230 chapter 11
As described by the Henderson-Hasselbalch equation, the ratio of bicarbonate to carbonic acid is 20 to 1 to help maintain the normal pH of arterial blood at _____.
7.4
primary sources of H= in contracting skeletal muscles
after carbonic acid is formed, bicarbonate is formed H+ lowers pH
Hydrogen ions exert their influence in biological systems by attaching to molecules and _____.
altering their shape and function
A molecule that lowers the hydrogen ion concentration of a solution is a(n) _____.
base
For a solution to be acidic, its pH value should be _____.
below 7
Some investigators have demonstrated that an improvement in performance in some types of exercise can be achieved by increasing blood _____ concentration.
bicarbonate
The most important buffer system in the body is the _____ buffer system.
bicarbonate
The principal means by which the kidneys regulate hydrogen ion concentration is by increasing or decreasing the _____ concentration.
bicarbonate
The principle extracellular buffer in the second line of defense against exercise-induced acidosis is _____.
blood bicarbonate
In the second line of defense against pH change during intense exercise, carbonic acid is eliminated by _____.
blowing off carbon dioxide
It is clear that high-intensity exercise results in a marked decrease in _____.
both muscle and blood pH
An important source of H+ ions in contracting muscles is the _____.
breakdown of adenosine triphosphate
One of the most important means of regulating hydrogen ion concentrations in body fluids is by the aid of _____.
buffers
Hemoglobin is a very effective buffer as it is better able to bind to the hydrogen ions formed when CO2 enters the blood from tissues. This is because _____.
deoxygenated hemoglobin is a better buffer than oxygenated hemoglobin
is extracellular buffers or intracellular buffers more important?
extracellular because of the bicarbonate (respiratory compensation)
The use of blood proteins as buffers during heavy exercise is limited because they are _____.
found in small quantities
The breakdown of ATP (adenosine triphosphate) into ADP (adenosine diphosphate) is in itself an important contributor to exercise-induced acidosis, because _____.
it releases H+ ions
The major classes of intracellular buffer systems are bicarbonate, _____.
phosphates, and cellular proteins
When the hydrogen ion concentration increases in body fluids, the kidneys respond by _____.
reducing the rate of bicarbonate excretion
Based on _____ equation, the pH of arterial blood can be determined by the ratio of the concentration of bicarbonate to the concentration of carbonic acid.
the Henderson-Hasselbalch
The second line of defense against exercise-induced acidosis is _____.
the blood buffering systems
In the condition termed alkalosis, there is a(n) _____ of the blood.
decrease in hydrogen ion concentration
During the final stages of an incremental exercise test or during severe exercise of short duration, there is a(n) _____
decrease in muscle pH
In the condition termed acidosis, there is a(n) _____ of the blood.
decrease in pH
Any atom that is missing electrons or has gained electrons is a(n) _____.
ion
Regulation of Acid-Base Balance During Exercise Muscle pH is always lower than blood pH (at rest and exercise) (you'll have more disfunction at the tissues/muscles first because blood pH can "blow off" H+)
*H+ production depends on: -exercise intensity -amount of muscle mass involved -duration of exercise *Blood pH: -declines with increasing intensity of exercise *Muscle pH: -declines with increasing intensity of exercise: muscle pH is lower than blood pH. *Muscle has lower buffering capacity*
Regulation of Acid-base balance via the kidneys Kidneys are important in long-term acid-base balance.. but
-Kidneys do NOT play a key role in acid-base balance during exercise -kidneys are permissive in their effect Kidneys contribute to acid-base balance (at rest) by regulating bicarbonate concentration in blood* -when blood pH decreases, bicarbonate excretion is reduces (hours later) & vise versa
Match the type of molecules with their description -Molecules that release hydrogen ions= -Molecules that combine with hydrogen ions=
-Molecules that release hydrogen ions= acids -Molecules that combine with hydrogen ions= bases
Identify the factors that determine the amount of hydrogen ions produced during exercise. (Check all that apply.)
-The IQ of the individual -The experience in participation in team sports by the individual
The principle extracellular buffer in the second line of defense against exercise-induced acidosis is _____. -blood bicarbonate -muscle bicarbonate -phosphate groups -intracellular proteins
-blood bicarbonate
The definition of pH can be written mathematically as _____.
-log10 [H+]
conditions and diseases that promote metabolic acidoses or alkalosis Metabolic alkalosis:
-loss of acids from the body -severe vomiting -kidney disease
The scale on which pH units are expressed range from _____.
0 to 14
Respiratory Influence on Acid-Base Balance pt 2
Carbonic acid (H2CO3) dissociation equation CO2+H20 → H2CO3 → H+HCO3- When pH decreases, [H+] increases -reaction above moves to the left -CO2 in "removed" by the lungs, eliminating H+ and increasing pH
acid-base buffer systems (upregulation of the following): Acid-base balance maintained by buffers: -release H+ ions when pH is high -accept H+ ions when pH is low
Extracellular buffers (blood): -bicarbonate (major buffer). (respiratory compensation) -hemoglobin (minor) -blood proteins (minor) Intracellular buffers (muscle): -proteins (60%) -phosphate groups (20-30%) -bicarbonate (HCO3-) (10-20%)
True or false: Kidneys respond to acid-base imbalance during exercise within a few seconds.
False
True or false: The importance of the concentration of hydrogen ions in biological systems is limited to chemical reactions and their rates.
False
The concentration of a gas in solution is directly proportional to its partial pressure. This is called _____.
Henry's law
Importance of acid-base balance during exercise ** important key terms for why
High intensity exercise results in production of lactic acid and increased [H+] in muscle fibers and blood* -Increased [H+] can impair performance: 1- inhibits glycolytic and TCA enzyme activity (ATP production from the citric acid cycle) 2- [H+] can impair muscle contraction by competing with Ca+2 for binding sites on troponin*
exercise and acid-base disturbances
High= 100-m swim, 400-m run, 800-m run why? lactate build up and carbonic acid buildup. These free up hydrogen ions
conditions and diseases that promote metabolic acidoses or alkalosis Metabolic acidosis:
Metabolic acidosis: -gain in the amount of acid in the body -high intensity exercise (above lactate threshold) lasting >30 seconds -long term starvation (results in increased fat metabolism and elevated production of ketoacids**) -uncontrolled diabetes (results in high rates of fat metabolism and DIABETIC KETOACIDOSES*)
what is a base
Molecule capable of combining with H+ -decreases H+ concentration a solution (increases pH) -Bicarbonate (HCO3-) is a strong base
what is an acid
Molecule that can liberate hydrogen ions (H+) -acids increase the H+ concentration in a solution -Lactic acid is a strong acid
Why is muscle pH always 0.4 to 0.6 pH units lower than blood pH?
Muscle hydrogen ion concentration is higher than that of blood.
Which of the following types of intracellular buffers is of particular importance at the beginning of an exercise?
Phosphate buffers
Respiratory Influence on Acid-Base Balance
Primarily moving CO2 from the tissues to the lungs and out of the body *CO2 is moved through the blood as bicarbonate (HCO3-)*
lines of defense in acid-base buffer systems
Proteins 60% containing histidine groups. -Histidine-dipeptides: primary component is carnosine -first line of defense is histidine groups and carnosine, but the most important is respiratory compensation
Identify the reason why the kidney is not an important regulator of acid-base balance during exercise.
The kidneys respond too slowly.
Which of the following statements is true of buffers? -The greater the concentration of a particular buffer, the less effective the buffer can be in preventing pH change. -They resist pH change by releasing hydrogen ions when the hydrogen ion concentration increases. -They often consist of a weak acid and its associated base. -All buffers are the same in their intrinsic physiochemical ability to act as buffers.
They often consist of a weak acid and its associated base.
High-intensity exercise can lead to _____.
a decrease in enzyme activity
Carbon dioxide is responsible for exercise-induced decrease in pH because it can be regarded as a(n) _____ by virtue of its ability to react with water and result in the formation of H+ and bicarbonate ions.
acid
Hydrogen ions hinder the muscle contractile process by competing with _____.
calcium ions for binding sites on troponin
One of the major histidine-dipeptides found in skeletal muscle is _____.
carnosine
The signal to the respiratory control center to increase alveolar ventilation occurs due to the stimulation of _____.
carotid bodies
Influence of Muscle Fiber Type and Exercise Training on Intracellular Buffer Capacity -increases in MCT and carosine*
compared to slow type 1 muscle fibers, fast (type 2) muscle fibers have a higher buffering capacity* -high intensity exercise training improves muscle buffering capacity due to: -increases in carnosine (these are intracellular proteins) -hydrogen ion transporters in the training muscle fibers (MCT transporter increases)
According to Henry's law, as the partial pressure increases, the _____, and vice versa.
concentration of the gas in solution increases
The major blood buffer during resting conditions is _____.
hemoglobin
The principle extracellular buffers found in blood are bicarbonate, _____.
hemoglobin, and proteins
The lactic acid that is produced during exercise is buffered by the respiratory system by _____.
increasing alveolar ventilation
The respiratory control center responds to the increasing hydrogen ion concentration by _____.
increasing alveolar ventilation
The first line of defense against a rise in acid production resides in the _____.
individual muscle fibers
An increase in the hydrogen ion concentration reduces the muscle's ability to produce ATP (adenosine triphosphate) by _____.
inhibiting key enzymes
Exercise involving high-intensity leg work, such as running, may reduce arterial pH from 7.4 to 7.0 within a few minutes because of the _____.
intensity and muscle mass that is involved
A hydrogen ion is formed by _____.
losing an electron
During exercise, the final 10% to 20% of muscle buffering capacity comes from _____.
muscle bicarbonate
The first line of defense in protecting against exercise-induced decreases in pH resides within the _____.
muscle fiber
Causes of acidosis and alkalosis
our body is 7.4 pH -normal resting pH= 7.4±.05 (pH of arterial blood)
pH expressed as the negative logarithm of H+ concentration
pH=-log10[H+] -since the pH scale is logarithmic, a change in 1 pH unit corresponds to a ten-fold change in [H+] -pH of pure water: pH(pure water)= -log10[H+] = 7.0
The concentration of carbonic acid in the blood is determined by the _____.
partial pressure of CO2
lines of defense against pH change during severe exercise
proteins, then phosphates, then bicarbonate) -MCT transport of H+ ions out of muscle -carsoine and histine groups help buffer H+ out *second line of define is most important*
Besides blood buffering systems, an important role in the second line of defense against pH change during intense exercise is played by _____.
respiratory compensation
At normal body pH, sulfuric acid liberates almost all of its hydrogen ions and therefore elevates the hydrogen ion concentration of the body because it is a _____.
strong acid
A bicarbonate ion is capable of combining with hydrogen ions to form a weak acid called carbonic acid because it is a _____.
strong base
CO2 is considered a _____ because it can be readily changed to carbonic acid.
volatile acid
The production of carbon dioxide is one of the causes for exercise-induced pH decrease. Since Co2 is a gas and can be eliminated by the lungs, it is often referred to as a(n) _____.
volatile acid
