Acid base regulation Flashcards

1
Q

why is pH important

A
  • if we don’t have the correct pH in the correct body parts this can cause the protein to denature and loose there biological activity
  • this is especially important for enzymes
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2
Q

why is pH important for enzymes

A
  • as you deviate form the pH the efficiency of the enzyme decreases this is because there is not a precision in forming the correct active site
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3
Q

name the pH for

  • pepsin
  • amylase
  • trypsin
A
  • pepsin - 0-6
  • amylase - 4-10
  • trypsin - 5-12
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4
Q

different parts of the cells have ….

A

different pH for example

  • In the mitochondria pH 8
  • Nucleus 7.2
  • Lysosomes 4.7
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5
Q

what is an acid

A

• An acid is any substance which can DONATE an H+ ion

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6
Q

what is a base

A

A base is any substance which can ACCEPT an H+ ion

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7
Q

write the dissociation equation of an acid

A

• When an acid (generically written as HA) is added to
water, it dissociates reversibly according to the reaction:
HA <=> H+ + A-

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8
Q

what happens when an acid dissociates

A

When an acid dissociates, it yields a free H+ and its conjugate base (A- is a base because it can combine with a H+ to form HA)

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9
Q

what is pH determined by

A

The numerical value of pH is determined by the molar concentration of hydronium (OH-) / hydrogen ions (H+)

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10
Q

what does the pH also control

A
  • it also controls the speed of our body biochemical reactions - does this by controlling the speed of enzyme activity as well as the speed of electrical reactions in our body
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11
Q

what is acidosis

A

acidosis (acidemia specifically in the blood)

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12
Q

what is alkalosis

A

alkalosis (alkalaemia- specifically in the blood)

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13
Q

what is the bodies normal pH range

A
  • 7.34 (venous) to 7.45 (arterial)
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14
Q

what happens if the bodies pH range is outside the normal range

A

still compatible with life but leads to disturbance of body functions, as it disrupts many enzyme systems and the electron transport chain in mitochondria

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15
Q

what pH canc sue death

A
  • Below 6.8 and above 8.0 = DEATH
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16
Q

what happens when carbon dioxide enters the blood stream

A
  • it is converted to carbonic acid by carbonic anhydrase

- this lowers the pH

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17
Q

what are the ways in which acid is produced

A
  • either intake it in the diet

- or they form via cellular metabolism

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18
Q

How does acid intake happen

A

the normal human diet is almost neutral containing only small amounts of acids. (diets with large amounts of proteins produce more acids than bases)

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19
Q

How does acid formation happen

A

Most hydrogen ions originate from cellular metabolsim, which produces large amounts of carbonic, sulphuric, phosphoric & other acids

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20
Q

What are the ways in which protons are continually produced

A

1- Acids produced during the breakdown of foods (esp. proteins)
2- CO2 metabolically produced and form carbonic acid with H2O
3- Acids resulting from other metabolic activity e.g. lactic acid in exercise

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21
Q

how do we produce hydrogen ions

A
  • Aerobic respiration of glucose which causes carbonic acid formation - most important produces about 15mol/d
  • Anaerobic respiration of glucose which forms lactic acid - produces about 1.5mol/d
  • Oxidation of sulphur containing amino acids and this forms sulfuric acid
  • Incomplete oxidation of fatty acids – this form acidic ketone bodies
  • Hydrolysis of phosphoproteins and nucleic acid – this forms phosphoric acid
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22
Q

how many mol/d of protons does acid in diet and acids produced by metabolism produce

A

• Acid in diet (eg, phosphoric, sulphuric) and acids produced by metabolism (eg, lactic and ketoacids) – about 60 mmol/d

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23
Q

name the ways in which there can be pathological formation of acid (hydrogen ions)

A
  • methanol poisoning can lead to formic acid production
  • ethylene glycerol poisoning can lead to glycolic acid, glyoxylic acid, oxalic acid
  • uncontrolled diabetes, starvation can lead to acetate and betahydroxyburlate production
  • hypotension and hypoxia leads to impaired o2 delivery which leads to anaerobic metabolic and lactic acid
  • liver disease leads to impaired lactate clearance and lactic acid production
  • drug and toxins inhibits oxidative phopsophoylated learning to anaerobic metabolism and lactic acid production
  • CO poisoning leads to impaired o2 delivery which leads to inhibition of oxidative phosphorylation and anaerobic metabolism producing lactic acid
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24
Q

name the three ways in which you can limit changes in Ph

A

1, Chemical buffer systems in the ECF and ICF
2, the respiratory centre in the brain stem
3, renal mechanisms

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25
Q

describe the three ways in which you can limit changes in pH

A

1- Chemical buffer systems in blood and ICF:

- Immediate action - but these will not get rid of the hydrogen ions, they simply buffer it  - look up the chemical buffers

2- The respiratory center in the brain stem:

- acts within 1-3 minutes - this acts quite rapidly, this allows you to regulate the respiration so you can get rid of carbon dioxide 

3- Renal mechanisms:

- Requires hours to days to affect pH changes - Longest one to take effect, useful as it is the best way to get rid of acid
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26
Q

what is a buffer

A

Buffer = solution that can resist pH change upon the addition of an acide or a base. Able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable.

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27
Q

what does a buffer consist of

A

Consist of a weak acid and the salt of that acid functioning as a weak base.

28
Q

name the three major chemical buffer systems in the body

A
  • bicarbonate - needs carbonic anhydrase to function - most important one
  • proteins hemoglobin & albumin) buffer system
  • phosphate (P043-) buffer system
29
Q

What is the most important buffering system

A

bicarbonate

30
Q

what is the bicarbonate buffer equation

A

C02 + H20 <=> H2CO2 <= >HCO3- + H+

31
Q

what chemical buffers happen in the ECF

A

Bicarbonate

Protein plasma buffers

32
Q

what chemical buffers happen in the ICF

A

phosphate buffer

haemoglobin buffer system

33
Q

what does the protein buffer system consist of

A

plasma protein, amino acid buffers, haemoglobin buffer system only

34
Q

what chemical buffers happen in the ECF and ICF

A

Amino acid buffer in the ICF and ECF

35
Q

describe the cellular control of pH

A
  • When there is a lot of hydrogen ions in the blood they are buffered by the protein buffer and they are traded for potassium into cells, hydrogen ions are shifted into the cells and the cells then release potassium ions
  • This can affect internal potassium ion distribution
  • Academia leads to hyperkalaemia
  • Conversely alkalosis causes the cells to take up potassium and this leads to hypokalaemia as hydrogen ions are drawn out of the cell into the blood
36
Q

describer how to work out th anion gap

A
  • Sodium – (bicarbonate + chloride) – can also add potassium
37
Q

what is the normal anion gap

A
  • Normal is 8-12mmmol (for just sodium) or 12 to 16(equation with potassium)
38
Q

define the anion gap

A
  • The unmeasured anions and there contribution to the blood in metabolic acidosis
  • don’t measure the anions as they cost a lot of money to measure
39
Q

name the unmeasured cations (positive ions)

A
  • Calcium
  • Magnesium
  • Proteins
40
Q

name the unmeasured anions(negative ions)

A
  • Phosphate
  • Sulphates
  • Proteins
41
Q

describe what causes normal gap metabolic acidosis

A
  • this is also called hyercloremic metabolic acidosis
  • this is what happens when bicarbonate decreases but the anion gap remains the same due to the increase in chloride ions
  • this is normally due to gut issues
  • it is seen when there is loss of bicarbonate and reduced excretion of hydrogen ions in the kidney - if the kidneys cannot excrete acids effectively then more bicarbonate is needed to buffer them causing a drop in the bicarbonate
42
Q

what are the causes of normal gap metabolic acidosis

A
  • severe diarrhea
  • chronic laxative abuse
  • villous adenoma
  • external drainage of pancreatic or biliary secretions (eg fistulas)
  • losses via NG tubes
  • administration of acidifying salts
  • urinary diversions
43
Q

what are the causes of elevated gap acidosis

A
  • ketoacidosis
  • lactic acidosis
  • renal failure
  • toxic ingestions
44
Q

what are the causes of low gap acidosis

A
  • Hypoalbuminaemia
  • albumin is the major unmeasured anion and contributes almost the whole of the value of the anion gap
  • if the albumin goes away lose ability to make meaningful surge of bicarbonate
45
Q

what is the major unmeasured anion

A

albumin

46
Q

how od you current the anion gap in low gap acidosis

A
  • correct anion gap = observed anion gap + 2.5(4-albumin)
47
Q

what are the causes of hypoalbuminemia

A
  • haemorrhage less able to do aerobic respiration shift to anaerobic metabolism, forms lactic acid
  • liver cirrhosis
48
Q

what is metabolic alkalosis

A

Metabolic alkalosis, particularly that due to vomiting or diuretic use, can be associated with a small increment in the serum anion gap, approximately 4 to 6 mEq/L

49
Q

describe respiratory control centre of pH

A
  • the respiratory system is the second line of defence of blood pH
  • the lungs only deal with volatile acids (CO2)
50
Q

what can only the kidney rid the body of

A

Only kidneys can rid the body of metabolic acids such as Phosphoric acid, uric acid, lactic acid and ketones and prevent metabolic acidosis.

51
Q

name the two ways in which the renal system control pH

A
  • – reabsorption of all the filtered bicarbonate

- - excrete the daily acid load

52
Q

how does the kidney system buffer

A
  • hydrogen secretion
  • bicarbonate reabsorption
  • excretion of hydrogen ions with urinary buffers = titratable acids (e.g H+ + HPO42-  H2PO4-) and ammonium (NH4+).
53
Q

what reabsorbs all of the bicarbonate

A
  • proximal convoluted tubule = reclaimed 4500mEq of bicarbonate each day 70-90%
  • ## normally if there is 10-30% left we reabsorb all of it to be reabsorbed
54
Q

excreting the daily load of acid depend on …

A
  • this depends on the acid base status

- active excretion of protons happens in the various parts of the distal kidney

55
Q

what are the names of the cells that control secretion and reabsorption of acid and bicarbonate

A

alpha intercalated cells

beta intercalated cells

56
Q

what do alpha intercalated cells secrete and reabsorb

A

secrete
- these cells secrete acid (via an atypical proton and ATPase and H+/K+ exchanger in the form of hydrogen ions

reasborbs
- bicarbonate (via band 3, a basolateral CL-/HCO3- exchanger

57
Q

what do beta intercalated cell secrete and reabsorb

A
  • secretes bicarbonate (via pendirin a specialised apical CL-/HCO3-)

reabsorbs
- acid (via a basal H+ ATPase)

58
Q

describe the hormonal and non hormonal regulation of acid base in the kidney

A
  • Potassium is involved in hyper and hypokalaemia
  • Angiotensin II regulate that as it influences potassium
  • pH aldosterone sodium increases, causes potassium and hydrogen ions to leave, puts sodium back into the system
  • if we are hypokalaemia need to reclaim potassium into the system and pump hydrogen ions back out
59
Q

what does parathyroid hormone do to pH

A

– reclaims the phosphate buffer, prevents the buffer leading the filtrate to make sure the phosphate stays buffer

60
Q

what happens when the body is in alkalosis in terms of tubular cell

A
  • tubular cells secrete bicarbonate ions and reclaim hydronium to acidify the blood.
  • This uses separate ATP-ases which can actively secrete hydronium.
  • In this system K+ ions are traded for H+ ions:
  • pH is alkanine need to reclaim some acid in the system, have proton pump on the basal side of the cell this will pump this out and trade bicarbonate out
61
Q

describe how each of these does acid elimination

  • lungs
  • kidneys
  • distal tubule
A
  • lungs – expire carbon dioxide
  • kidneys – reabsorb bicarbonate – proximal tubule
  • distal tubule – excretion of hydrogen ions as titratable acid for example phosphate and excretes ammonia
62
Q

what is the Henderson hassalebach equation used for

A

1, the pH of a buffer solution

2, the ratio of conjugate base to acid of the system

63
Q

how do you work out pH

A

pH = -log(H+)

64
Q

write out the Henderson hasselbach equation

A

pKa + log[conjugate base]/[acid]

65
Q

write out Henrys law

A

6.1 + log[HCO3-]/[0.03XPaCO2]

66
Q

what are the 4 types of acid base disturbances and describe what causes them

A

• Respiratory acidosis: CO2 retention
e.g. hypoventilation (COPD, etc)
Renal compensation (H + excretion, HCO3- gain)
• Respiratory alkalosis: CO2 loss
e.g. hyperventilation (anxiety or altitude)
Renal compensation (HCO3- loss, H+ retention)
• Metabolic acidosis: Gain of acid, loss of base.
e.g. diarrhoea, keto-acidosis, lactic acidosis
Respiratory compensation (CO2 loss, HCO3- falls)
• Metabolic alkalosis: Loss of acid, gain of base.
e.g. vomiting, hypokaleamia, ingestion of HCO3-
Respiratory compensation (CO2 & HCO3- rises

67
Q

how can you diagnose the acid base disturbances

A
  • clinical history
  • physical examination
  • ABG