Proteins and pH

Question 1

What protonates and what deprotonates in acid and base reactions?

Answer 1

• acids protonate (give a proton (H))

- bases deprotonate (take in proton (H))

Question 2

What are conjugate bases and conjugate acids? What are their pairs?

Answer 2

• conjugate base - after an acid loses its hydrogen (after protonation)
  - the former acid form is its conjugate pair
• conjugate acid - after a bases gains a hydrogen (after deprotonation)
  - the former base form is its conjugate pair

Question 3

What is water in an acid base reaction?

Answer 3

• water is amphoteric

- water can act both as an acid or base

Question 4

Whats are the differences between strong and weak acids?

Answer 4

• strong acids are entirely dissociated in solution (ex. HCl or sulfuric acid)
• strong acids typically form strong conjugate bases (like salts)
• weak acids are partially dissociated and are in equilibrium with the undissociated form

Question 5

What are some examples of strong and weak bases?

Answer 5

• ionic compounds such as NaOH or KOH

- molecular compounds such as NH3 and CH3NH2 (methylamine)

Question 6

What are polyprotic acids and what is an exception? What is its nomenclature?

Answer 6

• acids that can donate more than 1 proton
• exception is sufuric acid (H2SO4)
• monoprodic, diprodic, triprodic

Question 7

What are some things that a change in intracellular pH can potentially affect in cellular processes?

Answer 7

• metabolism
• membrane potential
• cell growth
• movement of substances across the surface membrane
• state of polymerization of cytoplasm

Question 8

What is a buffer?

Answer 8

• essentially resists pH changes/fluctuations
• a solution of a weak acid and its conjugate base
• it is able to accumulate the addition of strong acids and bases without pH of solution changing much

Question 9

What is Ka?

Answer 9

the acid equilibrium constant

Question 10

What does the equivalence point represent?

Answer 10

• represents how much base you have to add to fully convert

- represents the point when the titrant added is just enough to neutralize the solution

Question 11

How many pKas and equivalence points would a diprotic acid have?

Answer 11

2 pKas and 2 equivalence

Question 12

How does a protein change in acidic pH environment?

Answer 12

the amine group accepts a H+ and becomes positively charged

Question 13

How does protein change as pH increases?

Answer 13

(for non charged proteins)

• the carboxyl group first loses a H+
• then from anime group
• side chain may also lose H+…depends on pKa value