A&P - Acid Base Balance - Ch. 30
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- What is an acid?
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substance that dissociates to release H+ ions
- decreases pH - What is alkaline?
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- basic
- a solution with a predominance of hydroxide (OH-) ions - What is a base?
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a substance that dissociates to release hydroxide (OH-) ions or binds hydrogen (H+) ions
- causes an increase in pH - What is a buffer?
- a substance that tends to oppose changes in pH of a solution by removing ions or replacing hydrogen (H+) ions
- What is alkalosis?
- blood pH that is greater than 7.45
- What is Acidosis?
- blood pH that is lower than 7.35
- What is the relationship between H+ ion concentration and pH value?
- the more H+ ions the lower the pH
- What are 3 categories of acids in the human body?
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1. Volatile
2. Nonvolatile Fixed
3. Nonvolatile Organic -
What is a volatile acid?
Give an example -
an acid that can leave solution and enter the air
- ex. Carbonic acid (H2CO3)
- produced from CO2 -
What is a nonvolatile fixed acid?
Give 2 examples. -
acids that do not leave solution.
- remain in the body until eliminated by kidney
- ex. Sulfuric Acid (H2SO4)
Phosphoric Acid (H3PO4) -
What is a nonvolatile organic acid?
Give 2 examples. -
acids that are intermediates in metabolic pathways (normally metabolize rapidly)
- ex. Lactic Acid (anaerobic metabolism)
Ketone Bodies (starvation) - What are 3 main chemical buffering systems in the body?
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1. Protein
2. Carbonic acid-bicarbonate
3. Phosphate - What is the buffer pair for the protein buffer system?
- Na-Proteinate/Protein (weak acid)
- What is the buffer pair for the bicarbonate buffer system?
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NaHCO3/H2CO3
Sodium Bicarbonate/Carbonic Acid - What is a buffer pair?
- a weak acid and its conjugate base
- Which buffer system is responsible for buffering the ECF?
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Protein (limited)
Bicarbonate - Which buffer system is responsible for buffering the ICF?
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Phosphate Buffer System
Protein (slow process) - How does the protein buffer system respond to an acid or base?
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- if an acid is added, the pH level drops and carboxylate ion and amino group can accept H+
- if base is added, the pH rises and the carboxyl group dissociates releasing H+ - How does the bicarbonate buffer system respond to an acid or base?
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- if a strong acid is added, the H+ will combine with HCO3- to form a weak acid
- if a strong base is added, then more of the carbonic acid dissociates freeing H+ that can combine with a hydroxide (OH-) to form water - How does the phosphate buffer system respond to an acid or base?
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- if a strong acid is added, the weak base will pick up H+ from the strong acid to become a weak acid
- if a strong base is added, the weak acid will dissociate and release H+ that can combine with OH- to become water - Normal ratio of sodium bicarbonate/carbonic acid
- 20:1
- This system is an effective buffer for urine and ICF
- Phosphate Buffer System
- What is respiartory compensation?
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- pH changes outside of normal range causes changes in respiaratory rate that directly interact with the bicarbonate buffer system
- addition of an acid, causes a left shift in equilibrium --> increases CO2 which stimulates an increase in respirations --> lowers CO2
- with addition of an acid, respiratory compensation eliminates carbonic acid via releasing CO2
- addition of a base causes a right shift in equilibrium which releases H+ and causes an decrease in CO2. Low CO2 depresses respirations causing CO2 levels to rise
- when a base is added, respiratory compensation increases H2CO3 by retaining CO2 - What chemical buffer is found in urine?
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Phosphate
Na2HPO4 (weak base)
NaH2PO4 (weak acid)
Ammonia (NH3)
- weak base that removes H+ from a solution - Describe how the phosphate buffer system restores blood buffering capacity.
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- addition of a strong acid causes Na2HPO4 (weak base) to pick up H+ from the strong acid to form a weak acid (NaH2PO4)
HCL + Na2HPO4 NaH2PO4 + NaCl
- addition of a strong base (NaOH) causes NaH2PO4 (weak acid) to release H+ to form a weak base (Na2HPO4) + H2O
ex. NaOH + NaH2PO4 Na2HPO4 + H2O - Describe how ammonia excretion by the renal tubule can lead to HCO3 generation.
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- Renal tubule deaminate amino acid glutamine
- the amino group picks up H+ to become ammonia (NH3) which is secreted into the urine
- ammonia (NH3) acts as a base in the urine because it can pick up another H+ to become ammonium (NH4)
- deamination of glutamine also produces new bicarbonate ions from keto acids that will be added back to blood to help restore the buffering capacity of blood - What ions are usually exchanged for H+ and HCO3- by the renal tubules when these ions are secreted to maintain acid base balance?
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-Carbonic anhydrase in renal tubule generates H2CO3 from CO2 + H2O
- carbonic acid dissociates and the H+ is secreted by tubule in exchange for Na+
- NaHCO3 is then formed in the renal cell which can then be taken into the blood - Distinguish metabolic acidosis from respiratory acidosis on the basis of etiology (cause)
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Respiratory Acidosis
-lungs cannot remove excess CO2 (most common)
Causes:
- diseased lung
- shallow breathing
Metabolic Acidosis - excess of organic or fixed acids.
Causes:
-ingestion of too much alcohol (converted to acetic acid)
-excessive loss of bicarbonate ions (diarrhea)
- accumulation of lactic acid (exercise, shock)
- accumulation of ketone bodies (diabetic crisis, starvation)
- kidney failure - Distinguish metabolic acidosis from respiratory acidosis on the basis of PCO2 levels and HCO3- levels and the mechanism the body uses to repsond to each imbalance
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Respiratory Acidosis:
- low pH
- high CO2
- renal compensation works to correct respiratory imbalances
- kidney will change its pattern of HCO3 reabsorption or secretion to stabilize pH
- HOWEVER, PCO2 levels will remain abnormal until respiratory disturbance is corrected
Metabolic Acidosis:
- low pH
- low HCO3
- respiratory system will attempt to correct metabolic imbalances
- RR will change to release or retain CO2 to stabilize pH
- What are normal PCO2 levels?
- PCO2 --> 35-45 mmHg
- What are normal HCO3- levels?
- HCO3 --> 22-26 mEq/L
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Chronic obstructive lung disease is a primary cause of?
- respiratory acidosis
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Diabetes mellitus is a primary cause of?
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Metabolic acidosis
- What are chylomicrons?
- carry absorbed lipids from the intestinal tract to the bloodstream
- What is the role of VLDLs in the transport of lipids?
- transport triglycerides from the liver to peripheral tissues
- What is the role of LDLs in the transport of lipids?
- transport cholesterol from the liver to peripheral tissues
- What is the role of HDLs in the transport of lipids?
- transport cholesterol from the peripheral tissues to the liver to be excreted in bile
- Which is primarily involved in transporting excess cholesterol to the liver for disposal?
- HDLs
- Which has the highest triglyceride content?
- Chylomicrons (95% triglycerides)
- Which is considered the "bad fat" because it is delivering cholesterol to the peripheral tissue?
- LDL
- Which transport lipids from the intestines to the bloodstream?
- Chylomicrons
- When are where does deamination occur?
- Deamination occurs primarily in the liver when there is excess proteins that will be used as fuel or converted to fat (proteins cannot be stored)
- What is the fate of the amino group stripped from an amino acid during deamination?
- the amino group picks up H+ ions to become NH4 (ammonium) which is then converted to urea and excreted in urine
- What happens to the keto acid produced by deamination?
- It is converted to pyruvate acid, acetyl coa or enter the CAC