Acids, Bases, pH and Buffers

Question	Answer
Why is it important	Enzymes catalyse all the reactions in our bodies – very sensitive to pH changes •Respiration
Important Definitions	Acids and Bases are electrolytes; Acid •Substance that releases hydrogen ions (H+) •Proton donors Base •Substance that take up H+ •Proton acceptors •aka alkali
Ionize	To dissociate into electrically charged species” H2O → H++ OH-
Acids in the body ‐Metabolism	Cellular Respiraon → CO2 •Carbonic acid CO2+ H2O → H2CO3 •Lactic acid •Anaerobic exercise → lactoacidosis •Ketones •Fat metabolism → ketoacidosis; Carboxylic Acids •Fatty acids... •Bicarbonate Ion •Balances pH (“soaks up” H+ions) •Stomach Acids?
Bases	Produce hydroxide ions (OH‐) •Strong Base ‐dissociate completely in H2O NaOH→ Na++ OH•Weak Bases ‐small proportion dissociate HCO3‐+ H+↔ H2CO3 •Other important bases in the body: •Aqueous Ammonia in urine •Amino group in proteins
Corrosive	Strong acids and bases are very corrosive
pH Scale	Scale used to measure H+concentration •Ranges from 0 to 14 •Is a solution acidic or basic; ↑ H+= more acid = pH goes “down” = 6 → 1 ↓ H+= less acid = pH goes “up” = 1 → 6 ↑ OH‐= more alkali = pH goes “up” = 8 → 14 ↓ OH‐= less alkali = pH goes “down” = 14 → 8
pH Homeostasis	Very narrow range •Blood pH –7.35 to 7.45
Respiratory Acidosis	•↑ CO2→ ↑ H2CO3→ ↑H+ •Hypoventilation due to asthma, COPD, oedema •↓O2→ anaerobic glycolysis •↑ lacc acid •Lactoacidosis
Metabolic Acidosis	•↓HCO3•Diarrhoea •loss HCO3•Lactoacidosis •Fasting/ Starvation or Diabetes •gain other acid ketones •Kidney failure •↓ H+excretion; pH > 7.45 •pH > 7.8 •Overexcited Nervous system •Tetanus → Convulsions
Respiratory alkalosis	•↓ PCO2→ ↓ H+ → ↑ pH •Hyperventilation
Metabolic Alkalosis	•↑ HCO3•Voming → ↓HCl •Diurecs → ↑ urine output •Alkaline drugs •Severe dehydration
Buffers	Acid‐balance regulation •Fast working •Resist pH change •Maintain homeostatic range •Buffers can be acid or base •Various systems for different part of body; Buffers are compounds which maintain constant pH when acids or alkalis are added to them (they resist change in pH)
Carbonic acid/bicarbonate	Important ECF buffer CO2+ H2O ↔ H2CO3↔ H+ + HCO3‐↔ H++ CO32 •Acts as both an acid and a base… •pH, HCO3‐and pCO2are all used to assess the acid/base status of a person System fails with respiratory system problems
Haemoglobin in RBCs	•Transports O2 •Buffers CO2 CO2+ H2O → H2CO3 H2CO3→ HCO3‐+ H+ HbO2+ H+→ Hb‐H++ O2
Protein	Protein Buffer system •ICF and plasma •Amino acids •Release or take up H+
Other buffer systems	Ammonia •Kidneys NH3+ H+→ NH4+ NH4+ + Cl‐→ NH4Cl Phosphate Buffer system •ICF and Urine •H2PO4‐and HPO42

Why is it important

Enzymes catalyse all the reactions in our bodies – very sensitive to pH changes •Respiration

Important Definitions

Acids and Bases are electrolytes; Acid •Substance that releases hydrogen ions (H+) •Proton donors Base •Substance that take up H+ •Proton acceptors •aka alkali

Ionize

To dissociate into electrically charged species” H2O → H++ OH-

Acids in the body ‐Metabolism

Cellular Respiraon → CO2 •Carbonic acid CO2+ H2O → H2CO3 •Lactic acid •Anaerobic exercise → lactoacidosis •Ketones •Fat metabolism → ketoacidosis; Carboxylic Acids •Fatty acids... •Bicarbonate Ion •Balances pH (“soaks up” H+ions) •Stomach Acids?

Bases

Produce hydroxide ions (OH‐) •Strong Base ‐dissociate completely in H2O NaOH→ Na++ OH•Weak Bases ‐small proportion dissociate HCO3‐+ H+↔ H2CO3 •Other important bases in the body: •Aqueous Ammonia in urine •Amino group in proteins

Corrosive

Strong acids and bases are very corrosive

pH Scale

Scale used to measure H+concentration •Ranges from 0 to 14 •Is a solution acidic or basic; ↑ H+= more acid = pH goes “down” = 6 → 1 ↓ H+= less acid = pH goes “up” = 1 → 6 ↑ OH‐= more alkali = pH goes “up” = 8 → 14 ↓ OH‐= less alkali = pH goes “down” = 14 → 8

pH Homeostasis

Very narrow range •Blood pH –7.35 to 7.45

Respiratory Acidosis

•↑ CO2→ ↑ H2CO3→ ↑H+ •Hypoventilation due to asthma, COPD, oedema •↓O2→ anaerobic glycolysis •↑ lacc acid •Lactoacidosis

Metabolic Acidosis

•↓HCO3•Diarrhoea •loss HCO3•Lactoacidosis •Fasting/ Starvation or Diabetes •gain other acid ketones •Kidney failure •↓ H+excretion; pH > 7.45 •pH > 7.8 •Overexcited Nervous system •Tetanus → Convulsions

Respiratory alkalosis

•↓ PCO2→ ↓ H+ → ↑ pH •Hyperventilation

Metabolic Alkalosis

•↑ HCO3•Voming → ↓HCl •Diurecs → ↑ urine output •Alkaline drugs •Severe dehydration

Buffers

Acid‐balance regulation •Fast working •Resist pH change •Maintain homeostatic range •Buffers can be acid or base •Various systems for different part of body; Buffers are compounds which maintain constant pH when acids or alkalis are added to them (they resist change in pH)

Carbonic acid/bicarbonate

Important ECF buffer CO2+ H2O ↔ H2CO3↔ H+ + HCO3‐↔ H++ CO32 •Acts as both an acid and a base… •pH, HCO3‐and pCO2are all used to assess the acid/base status of a person System fails with respiratory system problems

Haemoglobin in RBCs

•Transports O2 •Buffers CO2 CO2+ H2O → H2CO3 H2CO3→ HCO3‐+ H+ HbO2+ H+→ Hb‐H++ O2

Protein

Protein Buffer system •ICF and plasma •Amino acids •Release or take up H+

Other buffer systems

Ammonia •Kidneys NH3+ H+→ NH4+ NH4+ + Cl‐→ NH4Cl Phosphate Buffer system •ICF and Urine •H2PO4‐and HPO42

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Acids, Bases, pH and Buffers

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	Created by kerryanne gill over 8 years ago