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IMMS > Acids, Bases + Buffers > Flashcards

Acids, Bases + Buffers Flashcards

1
Q

What is an acid?

A

H+ donor

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2
Q

What is a base?

A

H+ acceptor

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3
Q

What is a strong acid?

A

A compound that ionises completely in solution to form hydrogen ions and a base

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4
Q

What is a weak acid?

A

Compounds that are only partially ionised in solution

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5
Q

What is the function of a buffer?

A

Resists changes in PH when small quantities of strong acid or base are added.

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6
Q

What is the ideal PH of blood?

A

7.4

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7
Q

Give the Henderson-Hasselbach equation.

A

PH = pKa + log([HCO3-]/[CO2])

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8
Q

How are most of the H+ ions produced in the body?

A

As a result of CO2 release from aerobic metabolism. CO2 rapidly reacts with water forming carbonic acid that dissociates into H+ and HCO3-

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9
Q

Give the equation of CO2 - H+

A

CO2 + H20 > H2CO3 > HCO3- + H+

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10
Q

Which enzyme catalyses the conversion of CO2 to H+?

A

Carbonic anhydrase

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11
Q

Which three systems work to ensure PH remains in range?

A
  1. Blood and tissue buffering
  2. Excretion of CO2 by lungs
  3. Renal excretion of H+ and regeneration of HCO3-
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12
Q

Name the most important buffer system of the body.

A

Bicarbonate

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13
Q

How is the bicarbonate buffer efficiency improved (think lungs and kidneys)?

A
  1. CO2 is removed by lungs

2. Bicarbonate is regenerated at the kidneys

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14
Q

Proteins form buffers as well. Name a protein that is part of this system.

A

Albumin

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15
Q

How do proteins work as a buffer?

A

The protein matrix of bone buffers large amounts of H+ ion

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16
Q

How is haemoglobin a buffer?

A

It binds to both CO2 and H+, removing these from the blood.

CO2: CO2 diffuses into red cells down their concentration gradient.. It binds with haemoglobin reversibly to form carbaminohaemoglobin or with water to form carbonic acid.

H+: CO2 in red cells combines with water to form carbonic acid. This dissociates into bicarbonate and H+ ions. H+ ions bind to reduced haemoglobin to form HHb. HCO3- ions pass back into the plasma in exchange for Cl- ions.

17
Q

Which state of haemoglobin has the strongest affinity for CO2 and H+?

A

Deoxygenated haemoglobin

18
Q

In the lungs, what mathematical relationship is between arterial partial pressure of CO2 and the alveolar ventilation?

A

Arterial partial pressure is inversely proportional to alveolar ventilation - i.e. if alveolar ventilation falls, PaCO2 rises.

19
Q

What is alkalosis in terms of PH?

A

PH > 7.45

20
Q

What is acidosis in terms of PH?

A

PH < 7.35

21
Q

Name the types of alkalosis and acidosis.

A

Respiratory and metabolic.

22
Q

What is acidaemia?

A

Too many hydrogen ions in plasma

23
Q

What is alkalaemia?

A

Too few hydrogen ions in plasma

24
Q

What causes respiratory acidosis?

A

Common: Decreased alveolar ventilation, causes decreased excretion of CO2.

Less common: Excessive production of CO2 by aerobic metabolism, can be caused by fever.

25
Q

What is the PaCO2 in respiratory acidosis?

A

> 6kPa

26
Q

What causes respiratory alkalosis?

A

Excessive excretion of CO2. Caused by severe asthma and pulmonary embolism

27
Q

What is the PaCO2 in respiratory alkalosis?

A

<4.5kPa

28
Q

List the causes of metabolic acidosis.

A
  1. Excess H+ production from the excessive production of organic acids as a result of anaerobic metabolism.
  2. Low perfusion
  3. Reduced ability to use oxygen as a substrate e.g. in sepsis
  4. Renal tubular dysfunction leads to inadequate excretion of H+
  5. Diabetic ketoacidosis - unable to use glucose, resulting in the production of ketone bodies which releases H+
  6. Crohn’s disease where excessive diarrhoea results in large amounts of bicarbonate being lost
29
Q

List the causes of metabolic alkalosis.

A
  1. Excess H+ loss from prolonged vomiting

2. Excessive reabsorption of bicarbonates as a result of chloride loss through prolonged vomiting

30
Q

Which type of acidosis and alkalosis has a greater effect on the body and why?

A

Metabolic. This is because compensation is much slower in metabolic processes than respiratory, resulting in a delayed response.

31
Q

What is the anion gap?

A

The difference in serum concentration of cations (positive) and anions (negative).

32
Q

Which ions aren’t included when considering the anion gap?

A

K+, PO4-, SO4-

33
Q

What is the normal value of the anion gap?

A

Between 3-11 mEq/mol

34
Q

How does the anion gap help to diagnose the cause of metabolic acidosis?

A

If there is a high anion gap, it can be used to see if the cause is due to excessive loss of bicarbonate or excess H+ production

IMMS (12 decks)

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