g1. Primary and secondary structure (proteins)

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What does primary structure mean?

The particular amino acids in a chain and the sequence in which they are joined

What does polypeptide mean?

Several thousand amino acids linked together in a long chain

What does secondary structure mean?

The shape that the polypeptide forms as a result of hydrogen bonds between amino and carboxyl groups of amino acids

What are the two most common types of secondary structure?

Alpha helix and beta-pleated sheet

How does an alpha helix form?

Hydrogen bonds form between the oxygen of the carboxyl group of one amino acid and the hydrogen of the amino acid of the amino acid 4 places ahead of it

What do the hydrogen bonds allow the secondary structure to do?

Twists the chain into a spiral shape

Example of alpha helix

Keratin

How does a beta-pleated sheet form?

2 or more segments of one polypeptide line up next to each other, forming a sheet like structure

How is the beta-pleated sheet held?

Hydrogen bonds formed between carboxyl part of one segment and amino part of another segment

How is the beta-pleated sheet different to the alpha helix?

Stronger but less elastic structure

Example of a beta-pleated sheet

Fibroin - protein found in silk