BCH 201 Acid Base Chemistry

Question 1

Functions of H+

Answer 1

1. The gradient of H concentration between inner and outer mitochondrial membrane acts as the driving for oxidative phosphorylation
2. The surface charge and physical configuration of proteins are affected by changes in H+ concentration
3. H+ ion concentration decides the ionization of weak acids and this affects their physiological function

Question 2

Normal blood pH of arterial and venous blood

Answer 2

Arterial - 7.4
Venous - 7.35

Question 3

Bronsted Lowry acid

Answer 3

A substance capable of donating protons

Question 4

Bronsted Lowry base

Answer 4

A substance that accepts protons of H+ ions

Question 5

Arrhenius acid

Answer 5

A hydrogen containing compound which gives hydrogen ions upon dissociation in water

Question 6

Arrhenius base

Answer 6

A hydroxide compound which gives hydroxide ions association in water

Question 7

Lewis acid

Answer 7

A substance capable of accept in a non-bonding pair of electrons a.k.a. electron deficient species or electrophile

Question 8

Lewis Base

Answer 8

A substance which has the capability to donate electron pair a.k.a. electron-rich species or nucleophile 

Question 9

Conjugate acid

Answer 9

Formed when a base accepts a proton

Question 10

Conjugate base

Answer 10

Formed when an acid donates a proton

Question 11

Buffer solution

Answer 11

A solution that resists the change in pH of a solution when small amounts of acid or base is added
It is able to neutralize small amounts of added acid or base thus maintaining the pH of the solution

Question 12

What are the mechanisms for the regulation of blood pH

Answer 12

1. Buffer mechanism
2. Respiratory mechanism
3. Renal mechanism

Question 13

Examples of extracellular and intracellular blood buffers

Answer 13

1. bicarbonate buffer
2. Phosphate buffers
3. protein buffers

Question 14

What is the most important extracellular buffer

Answer 14

The bicarbonate buffer

Question 15

Which buffer solution plays a major role in buffering renal tubular fluid and intracellular fluid

Answer 15

Phosphate buffer system

Question 16

Why can plasma proteins especially albumin act as a buffer

Answer 16

– Proteins contain a large number of dissociable acidic (COOH) and basic (NH2) groups in their structure.
– In acid solution, they act as a buffer in that, the basic amino group (NH2) takes up excess H+ ions forming (NH3+)
– Whereas in basic solutions the acidic COOH
groups give up hydrogen ion forming OH–
of alkali to water.
– Another important buffer groups of proteins in the physiological pH range, are the imidazole group of histidine. Each albumin molecule contains 16 histidine residues

Question 17

How does the respirator mechanism regulate increase in acid conc?

Answer 17

An increase in hydrogen ion or H2CO3 concentration stimulates the respiratory center to increase the rate of respiratory ventilation

A increase in ventilation rates will cause a increase in the release of CO2 from the blood the reduced blood CO2 results in the lack of formation of H2CO3 thus there will be an increase in pH

Question 18

How does the respirator mechanism regulate increase in base conc?

Answer 18

An increase in OH- or HCO3- depresses respiratory ventilation

A decrease in ventilation rates will cause a decrease in the release of CO2 from the blood the increased blood CO2 results in the formation of H2CO3 thus there will be a decrease in pH

Question 19

What are the four mechanisms the kidney uses to conserve HCO3- and excrete acid in the acid-base regulation?

Answer 19

1. Exchange of H+ for Na+ of tubular fluid
2. reabsorption of carbonates from tubular fluids
3. formation of ammonia and excretion of ammonium in the urine
4. excretion of H+ as H2PO4- in urine

Question 20

Acidosis

Answer 20

An abnormal condition caused by excess acid accumulation in the body by the loss of alkali from the body

Question 21

Alkalosis

Answer 21

The abnormal condition caused by the accumulation of excess alkali body or by the loss of acid from the body

Question 22

Mechanism of action of bicarbonate buffer (SA added)

Answer 22

• When a strong acid, such as HCI, is added to the bicarbonate buffer solution, the increased hydrogen ions are buffered by HCO3
• Thus, hydrogen ions from strong acid HCI react withHCO3 to form very weak acid H2CO3

Question 23

Mechanism of action of bicarbonate buffer (SB added)

Answer 23

when a strong base such as sodium hydroxide (NaOH), is added to the bicarbonate buffer solution, the hydroxyl ion (OH–) from NaOH combines with H2CO3 to form weak base HCO3
Thus, a strong base NaOH is replaced by a weak base NaHCO3

Question 24

What is the alkali reserve?

Answer 24

Plasma bicarbonate is a measure of the base that remains after all acids, stronger than carbonic, have been neutralized. It represents the reserve of alkali available for the neutralization of such strong acids and it has been termed, the alkali reserve

Question 25

Mechanism of action of phosphate buffer (when SA is added)

Answer 25

* The main elements of the phosphate buffer system are HPO4 – – and H2PO4 . When a strong acid such as HCl is added to a phosphate buffer system, the H+ is accepted by the base HPO4 – – and converted to H2PO4 and the strong acid HCl is replaced by a weak acid H2PO4 and the decrease in pH is minimized.

Question 26

Mechanism of action of phosphate buffer (when SB is added)

Answer 26

When strong base, such as NaOH, is added to the buffer system, the OH– is buffered by the H2PO4 – to form HPO4 – – and water. Thus, a strong base NaOH is replaced by weak base HPO4 – –, causing slight increase in the pH

Question 27

What is the ratio of HPO4 – – : H2PO4 – at a plasma pH of 7.4?

Answer 27

HPO4 – – : H2PO4 – is 4:1

Question 28

What is buffering capacity?

Answer 28

The buffering capacity of a buffer is defined as the ability of the buffer to resist changes in pH when an acid or base is added.

Question 29

Under physiological conditions, with a plasma pH 7.4, the ratio of bicarbonate to carbonic acid (HCO3– / H2CO3) is

Answer 29

20:1