Unit 3.4.8 - Amino Acids

Question 1

What two functional groups to amino acids contain?

Answer 1

An amino group -NH₂ and a carboxyl group -COOH

Question 2

What differs between all amino acids?

Answer 2

They R group, the side chains

Question 3

What does amphoteric mean?

Answer 3

It means something has both acidic and basic properties

Question 4

Why are amino acids amphoteric?

Answer 4

Because they have the -COOH group which acts as an acid and can donate a proton but they also have a -NH₂ group which acts as a base and accepts protons

Question 5

Why are amino acids chiral molecules?

Answer 5

They usually have four different groups attached to one carbon

Question 6

How do you name amino acids

Answer 6

Longest chain attached to the carboxylic group, and then write this down as the suffix, and then use the prefix amino- for any amino groups, using the carbon in the carboxylic group as carbon-1

Question 7

What can amino acids exist as?

Answer 7

Zwitterions

Question 8

What is a zwitterion?

Answer 8

A diploar ion which has both positive and a negative charge in different parts of the molecule

Question 9

When can amino acids exist as zwitterions?

Answer 9

Near the isoelectric point, this is where the overall charge on the amino acid is zero

Question 10

How can an amino acid become a zwitterion?

Answer 10

When a H⁺ is donated to the amino group to become NH₄⁺ and one is removed from the carboxyl group to be COO⁻

Question 11

If an amino group has gained a H⁺ what is said to be?

Answer 11

Protonated

Question 12

If a carboxyl group has lost a H⁺ what is said to be?

Answer 12

Deprotonated

Question 13

What do amino acids look like in more acidic conditions?

Answer 13

With a NH₄⁺

Question 14

What do amino acids look like in more basic conditions?

Answer 14

With a COO⁻

Question 15

What are proteins?

Answer 15

Long chains of amino acids

Question 16

What type of bond joins two amino acids together

Answer 16

A peptide bond

Question 17

What type of reaction joins together two amino acids?

Answer 17

Condensation reaction

Question 18

What type of reaction breaks down chains of amino acids?

Answer 18

Hydrolysis reaction

Question 19

Why is it possible to from two different dipeptides when joining two amino acids together?

Answer 19

The amino acids can join together at either ends

Question 20

What conditions do you have to use to break apart a protein through hydrolysis?

Answer 20

Harsh conditions like strong hydrochloric acid and heated under reflux for 24 hours

Question 21

Why do chains of proteins fold and twist?

Answer 21

Due to intermolecular and intramolecular forces like hydrogen bonding

Question 22

Where does hydrogen occur between in proteins and why?

Answer 22

The O and N are electronegative atoms which induces a partial positive charge on the hydrogen atom, which means the hydrogen atom is attracted to a lone pair of electrons on the adjacent group like the O or N and so a hydrogen bond is formed

Question 23

What is vital to how proteins function?

Answer 23

Their shape

Question 24

Why is their shape vital to how proteins function?

Answer 24

If there were to change shape it could lead to non functional enzymes

Question 25

What two factors affect a proteins shape and why?

Answer 25

pH and temperature because they affect the hydrogen bonding holding the protein together in its shape

Question 26

What can you use to separate a mixture of amino acids?

Answer 26

Chromatography

Question 27

In five steps describe how you would carry out chromatography to separate a mixture of amino acids?

Answer 27

1.) Draw a pencil line near the bottom of a piece of chromatography paper 2.) Place a concentrated spot of the mixture of amino acids on this line 3.) Dip the bottom of the paper into a solvent 4.) As the solvent spreads up the paper the different amino acids with move with it but at different rates so separate out 5.) You can compare how far each spot has moved up against the standard to identify which amino acid it is

Question 28

What do you have to spray chromatography paper with when separating out amino acids?

Answer 28

Ninhydrin solution

Question 29

Why do you have to spray chromatography paper with ninhydrin solution when separating out amino acids?

Answer 29

The spots would otherwise be colourlesss, the ninhydrin solution turns them purple

Question 30

Draw the general structure of an amino acid.

Answer 30

Question 31

Draw a diagram to show how amino acids can be chiral molecules.

Answer 31

Question 32

Draw the reversible condensation reaction that joins two amino acids together.

Answer 32

Question 33

Draw an amino acid at its isoelectric point.

Answer 33

Question 34

Draw an amino acid at high pH.

Answer 34

Question 35

Draw an amino acid at low pH.

Answer 35