Acid Base

Question 1

Acid Definition

Answer 1

An acid is a substance that releases H+ ions in a solution

Question 2

Base Definition

Answer 2

A base is a substance that accepts H+ ions in a solution

Question 3

Normal pH Range

Answer 3

Normal pH 7.35 - 7.45

Question 4

Abnormal pH effects

Answer 4

Instability cell membrane
Alteration in structure of proteins
Change activities enzymes

Question 5

Methods of Acid Production

Answer 5

1. Protein catabolism: Sulfuric acid, phosphoric, & uric acids
2. Fat oxidation: Ketone bodies
3. Anaerobic glucose catabolism: Lactic acid
4. Intracellular metabolism: Carbon dioxide (considered an acid)

Question 6

Acidosis definition and effect

Answer 6

1. Acidosis is a blood pH below 7.35

2. Principal effect is depression of the central nervous system by depressing synaptic transmissions

Question 7

Alkalosis definition and effect

Answer 7

1. Alkalosis is a blood pH above 7.45

2. Principal effect is overexcitability of the central nervous system through facilitation of synaptic transmission

Question 8

Three Systems that Regulate Acid-Base Balance

Answer 8

1. Chemical buffers:
   Instantly combine with offending acid or base, neutralizing harmful effects
2. Respiratory system:
   Uses hypoventilation or hyperventilation to regulate acid excretion or retention within minutes of pH change
3. Renal System: Excrete or retain more acids or bases as needed within hours or days

Question 9

Buffer definition

Answer 9

1. A buffer is a solution whose function is to minimize the change in pH when a base or an acid is added to the solution
2. Most buffers consist of a weak acid (which releases H+ ions) and a weak base (which binds H+ ions)

Question 10

What happens when a acidic solution is added to a buffer solution?

Answer 10

the buffer will combine with the extra H+ ions and help to maintain the pH

Question 11

What happens when a basic solution is added to a buffer solution?

Answer 11

the buffer will release H+ ions to help maintain the pH

Question 12

What are some common chemical buffers and where do they function?

Answer 12

1. Sodium bicarbonate-carbonic acid: Major buffer in ECF
2. Phosphate:
   Major buffer in ICF & urine
3. Protein:
   Buffer in ECF & ICF

Question 13

Bicarbonate Buffer System definition and function

Answer 13

1. Mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate (NaHCO3)
2. If strong acid is added:
   Hydrogen ions combine with the bicarbonate ions and form carbonic acid
   The pH of the solution decreases only slightly
3. If strong base is added:
   It reacts with the carbonic acid to form sodium bicarbonate
   The pH of the solution rises only slightly

Question 14

Phosphate Buffer System definition and function

Answer 14

1. Important buffer in ICF & urine
2. Functions similarly to sodium bicarbonate carbonic acid buffer system
3. Regulates pH of ICF & fluids as they pass through kidneys
4. Acidic component is H2PO4
5. Alkaline component is Na2HPO4

Question 15

Protein Buffer System definition and function

Answer 15

1. Regulates pH in ECF & ICF
2. Depends on the ability of amino acids to respond to pH changes by accepting or releasing a hydrogen ion
3. If pH increases, carboxyl group (-COOH) of amino acid dissociates, releasing hydrogen ion
4. If pH drops, carboxylate ion (-COO) and amino group (-NH2) can accept hydogen ions

Question 16

Hemoglobin Buffer System definition and function

Answer 16

1. Part of protein buffer system
2. RBC’s can absorb CO2 from plasma & convert it to H2CO3
3. Helps to prevent drastic changes in pH as a result of pCO2 changes

Question 17

Respiratory Buffer System definition and function

Answer 17

1. There is a reversible equilibrium between:
   Dissolved carbon dioxide and water
   Carbonic acid and the hydrogen and bicarbonate ions
   CO2 + H2O > H2CO3 < H+ + HCO3¯

Question 18

How does the respiratory system compensate for hypercapnia?

Answer 18

1. Deeper and more rapid breathing expels more carbon dioxide
2. Hydrogen ion concentration is reduced

Question 19

How does the respiraotry system compensate for alklosis?

Answer 19

slower, more shallow breathing, causing H+ to increase

Question 20

Which buffering system rids the body of metabolic acids?

Answer 20

Renal

Question 21

How does the renal system provide acid-base regulation?

Answer 21

1. The most important renal mechanisms for regulating acid-base balance are reabsorbing or generating new bicarbonate ions and excreting bicarbonate ions
2. Losing a bicarbonate ion is the same as gaining a hydrogen ion
3. Reabsorbing a bicarbonate ion is the same as losing a hydrogen ion

Question 22

How is bicarbonate reabsorbed?

Answer 22

1. Carbonic acid formed in filtrate dissociates to release carbon dioxide and water
2. Carbon dioxide then diffuses into tubule cells, where it acts to trigger further hydrogen ion secretion
3. For each hydrogen ion secreted, a sodium ion and a bicarbonate ion are reabsorbed by the PCT cells
4. Secreted hydrogen ions form carbonic acid

Question 23

Steps of Renal acid base balance

Answer 23

1. Na+ is reabsorbed to maintain bp, anti-port of H+ ions from the proximal convoluted tubule. Na eventually is reabsorbed into the preitubular capillaries
2. H+ ions that were secreted combine with HCO3  carbonic acid  CO2 + H2O. In the proximal tubule cell, the CO2 and H2O form H+ and HCO3 in the presence of carbonic anhydrase
3. H+ ion from above rxn is recycled to the Na antiport system.
4. HCO3 is reabsorbed via cotransport from the proximal tubule cell to the peritubular capillary
5. Glutamate is metabolized to ammonium and HCO3-. Ammonium is excreted in urine.
   HCO3 is reabsorbed via cotransport with Na from the proximal tubule cell to the peritubular capillary

Question 24

Ammonium Ion Excretion

Answer 24

1. This method uses ammonium ions produced by the metabolism of glutamine in PCT cells
2. Each glutamine metabolized produces two ammonium ions and two bicarbonate ions
3. Bicarbonate moves to the blood and ammonium ions are excreted in urine

Question 25

Phosphate Buffer System in the Kidneys

Answer 25

1. Carbonic anhydrase is present in renal tubule cells 2. Therefore, any CO2 that enters tubules can combine with water forming H2CO3 3. H+ generated can be pumped into lumen of tubules where it combines with HPO4 to form H2PO4 4. H2PO4 is excreted in tubular fluid

Question 26

Hydrogen Ion Secretion

Answer 26

1. in response to acidosis Hydrogen ions must be counteracted by generating new bicarbonate 2. Kidneys generate bicarbonate ions and add them to the blood 3. An equal amount of hydrogen ions are added to the urine 4. The excreted hydrogen ions must bind to buffers (phosphate buffer system) in the urine and excreted 5. Generated bicarbonate is: Moved into the interstitial space via a cotransport system Passively moved into the peritubular capillary blood

Question 27

Bicarbonate Ion Secretion

Answer 27

1. When the body is in alkalosis, tubular cells secrete bicarbonate ions and reclaim hydrogen ions and acidify the blood 2. The mechanism is the opposite of bicarbonate ion reabsorption process