3.3.13 - Amino Acids, Proteins And DNA

Question 1

What is an amino acid

Answer 1

Carbon attached to carboxylic acid, amine group
Monomer which makes up protein (polypeptide)

Question 2

Peptide =

Answer 2

2 more amino acid linked in a chain by peptid bonds

Question 3

Proteins acts as

Answer 3

Enzymes
Hormones
Antibodies etc

Question 4

Alpha amino acid struc and general formula

Answer 4

RCH(NH2)COOH
Carbon w Amine carboxylic acid r and hydrogen attached
R group is an alkyl chain that can also contain OH, SH, COOH, NH2

Question 5

Amino acids can behave as both …. Bc …

Answer 5

Bases and acids
Contains carboxylic acid and amine functional groups

Question 6

Reaction of the amine group

Answer 6

In acidic conditions the N in the amine group can accept a h+ ion
Lone pair of e- on N forms dative covalent bond
With h+
Gives N on amine to have positive charge
Amine group has been protonated

Question 7

Important in drawing amino acid

Answer 7

Carbon must be bonded to n in amine and a c in carboxylic acid so may have to write something backwards

Question 8

Reactions of the carboxylic acid group

Answer 8

In alkaline cond
Amino acid acts as a acid
The COOH looses a h+ ion
Oxygen Atom has now been left w a neg charge
So carboxylic acid group has been deprotonated

Question 9

Under the right conditions amino acid can exist as a …

Answer 9

Zwitterion

Question 10

Zwitterion

Answer 10

Proton is transferred from the carboxylic acid group to the amine group
Creating both a pos and neg charge on diff parts on the mol
Thus Zwitterion has no overall chargw bc pos and neg charges cancel out

Question 11

Physical properties of amino acid

Answer 11

Behave like ionic salts bc of their struc
High mp and are soluble in water but not in non polar solvents
At room temp most pure amino acids will be a white solid

Question 12

Optical activity in amino acids

Answer 12

Natural occurring alpha amino acid are optically active
They all exist as the same enantiomer meaning they rotate plane polarised light anti clockwise

Question 13

Exception (amino acid which doesn’t show optical activity) is …

Answer 13

Glycine
Bc the R group is just a H so carbon only bonded to 3 other groups

Question 14

Polymers of amino acids are known as

Answer 14

Peptides

Question 15

Amide link referred to as

Answer 15

Peptide link
Water mol eliminated when peptide link is formed

Question 16

Hydrolysis of polypeptides occurs why they react w….

Answer 16

Boiling water
Acid
Alkali
Enzyme catalysing the reaction