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PROTEINS

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Learning Outcomes/Objectives:

State the elements in proteins.

State the various structure of proteins.

Explain the formation and breakdown of dipeptides and polypeptides.

Explain the meanings of essential amino acids and non essential amino acids.

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Introduction

Protein are large complex organic molecules which play diverse roles in living organisms.

Proteins made up of such elements as carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus.

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Amino acid + amino acid dipeptide + water

Polypeptides + water dipeptides or amino acids

condensation

hydrolysis

hydrolysis

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Examples

Protein sources: egg, meat, milk, yoghurt and etc.

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Protein Structures

a) Primary structure

b) Secondary structure- alpha-helix- beta-pleated sheets

c) Tertiary structure

d) Quaternary structure

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a) Primary structure

The linear sequence of amino acids in a polypeptide chain.

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b) Secondary structure

i) Alpha-helix- Three dimensional arrangement of amino acids with the polypeptide chain in a cork screw shape.

ii) Beta-pleated sheet- Polypeptide chains are arranged side by side.

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c) Tertiary structure

The overall three dimensional shape of a polypeptide chain.

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d) Quaternary structure

The combination of two or more tertiary polypeptides that makes up a protein.

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Amino Acids

There have two types of amino acids:i) essential amino acidsii) non essential amino acids

Essential amino acids are amino acids that cannot be synthesized by the body. Example: Leucine

Non essential amino acids are amino acids that can be synthesized by the body. There are 11-non essential amino acids. Example: Alanine

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Thank You