# 26.4 Acid-base balance

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By the end of this section, you will be able to:
• Identify the most powerful buffer system in the body
• Explain the way in which the respiratory system affects blood pH

Proper physiological functioning depends on a very tight balance between the concentrations of acids and bases in the blood. Acid-balance balance is measured using the pH scale, as shown in [link] . A variety of buffering systems permits blood and other bodily fluids to maintain a narrow pH range, even in the face of perturbations. A buffer is a chemical system that prevents a radical change in fluid pH by dampening the change in hydrogen ion concentrations in the case of excess acid or base. Most commonly, the substance that absorbs the ions is either a weak acid, which takes up hydroxyl ions, or a weak base, which takes up hydrogen ions.

## Buffer systems in the body

The buffer systems in the human body are extremely efficient, and different systems work at different rates. It takes only seconds for the chemical buffers in the blood to make adjustments to pH. The respiratory tract can adjust the blood pH upward in minutes by exhaling CO 2 from the body. The renal system can also adjust blood pH through the excretion of hydrogen ions (H + ) and the conservation of bicarbonate, but this process takes hours to days to have an effect.

The buffer systems functioning in blood plasma include plasma proteins, phosphate, and bicarbonate and carbonic acid buffers. The kidneys help control acid-base balance by excreting hydrogen ions and generating bicarbonate that helps maintain blood plasma pH within a normal range. Protein buffer systems work predominantly inside cells.

## Protein buffers in blood plasma and cells

Nearly all proteins can function as buffers. Proteins are made up of amino acids, which contain positively charged amino groups and negatively charged carboxyl groups. The charged regions of these molecules can bind hydrogen and hydroxyl ions, and thus function as buffers. Buffering by proteins accounts for two-thirds of the buffering power of the blood and most of the buffering within cells.

## Hemoglobin as a buffer

Hemoglobin is the principal protein inside of red blood cells and accounts for one-third of the mass of the cell. During the conversion of CO 2 into bicarbonate, hydrogen ions liberated in the reaction are buffered by hemoglobin, which is reduced by the dissociation of oxygen. This buffering helps maintain normal pH. The process is reversed in the pulmonary capillaries to re-form CO 2 , which then can diffuse into the air sacs to be exhaled into the atmosphere. This process is discussed in detail in the chapter on the respiratory system.

## Phosphate buffer

Phosphates are found in the blood in two forms: sodium dihydrogen phosphate ( ${\text{Na}}_{2}{\text{H}}_{2}{\text{PO}}_{4}{}^{-}$ ), which is a weak acid, and sodium monohydrogen phosphate ( ${\text{Na}}_{\text{2}}{\text{HPO}}_{\text{4}}^{\text{2-}}$ ), which is a weak base. When ${\text{Na}}_{\text{2}}{\text{HPO}}_{\text{4}}^{\text{2-}}$ comes into contact with a strong acid, such as HCl, the base picks up a second hydrogen ion to form the weak acid ${\text{Na}}_{2}{\text{H}}_{\text{2}}{\text{PO}}_{\text{4}}{}^{-}$ and sodium chloride, NaCl. When ${\text{Na}}_{2}{\text{HPO}}_{\text{4}}^{2}{}^{-}$ (the weak acid) comes into contact with a strong base, such as sodium hydroxide (NaOH), the weak acid reverts back to the weak base and produces water. Acids and bases are still present, but they hold onto the ions.

Card 5 / 12: For whom would an appreciation of the structural characteristics of the human heart come more easily: an alien who lands on Earth, abducts a human, and dissects his heart, or an anatomy and physiology student performing a dissection of the heart on her very first day of class? Why?
what are regular shaped cells with granules in the cytoplasam
PMNL
Dinu
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cholesterol normal value is
less than 200mg/dl
Ashis
100 to159mg/dL
Dinu
Early this wk. I had some "A & P" questions & answers unfortunately didn't save them, Is there any way I can have them back ,so as 2 save them?. Thnx.
Kechi
what are the functions of the female reproductive system
it produces the female egg necessary for reproduction, called the Ova or Oocytes. The system is designed to transport the Ova to the site of fertilization.
Kechi
Female reproductive system was mainly functioned to produce ova(ovum) (female eggs) Into which will be fertilized by male gamete to produce zygote
Omary
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Khaliil
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Ahmed
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Khaliil
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Ahmed
asc if I try female reproductive system has two function the first is to produce egg cell and the second is to protact and nourish the offspring until birth
Muriidi
what is stercobilinogen
fecal urobilinogen. Created by bacteria in the gut. a chemical that gives feces brown color.
Blayne
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Kechi
The rate of diffusion increases if the
stella
Kechi
it's a breaking down of haemoglobin and it's a chemical made by bacteria
Dev
Thnx Dev Raj.
Kechi
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Dev
yes I sure do need more "Questions" & "Answers". I'm learning whole lot. Thnx.
Kechi
what is the greatest muscle of the body
gluteus maximus
ABDULLAH
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Kechi
Gluteus maximus
THE
Describe anatomy of cardiovascular system?
cardiovascular system is a group of organs coming together to perform the circulation of blood. The organs invoked are the heart and the blood vessels with blood being the tissue. The heart is a pump and it pumps oxygenated blood through the systemic circuit and deoxygenated blood through the pulmon
bernard
pulmonary circuit.
bernard
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Kechi
If an ANOVA yields a significant F value, you could rely on ________ to test significant differences between group means.
what's ANOVA
Cassandra
analysis of variance
Blayne
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Fatima
anova means analysis of variance, a statistical method in which the variation in a set of observations is divided into distinct components.
Blayne
M value ot test
ABDULLAH
What does it mean by M value ot test?
Orpha
formation of red blood cells
explain why... lower back pain in ovarian cancer
we says that protoplasm is the living part of us How?
is the leaving part of our cellular structure.
Eric
it is the leaving part of our blood cellular structure also
ABDULLAH
what is receptor?
an organ or cell able to respond to light, heat, or other external stimulus and transmit a signal to a sensory nerve.
Jessi
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Sandra
yes
yahye
yes
Allan
hey what is the process after your food is swallowed? how long does it take to get to the stomache until it is released as waste?
that is such a broad question. as you begin to swallow its various doses down the alimentary canal that brings the food into your stomach.then depending on whether it's a protein carbohydrate fat that dictates what function takes place in your stomach. these are all steps of digestion.
Joseph
typo sorry it's peristalsis , wave-like projections that push food down your alimentary canal etc. digestion starts in your mouth ends in your large intestines (colon anus)
Joseph
some of the many processes of digestion include hydrolysis dehydration synthesis denaturation of proteins etc. you have to be more specific.
Joseph
there's many different contributing factors the how long it takes food to convert into waste. remember fats, triglycerides proteins and carbohydrates all breakdown two different monomers and structures. you should be looking up metabolic processes.
Joseph
depending how much fiber you have in your diet dictates how much water is brought to your intestines that has to do with excretion whether fiber is insoluble or soluble. this is an anatomy and physiology app. to simply say the stomach will empty its contents in 2 to 3 hours would do you a disservice
Joseph
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Khh
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Jessi
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Sherif
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Cassandra
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Kevin
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abel
what are the major branches of the aorta?
Kevin
Jessi