PROTEINS

Question 1

what are proteins

Answer 1

diverse group of large and complex polymer molecules, made of long chains of amino acids

Question 2

what are amino acids

Answer 2

basic monomer units which combine to form a polymer called polypeptide, which can be combined to form proteins

Question 3

role of proteins

Answer 3

structural-proteins are the main component of body tissues, such as muscle, skin, ligaments and hair
catalytic- all enzyme are proteins catalyzing many biochemical reactions
signaling-many hormones ad receptors are proteins
immunological-all antibodies are proteins

Question 4

how many naturally occuring amino acids are there

Answer 4

20

Question 5

formation of a peptide bond

Answer 5

Amino acid monomers combine to form a dipeptide, containing a peptide bond, by a condensation reaction

Question 6

how is a polypeptide formed

Answer 6

The –OH group from one of the amino acids combine with the –H from amino group of the other amino acid

Question 7

describe the primary structure of a protein

Answer 7

sequence of amino acids within proteins
the sequence is determined through an organisms DNA
determines the ultimate shape and therefore function of a protein
a change in a single amino acid can change the shape of the protein and stop it from functioning

Question 8

describe the secondary structure of proteins

Answer 8

hydrogen on the -NH has a positive charge, while the Oxygen in -C=O has a negative charge
these two groups form weak bonds called hydrogen bonds
this causes the chain to be twisted into an alpha helix, creating a 3D shape

Question 9

describe the tertiary structure of proteins

Answer 9

alpha helix can be twisted and folded even further to give the complex 3D structure of each protein
maintained by a different number of bonds:
disulfide bonds-fairly strong and only occur if the protein has amino acids containing sulphur
ionic bonds- formed between carboxyl and amino group which are easily broken
hydrogen bonds- numerous but easily broken

Question 10

describe the quaternary structure of proteins

Answer 10

large and complex molecule
contains a number of individual polypeptide chains that are linked in various ways
may also be a non-protein group associated with the molecule, which helps with its function
e.g. hemoglobin contains an iron-containing haem group