Acid-base (physiology)

Question 1

What is pH?

Answer 1

The negative log of hydrogen ion concentration.

Question 2

pH of the human body

Answer 2

7.35-7.45

Question 3

Why is pH important? (3)

Answer 3

It is NB bcs it affects:
- Oxygen delivery to tissues.
- Protein structure
- Enzymatic reactions

Question 4

What is an acid according to arrhenius theory? (2)

Answer 4

-It is a compound that increases the concentration of hydrogen ions when added to water.
-These hydrogen ions form hydronium ions when they combine with the water molecule.

Question 5

What is a base according to arrhenius theory?

Answer 5

-It is a compound that increases the concentration of hydroxide ions when added to water.

Question 6

What is the problem with the arrhenius theory?

Answer 6

Does not explain how Flouride ion(F-) and nitrite(NO2-) can make basic solutions when they do not have hydroxide ions.

Question 7

What is a base and an acid according to bronsted-lowry theory?

Answer 7

An acid is a proton donor, a base is a proton acceptor.

Question 8

What is the diff btwn strong acids and weak acids?

Answer 8

Strong acids completely dissociate while weak acids incompletely dissociate.

Question 9

What is a buffer?

Answer 9

It is a solution that can resist pH changes upon addition of an acidic or basic component.

Question 10

What condition has to be met in order for a buffer to perform its function?

Answer 10

The buffer must consist of a weak conjugate acid-base pair.

Question 11

How does the buffer resist pH changes?

Answer 11

The weak acids/bases partially dissociate in solution to neutralise excess hydrogen or hydroxide ions.

Question 12

Do acidic foods cause a change in pH?

Answer 12

No they don’t

Question 13

Explain the three mechanisms in which the pH in bodyfluids is regulated.

Answer 13

•The chemical acid-base buffer of the body fluids.
•The respiratory center, which regulates the removal of CO2.
•The kidneys, which can either excrete an acidic or basic urine.

Question 14

Explain the three lines of defence when hydrogen concentration changes. (3)

Answer 14

1. The buffer system tries to resist this change, note that it does not add nor remove hydrogen ions from the body.
2. The respiratory center regulates the capacity of blood buffer system by removing CO2.
3. The kidneys can eliminate the excess acid or base from the body.

Question 15

Two ingredients of the bicarbonate buffer system

Answer 15

A weak acid
Bicarbonate salt

Question 16

Explain how the bicarbonate buffer system works as the 1st line of defence. (3)

Answer 16

•Water and carbon dioxide react to form carbonic acid.
• Carbonic acid(weak acid) dissociates to form bicarbonate and hydrogen ions.
•The weak acid(carbonic acid) and its conjugate base(bicarbonate) neutralize excess acid or base added to the system.

Question 17

Explain the 2nd line of defence in a bicarbonate buffer system (3)

Answer 17

•Co2 is transported around the blood in the form of bicarbonate.
•While the bicarbonate is in the blood, it play a role in neutralizing acids.
•When bicarbonate reaches the lungs, it gets converted back to CO2 for expulsion through exhalation.

Question 18

How does the respiratory system regulate an increase in blood acidity? (4)

Answer 18

-Increases ventilation.
- Increases CO2 expulsion.
-Reaction shifts to the left.
- Blood acidity decreases.

Question 19

The Henderson-Hasselbalch equation shows what?

Answer 19

The relationship between the pH of acids and their pKa.

Question 20

How does the ff influence bicarbonate/partial pressure of CO2:
1. Metabolic acidosis
2. Metabolic alkalosis
3. Respiratory acid-base disorders
4. Respiratory acidosis
5. Respiratory alkalosis

Answer 20

1. Decreases bicarbonate.
2. Increases bicarbonate.
3. Disturbance in PCO2.
4. Increases PCO2.
5. Decreases PCO2.

Question 21

Urinary regulation of acid base balance (bicarbonate buffer system) (4)

Answer 21

The kidney can influence the excretion of hydrogen ions, either in the form of dihydrogen phosphate (hydrogen ions are pumped into tubules and phosphate binds to them), or ammonium.

-The conversion of glutamine to glutamate in the kidneys (proximal convoluted tubule) produces ammonia.
-Ammonia can also bind to hydrogen ions to be excreted.
-Glutamate can also form bicarbonate.

Question 22

How do kidneys secrete hydrogen ions and bicarbonate? (3)

Answer 22

•Type A intercalated cells secrete protons via a H+ ATPase into the lumen and reabsorbs bicarbonate in exchange for chloride ions into the blood through the Chloride/bicarbonate exchanger which is located in the basolateral plasma membrane.

•Type B intercalated cells secrete bicarbonateby an apical chloride/bicarbonate exchanger into the lumen, and reabsorps hydrogen ions via H+ ATPase into the blood.

Question 23

What is the dominant buffer in the ICF?

Answer 23

Proteins

Question 24

Why are proteins dominant buffers, and which other compound in blood is an effective buffer and why?

Answer 24

They have an amino or carboxylic acid group at their ends where hydrogen or hydroxide ions can bind, haemoglobin bcs it has histidine amino acids.

Question 25

How do the amino acids helps in buffering?

Answer 25

In an alkaline medium they act as an acid and produce hydrogen ions, in an acidic medium they act as a base and receive hydrogen ions.

Question 26

How do the bones act as buffers? (2)

Answer 26

-It can absorb hydrogen ions in exchange for cations such as sodium, potassium and calcium ions.
-It can release bicarbonate, carbonate or hydrogenphosphate ions in response to bone breakdown.

Question 27

Two major mechanisms of bone breakdown

Answer 27

Dissolution in response to excess hydrogen ions.
Osteoclast activity

Question 28

Briefly explain metabolic acidosis, causes and symptoms. (10)

Answer 28

It is when the blood pH is less than 7.35.

CAUSES
Addison’s disease
Kidney disorders
Diarrhoea
DKA
Certain drugs
Starvation

SIGNS AND SYMPTOMS
-Hyperventilation
-Hyperkalaemia
-Confusion
-Tachycardia

Question 29

Briefly explain metabolic alkalosis, causes and signs and symptoms

Answer 29

When the blood pH is greater than 7.45
CAUSES
-Excessive vomiting
-Diuretic usage

Symptoms and Signs
-Confusion
-Hypoventilation

Question 30

What is diabetic acidosis and what are its signs and symptoms?

Answer 30

It is the build up of ketone bodies.
SIGNS AND SYMPTOMS
-Low blood pH.
-Very acidic urine.
-Excessive thirst.
-Abdominal pains.
-Sweet smelling breath.
-Nausea and vomiting.
-Cerebral oedema

Question 31

How does diabetic ketoacidosis form? (2)

Answer 31

If we have low levels of oxaloacetate in our body, the acetylcoa gets shunted to ketogenesis which forms ketone bodies.
Those ketone bodies build up and form DKA.