Module 12

Question 1

Define an acid

Answer 1

Any molecule that will release hydrogen ions when put in a solution

Question 2

Define a base

Answer 2

Any molecule that will accept a hydrogen ion

Question 3

Define a hydrogen atom

Answer 3

A single proton (positive charge) and a single election (negative charge) resulting in an electrically neutral element

Question 4

Define a hydrogen ion

Answer 4

A hydrogen atom that has lost its electron, leaving only the positively charged proton, sometimes called just a proton

Question 5

Describe the pH scale

Answer 5

A way of quantifying the concentration of H+ in any solution

Goes from 0 to 14 with 7 being neutral

Below 7 is acidic, above 7 is basic or alkaline

Question 6

Describe how pH is calculated

Answer 6

It is a negative logarithm (base 10) of the H+ concentration

Question 7

Define the normal pH of body fluids

Answer 7

Between 7.35 and 7.45, with an average of 7.4

Arterial blood has a pH of 7.45 while venous blood has a pH of 7.35

Question 8

Define acidosis

Answer 8

Body fluids when the pH is below 7.4

When there is either too much acid (H+) in the body or too little bicarbonate (HCO3-)

Two types: respiratory or metabolic

Question 9

Define alkalosis

Answer 9

Body fluids when the pH is above 7.4

When there is either too much bicarbonate (HCO3-) or too little acid (H+)

Two types: respiratory or metabolic

Question 10

Describe the pH of body fluids that are lethal

Answer 10

Below 6.8 or above 7.8 for long periods of time

Question 11

Define a volatile acid

Answer 11

An acid that comes from the interaction of CO2 and water forming carbonic acid, no net increase in free H+ because the reaction is reversible and CO2 is removed at the lungs

Question 12

Define a nonvolatile acid

Answer 12

Any acid that cannot be removed by the lungs

Examples: sulphuric acid, phosphoric acid, lactic acid, hydrochloric acid, and other organic acids produced by metabolic breakdown

Question 13

List three mechanisms the body uses to regulate free H+ concentrations

Answer 13

Buffers, the respiratory system, and the kidneys

Question 14

Define a buffer

Answer 14

Any molecule that can reversibly bind or release free H+

Question 15

Describe how buffers work

Answer 15

Reacts almost immediately to sudden, brief changes in free H+, do not remove H+ from the body or alter pH, just bind up free H+ to stabilize pH until balance can be re-established

General reaction: X + H+ XH

Minimize the pH change until free H+ can be removed by the lungs or kidneys

Question 16

List examples of intracellular buffers

Answer 16

Buffers inside RBCs, like phosphates and intracellular proteins like hemoglobin

Question 17

Give an example of an extracellular buffer

Answer 17

Bicarbonate ions, the most powerful extracellular buffer, normally works in the blood

Question 18

Describe how the respiratory system maintains body fluid pH

Answer 18

CO2 is potentially a very large source of free H+ when reacting with water and forming carbonic acid, and the respiratory system removes CO2 from the body

CO2 levels are regulated in the blood using central and peripheral chemoreceptors, and when CO2 levels rise, both receptors detect it and increase ventilation to cause more CO2 removal from the body

This keeps CO2 levels in the body relatively constant, thus keeping the blood pH relatively constant

Question 19

List 3 ways the kidney regulates pH

Answer 19

Excreting H+ from nonvolatile acids
Attempting to reabsorb all bicarbonate ions
Creating new bicarbonate ions

Question 20

Describe how the kidney excretes H+

Answer 20

In the proximal tubule using the Na+/H+ exchanger (secondary active transport)
In the late distal tubule and collecting duct by a H+/ATP pump (active transport)

Question 21

Describe how the kidney reabsorbs bicarbonate ions

Answer 21

In the proximal tubule, cannot be directly reabsorbed, are converted to CO2 to be reabsorbed into tubule cells, then combines with water to form carbonic acid and dissociates into bicarbonate and H+
Bicarbonate leaves tubule cells by diffusion and are reabsorbed, H+ is secreted into lumen by Na+/H+ exchanger

For every bicarbonate ions reabsorbed, one H+ must be secreted

Question 22

Describe respiratory acidosis, its causes, and what mechanism maintains body pH

Answer 22

Caused by decreased ventilation and increased PCO2

Can occur if respiratory centers in brain stem are damaged, or from lung damage, result is decreased ability to remove CO2 from blood

Buffers in blood and kidney excretion will counteract it

Question 23

Describe respiratory aklalosis, its causes, and what mechanism maintains body pH

Answer 23

Caused by increased ventilation and decreased PCO2

Stress or emotionally induced hyperventilation (too much CO2 being removed from blood) or high altitudes (low O2 levels in air cause low PO2 levels in blood, stimulating hyperventilation) can cause this

Kidneys will excrete bicarbonate ions

Question 24

Describe metabolic acidosis and its causes

Answer 24

Many factors, but generally a decrease in extracellular bicarbonate ions (does not involve blood CO2 levels)

Causes include kidney failure (can’t excrete acids or can’t reabsorb bicarbonate), forming excess metabolic acids in the body, ingesting acids (like aspirin and methyl alcohol), or loss of bicarbonate in diarrhea (MOST COMMON)

Question 25

Describe metabolic alkalosis and its causes

Answer 25

Caused by either a buildup of bicarbonate ions or loss of H+, most commonly loss of HCl from the stomach when vomiting, but also from ingesting alkaline drugs like sodium bicarbonate for treating ulcers