Amino acids, proteins and DNA (Organic) (complete)

Question 1

Describe the structure of a zwitterion

Answer 1

An amino acid with a positive charge on the amine group and a negative charge on the carboxyl group.
Occurs due to each amine group being protonated by a carboxyl group on another molecule.

Question 2

Name the need to know amino acid and describe its structure.

Answer 2

Glycine - Usual amine group, cabocyl group and hydrogen atom, but R group is also a H atom.

Question 3

Explain how amino acids show optical isomerism, and how this is presented in nature

Answer 3

• All but glycine show optical isomerism as they have four different groups on the chiral carbon atom.
• In nature only one enantiomer is present.

Question 4

Describe how dipeptides are formed

Answer 4

Amino acids are joined together in a condensation reaction, eliminating water and forming an amide link (peptide bond) between the amine group on one amino acid and the carboxyl group on another.

Question 5

Give the definition of enzymes

Answer 5

proteins that act as catalysts in biological systems

Question 6

Which base pair (GC or AT) would require more energy to break apart?

Answer 6

GC as they contain three hydrogen bonds between the bases while AT only contain two hydrogen bonds between the bases.

Question 7

Describe the 3’ , 5’ direction found in DNA

Answer 7

• When the DNA strand is formed, the 1st nucleotide has a free OH- group on the 3rd carbon (3’ prime) and the last nucleotide has a free phosphate group on the 5th carbon (5’ prime)

Question 8

Describe how cis-platin stops DNA replication and so acts as an anti-cancer drug

Answer 8

Being square planar, the cis-platin can fit between DNA coils, so allowing the CL- to come off and the two Pt to bind to the guanine groups in the DNA on either strand, blocking the enzyme from unzipping the DNA strand and preventing DNA replication, so prevent uncontrolled cell division.

Question 9

Why would trans-platin not work in preventin DNA replication?

Answer 9

• trans-platin would only have one Cl- in the correct orientation to come off and allow the Pt to bind to the DNA, so no blocking of the enzyme would happen, and the DNA could still be unzipped.

Question 10

What are developing agents?

Answer 10

• used to locate amino acids on a chromatogram (e.g: ninhydrin and UV light)