1.4 proteins

Question 1

what’s the general structure of an amino acid?

Answer 1

-COOH carboxyl group

-R variable side group

-NH2 amine/amino group

Question 2

describe how to test for proteins in a sample

Answer 2

Biuret test confirms a presence of a peptide bond

1) add equal volume of sodium hydroxide to sample at room temperature

2) add drops of dilute copper sulfate, mix

3)positive result: colour changes from blue to purple

negative results: solution remains blue

Question 3

How many amino acids are there and how do they differ from one another?

Answer 3

20
differ only by one side group (R group)

Question 4

how do dipeptides and polypeptides form?

Answer 4

-condensation reaction forms peptide bond & eliminates a molecule of water

-dipeptide: 2 amino acids
-polypeptide: 3 or more amino acids

Question 5

How many levels of protein structure are there?

Answer 5

4

Question 6

define primary structure of a protein

Answer 6

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

Question 7

define secondary structure of a protein

Answer 7

-hydrogen bonding between the amino acids
-causes the polypeptide chain to fold into a repeated pattern
e.g alpha helix or beta pleated sheet

Question 8

define tertiary structure of a protein

Answer 8

overall 3D structure of a polypeptide
held together by ionic bonds, hydrogen bonds and disulfide bridges.

Question 9

define quaternary structure of a protein

Answer 9

made from 2 or more polypeptide chains
held together by ionic, hydrogen and disulfide bonds.

Question 10

examples of proteins

Answer 10

enzymes, antibodies

Question 11

whats the biuret test used to indicate?

Answer 11

if proteins are present