Amino Acids, Proteins And DNA

Question 1

What is the structure of an amino acid?

Answer 1

Contains both an amine and carboxyl group

NH2RCHCOOH

Question 2

What are zwitter ions?

Answer 2

Amino acids exist as zwitter ions

Where the amine group has accepted an extra hydrogen to become positively charged and the carboxyl group has donate a hydrogen to become negatively charged

Gives amino acids it’s amphoteric properties

Question 3

What are the amphoteric properties of amino acids?

Answer 3

The amine group is able to accept hydrogen atoms and therefore act as a base

The carboxyl group can donate hydrogen atoms and act as an acid

Question 4

What reactions can take place with the acid end of an amino acid?

Answer 4

React with:

Metal oxides to form a salt and water

Alkalis to form a slay and water

Carbonates to form a salt CO2 and water

Alcohols to form an Ester and water

Question 5

What reactions can take place with the amine end of an amino acid?

Answer 5

The lone pair of electrons in the nitrogen can accept a hydrogen atom and form an ammonium salt.

Question 6

How are proteins formed?

Answer 6

Via a condensation reaction between the carboxyl is acid end of one amino acid and the amine group of another amino acid

Forms a peptide bond

Proteins are polypeptides (50+ amino acids)

Question 7

How can proteins be hydrolysed?

Answer 7

By heating with conc HCL

Question 8

How can individual amino acids be separated?

Answer 8

Using thin layer chromatography

Use ninhydrin to make them visible

Question 9

What is the primary structure of a protein?

Answer 9

Sequence of amino acids in the polypeptide chain

Question 10

What is the secondary structure of a protein?

Answer 10

How the amino acid forms an alpha helix or beta pleated sheet due to hydrogen bonding.

This can easily be disrupted by temperature or pH

Question 11

What is the tertiary structure of a protein?

Answer 11

The 3D shape the alpha helix or beta pleated sheet is folded into.
This is held together by hydrogen bonds, ionic bonds or disulphide bridges between the R groups of the amino acids.

Question 12

Are amino acids chiral molecules?

Answer 12

Yes all except from glycine which has the R group of H

Question 13

What are enzymes?

Answer 13

Biological catalysts which increase the rate of metabolic reactions

Question 14

What are the structures of enzymes?

Answer 14

Usually globular tertiary proteins

Catalytic activity at the active site

Substrates fit into the active site and bind temporarily via intermolecular forces

This bonding promotes the movement of electrons within the substrate lowering the activation energy for the reaction

Question 15

Why are enzymes said to have stereospecificity?

Answer 15

Only the complementary shape substrate will fit into the active site as the bonds have to be in exactly the right place.

Even the wrong stereoisomers (enantiomer) will not be catalysed by the enzyme.

Question 16

How can enzymes be inhibited?

Answer 16

Denaturing the enzyme via heating or pH changes will change the active site shape and therefore mean the enzyme will no longer function.

Inhibitors also bind to an enzyme preventing an enzyme from functioning.

Doctors can use inhibitors as drugs to prevent harmful reactions taking place (penicillin)

Question 17

Why is computer modelling used in drug discovery

Answer 17

Chemists can use computer programs to model complex molecules before synthesis enabling hem to understand the properties of he molecule before they have made it.

Question 18

What are the components of DNA?

Answer 18

A phosphate group

Pentose sugar (deoxyribose)

A nitrogenous base:

Adenine, thymine, cytosine, guanine

These parts create a nucleotide.

Question 19

What is the structure of DNA?

Answer 19

A polynucleotide with strands formed via condensation reactions of phosphate groups and sugars.

This creates a sugar phosphate backbone.

DNA exists as a double helix

The two complementary strands of DNA are held together via hydrogen bonds between the bases. A=T C=G

Question 20

How is DNA replicated?

Answer 20

The strands are separated by DNA helicase and then each strand acts as a template for a new complementary strand to be synthesised onto.

Free complementary nucleotides hydrogen bond to the template strands and form new daughter strands via the hell of DNA polymerase.

Question 21

What is Cis-platin?

Answer 21

An anti cancer drug

Platinum is bonded to two chlorine and two Ammonia molecules via dative covalent bonds.

Has a square planar structure

Question 22

How does Cis-platin prevent cancer?

Answer 22

1. It binds to the nitrogen atoms on two adjacent guanine molecules via a ligand exchange reaction with the chlorine molecules.
2. The nitrogen atoms are better Ligands and therefor displace he chloride ions.
3. This causes a kink in the structure of DNA preventing the DNA from replicating

Question 23

Why does Cis-platin cause side effects?

Answer 23

Cos-platin does not just attack cancer cells but all cells that divide quickly (such as hair follicles) and therefore prevents these cells dividing

Side effects include:

Hair loss
Sickness
Fatigue

Question 24

Why is trans-platin not an effective cancer drug?

Answer 24

Only 1 guanine molecule can bind to the drug either side of the molecule (not adjacent) and therefore his can easily be corrected by the body and does not produce a kink in the DNA structure