3.13 Amino Acids,DNA And Proteins

Question 1

What groups make up an amino acid?

Answer 1

1. Amine
2. Carboxylic acid
3. R group

Question 2

What are the features of chirality in amino acids?

Answer 2

• All chiral except glycine
• Form two non super impossible mirror images as enantiomers

Question 3

Are Amino acids an acid or a base?

Answer 3

Both as they are amphoteric

Question 4

How do amino acids react with acids/bases?

Answer 4

• Acids= Amine group reacts
• Bases= Acid group reacts

Question 5

What happens if the R group is also an amine/acid group in an acid base reaction?

Answer 5

Both of the reacting groups will react

Question 6

What is a zwitterion?

Answer 6

A species with two ions

Question 7

What are the properties of an amino acid?

Answer 7

• FOund as white solids
• Conduct electricity when aqueous/molten

Question 8

What reactions do amino acids undergo?

Answer 8

• Acid + Base
• Acid + Alcohol—> Ester + H2O
• Nucleophilic substitution with a halogenoalkane
• Nucleophilic addition-elimination with an acyl chloride
• Condensation reaction to make proteins

Question 9

How can peptides/polypeptides be hydrolysed?

Answer 9

• Can be heated with conc HCl or conc NaOH
• Hydrolyses the substance and breaks the peptide bond

Question 10

How are proteins formed?

Answer 10

Condensation reactions between amino acids

Question 11

What bonds bond proteins?

Answer 11

Peptide bonds

Question 12

What is the primary structure of a protein?

Answer 12

• The sequence of amino acids in proteins/polypeptide

Question 13

What is the secondary structure of proteins?

Answer 13

• Alpha Helix- corkscrew/spiralling of chain held in place by hydrogen bonds
• Beta pleated sheets- chains fold into parallel strands and H bond occurs further down the chain

Question 14

What is the tertiary structure of proteins?

Answer 14

• The folding og the secondary structure into more complex shapes

Question 15

What interactions occur within the tertiary structure of a protein?

Answer 15

• Hydrogen bonding
• van der waals
• disulfide bridges
• Ionic bonds
• Permanent dipole

Question 16

What is the quaternary structure of a protein?

Answer 16

• Overall folding into a complex 3D shape so more than one polypeptide interacts with

Question 17

What is stereospecificity?

Answer 17

The active site of an enzyme is selective of a shape of a substrate meaning it can catalyse only one of the enantiomers

Question 18

What needs to be in place for an enzyme to work?

Answer 18

• Interactions between active site and enzyme need to be strong enough for substrate to be held in place long enough for it to be catalysed and weak enough for it to be released

Question 19

How do drugstore work as enzyme inhibitiors?

Answer 19

• Enter active site and bind strongly to block it
• Bind to another part of enzyme which changes shape of active site

Question 20

What are the three parts of DNA?

Answer 20

• A sugar
  -A phosphate
• A NItrogenous base

Question 21

How many hydrogen bonds do G and C form?

Answer 21

3

Question 22

How many hydrogen bonds do A and T form?

Answer 22

2

Question 23

How does cisplatin stop a cancer tumour growing?

Answer 23

• Stops DNA replication
  -Pt binds to N in guanine in DNA

Question 24

What are some side effects of cisplatin as an anti-cancer drug and why?

Answer 24

• Stops healthy cell replication
• Can cause weakened immunity,hair loss etc.

Question 25

Why do amino acids have different solubilities in chromatography?

Answer 25

• Different solubilities in mobile phase
• Different attraction to stationery phase