبيبتيدية

Peptide bond formed between the Peptide bond formed between the carboxyl groupcarboxyl group of one amino acid of one amino acid and the and the amino groupamino group of the other by dehydration. of the other by dehydration.

OOHHCC CC

HH

RR

NNHH

HH

OO

HHCC

HH

RR

NN

HH

CCOOHH

OO

Peptide bond

Polypeptide (Protein)

DehydrationDehydrationالماء الماء نزع نزع

Amino acids PeptideAmino acids Peptide

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• Amino acids are joined together when a Amino acids are joined together when a dehydration reactiondehydration reaction removes a removes a hydroxyl group from the carboxyl end of one amino acid and a hydrogen hydroxyl group from the carboxyl end of one amino acid and a hydrogen from the amino group of another. The resulting covalent bond is called a from the amino group of another. The resulting covalent bond is called a peptide bondpeptide bond. .

• The repeated sequence (The repeated sequence (N-C-CN-C-C) is the ) is the polypeptidepolypeptide backbone. backbone.

• Attached to the backbone are the various Attached to the backbone are the various RR groups. groups.

• Polypeptides range in size from a few monomers to thousands.Polypeptides range in size from a few monomers to thousands.

Amino Amino acidsacids

Amino Amino acidsacids

Peptides

Peptides

Peptides

Peptides

Peptide bonds

Peptide bonds

Dehydration

Dehydration

Hydrophobic (Hydrophobic (non-polar R group))

Hydrophilic (Hydrophilic (polar R group))

Ionized (Ionized (charged charged functional groupsfunctional groups)

ProteinsProteinsProteinsProteinsPolypeptidesPolypeptides

There are four levels of protein structure:There are four levels of protein structure:

A.A. Primary Structure Primary Structure ) بسيط ) (أولي بسيط ) أولي

B.B. Secondary Structure Secondary Structure ثنائيثنائي

C.C. Tertiary Structure Tertiary Structure ثالثيثالثي

D.D. Quaternary StructureQuaternary Structure رباعيرباعي

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3-Lipids;3-Lipids;

1.1. FatsFats store large amounts of energy store large amounts of energy

2.2. PhospholipidsPhospholipids are major components of cell membranes are major components of cell membranes

3.3. SteroidsSteroids include cholesterol and certain hormones include cholesterol and certain hormones

1.1. FatsFats store large amounts of energy store large amounts of energy

2.2. PhospholipidsPhospholipids are major components of cell membranes are major components of cell membranes

3.3. SteroidsSteroids include cholesterol and certain hormones include cholesterol and certain hormones

It is the general term for compounds which are not soluble not soluble in waterin water.

Functions of lipids:Functions of lipids:

1.1. Long term energy storageLong term energy storage2.2. Protection against heat loss (insulation)Protection against heat loss (insulation)3.3. Protection against physical shockProtection against physical shock4.4. Protection against water lossProtection against water loss5.5. Chemical messengers (hormones)Chemical messengers (hormones)6.6. Major component of membranes (phospholipids)Major component of membranes (phospholipids)

Structure of Fatty AcidsStructure of Fatty Acids• Long chains of mostly carbon and hydrogen atoms with a -COOH group at Long chains of mostly carbon and hydrogen atoms with a -COOH group at

one end.one end.

• When they are part of lipids, the fatty acids resemble long flexible tails.When they are part of lipids, the fatty acids resemble long flexible tails.

OH

H H

CC

CCC

C HHH

HH H

H

H

H

O

OC

C

C

H

H

H

H

OH

OH

H

H

DehydrationDehydration

Fatty AcidGlycerol

Ester linkEster link

In a fat, three fatty acids are joined to a single glycerol by an In a fat, three fatty acids are joined to a single glycerol by an ester linkageester linkage, , إستيرية إستيرية رابطة . .creating a creating a triacylglyceroltriacylglycerol رابطة

Structure of Fat moleculeStructure of Fat molecule

1)- Saturated Fats1)- Saturated Fats المشبعة المشبعة الدهون الدهون

The Fatty acid components are saturated when there is no double bond The Fatty acid components are saturated when there is no double bond between the carbons. All between the carbons. All CarbnCarbn are linked with are linked with Hydrogen Hydrogen . .

Most animal fats are saturated.

These double bonds are formed by the removal of These double bonds are formed by the removal of H H atoms. atoms.

They can be synthetically converted to saturated (solid) by adding They can be synthetically converted to saturated (solid) by adding HH ((Hydrogenation Hydrogenation چَـة چَـةالَه5د6ر5 .( .(الَه5د6ر5

2)- Un-saturated Fats2)- Un-saturated Fats الدهونالدهون مشبعةمشبعة الغيرالغير

Types of fatsTypes of fats

– liquid at room templiquid at room temp– one or more double bonds between carbons in the fatty acids allows for one or more double bonds between carbons in the fatty acids allows for

“kinks” in the tails“kinks” in the tails– Include most plant fatsInclude most plant fats

– The Fatty acid components are saturated )there is The Fatty acid components are saturated )there is no double bonds between the carbons. All no double bonds between the carbons. All CC are are linked with linked with HH..

– have only single C-C bonds in fatty acid tailshave only single C-C bonds in fatty acid tails– solid at room tempsolid at room temp– Include most animal fatsInclude most animal fats

Most plant fats are unsaturated.

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• PhospholipidsPhospholipids have two fatty acids attached to glycerol and a have two fatty acids attached to glycerol and a phosphate groupphosphate group at the third position.at the third position.

– The phosphate group carries a The phosphate group carries a negativenegative chargecharge.

1- Phospholipids1- Phospholipids:: are the major components of cell membranesare the major components of cell membranes

• The fatty acid The fatty acid tailstails are are hydrophobichydrophobic, but the , but the phosphate group and its attachments form a phosphate group and its attachments form a hydrophilichydrophilic headhead..

• Thus, it is Thus, it is amphipathicamphipathic

Other lipids have structural, hormonal, or Other lipids have structural, hormonal, or protective functionsprotective functions

2.2. SteroidsSteroids: are hydrophobic molecules : are hydrophobic molecules that pass through plasma membranesthat pass through plasma membranes

3.3. WaxesWaxes:: are hydrophobic molecules are hydrophobic molecules used for waterproofingused for waterproofing

F a t sF a t s

SaturatedSaturatedSaturatedSaturated UnsaturatedUnsaturatedUnsaturatedUnsaturated PhospholipidsPhospholipidsPhospholipidsPhospholipids

Animal Fats Vegetable Fats Bi-layer of cell Bi-layer of cell membranemembrane

HydrogenationHydrogenation

چَــــــــ �ـد�َر �چَــــــــَه �ـد�َر �َهـةـة

SteroidsSteroidsSteroidsSteroids

Sex Hormones Sex Hormones & Cholesterol & Cholesterol

WaxesWaxesWaxesWaxes

(Composed of Lipids)