Topic 2.4

Essential idea: Proteins have a very wide range of functions in living organisms.


Amino acid structure

Amino acid structure

2.4.U1 Amino acids are linked together by condensation to form polypeptides

Condensation reactions involve joining together monomers to form larger, more complex macromolecules. This chemical process involves the removal of water molecules. A monomer is a chemical subunit that serves as a building block of a polymer. Outlined below are the condensation reactions of (i) amino acids into dipeptides with the formation of a peptide linkage and (ii) amino acids into polypeptides through the formation of peptide linkages.

Place your mouse over the particular number to see the products of the reaction.

(i)Dipeptide Condensation
(ii)Dipeptide Condensation

2.4.U2 There are 20 different amino acids in polypeptides synthesized on ribosomes

amino acids make up proteins

2.4.U3 Amino acids can be linked together in any sequence giving a huge range of possible polypeptides

Huge range of polypeptides

2.4.U4 The amino acid sequence of polypeptides is coded for by genes

Genes code for amino acid sequence

2.4.U5 A protein may consist of a single polypeptide or more than one polypeptide linked together

Structures in proteins

2.4.U6 The amino acid sequence determines the three-dimensional conformation of a protein

Primary structures in proteins

2.4.U7 Living organisms synthesize many different proteins with a wide range of functions

Types and functions of proteins

2.4.U8 Every individual has a unique proteome

Genome vs Proteome


2.4.A1 Rubisco, insulin, immunoglobulins, rhodopsin, collagen and spider silk as examples of the range of protein functions

Type Function Example Example
Enzymes Increase the rate of a reaction Rubisco Ivolved in the first major step of carbon fixation in the light-independent reaction.
Hormone Chemical substance that affect the activity of another part of the body (target site). Insulin Regulates glucose metabolism.
Protective Antibodies involved in the immune system. Immuniglobulins Antibodies that react against antigens in the body.
Cell-surface receptor Transmission of a nerve impulse. Rhodopsins A pigment that absorbs light energy and allows to see in low light.
Support Give shape and structure to cells and organelles. Collagen Supports body tissues.
Structural Provide support, strength and protection. Spider silk Catching, wrapping and immobiliz

2.4.A2 Denaturation of proteins by heat or by deviation of pH from the optimum

Denaturation of proteins


2.4.S1 Drawing molecular diagrams to show the formation of a peptide bond

Dipeptide condensation
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