1.4.1 Proteins

Question 1

describe the general structure of an amino acid

Answer 1

● COOH = carboxyl group
● R = variable side chain / group
● H2N = amine group

Question 2

how many amino acids are common in all organisms?

Answer 2

20

Question 3

how do amino acids vary

Answer 3

-in their side group (R)

Question 4

describe how amino acids join together

Answer 4

-condensation reaction
-removing a water molecule
-between carboxyl / COOH group of one and amine / NH2 group of another
-forming a peptide bond

Question 5

what are dipeptides

Answer 5

-2 amino acids joined together

Question 6

what are polypeptides

Answer 6

-many amino acids joined together

Question 7

what does a functional protein contain

Answer 7

-one or more polypeptides

Question 8

describe the primary structure of a protein

Answer 8

-sequence of amino acids in a polypeptide chain, joined by peptide bonds

Question 9

describe the secondary structure of a protein

Answer 9

-folding (repeating patterns) of polypeptide chain eg.
alpha helix / beta pleated sheets
-due to hydrogen bonding between amino acids
-between NH (group of one amino acid) and C=O (group)

Question 10

describe the tertiary structure of a protein

Answer 10

-3D folding of polypeptide chain
-due to interactions between amino acid R groups (dependent on sequence of amino acids)
-forming hydrogen bonds, ionic bonds and disulfide bridges

Question 11

describe the quaternary structure of a protein

Answer 11

-more than one polypeptide chain
-formed by interactions between polypeptides
(hydrogen bonds, ionic bonds, disulfide bridges)

Question 12

describe the test for proteins

Answer 12

1. add biuret reagent (sodium hydroxide + copper (II) sulphate)
2. positive result = purple / lilac colour (indicating presence of peptide bonds)