Amino acids, Carbohydrates and DNA

Question 1

Describe the structure of an amino acid

Answer 1

• A basic amino group (NH2+)
• An acidic carboxyl group (COO-)
• A side chain - R group

All are attached to CH group to form an alpha amino acid

Question 2

Chirality of amino acids

Answer 2

• Glycine is achiral
• Every other amino acid is chiral
• alpha-carbon is the centres of chirality

Question 3

what bond holds together amino acids?

Answer 3

Amide bonds between the NH2 and CO2H of two amino acids

Question 4

Difference between peptide and protein?

Answer 4

• peptides: smaller chains with fewer than 50 units

* large chains that have structural or catalytic functions in biology

Question 5

What are the terminals found on peptides/proteins?

Answer 5

• N-terminus (Drawn on the left side) - side with amine group
• C-terminus (Drawn on the right side) - side with carboxyl group

Question 6

How do you determine the sequence of amino acids in a peptide/protein?

Answer 6

• need to break amide bond - can be done chemically or using enzymes

1. non selective - break all amide bonds
2. selective - break specific amid bonds

Question 7

What are the steps in identifying the amino acid sequence from partial acid hydrolysis?

Answer 7

1. identify the N-terminus
2. partial acid hydrolysis
3. Identify the common amino acids and align the peptides to obtain the sequence

Question 8

Describe the steps that occur to produce peptide ‘Ala-leu’

Answer 8

1. amino group of ala is protected as BOC derivative
2. Carboxyl groups of leu protected as the methyl ester
3. two protected amino acids are coupled using DCC
4. The BOC protecting groups is removed by acid treatment
5. Methyl ester is removed by basic hydrolysis

Protection ensure the carboxyl group of ala bonds with amino group of leu to produce ala-leu, in that order

Question 9

What are carbohydrates?

Answer 9

• an energy storage material that allows the utilisation of solar energy
• most abundant biomolecule on earth

Question 10

What are carbohydrates named according to?

Answer 10

1. whether they are an aldehyde or ketone
2. number of carbons (tri-, tetra-, penta-)
3. the suffix ‘ose’ to indicate a saccharide
4. ‘D-‘ or ‘L-‘ depending on the stereochemistry of the highest numbered stereogenic centre

Question 11

Describe the steps involved in the formation of a peptide

Answer 11

1. using BOC derivative protect the N-terminus of first amino acid
2. protect carboxyl group of 2nd amino acid using the methyl ester
3. the two protected amino acids are joined using DCC
4. BOC protecting group removed by acid treatment and methyl ester removed by basic hydrolysis

Question 12

What is used to protect amino group?

Answer 12

Boc derivative us the group used to protect amino group

Question 13

What is used to join the amino acids together

Answer 13

DCC

Question 14

What is used to protect carboxyl group?

Answer 14

Methyl ester with H+ catalyst

Question 15

How are the protective groups removed from animo and carboxyl groups

Answer 15

Amino: Boc removed by acid treatment (CF3CO2H)

Carboxyl: methyl ester removed by basic hydrolysis (NaOH, H2O)