pH and buffering

Question 1

What is pH?

Answer 1

Measure of H+ concentration

Question 2

What does acidity depend on?

Answer 2

Depends only on free H+

Question 3

Blood pH

Answer 3

7.35-7.45

Question 4

Acidosis

Answer 4

Blood pH lower than required

Question 5

Alkalosis

Answer 5

Blood pH higher than required

Question 6

Where is acid base balance regulated in the body?

Answer 6

The lungs
The kidneys
Chemical buffers in the blood

Question 7

How are acids formed in the body?

Answer 7

Through food
Breakdown of food
Incomplete oxidation of fats or glucose
Loading and transport of CO2 in the blood

Question 8

Buffer

Answer 8

Chemical systems that resist abrupt and large changes in pH

Question 9

Ionic product of water

Answer 9

[H+] [OH-] = 1 X 10^-14

Question 10

pH and [H+] relationship

Answer 10

pH = -log[H+]

Question 11

What is Ka?

Answer 11

Dissociation constant
pH at which the acid is half dissociated

Question 12

Lower pKa..

Answer 12

Means stronger acid

Question 13

Henderson-Hasselbach equation

Answer 13

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

Question 14

When is buffering best?

Answer 14

At the pKa

Question 15

How to measure concentration of H2CO3 in the blood?

Answer 15

H2CO3 is proportional to CO2

Question 16

Amino acids as buffers

Answer 16

Best buffering around two pKa values
No buffering by the zwitterion

Question 17

Best amino acid for buffering in the blood

Answer 17

Depends on R group, if it dissociates
Histidine works best

Question 18

Why is haemoglobin a good blood buffer?

Answer 18

There are a large number of histidine molecules

Question 19

Change of pKa of a group

Answer 19

pKa of Histidine in Hb is different to pKa of free histidine

Question 20

Which is the better buffer for H+ produced in metabolism - oxyhaemoglobin or deoxyhaemoglobin

Answer 20

Deoxyhaemoglobin - pH is below pKa so more dissociation and less H+ attached