Plasma CO2 Destinations (3, c frequency)

70% = buffered in carbonic acid-bicarb system 20% = combined c hemoglobin to form carbaminohemoglobin 10% = dissolved in plasma

Acid Base Balance Flashcards by Tina Mindich

Define Acid and Base

acid - substance that releases H+ ions in a solution

base - substance that accepts H+ ions in a solution

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Normal pH Range

(list values, 3 implications of deviation)

Normal: 7.35 - 7.45

Deviation:

Cell membraine instability
Protein structure change
Enzyme activity change

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Acid Production Mechanisms

(4)

All work by releasing H+ ions

Protein catabolism
- Methods - sulfuric, phosphytics, and uric acids
- Example - meals
Fat oxidation
- Methods - ketone bodies
- Example - starvation, inability to metabolize glucose
Anaerobic glucose catabolism
- Methods - lactic acid
- Example - MI
Intracellular metabolism
- Methods - CO₂
- Example - all life processes

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Acidosis

(definition, effect)

Defintion: pH < 7.35

Effect: **depressing ** CNS synaptic transmission, thus organism-wide functional depression

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Alkalosis

(define, effect)

Definition: pH > 7.45

Effect: overexcited CNS synaptic transmission, increased organism activity

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pH Regulatory Systems

(3, general MOA and timeline)

Chemical buffers - instant neutralization *via *combination c offending agent
Respiratory system - transcient change in minutes via hypoventilation/hyperventilation acid excretion and retention* *
Renal system - **excretion and retention **balance over hours or days

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Overview, Acid-Base Balance

(diagram)

see attached

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Chemical Buffer Systems

(function, 2 components, general MOA)

Function: Solution designed to minimize the charge in pH when a base or acid is added to the soln. Note that independently, this soln is balanced

Components:

Weak acid (releases H⁺ ions)
Weak base (binds H⁺ ions)

MOA:

If acidic soln is added to buffer, the buffer’s weak base will bind excess H⁺ ions to maintain the pH
If basic soln is added to buffer, the buffer’s weak acid will release H⁺ ions to maintain the pH

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Chemical Buffers

(list 3 c main locations)

Sodium bicarbonate-carbonic acid
- Major Location - ECF
Phosphate
- Major Location - ICF, urine
Protein
- Major Location - ECF, ICF

Note - know this (as per Sandy)

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Bicarbonate Buffer System

(2 components, 2 MOAs)

Components:

Acid, carbonic acid: H₂CO3
Salt, sodium bicarbonate: NaHCO₃

MOA: both rxns catalyzed by enzyme carbonic anhydrase

Acidic Environment: H⁺ ions combine c biarbonate ions (HCO₂^-) to form carbonic acid (H₂CO₃), resulting in slight pH decrease
Baisc Environment: basic ions react c carbonic acid (H₂CO₃) to form sodium bicarbonate (NaHCO₃)_,resulting in slight pH increase

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Phosphate Buffer System

(location, components, MOA)

Locations: action while passing thru kidneys

ICF
Urine

Components:

Acid: H₂PO₄
Salt/Alcaline: Na₂HPO₄

MOA: similar to sodium bicarb-carbonic acid system, used as its backup

Acidic Environment: H+ ions combine c basic ions (HPO₄^2-) to form acid (H₂PO₄), resulting in slight pH decrease
Basic Environment: basic ions react c acid (H₂PO₄) to form a base (Na₂HPO₄), resulting in slight pH increase

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Protein Buffer System

(location, component, MOA)

Location: ECF and ICF

Component: amino acids carboxyl/carboxylate groups and amino groups

MOA:

Acidic Environment: H+ ions combine c carboxylate ion (-COO) or amino group (-NH₂) to form carboxyl group (-COOH) or -NH₃, resulting in slight pH decrease
Basic Environment: basic ions react c carboxyl group (-COOH) to form a carboxylate ion (-COO), resulting in slight pH increase

Note - includes hemoglobin buffer system

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Hemoglobin Buffer System

(category, function, MOA)

Category: part of protein buffer system

Function: prevent drastic pH changes due to pCO₂ variation

MOA: Absorbs plasma CO₂ and convert it to H₂CO₃(carbaminohemoglobin)

Note: carbonic acid-bicarb buffers also happen in RBC’s.

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Plasma CO₂ Destinations

(3, c frequency)

70% = buffered in carbonic acid-bicarb system
20% = combined c hemoglobin to form carbaminohemoglobin
10% = dissolved in plasma

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Acid-Base Balance Maintanence

(general principles)

temporary fix - buffer systems
permanent removal - respiratory and renal mechanisms

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Respiratory Buffer System

(buffer system category, describe homeostasis)

Buffer System Category: physiological system

Equilibrium State: Balance between…

CO₂ and H₂O
H₂CO₃ (Carbonic acid) and H⁺/HCO₃^- (hydrogen and bicarb ions)

**CO₂ + H₂O ⇔H₂CO₃ ⇔H⁺+ HCO₃^- **

Hypercapnia

(define, physiology)

Def: increased H⁺ in blood

Physiology: deeper and more rapid breathing expel more acidic CO₂, reducing H⁺ ion (respiratory acidosis)

Respiratory Alkalosis

(define, physiology, tx)

Define: acid-base imbalance c too much base

Physiology: slower, shallower breathing to conserve H⁺ and decrease CO₂ expulsion

Tx: rebreathe CO₂ from brown paper bag

Renal Acid-Base Balance

(function, involved ions, general MOA)

Function: eliminate metabolic acids and prevent metabolic acidosis. The “ultimate acid-base regulatory organs.”

Eliminated acids:

Phosphoric acid
Uric acid
Lactic acid
Ketones

MOA:

Eliminating bicarbonate ions thru excretion (less basic, therefore more acidic)
Reabsorbing bicarbonate ions (more basic, therefore more acidic)

Renal Bicarbonate Reabsorption

In filtrate: H₂CO₃ → H₂O + CO₂ (dissociation c help of carbonic anhydrase)
CO₂ diffucses into tubule cells
H⁺ secretion to compensate for extra acid in cell from CO₂
For each H⁺ secreted, a Na⁺ and HCO₃^- are reabsorbed by PCT cells
Secreted H⁺ions form carbonic acid
Na⁺ and HCO₃^- continue to recycle and the process continues

Ammonium Ion Excretion

(definition, MOA, results)

Definition: Renal excretion in the proximal convoluted tubule, characterized by glutamate metabolism.

MOA:

Glutamate is metabolized to produce end products -
- **2 ammonium ions **(acid)
- **2 bicarbonate ions **(base)
Metabolites leave proximal convoluted tubule
- Ammonium secretion/excretion
- Bicarbonate reabsorption and retention

Result: reduce acidosis (increase alkylosis)

Phosphate Buffer System

(define, MOA, result)

Definition: backup renal buffering system concerning carbonic anhydrase

MOA:

Carbonic anhydrase is always present in renal tubules
Entering CO₂ combines c preexisting H₂O → H₂CO₃
End product includes H⁺ions
H+ secreted
In tubules, H⁺ combines c HPO₄ → H₂PO₄ (dihydrogen phosphate)
H₂PO₄ excretion

Result: Decrease acidosis (increase aklylosis)

Renal Buffers

(3, summarize each)

Listed in order they appear on diagram:

Bicarb buffer system
Phosphate buffer system
Protein buffers c ammonia (A-)

Hydrogen Ion Secretion

(define, MOA, result)

Definition: Renal management of excess H⁺ flow thru nephron

MOA:

Excess H⁺ flow thru nephrons
Kidney generates bicarb ions for reabsorption
Bicarb moved into interstitial space actively via cotransport system
Bicarb moved into peritubular capillary system passive diffusion
H⁺ secretion in response to oppositely charged bicarb
H⁺ remains in tubules after binding to buffers via phosphate buffer system
Excretion

Result: Decreased acidosis, increased alkalosis

Bicarbonate Ion Secretion | (definition, MOA, result)

_Definition_: Renal defense against extreme alkalosis _MOA_: 1. Tubular **secretion of bicarbonate ions via Cl^- antiporters** (dual negative charge maintains ionic balance within the cells) 2. Ions reclaim H⁺ ions 3. Blood pH decreases _Result_: Increased acidosis (decreased alkalosis), opposite of bicarbonate ion reabsorption *Note: most cases of alkalosis are due to excess baking soda ingestion*

Nephron Acidification Location

Collecting ducts ## Footnote *The reaction that is primarily responsible for H+ secretion in the proximal tubules is Na+–H+ exchange. Na is absorbed from the lumen of the tubule and H is excreted*

Lowest Possible Urine pH

4. 5 * Explaination - this pH corresponds with the T_m of H⁺ excretion transport gradient* * Rxns involving the following work together to achieve that T_m if necessary:* * Reactions with HCO3– to form CO2 and H2O, with HPO42– to form H2PO4–, and with NH3 to form NH4+*