Acid-base (physiology) Flashcards
What is pH?
The negative log of hydrogen ion concentration.
pH of the human body
7.35-7.45
Why is pH important? (3)
It is NB bcs it affects:
- Oxygen delivery to tissues.
- Protein structure
- Enzymatic reactions
What is an acid according to arrhenius theory? (2)
-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.
What is a base according to arrhenius theory?
-It is a compound that increases the concentration of hydroxide ions when added to water.
What is the problem with the arrhenius theory?
Does not explain how Flouride ion(F-) and nitrite(NO2-) can make basic solutions when they do not have hydroxide ions.
What is a base and an acid according to bronsted-lowry theory?
An acid is a proton donor, a base is a proton acceptor.
What is the diff btwn strong acids and weak acids?
Strong acids completely dissociate while weak acids incompletely dissociate.
What is a buffer?
It is a solution that can resist pH changes upon addition of an acidic or basic component.
What condition has to be met in order for a buffer to perform its function?
The buffer must consist of a weak conjugate acid-base pair.
How does the buffer resist pH changes?
The weak acids/bases partially dissociate in solution to neutralise excess hydrogen or hydroxide ions.
Do acidic foods cause a change in pH?
No they don’t
Explain the three mechanisms in which the pH in bodyfluids is regulated.
•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.
Explain the three lines of defence when hydrogen concentration changes. (3)
- The buffer system tries to resist this change, note that it does not add nor remove hydrogen ions from the body.
- The respiratory center regulates the capacity of blood buffer system by removing CO2.
- The kidneys can eliminate the excess acid or base from the body.
Two ingredients of the bicarbonate buffer system
A weak acid
Bicarbonate salt
Explain how the bicarbonate buffer system works as the 1st line of defence. (3)
•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.
Explain the 2nd line of defence in a bicarbonate buffer system (3)
•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.
How does the respiratory system regulate an increase in blood acidity? (4)
-Increases ventilation.
- Increases CO2 expulsion.
-Reaction shifts to the left.
- Blood acidity decreases.
The Henderson-Hasselbalch equation shows what?
The relationship between the pH of acids and their pKa.
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
- Decreases bicarbonate.
- Increases bicarbonate.
- Disturbance in PCO2.
- Increases PCO2.
- Decreases PCO2.
Urinary regulation of acid base balance (bicarbonate buffer system) (4)
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.
How do kidneys secrete hydrogen ions and bicarbonate? (3)
•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.
What is the dominant buffer in the ICF?
Proteins
Why are proteins dominant buffers, and which other compound in blood is an effective buffer and why?
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.
How do the amino acids helps in buffering?
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.
How do the bones act as buffers? (2)
-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.
Two major mechanisms of bone breakdown
Dissolution in response to excess hydrogen ions.
Osteoclast activity
Briefly explain metabolic acidosis, causes and symptoms. (10)
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
Briefly explain metabolic alkalosis, causes and signs and symptoms
When the blood pH is greater than 7.45
CAUSES
-Excessive vomiting
-Diuretic usage
Symptoms and Signs
-Confusion
-Hypoventilation
What is diabetic acidosis and what are its signs and symptoms?
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
How does diabetic ketoacidosis form? (2)
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.
