PL.4

Question 1

What functional groups does amino acids contain?

Answer 1

At least one amino group, -NH2 and one carboxylic group, -COOH.

Question 2

When is an amino acid an 𝛂 amino acid?

Answer 2

When the 𝛂 carbon is attached to a COOH group, NH2 group, a H and a R group respectively.

Question 3

Amino acids are an example of what type of compound?

Answer 3

Bifunctional compound.

Question 4

Amino acids show properties of both functional group such as?

Answer 4

Amine’s base properties, such as reacting with acids to form salts, and the carboxylic acid’s acidic properties, such as reacting with bases to form salts.

Question 5

What type of ion is formed with the proton donating COOH group interact with the proton accepting NH2 group?

Answer 5

A zwitterion.

Question 6

What is a zwitterion?

Answer 6

An ion that contains both negatively charged group and positively charge group.

Question 7

In aqueous solutions, in what form are amino acids normally present in?

Answer 7

As zwitterions, this means that amino acids are very soluble in water as they are effectively ionic.

Question 8

Are amino acids always neutral in the respect that they occur as zwitterions?

Answer 8

Not always, as some amino acids may have extra NH2 groups or COOH groups present in the R group.

Question 9

What is the general formula of amino acids in neutral solutions?

Answer 9

H3N+CHRCOO-

Question 10

What is the general formula of amino acids in acidic solutions?

Answer 10

H3N+CHRCOOH

Question 11

What is the general formula of amino acids in alkaline solutions?

Answer 11

H2NCHRCOO-

Question 12

A solution like amino acid that can withstand the addition of small amounts of acid or alkali without much change in pH is known as what?

Answer 12

Buffer solutions.

Question 13

What type of isomerism do amino acids show?

Answer 13

Optical isomerism.

Question 14

Why do amino acids show optical isomerism?

Answer 14

Because they usually have four different groups around a carbon atom.

Question 15

Optical isomerism is a type of what isomerism?

Answer 15

Stereoisomerism. Where groups can be arranged differently in space.

Question 16

What is the carbon atom called that has four different groups attached to it?

Answer 16

It is called a chiral carbon.

Question 17

What type of mirror image do molecules exert when they have a chiral centre?

Answer 17

Non superimposable mirror images.

Question 18

What are the different forms of optical isomers known as?

Answer 18

Enantiomers.

Question 19

Do amino acids in our bodies exist as different enantiomers?

Answer 19

No, they only exist as one enantiomer of each amino acid, also known as L enantiomers.

Question 20

What is the mixture called when it contains 50:50 of each enantiomer?

Answer 20

Racemic mixture.

Question 21

When two amino acids join together by a secondary amide link, what is the secondary amide group also known as?

Answer 21

A peptide link.

Question 22

When two amino acids are joined together, what is it called?

Answer 22

Dipeptide.

Question 23

When naming a dipeptide, the first part of the name refers to which amino acid?

Answer 23

The one reacting with its COOH group.

Question 24

When naming a dipeptide, the second part of the name refers to which amino acid?

Answer 24

The one reacting with its NH2 group.

Question 25

What are proteins?

Answer 25

Naturally occurring condensation polymers made from amino acid monomer joined together by peptide links.

Question 26

All proteins are built from how many different amino acids arranged in different ways?

Answer 26

20

Question 27

Why are amino acids referred to as residues in context of proteins?

Answer 27

Residue is when an amino acid has lost the element of water in forming proteins.