Chapter 30 - Amino acids, protein, and DNA

Question 1

Are amino acids chiral?

Answer 1

• Yes
• Mostly exist at (-) enantiomer

Question 2

Describe how the carboxylic acid group of an amino acid reacts

Answer 2

• Lose proton/acts as an acid

Question 3

Describe how the amine group of an amino acid reacts

Answer 3

• Accept proton/acts as a base

Question 4

What is an alpha amino acid?

Answer 4

An amino acid with 1 carbon between the amine group and the carboxylic acid group

Question 5

Define zwitterion

Answer 5

An ion that has two charges at the same time

Question 6

Describe the charge on an amino acid

Answer 6

• In the solid state, all amino acids exist as zwitterions
• H falls off carboxylic acid group and attaches to amine group
• Positive charge on N, - charge on O

Question 7

Describe and explain the physical properties of amino acids

Answer 7

Ionic

• Have high melting points (Solid at room temp)
• Soluble in water

Question 8

List the reactions that can be undergone by the amine group of an amino acid

Answer 8

• Protonated by acids
• Acylation with acyl chloride/acid anhydride
• Nucleophilic substitution with haloalkanes

Question 9

List the reactions that can be undergone by the carboxylic acid group of an amino acid

Answer 9

• Deprotonated by bases
• Acylation
• Esterification with alcohols

Question 10

Describe the bonding present in the secondary structure of a polypeptide

Answer 10

• H bonding
• N and O are very electronegative so C=O and N-H are polar
• Lone pair on O of amino acid attracted to the partially postivive H on another

Question 11

What is a disulphide bond?

Answer 11

A covalent bond between two sulphurs

Question 12

How do enzymes work as biological catalysts?

Answer 12

• Lock and key theory
• Active sites are stereospecific to substrates

Question 13

How does enzyme inhibition work?

Answer 13

• Similar shape to enzyme active site
• Block the active site so no substrate can fit

Question 14

Give the 4 DNA bases in their pairs

Answer 14

• Adenine - Thymine
• Guanine - Cytosine

Question 15

Describe how nucleotides form

Answer 15

• Phospate attachs on the 5’ carbon in the sugar
• Bases attach to the 1’ carbon

Question 16

How do you number the carbons in a deoxyribose sugar?

Answer 16

Number from the right of the oxygen and move clockwise

Question 17

What is cisplatin and how does it work?

Answer 17

• cis-diamminedichloroplatinum (II)
• Cisplatin attaches to N atoms of guanine bases in a ligand replacements reaction
• This stops the DNA strands unwinding so DNA replication cannot happen
• Cancer cells can no longer divide

Question 18

Describe the side-effects of treatment with cisplatin

Answer 18

• Hair loss
• Nausea
• Immunosuppression

Question 19

Give some ways of reducing the side-effects of treatment with cisplatin

Answer 19

• Use lowest therapeutic dose
• Develop new drugs
• Find ways of targeting cancer cells directly