Proteins

Wilhelmina Annie MensahDept. Of Med. Bchem.

UGMS , Ghana 105/01/23

Amino acids are the basic unit of proteins

Amino acids consist of C, H, O and N (S & P)

Proteins have a 3 dimensional globular shape

Proteins

• Peptide bonds connect amino acids to form polypeptide chains

• One or more polypeptide chains make up a protein

Proteins Structure

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levels of Proteins Structure

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Functions of Proteins 1. Transport of substances in the body .

E.g. Haemoglobin transports oxygen.

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Functions of Proteins 2.Enzymes which catalyze chemical reactions in the

body are proteins

Substrate (lactose) Glucose Galactose

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Functions of Proteins 3.Defence function .e.g Immunoglobulins(antibodies)

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Functions of Proteins 4.In gene expression: Histones are the proteins which the DNA double helix is wrapped around

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6. Nutrient and storage .E.g albumen of egg, Ferritin that stores iron.

Functions of Proteins

7.Proteins are infective agents.e.g Prions which cause mad cow disease are proteins

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8.Some toxins are proteins E.g Enterotoxin of cholera microorganism.

9.Some proteins provide structural strength and elasticity to the organs and vascular system. E.g Collagen and elastin of bone matrix and ligaments.

10. Some proteins are components of structures of tissues. E.g α-keratin is present in hair and epidermis

Functions of Proteins

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Nucleic Acids

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• They are made up of C, H, N, O, P

• The basic unit is a nucleotide

(nucleoside)

Nucleic Acids

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Sugar

Base

= Sugar + Base= Sugar + Base

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Sugar

Base

Phosphate

NucleosideNucleoside

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Glycosidic Bond is a bond between a sugar and another group

Ester Bond

Glycosidic Bond

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Composition of Nucleotides

Sugar

Bases

Phosphate

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Composition of Nucleotides

• Pentoses (5-C sugars or carbohydrate)• Numbering of sugars is “primed”

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Sugars

Ribose : forming Ribonucelotides

Deoxyribose: forming Deoxynucelotides (d-Nucleotides)

Oxygen missing

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Sugar (types)

fused five- and six-membered rings

Pyrimidines – N 1 forms glycosidic bond with sugarPurines -N 9 forms glycosidic bond with the sugar

six membered rings

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Bases

Adenine A

Guanine G

Thymine T Uracil U

Cytosine C2005/01/23

Bases

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Bases

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Bases

Bases Occurrence Bases Occurrence

Ribonucleotides only

Ribonucleotides & D-nucleotides

D-nucloetides only

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• Phosphates can be bonded to either C5 or C3Phosphate GroupsPhosphate Groups

Ester Bond

•They are linked by an Ester bond

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Mono, Di, Tri phosphate GroupsMono, Di, Tri phosphate Groups

Nucleoside 5’-Monophosphate

Nucleoside 5’- Diphosphate

Nucleoside 5’- Triphosphate

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• Purine nucleosides end in “-sine” “-sine” – Ribonucleoside Deoxynucleoside

• Adenosine Deoxyadenosine• Guanosine Deoxyguanosine

Naming Conventions of NucleosidesNaming Conventions of Nucleosides

Pyrimidine nucleosides end in “-dine”“-dine”– Ribonucleoside Deoxynucleoside

• Deoxythymidine • Cytidine Deoxycytidine• Uridine 2605/01/23

Start with the nucleoside name from above and add “mono-”, “di-”, or “triphosphate”

Naming Conventions of NucleotidesNaming Conventions of Nucleotides

RibonucleotidesRibonucleotides

PurinesPurinesAdenosine monophosphate(AMP), ADP, ATPGuanosine monophosphate(GMP), GDP, GTP

PyrimindinesPyrimindinesCytidine Monophosphate, CDP, CTPUridine Monophosphate, UDP, UTP

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Naming Conventions of NucleotidesNaming Conventions of Nucleotides

DeoxynucleotidesDeoxynucleotides

PurinesPurinesDeoxyadenosine monophosphate (d-AMP), d-ADP, d-ATPd- Guanosine Monophosphate, d-GDP, d-GTP

PyrimindinesPyrimindinesd- Cytidine Monophosphate, d-CDP, d-CTPd- thymidine Monophosphate, d-TDP, d-TPP

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Nucleotides are joined together by Phosphodiester bonds

ester bondester bond

ester bondester bond

Phosphodiester bondPhosphodiester bond

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Phosphodiester Bond (linkages)

Voet, Voet & Pratt 2013 Fig 3.3a,b

Nucleic Acids : Polymers of nucleotidesNucleic Acids : Polymers of nucleotides

Nucleic acid with deoxy ribose sugars---Deoxyribonucleic acid (DNA)

Nucleic acid with Contains ribose sugar---Ribonucleic acid(RNA)

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Bases in Nucleic Acids

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Memory Check

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Double helix ( 2 polynucleotide chains wound into the double helix) Base pairing between chains with H bonds

In base pairing A – T (double bond) C – G (triple bond)

Nucleic Acids : DNANucleic Acids : DNA

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Single stranded

It is made from the DNA template molecule

Uracil replaces the base thymine

During base pairing U----A

Nucleic Acids : RNANucleic Acids : RNA

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1. They are involved in the storage of genetic information.

Functions of nucleic acid in the cell

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1. They are involved in the expression of genetic information.

Functions of nucleic acid in the cell

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Functions of nucleic acid in the cell

1. They are involved in the transfer of genetic information.

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Some nucleic acids acts as enzymes and coenzymes. E.g. RNA (ribozyme) is coenzyme for telomerase which seals ends of chromosomes.

Functions of nucleic acid in the cell

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Nucleoside Derivatives and their functions

Adenosine derivatives

Guanosine derivative

Cytidine derivatives

Uridine derivatives

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Adenosine Triphosphate (ATP)

3'-5'-Cyclic Adenosine Monophosphate, “(cAMP or cyclic AMP)

Flavin Adenine Dinucleotide (FAD & FMN)

Nicotinaminde Adenine Dinucleotide (NAD+ & NADP)

S-adenosylmethionine (SAM)

Common Adenosine Derivatives

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ATP StructureATP Structure

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Adenosine Derivatives

1. Energy storage and transfer

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Cyclic AMP StructureCyclic AMP Structure

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Adenosine Derivatives

1. Second messenger in signal transduction

2.Regulate metabolism e.g. glycogen breakdown, lipids breakdown etc

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Flavin Adenine Dinucleotide (FAD(HFlavin Adenine Dinucleotide (FAD(H22)) & FMN(H & FMN(H22) Structure) Structure

Flavin Mononucloetide

(FMN)

Flavin

Coenzyme functioning as carrier of hydrogen and electrons in some redox reactions

sugar

+ H2

Riboflavin(Vit B 2)

FAD

FMN(HFMN(H22) or FAD(H) or FAD(H22))

phosphate

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Nicotinamide Adenine DinucleotideNicotinamide Adenine DinucleotideNAD (H)NAD (H)++ and NADP(H) and NADP(H)++ Structures Structures

+ H

Coenzyme functioning as carrier of hydrogen

and electrons some redox reactions

NADP

NADPH

NAD

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Coenzyme A StructureCoenzyme A Structure

Coenzyme serving as acyl group – R(CO) carrier in certain enzymatic reactions

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S- adenosylmethionine StructureS- adenosylmethionine Structure

Methyl (CH3) donor in methylation reactions4805/01/23

S-adenosylmethionine (SAM)

Common Adenosine Derivatives

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Guanosine Derivative

1. Energy store

2.Energy source for Protein synthesis and Gluconeogenesis

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Uracil Derivatives

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Cytidine Derivatives

CMP-N acetylneuraminic acid (CMP-NANA) required for the biosynthesis of glycoproteins

CDP-choline- required for the biosynthesis of sphingolipids (component of cell membrane of brain and nervious tissues).

CTP- required for the biosynthesis of phosphoglycerides (component of cell membrane)

sphingosine

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Synthetic Analogues of Nucleotides

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Synthetic Analogues of Nucleotides:Anti-tumour agents used in chemotherapy

Interfere with the synthesis of DNA and thereby preferentially kill rapidly dividing cells such as tumor cells.

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Synthetic Analogues of Nucleotides:Anti-tumour agents used in chemotherapy

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Synthetic Analogues of Nucleotides:Anti-Viral agents

Used to interfere with the replication of viruses by terminating DNA synthesis

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Synthetic Analogues of Nucleotides:Treatment of Gout

Caused by accumulation of uric acid

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Precursors of nucleic acids, DNA & RNA

Components of important co-enzymes ( like NAD+ and FAD, Co-enzyme A)

Storage and transfer of energy (ATP and GTP )

Storage and transfer of genetic information (DNA & RNA)

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Biomedical importance of nucleotides

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Biomedical importance of nucleotides

Memory Check

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Memory CheckMemory Check

Ribonucleotides only

Ribonucleotides & D-nucleotides

D-nucloetides only

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S-adenosylmethionine (SAM)

Memory CheckMemory Check

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Memory CheckMemory Check

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Memory CheckMemory Check

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Memory CheckMemory Check

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Memory CheckMemory Check

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Memory CheckMemory Check

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Memory CheckMemory Check

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Memory Check

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Memory CheckMemory Check

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Memory CheckMemory Check

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Memory checkMemory check

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Nucleotide ChemistryNucleotide ChemistryBAHS 233BAHS 233

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Minor Pyrimidine nucleosides

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Minor Purine Nucleosides

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