Physiologic pH and buffers - acid-base physiology
Summary
TLDRThis script explains the concept of physiologic pH, which is crucial for maintaining the optimal functioning of cells and enzymes. It details how the body uses logarithmic pH to manage hydrogen ion concentrations, with a balanced pH of around 7.4 being essential. The video discusses the role of buffers, such as the bicarbonate system, phosphate buffers, and plasma proteins, in stabilizing pH levels against fluctuations caused by acids and bases. It also touches on the importance of intracellular buffers like hemoglobin and organic phosphates in maintaining cellular pH balance.
Takeaways
- 🔍 Physiologic pH is a measure of the balance between acids and bases in the body, determined by the concentration of hydrogen ions.
- ⚗️ The pH scale is logarithmic, with a pH of 7.4 representing an optimal hydrogen ion concentration of 40 nanoequivalents per liter.
- 📉 As hydrogen ion concentration increases, pH decreases due to the negative sign in the pH formula.
- 🔄 The relationship between pH and hydrogen ion concentration is not linear, with changes in pH reflecting exponential changes in ion concentration.
- 🌡️ The body maintains a narrow pH range between 7.37 and 7.42, which is crucial for cellular function.
- 🛡️ Buffers act as protective mechanisms to prevent rapid changes in pH, using a weak acid and its conjugate base or a weak base and its conjugate acid.
- 💧 The bicarbonate buffering system, involving carbonic acid (H2CO3) and bicarbonate ions (HCO3-), is the most important in the body.
- 🌬️ Excess carbon dioxide can be eliminated through the lungs, helping to regulate the bicarbonate buffer system.
- 🧬 Proteins, such as hemoglobin in red blood cells, serve as intracellular buffers, binding or releasing hydrogen ions based on the pH environment.
- 🧪 The phosphate buffer system involves dihydrogen phosphate (H2PO4-) and monohydrogen phosphate (HPO4^2-), contributing to pH balance.
- 🏗️ Organic phosphates like ATP and glucose 6-phosphate also act as intracellular buffers, managing excess hydrogen ions within cells.
Q & A
What is the definition of physiologic pH?
-Physiologic pH is a measure of the balance between acids and bases in the body, defined by the concentration of hydrogen ions and expressed with the equation pH = -log base 10 of the hydrogen ion concentration.
What is the optimal hydrogen ion concentration for cells and enzymes in our tissues and organs?
-The optimal hydrogen ion concentration for cells and enzymes is 40 times 10 to the minus 9 equivalents per liter, or 40 nanoequivalents per liter.
Why is it important to express the hydrogen ion concentration as pH rather than using the actual concentration?
-Expressing the hydrogen ion concentration as pH is important because the actual concentrations are very small and difficult to work with. The pH scale is a logarithmic function that simplifies these tiny numbers into a more manageable scale.
How does the pH scale relate to the concentration of hydrogen ions?
-The pH scale is a logarithmic inverse relationship to the hydrogen ion concentration. As hydrogen ion concentrations increase, the pH decreases, and vice versa, due to the negative sign in the pH equation.
What is the normal pH range for the human body?
-The normal pH range for the human body is between 7.37 and 7.42.
What happens when the body's pH drops below 7.4?
-When the body's pH drops below 7.4, it is considered acidemia, indicating a more acidic state.
What is the role of buffers in maintaining the body's pH?
-Buffers act like a protective cushion or shield to prevent the pH from rising or falling too quickly. They handle excess hydrogen ions without causing a major shift in the overall pH.
What is the most important buffer in the body and how does it work?
-The most important buffer in the body is the bicarbonate buffer system, consisting of the weak acid carbonic acid (H2CO3) and its conjugate base bicarbonate ion (HCO3-). It works by taking on extra hydrogen ions to form carbonic acid, which can then be converted to carbon dioxide and water, helping to maintain pH balance.
How does the body handle excess carbon dioxide or bicarbonate ions?
-Excess carbon dioxide is eliminated through the lungs by breathing, while excess bicarbonate ions are removed by the kidneys in the urine.
What are the other buffering systems in the body besides the bicarbonate buffer system?
-Besides the bicarbonate buffer system, the body also has the phosphate buffer system and plasma proteins, which serve as important buffering systems to maintain pH balance.
How do intracellular buffers, such as hemoglobin, help maintain the pH inside cells?
-Intracellular buffers like hemoglobin can reversibly bind to hydrogen ions or oxygen. When there is a buildup of hydrogen ions, deoxygenated hemoglobin binds to them, preventing the pH from falling too quickly. This process also involves the chloride shift, which helps maintain charge balance.
What is the significance of organic phosphates like ATP in intracellular buffering?
-Organic phosphates like ATP are significant intracellular buffers because their phosphate groups can serve as a source or sink for excess hydrogen ions, helping to maintain the pH balance inside cells.
Outlines
🧪 Understanding pH Balance and Buffers
This paragraph explains the concept of pH as a measure of acidity and alkalinity in the body, based on hydrogen ion concentration. It details the logarithmic relationship between pH and hydrogen ion concentration, emphasizing the importance of maintaining a pH of around 7.4 for optimal cellular and enzymatic function. The paragraph further describes how changes in pH levels affect hydrogen ion concentrations non-linearly and introduces the concept of acidemia and alkalemia. It also explains the role of buffers in stabilizing pH levels, using the bicarbonate buffer system as a primary example, illustrating how it prevents drastic pH changes through the reversible reactions involving carbonic acid and bicarbonate ions. The summary concludes with the explanation of how the body manages excess carbon dioxide and bicarbonate ions through respiration and urinary excretion.
🌡 Buffer Systems in Maintaining Physiological pH
The second paragraph delves into the mechanisms by which the body maintains its physiological pH using various buffer systems. It starts by describing the response of the bicarbonate buffer system to the introduction of a strong base (NaOH) and a strong acid (HCL), showing how these buffers neutralize the impact of added substances to keep pH stable. The paragraph also introduces the phosphate buffer system and the role of plasma proteins as buffers, highlighting their capacity to act as both acids and bases depending on pH conditions. Additionally, it discusses the limitations of protein buffering due to their limited quantities in plasma. The paragraph further explains the importance of intracellular pH balance, using hemoglobin in red blood cells as an example of an intracellular buffer, and describes the process of the chloride shift that helps maintain charge balance. It concludes by summarizing the role of organic phosphates like ATP as intracellular buffers and recaps the overall function of buffers in resisting pH changes.
🛡️ Key Buffers in Extracellular and Intracellular Fluids
The final paragraph succinctly outlines the most important buffers in both extracellular and intracellular environments. It identifies bicarbonate, phosphate, and plasma proteins as the key extracellular buffers, while hemoglobin and organic phosphates like ATP are highlighted as the primary intracellular buffers. This paragraph serves as a concise summary of the primary buffering agents in the body, emphasizing their crucial role in maintaining the pH balance necessary for life.
Mindmap
Keywords
💡Physiologic pH
💡Hydrogen Ion Concentration
💡Logarithmic Function
💡Acidemia
💡Alkalemia
💡Buffers
💡Carbonic Acid (H2CO3)
💡Bicarbonate Ion (HCO3-)
💡Chloride Shift
💡Hemoglobin
💡Organic Phosphates
Highlights
Physiological pH is a measure of the balance between acids and bases in the body.
pH is calculated using the equation pH = -log10 of hydrogen ion concentration.
Cells and enzymes function optimally at a hydrogen ion concentration of 40 nEq/L.
A logarithmic function is used to express hydrogen ion concentration as pH.
An increase in hydrogen ion concentration leads to a decrease in pH.
pH and hydrogen ion concentration have a non-linear relationship.
Acidemia is defined as a body pH below 7.4, and alkalemia as above 7.4.
Buffers act as protective shields to prevent rapid pH changes.
The body constantly generates acids that can shift pH into the acidic zone.
Buffers are typically a weak acid and its conjugate base or a weak base and its conjugate acid.
Carbonic acid (H2CO3) and bicarbonate ion (HCO3-) are the most important body buffers.
The body maintains pH balance through reversible reactions of carbonic acid and bicarbonate.
Excess carbon dioxide is eliminated by the lungs, and bicarbonate by the kidneys.
The phosphate buffer system involves dihydrogen phosphate and monohydrogen phosphate.
Proteins like albumin in plasma serve as important buffer systems.
Proteins can function as both acids and bases, depending on pH conditions.
Intracellular pH balance is maintained by proteins like hemoglobin and organic phosphates.
Hemoglobin binds hydrogen ions when oxygen levels are low and releases them when oxygen levels are high.
Intracellular buffers like ATP help maintain pH balance by binding or releasing hydrogen ions.
Transcripts
foreign
physiologic pH is a way of quantifying
the balance between acids and bases in
the body
in fact the pH depends on the
concentration of hydrogen ions and can
be described with this equation pH
equals negative log base 10 of the
hydrogen ion concentration
now the cells and enzymes in our tissues
and organs work best when the
concentration of hydrogen ions is 40
times 10 to the minus 9 equivalents per
liter
otherwise known as 40 Nano equivalents
per liter
small changes to that number matter a
ton and because it can get annoying
working with such tiny numbers
scientists converted this concentration
into a logarithmic function and
expressed it as pH
in this case a hydrogen ion
concentration of 40 times 10 to the
minus 9 equivalents per liter works out
to a pH of about 7.4
with this logarithmic function there are
two important aspects to remember
first as hydrogen concentrations
increase the pH decreases this is
because of the negative sign in front of
the log
second since it's a logarithmic function
pH and the hydrogen ion concentration
don't have a linear relationship
for example an increase in PH from 7.4
to 7.6 means a decrease in the hydrogen
concentration of 15 Nano equivalents per
liter
taking the same change in PH but going
the other way from 7.4 to 7.2 means an
increase in the hydrogen concentration
of 23 Nano equivalents per liter
this is why the graph of hydrogen ion
concentration versus pH has a curve to
it rather than being a straight line
for simplicity's sake when the body's pH
drops below 7.4 it's considered acidemia
and when it goes above 7.4 it's
considered alkalemia
so due to this logarithmic relationship
a change in PH in the acidic range or
below 7.4 will show a larger change in
hydrogen concentrations than if the same
change happened in BH in the alkaline
range or pH above 7.4
now maintaining a pH between about 7.37
and 7.42 is essential for the human body
and this is accomplished with buffers
in everyday language a buffer is
something that acts like a protective
cushion or Shield
and the same is true of physiologic
buffers they Shield or prevent the pH
from rising or falling too fast
the reason the body needs buffers is
that acids or molecules that readily
give up their hydrogen ion are being
generated by the body all the time
these extra hydrogen ions would shift
the pH into the acidic Zone so the body
needs a way to handle them without a
major shift in the overall pH
to accomplish this buffers can
essentially take on some of these extra
hydrogen ions and therefore keep the pH
from dropping too much
buffers are usually a weak acid with its
conjugate base or a weak base with its
conjugate acid
the most important buffer in the body is
the weak acid carbonic acid or h2co3 and
its conjugate base bicarbonate ion hco3
minus
carbonic acid forms when carbon dioxide
combines with water with the help of the
enzyme Carbonic anhydrase
as a weak acid carbonic acid easily
dissociates into hydrogen ions and
bicarbonate ions
of course these reactions are reversible
and can happen in the opposite direction
as well
in fact because carbonic acid is such a
weak acid when hydrogen ion
concentrations Get Low it'll drop off
its hydrogen ion and the equation moves
to the right producing more bicarbonate
and a hydrogen ion and when there are
lots of hydrogen ions around the
bicarbonate will bind to one and form
carbonic acid which can go the other way
and split into water and carbon dioxide
at that point the extra carbon dioxide
can be breathed out through the lungs
all right so imagine you've got some
extracellular fluid it has a normal
amount of hydrogen ions in it which puts
it in the normal physiologic PH range
now we drop some NaOH in or sodium
hydroxide which is a strong base
that means that in water it completely
dissociates into sodium or na plus ions
and hydroxide or oh minus ions
the hydroxide ions bind to hydrogen ions
and form water which makes the fluid
more basic since there's a decrease in
hydrogen ions which increases the pH a
lot
when there's plenty of carbon dioxide
around though it reacts with the water
to form more carbonic acid which splits
into bicarbonate ions and hydrogen ions
which quickly replaces the hydrogen ions
and therefore buffers the ph and keeps
it in a normal range
on the flip side imagine tossing HCL
into the fluid or hydrochloric acid
which this time is a strong acid
it would fully dissociate into hydrogen
ions and a bunch of chloride ions
without a buffer this would cause it to
become acidic since there's more
hydrogen ions and therefore the pH would
go down
the new hydrogen ions though get
instantly picked up by bicarbonate ions
and converted to carbonic acid which
would then dissociate into carbon
dioxide in water once again this buffer
normalizes the pH
now the great thing here is that there's
a huge supply of carbonic acid in the
body
because it's formed from carbon dioxide
in water which are an abundant Supply in
the body
finally as a last point if there's too
much carbon dioxide it gets blown off by
the lungs and if there are too many
bicarbonate ions then the kidneys
eliminate them in the urine
apart from the bicarbonate buffer system
there's also the phosphate buffer system
this is a mixture of the weak acid
dihydrogen phosphate or h2po4 minus and
its conjugate base monohydrogen
phosphate
or hpo4 2 minus
dihydrogen phosphate has two hydrogens
and it's always ready to give off one of
them and get converted to monohydrogen
phosphate which has a single hydrogen
now the extracellular fluid and
especially the plasma is also full of
proteins like albumin which serve as
another extremely important buffer
system
this is because some of the proteins
amino acids have exposed carboxyl groups
or cooh that act as weak acids meaning
that they're ready to release hydrogen
ions when the pH starts to rise
at the same time other amino acids might
have exposed nh2 or amine groups that
act as weak bases meaning that they can
bind a hydrogen ion and prevent it from
decreasing the pH in other words a
single protein molecule can function
both as an acid as well as a base
depending on the pH it has to deal with
but unlike the bicarbonate buffering
system there are only a limited number
of proteins in our plasma which limits
how much they can buffer
okay until now we've explored the
extracellular fluid but intracellular pH
has to stay balanced as well and this is
the pH inside cells
all cells are full of proteins and those
proteins are the most significant
intracellular buffer
an example is hemoglobin inside red
blood cells
hemoglobin can reversibly bind either
hydrogen ions which bind to the protein
itself or oxygen which binds to the iron
of the heme group
and the interesting thing is that when
one of these is bound the other is
released
so when red blood cells are in the
capillaries of various tissues the
oxygen levels are low and the carbon
dioxide levels are high
in this case carbon dioxide diffuses
into red blood cells where Carbonic
anhydrous enzyme combines water and
carbon dioxide to form carbonic acid
which then dissociates the hydrogen ion
in bicarbonate
because there's so much carbon dioxide
around the reaction continues in the
direction of generating more hydrogen
ion and bicarbonate and over time the
buildup of hydrogen ions can cause the
pH to fall
to prevent the hydrogen ion
concentration from rising too quickly
each deoxygenated hemoglobin binds
hydrogen ions
the bicarbonate on the other hand moves
into the plasma in exchange for chloride
ions
this exchange called the chloride shift
keeps positive and negative charges
balanced
now once the red blood cell gets into
the capillaries of the lungs there's a
low level of carbon dioxide and a high
level of oxygen so the process reverses
oxygen binds to hemoglobin and hydrogen
ions get released
bicarbonate re-enters the red blood
cells and combines with hydrogen ions to
form carbonic acid which dissociates
into water and carbon dioxide then the
carbon dioxide gets breathed out by the
lungs
intracellular fluid also has large
amounts of organic phosphates like
adenosine triphosphate or ATP and
glucose 6-phosphate
which can both serve as intracellular
buffers
the phosphate group of these organic
molecules can serve as a source or a
sink for excess hydrogen ions
alright as a quick recap
between 7.37 and 7.42 is physiologic pH
and the body uses buffering systems to
maintain pH within this range
buffers are pairs of a weak acid in its
conjugate base or a weak base in its
conjugate acid and their physiologic
role in our body is to resist pH changes
the most important buffers in the
extracellular fluid are bicarbonate
phosphate and plasma proteins
and the most important buffers within
cells are proteins like hemoglobin and
organic phosphates like ATP
Voir Plus de Vidéos Connexes
5.0 / 5 (0 votes)