structure of proteins

Question 1

how do proteins vary?

Answer 1

proteins vary in the number, type and sequence of amino acids they contain, which produces a vast number of different protein molecules, and they can be classified according to their structure

Question 2

what is the primary structure of a protein?

Answer 2

primary structure refers to the sequence of amino acids joined by peptide bonds in the polypeptide chain and this sequence determines the specific shape and therefore function of the protein

Question 3

what is the secondary structure of a protein?

Answer 3

secondary structure represents the folding or coiling of the polypeptide chain as a result of hydrogen bonding between amino acids, secondary structures include the α helix and β pleated sheet formed by hydrogen bonding between amino acids in the chain

Question 4

what is the tertiary structure of a protein?

Answer 4

tertiary structure represents further folding and coiling of the secondary structure due to hydrogen bonds, ionic bonds and disulphide bridges, the tertiary structure of enzymes determines the shape of it’s active site and it’s precise function

Question 5

describe the properties of
- disulphide bridges
- ionic bonds
- hydrogen bonds
- hydrophobic interactions

Answer 5

disulphide bridges are fairly strong and not easily broken
ionic bonds are weaker and easily broken between changes in pH
hydrogen bonds are weak but many of them are strong
hydrophobic interactions is when amino acids that are hydrophobic cluster together on the inside of the protein and amino acids that are hydrophilic are on the outside so they interact with water

Question 6

what bonds will break first when temperature increases?

Answer 6

ionic and hydrogen bonds

Question 7

what are globular proteins?

Answer 7

globular proteins consist of a highly folded and coiled polypeptide chain or chains to produce a compact, complex tertiary structure. they include enzymes and antibodies, they are soluble and have a specific tertiary structure

Question 8

what are fibrous proteins?

Answer 8

fibrous proteins are typically long, thin, insoluble and usually have structural functions eg keratin in hair and collagen in connective tissue

Question 9

what’s the quaternary structure of proteins?

Answer 9

the quaternary structure relates to highly complex proteins consisting of more than one polypeptide chain, where the chains are held together by ionic bonds, hydrogen bonds, disulphide bridges and hydrophobic interactions eg haemoglobin consists of four polypeptide chains

Question 10

what is the prosthetic group?

Answer 10

not a protein that is attatched