[FMS] CBS - pH

Question 1

What is PH

Answer 1

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 blood pH range?

Answer 3

Blood pH range: 7.35-7.45

Question 4

when does acidosis and alkalosis happen?

Answer 4

• Acidosis: pH lower than 7
• Alkalosis: pH greater than 7.8

Question 5

which 5 places does acids come from in the body?

Answer 5

food
protein breakdown
incomplete fats
glucose oxidation
loading and transport of CO2 in blood.

Question 6

which 3 places in the body regulate the acid-base balance? which one is long terms and which one is short term?

Answer 6

• Kidney
• Lungs
• Chemical buffers

(where kidneys and lungs are longterm, and chemical buffers are short term)

Question 7

what is buffering?

Answer 7

Buffers resist abrupt and large swings in the pH of body fluids by:

when pH increases, releasing H+ (acting as acids), OH- increases

When pH decreases, binding H+ (acting as bases), H+ increases

Question 8

how many moles is pure water?

Answer 8

Pure water is a 55.6M solution

Question 9

what is the value of ionic product of water

Answer 9

Ionic product of water: [H+] x [OH-] = 10^-14 M2

Question 10

what is the ionic product of water at neutrality

Answer 10

Neutrality: [H+] = [OH-] = 10^-7M

Question 11

what is the equation for pH

Answer 11

pH = -log[H+]

Question 12

when [H+] is 10-2, then what is the value for [OH-]

Answer 12

Use equation for ionic product of water

where Kw = [H+][OH-]

Kw = 1x 10^-14

10^-14 = [10^-2][OH-]

rearrange and put in the calculator

then [OH-] is 10^12

Question 13

when [H+] is 10-4, then what is the value for [OH-]

Answer 13

Use equation for ionic product of water

where Kw = [H+][OH-]

Kw = 1x 10^-14

10^-14 = [10^-4][OH-]

rearrange and put in the calculator

then [OH-] is 10^10

Question 14

what is pKa equation?

Answer 14

pKa= -log Ka

Question 15

what is Ka?

Answer 15

Ka is dissociation constant

Question 16

what is pKa?

Answer 16

pKa is the pH at which the acid is half dissociated (equal amounts of undissociated acid and its conjugate base)

Question 17

when pKa is low, is the acid strong or weak?

Answer 17

lower pKa = stronger acid

Question 18

what is the henderson hasselbalch equation?

Answer 18

Question 19

the lower the pKa the _____ the acid

Answer 19

The lower the pKa , the stronger the acid

Question 20

at the ___ buffering is best

Answer 20

At pKa buffering is best

So, if you know the pKa of your acid, you know at what pH it will buffer best

Question 21

what are the 4 physiologically important buffers?

Answer 21

H2CO3→HCO3- pKa 6.1

H2PO4- → HPO42- pKa 6.8

Protein → protein-
protein+ → protein

Question 22

are amino acids good physiological buffers?

Answer 22

No - even if they are, they are caught in peptide bond = no dissociation

Question 23

what complication does high carbonic acid (H2CO3) lead to?

Answer 23

respiratory acidosis

Question 24

what complication does low bicarbonate (HCO3-) lead to?

Answer 24

metabolic acidosis (diabetic)

Question 25

which amino acid groups dont dissociate?

Answer 25

anything with methyl ch3 group

Question 26

what needs to be present in large numbers for Hb to be a good buffer?

Answer 26

histidine

Question 27

what is the pKa of histidine

Answer 27

6

Question 28

what affects the pKa of the histidine in Hb

Answer 28

it increases in proteins due to the ionic environment
of the side chains. As Hb changes shape, the pKa of histidine changes.

OxyHb pKa = 6.8
DeoxyHb pKa = 7.8

Question 29

which is a better buffer, OxyHb or DeoxyHb?

Answer 29

DeoxyHb is a better buffer for H+ because it has a HIGHER PKA - therefore it is carrying more H+ at pH of blood

Question 30

try the pH and buffers quiz on keats then come back

Answer 30

https://keats.kcl.ac.uk/mod/quiz/view.php?id=6694265

Question 31

In what order are H+ lost from H3PO4

Answer 31

First Proton (H⁺) Loss: Phosphoric acid loses its first proton to form dihydrogen phosphate ion (H2PO4⁻).
H3PO4→H2PO4-

Second Proton (H⁺) Loss: Dihydrogen phosphate ion loses its second proton to form hydrogen phosphate ion (HPO4^2⁻).
H2PO4- →HPO42-

Third Proton (H⁺) Loss: Hydrogen phosphate ion loses its third proton to form phosphate ion (PO4^3⁻).
HPO42- →POA3-

Question 32

What does a not steep titration curve mean

Answer 32

There is buffering

Question 33

Why do most amino acids side-chains not buffer in physiological range

Answer 33

pKa outside range

Question 34

amino acids involved in physiological buffering (state pKa)

Answer 34

Histidine (pKa 6)

Question 35

How can histidine be involved in blood buffering when pKa below blood
range

Answer 35

pKa different in Hb than when free

Question 36

A globular protein X found in blood can act as a buffer. If the pKa of the protein is increased because of conformational changes in that protein how will the buffering/ hydrogen ion binding properties be affected?

A) The protein will not be able to act as a physiological buffer

B) They will not be affected because the dissociating groups of the protein will still be the same

C) The protein will bind fewer Hydrogen ions

D)The protein will bind more Hydrogen ion

Answer 36

ANSWER = D, he protein will bind more Hydrogen ion

REMEMBER, IF THE PKA IS HIGHER THAN PH THEN IT WILL BIND MORE H+ IONS

Question 37

What is respiratory acidosis caused by

Answer 37

HIGH H2CO3

Question 38

What is metabolic acidosis caused by

Answer 38

LOW HCO3