pH and buffering

Question 1

What is pH?

Answer 1

-A measure of hydrogen ion concentration (acidity or alkalinity of a solution)

Question 2

What does acidity depend on?

Answer 2

-Acidity depends only on free hydrogen ions
-Not those still bound to anions

Question 3

What is the normal range of pH in the body?

Answer 3

7.0 - 7.8
7.4 is healthy

Question 4

What regulates acid base balance?

Answer 4

-Lungs
-Kidneys
-Chemical buffers

Question 5

How do buffers maintain pH of body fluids?

Answer 5

-Release H+ when pH begins to rise
-Binds H+ when pH drops

Question 6

When H+ = 10^-2 M, what is the pH?

Answer 6

pH 2

Question 7

When H+ is 10^-2, what is OH-?

Answer 7

10^-12

Question 8

log reminder

Answer 8

Question 9

How many more H+ ions are there for 7.4 to 7.3

Answer 9

• 10 times as many

Question 10

Difference between acids and bases

Answer 10

-Acids are proton (H+) donors
-Bases are proton (H+) acceptors

Question 11

Difference between strong acids and weak acids

Answer 11

-Strong acids dissociate completely in solution
-Weak acids dissociate incompletely in solution (can dissociate completely at the right pH)

Question 12

What is the pKa?

Answer 12

-The pH at which you have equal amounts of dissociated and non-dissociated forms of acid (conjugate base and acid)
-Lower the pKa, stronger the acid
-At pKa buffering is best

Question 13

How do you know if solution is buffering?

Answer 13

Flat graph = buffering
Line shoots up = Not buffering

Question 14

Triple dissociation of phosphoric acid

Answer 14

Question 15

What are buffers?

Answer 15

-Buffers are mixtures of weak acids and their conjugate bases
-Buffering is the ability of a solution to resist a change in pH when acid or alkali is added

Question 16

What are some physiological buffers?

Answer 16

-Bicarbonate
-Phosphate
-Plasma proteins

Question 17

How can plasma proteins be used as physiological buffers?

Answer 17

-Proteins lose hydrogen to form negatively charged protein
-Positively charged proteins can lose hydrogen to form neutral proteins

Question 18

What makes haemoglobin a good blood buffer?

Answer 18

-The presence of a large number of histidine residues

Question 19

If pH of blood is 7.4, is oxyhaemoglobin (pKa 6.8) or deoxyhaemoglobin (pKa 7.8) better able to pick up and carry H+ ions?

Answer 19

Deoxyhaemoglobin (pKa 7.8) carries more H+ ions than oxyhaemoglobin (pKa 6.8) at blood pH of 7.4

Question 20

Aspirin has a pKa of around 3. At which pH would it cross a membrane more easily? pH 8 or pH 2?

Answer 20

pH 2
-At a pH above the pKa, an acid will dissociate and become charged
-Therefore, at pH 8 aspirin would dissociate and become charged, at pH 2 it would not
-Uncharged molecules pass more easily through membranes

Question 21

If pH is above/below pKa of an acid, how will it affect its dissociation?

Answer 21

-At a pH below the pKa, an acid will remain undissociated
-At a pH above the pKa, an acid will dissociate and become charged
-It will carry more H+ ions