Acid Base Balance

Question 1

Define Acid and Base

Answer 1

acid - substance that releases H+ ions in a solution

base - substance that accepts H+ ions in a solution

Question 2

Normal pH Range

(list values, 3 implications of deviation)

Answer 2

Normal: 7.35 - 7.45

Deviation:

1. Cell membraine instability
2. Protein structure change
3. Enzyme activity change

Question 3

Acid Production Mechanisms

(4)

Answer 3

All work by releasing H+ ions

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

Question 4

Acidosis

(definition, effect)

Answer 4

Defintion: pH < 7.35

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

Question 5

Alkalosis

(define, effect)

Answer 5

Definition: pH > 7.45

Effect: overexcited CNS synaptic transmission, increased organism activity

Question 6

pH Regulatory Systems

(3, general MOA and timeline)

Answer 6

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

Question 7

Overview, Acid-Base Balance

(diagram)

Answer 7

see attached

Question 8

Chemical Buffer Systems

(function, 2 components, general MOA)

Answer 8

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:

1. Weak acid (releases H⁺ ions)
2. Weak base (binds H⁺ ions)

MOA:

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

Question 9

Chemical Buffers

(list 3 c main locations)

Answer 9

1. Sodium bicarbonate-carbonic acid
   
   • ​Major Location - ECF
2. Phosphate
   
   • ​Major Location - ICF, urine
3. Protein
   
   • ​Major Location - ECF, ICF

Note - know this (as per Sandy)

Question 10

Bicarbonate Buffer System

(2 components, 2 MOAs)

Answer 10

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

Question 11

Phosphate Buffer System

(location, components, MOA)

Answer 11

Locations: action while passing thru kidneys

1. ICF
2. 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

Question 12

Protein Buffer System

(location, component, MOA)

Answer 12

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

Question 13

Hemoglobin Buffer System

(category, function, MOA)

Answer 13

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.

Question 14

Plasma CO₂ Destinations

(3, c frequency)

Answer 14

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

Question 15

Acid-Base Balance Maintanence

(general principles)

Answer 15

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

Question 16

Respiratory Buffer System

(buffer system category, describe homeostasis)

Answer 16

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^- **

Question 17

Hypercapnia

(define, physiology)

Answer 17

Def: increased H⁺ in blood

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

Question 18

Respiratory Alkalosis

(define, physiology, tx)

Answer 18

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

Question 19

Renal Acid-Base Balance

(function, involved ions, general MOA)

Answer 19

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

Eliminated acids:

1. Phosphoric acid
2. Uric acid
3. Lactic acid
4. Ketones

MOA:

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

Question 20

Renal Bicarbonate Reabsorption

Answer 20

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

Question 21

Ammonium Ion Excretion

(definition, MOA, results)

Answer 21

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

MOA:

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

Result: reduce acidosis (increase alkylosis)

Question 22

Phosphate Buffer System

(define, MOA, result)

Answer 22

Definition: backup renal buffering system concerning carbonic anhydrase

MOA:

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

Result: Decrease acidosis (increase aklylosis)

Question 23

Renal Buffers

(3, summarize each)

Answer 23

​Listed in order they appear on diagram:

1. Bicarb buffer system
2. Phosphate buffer system
3. Protein buffers c ammonia (A-)

Question 24

Hydrogen Ion Secretion

(define, MOA, result)

Answer 24

Definition: Renal management of excess H⁺ flow thru nephron

MOA:

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

Result: Decreased acidosis, increased alkalosis

Question 25

Bicarbonate Ion Secretion

(definition, MOA, result)

Answer 25

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

Question 26

Nephron Acidification Location

Answer 26

Collecting ducts

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

Question 27

Lowest Possible Urine pH

Answer 27

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+*