3. Acids, bases and charge on biomolecules .

Question 1

What is the Henderson-Haselbalch equation?

Answer 1

pH = pKa + log[A-]/[HA]

Question 2

When are the protonated and unprotonated forms favoured?

Answer 2

When pH is lower than the pKa then the protonated form of the molecule is favoured. If the pH is higher than the pKa then the unprotonated form will be favoured, as there is a low concentration of H+

Question 3

Which molecules have a high pKa?

Answer 3

Lysine and Arginine - they have basic side chains.

Question 4

Which molecules have a low pKa?

Answer 4

Glutamic acid and Asparatic acid - they have acidic side chains.

Question 5

What shape is Pi?

Answer 5

Tetrahedral

Question 6

What is special about the side chain in arginine?
CH2- CH2- CH2-NH-C=NH
|
NH2

Answer 6

The electrons can move between the carbon and nitrogens resulting in the movement of charge and double bond.