SIMON’S GUIDE TO PROTEINS Some foods containing protein

FUNCTIONS OF PROTEINS Protein has a range of essential functions in the body, including the following: Required for building and repair of body tissues (including muscle) Enzymes, hormones, and many immune molecules are proteins Essential body processes such as water balancing, nutrient transport, and muscle contractions require protein to function. Protein is a source of energy. Protein helps keep skin, hair, and nails healthy. Protein, like most other essential nutrients, is absolutely crucial for overall good health.

PROTEINS AND YOUR DIET Proteins are therefore an essential component of your daily diet. The Recommended Daily Allowance (RDA) of protein according to U.S. government standards is 0.8 gram per kilogram (2.2 pounds) of ideal body weight for the adult. A person weighing 10 stone (about 64 kg) therefore needs about 50 g of protein per day

WHAT ARE PROTEINS? Proteins are condensation polymers made from amino acids. The structure, and therefore the function, of a protein depends entirely on the amino acid sequence. During digestion, proteins undergo hydrolysis and are split up into their component amino acids. The body can then use these as building blocks to make the proteins it needs.

This structure is known as a zwitterion. Amino acids are therefore solids that are soluble in water, like other ionic compounds.

Which is the only amino acid that does not show optical isomerism?

IONISATION OF AMINO ACIDS In solution at pH 7, amino acids occur as zwitterions. Below pH 7 the carboxyl group will become increasingly less ionised (like any carboxylic acid), whilst the amino group remains ionised: + H 3 NCHRCOO - + H + = + H 3 NCHRCOOH If the R group contains carboxyl groups or amino groups then these will be affected similarly. Above pH 7, the amino group will become increasingly less ionised (like any amine), whilst the carboxyl group remains ionised: + H 3 NCHRCOO - + OH - = H 2 NCHRCOO - + H 2 O If the R group contains carboxyl groups or amino groups then these will be affected similarly. These properties affect the separation of amino acids by a process called electrophoresis which you will learn about later.

LEVELS OF PROTEIN STRUCTURE Primary: the sequence of amino acids in the chain Secondary: folding of the chain caused by hydrogen bonding between different peptide bonds Tertiary: folding of the chain caused by interactions between the R groups Quaternary: interactions between different chains (subunits) of the same protein

PRIMARY PROTEIN STRUCTURE

SECONDARY PROTEIN STRUCTURE

TERTIARY PROTEIN STRUCTURE

QUATERNARY PROTEIN STRUCTURE

OVERALL PROTEIN STRUCTURE

And now for something completely different … One of Simon’s holiday pictures Where was this picture taken? (Answer on final slide ) About time, too!

Where are Simon and Dee sheltering from the rain?

Answer Hiroshima, Japan The “A bomb dome” THE END