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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.

The ph scale

This table gives examples of solutions from PH of zero to 14. Examples of solutions with a PH of zero include battery acid and strong hydrofluoric acid. An example of a solution with a pH of one is the hydrochloric acid secreted by the stomach lining. Examples of solutions with a PH of two include lemon juice and vinegar. Examples of solutions with a PH of three include grapefruit juice, orange juice and soda. Examples of solutions with a PH of four include tomato juice and acid rain. Examples of solutions with a PH of five include soft drinking water and black coffee. Examples of solutions with a PH of  six include urine and saliva. An example of a solution with a PH of seven is pure water. An example of a solution with a PH of eight is sea water. An example of a solution with a PH of nine is baking soda. Examples of solutions with a PH of ten  include saline lake water and milk of magnesia. An example of a solution with a PH of eleven is an ammonia solution. An example of a solution with a PH of twelve is soapy water. Examples of solutions with a PH of  thirteen include bleach and oven cleaner. An example of a solution with a PH of fourteen is liquid drain cleaner.
This chart shows where many common substances fall on the pH scale.

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 ( Na 2 H 2 PO 4 ), which is a weak acid, and sodium monohydrogen phosphate ( Na 2 HPO 4 2- ), which is a weak base. When Na 2 HPO 4 2- comes into contact with a strong acid, such as HCl, the base picks up a second hydrogen ion to form the weak acid Na 2 H 2 PO 4 and sodium chloride, NaCl. When Na 2 HPO 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.

Questions & Answers

what is oesophagus?
Bhavani Reply
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Beryl Reply
what's the meaning of polar?
Jackson Reply
Sign of anaemia or whitish color or Hgb luck
Kassahn
Are you talking of Polar anaemia or what, because the word polar doesnt have one meaning
Kingsley
what are the three types of adrenocorticoids hormones
Lubega Reply
glucocorticoids mineralocorticoid and catecholamines
Kartik
what is polar and non-polar
Jackson Reply
polar unequal share of electron while non polar is equal share
Quran
why are phosphate molecules negatively charged?
Jackson Reply
Bocz of unpaired elections
Javid
because of unpaired electrons
ABDULLAH
what are amphipathic molecules?
Jackson Reply
Amphipathic molecules are molecules with both polar and non polar regions
Mohammed
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MADUBULA Reply
Hw does the male organ develop
MADUBULA
Review your questions madam
Aliyu
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Rugut Reply
it is an imagency condition resulting from abnormal and immediate alagic response to a substance to which the body has become intensively sensitized
Lubega
different between drug and medicine
ado Reply
drugs have no medical application (cocaine, heroin, crystal meth). medicine have medical purpose (fentanyl, albuterol, aspirin, ect ect)
Jordan
medicine is a substance or preparation used in treating disease,drug is chemical compound medicine are drugs but all drugs are not medicines
Wafa
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Sidra
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Zwanga Reply
what are the smooth muscles of the heart
Sintung Reply
stomach
Sidra
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saba Reply
kidney weight on males?
saba
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saba
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saba
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saba
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Javid
O-olfactory O-optic O-occumulator T-trochlear T-trigemenal A-abducent F-facial A-auditory G-glossopharyngeal V-vagus A-acessory
Aniee
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Shahab
out patient department
mahesh
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Areeej
Read KD Tripathi book of Pharmacology.
mayank
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mayank
CT Scan means
Sintung
what's health?
Sintung
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Philip
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Sintung
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Vivek
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Dee
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Sintung
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saba
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Gideon
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shahid
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how hemolytic anemia cause due to gas gangrene?
Huma Reply
what's gangrene?
Sidra
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Huma Reply

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Source:  OpenStax, Anatomy & Physiology. OpenStax CNX. Feb 04, 2016 Download for free at http://legacy.cnx.org/content/col11496/1.8
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