pH

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What does the pH scale measure?
Hydrogen ion concentration
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Why does pH need to be regulated?
Adding/removing H+ from proteins causes conformational change (denaturation) and effects the functioning of enzymes which can be irreversible
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What is the maximum tolerated range of pH?
6.8-7.8
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What are the typical mammalian pH values in extracellular fluid?
7.36-7.44
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What are the typical mammalian pH values in intracellular fluid?
7.10-7.20
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What is a conjugate acid?
A base that will accept a proton
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Define a weak acid/alkali
It doesn't dissociate fully in solution
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Where do H+ come from in body fluids?
Volatile acids derived from CO2 and non volatile acids produced during metabolism eg phosphoric acid and lactic acid
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Carnivores are net _______ producers
acid
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What are carbohydrates and fats broken down to?
CO2 and H2O
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What are proteins broken down to?
HCl and H2SO4 or HCO3-
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What are organic anions broken down to?
HCO3-
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How can H+ concentration be regulated?
Buffer systems in the body, respiratory centres respond to changes in H+ concentration (mins) and kidneys can adjust [H+] (hours)
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What do buffers do?
They minimise the change in pH when acid or base is added
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What are amphoteric buffers?
These accept or donate protons
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How can we predict changes in pH?
pH=pK + log[base]/[acid]
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When do buffers work best?
When pH=pK as changes in [H+] do not have much effect on pH
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What buffering systems are in the body?
Dilution in whole body water, buffering in blood, buffers in ECF, ICF buffers, carbonate in bone and ion exchange in bone
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What buffers are in the blood?
HCO3-, haemoglobin and inorganic phosphates
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What buffers are in ECF?
Mostly HCO3-
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What buffers are in ICF?
Protein, inorganic phosphate and organic phosphate
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Why is carbonate in bone a buffer?
Contributes HCO3- to plasma and ECF
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How does ion exchange in bone act as a buffer?
H+ exchanged for Na+, Ca2+, K+ and Mg2+
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How do kidneys control [H+] in ECF?
They produce acid or alkaline urine
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What urinary buffers are there?
Inorganic phosphate and ammonia/ammonium (they act to attenuate pH changes in urine and allow the excretion of more H+)
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Name some inorganic phosphates
Na2HPO4 (alkaline) and NaH2PO4 (acid)
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What type of homeostatic mechanisms are there for pH?
Compensation and correction
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Define compensation
Rapid, short term pH regulation
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Define correction
Longer term, retuning HCO3- and pCO2 to normal levels
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Card 2

Front

Why does pH need to be regulated?

Back

Adding/removing H+ from proteins causes conformational change (denaturation) and effects the functioning of enzymes which can be irreversible

Card 3

Front

What is the maximum tolerated range of pH?

Back

Preview of the front of card 3

Card 4

Front

What are the typical mammalian pH values in extracellular fluid?

Back

Preview of the front of card 4

Card 5

Front

What are the typical mammalian pH values in intracellular fluid?

Back

Preview of the front of card 5
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