3.3.13 Amino Acids, Proetins and DNA

Question 1

How do hydrogen bonds and sulfur-sulfur bonding form in proteins

Answer 1

H- between -OH and -NH2 polar groups (contain electronegative atoms, slight positively charged H is attracted to lone pairs of electrons on adjacent polar groups)
S- -2 thiol groups- SH group loses H atoms and forms S-S bond
Stabilise tertiary structure

Question 2

How can stereospecific active site only bind to one enantiomer

Answer 2

Arranged differently in space so only one will fit properly

Question 3

How does cisplatin work

Answer 3

Square planar molecule (with optical isomers)
Passes through cell membrane
Undergoes ligand exchange
Chlorines replaced by water molecules
Adenine/Guanine forms dative bonds with cis-platin + water ligands removed
Cis-platin disrupts DNA structure + prevents it from replicating and dividing

Question 4

Adverse affects of cisplatin

Answer 4

Binds to healthy cells as well as cancer cells (affects cancer cells more due to faster division)
Hair loss

Question 5

What helps design drugs (stereospecific)

Answer 5

Computers

Question 6

What type of amino acids are found in the body

Answer 6

Alpha

Question 7

Which enantiomer do alpha amino acids exist as in nature

Answer 7

(-)

Question 8

In what form do amino acids exist a solids

Answer 8

Zwitterions

Question 9

Zwitterion properties

Answer 9

High melting and boiling point

Question 10

Peptide linkage

Answer 10

-CONH-

Question 11

Conditions for hydrolysis of peptides

Answer 11

6moldm^-3
HCl
Reflux for 24 hours

Question 12

Protein tertiary structure

Answer 12

Folding of secondary structure into complex 3D shape

Question 13

Tertiary structure bonds

Answer 13

Hydrogen
Ionic
Sulfur sulfur
Van der Waals

Question 14

What is TLC plate made of

Answer 14

Plastic sheet coated with silica
Stationary phase

Question 15

How does DNA polymerase

Answer 15

OH on phosphate group and OH on 3rd carbon of 2-deoxyribose reacts to eliminate molecule of H2O

Question 16

Draw cisplatin

Question 17

Why can Cl^- ions be replaced by N in cisplatin

Answer 17

N atoms have lone pairs of electrons that can co-ordinately bond to the Pt ion
N atoms are better ligands so replace them

Question 18

What happens if an amino acid is added to an excess of methanol in presence of sulfuric acid

Answer 18

Methyl ester forms with COOH group
NH2 protonated by the acid to form NH3^+

Question 19

What happens when excess bromomethane is added to amino acid

Answer 19

Every H on the N atom and lone pair on N replaced by CH3 group
Quaternary ammonium, ion
Forms salt with Br^-