2A functional diversity of proteins

• Proteins also known as polypeptides are large complex structures that are crucial to the functioning and development in all living organisms. .
• Proteome refers to collection of proteins in a cell.
• Enzymes are organic catalysts that speed up chemical reactions.
• Transport proteins facilitate the control of entry and exit of molecules across the membrane.
• Proteins made for defence are involved in the immune system, they recognise and destroy pathogens.
• Hormones (proteins) function as chemical messengers to communicate and induce changes in the cell.
• Motor/contractile (proteins) responsible for the contraction and movement in muscles.
• Storage (proteins) act as reserves for ions and other molecules.
• Amino acids are the building blocks of proteins (monomers). They're made up of a central carbon atom bonded to a hydrogen atom, contain a carboxyl group (COOH), an amino group (NH2) and an R-group.
• The R-group in amino acids affect how different amino acids within a protein interact with each other.
• When amino acids join together they form a long chain of polypeptides (protein). Joining occurs at the cell's ribosome via a condensation reaction, water is created which then results in peptide bonds between adjacent amino acids.
• The shape of a protein determines its function. 4 levels of protein structure that describe how polypeptide chains fold to form a protein with a specific function - Primary, secondary, tertiary and quaternary.
• Primary level describes the sequence of amino acids in a polypeptide chain.
• Secondary level describes when the polypeptide chain folds and coils by forming hydrogen bonds between amino acids. These are labelled as alpha helices, beta-pleated sheets and random coils.
• Tertiary level is the overall 3D shape of a protein formed when secondary structures are further folded by forming bonds and interactions between amino acids and r-groups. Disulphide bonds form between cystine amino acids due to the presence of sulphur.
• Quaternary level is when there are 2 or more polypeptide chains joined together. Not all proteins have a quaternary structure.