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A&P - Acid Base Balance - Ch. 30

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What is an acid?
substance that dissociates to release H+ ions
- decreases pH
What is alkaline?
- basic
- a solution with a predominance of hydroxide (OH-) ions
What is a base?
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?
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?
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?
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?
Protein (limited)
Bicarbonate
Which buffer system is responsible for buffering the ICF?
Phosphate Buffer System
Protein (slow process)
How does the protein buffer system respond to an acid or base?
- 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?
- 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?
- 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?
- 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?
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.
- 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.
- 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?
-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)
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
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
Chronic obstructive lung disease is a primary cause of?

respiratory acidosis
Diabetes mellitus is a primary cause of?

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

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