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Diseases like sickle cell anemia and thalassemia decrease the blood’s ability to deliver oxygen to tissues and its oxygen-carrying capacity. In sickle cell anemia    , the shape of the red blood cell is crescent-shaped, elongated, and stiffened, reducing its ability to deliver oxygen ( [link] ). In this form, red blood cells cannot pass through the capillaries. This is painful when it occurs. Thalassemia is a rare genetic disease caused by a defect in either the alpha or the beta subunit of Hb. Patients with thalassemia produce a high number of red blood cells, but these cells have lower-than-normal levels of hemoglobin. Therefore, the oxygen-carrying capacity is diminished.

The micrograph shows a smear of red blood cells, some are disc-shaped and compressed in the center, whereas some are crescent-shaped. Each red blood cell is about five microns across.
Individuals with sickle cell anemia have crescent-shaped red blood cells. (credit: modification of work by Ed Uthman; scale-bar data from Matt Russell)

Transport of carbon dioxide in the blood

Carbon dioxide molecules are transported in the blood from body tissues to the lungs by one of three methods: dissolution directly into the blood, binding to hemoglobin, or carried as a bicarbonate ion. Several properties of carbon dioxide in the blood affect its transport. First, carbon dioxide is more soluble in blood than oxygen. About 5 to 7 percent of all carbon dioxide is dissolved in the plasma. Second, carbon dioxide can bind to plasma proteins or can enter red blood cells and bind to hemoglobin. This form transports about 10 percent of the carbon dioxide. When carbon dioxide binds to hemoglobin, a molecule called carbaminohemoglobin    is formed. Binding of carbon dioxide to hemoglobin is reversible. Therefore, when it reaches the lungs, the carbon dioxide can freely dissociate from the hemoglobin and be expelled from the body.

Third, the majority of carbon dioxide molecules (85 percent) are carried as part of the bicarbonate buffer system    . In this system, carbon dioxide diffuses into the red blood cells. Carbonic anhydrase (CA) within the red blood cells quickly converts the carbon dioxide into carbonic acid (H 2 CO 3 ). Carbonic acid is an unstable intermediate molecule that immediately dissociates into bicarbonate ions (HCO 3 ) and hydrogen (H + ) ions. Since carbon dioxide is quickly converted into bicarbonate ions, this reaction allows for the continued uptake of carbon dioxide into the blood down its concentration gradient. It also results in the production of H + ions. If too much H + is produced, it can alter blood pH. However, hemoglobin binds to the free H + ions and thus limits shifts in pH. The newly synthesized bicarbonate ion is transported out of the red blood cell into the liquid component of the blood in exchange for a chloride ion (Cl - ); this is called the chloride shift    . When the blood reaches the lungs, the bicarbonate ion is transported back into the red blood cell in exchange for the chloride ion. The H + ion dissociates from the hemoglobin and binds to the bicarbonate ion. This produces the carbonic acid intermediate, which is converted back into carbon dioxide through the enzymatic action of CA. The carbon dioxide produced is expelled through the lungs during exhalation.

Questions & Answers

what does the letters DNA stand for?
Princess Reply
desoxyribonucleic acid
MissMeriiit
It simply means 'decoy ribonucleic acid'
Mustapha
sorry ... deoxyribonucleic acid...
Mustapha
what are some functions of the DNA
Seth Reply
What is biodiversity
Chati Reply
the diversity of plants and animals life in a particula habitat
Harry
Biodiversity is the variety of organisms in their common groups
Osei
what is glycolisis
David Reply
glycolisis is the breakdown of glucose
Yazi
the answer is incomplete the breakdown of glucose to what
David
what is biodiversity?
Hope Reply
What is biodiversity
Chati
what is taxonomy
Patience Reply
Taxonomy is a branch of biology that deals with the description, identification, nomenclature, and classification of organisms
Farco
what is nomenclature
John
nomenclature is the scientific naming of organisms
Bigenis
state the structural differences between the termites
Massa
what causes the DNA results of an offspring
venius Reply
how are proteins digested?
Trox Reply
how are proteins digested
Kaka
guys what is locomotion?
Misheal Reply
what is anatomy
Mohamed Reply
no idea
Benard
Anatomy is the branch of science that deals with the study of internal and external structures of an organism
Bigenis
Anatomy is the branch of science that deals with the study of the internal structure of an organism
Nana
what is locomotion?
Misheal
no idea
John
Locomotion may simply mean the movement of an organism from one point to another without permanent displacement of the organidm it'self
Bigenis
simply, its the ability to move
MissMeriiit
Thanks guys
Misheal
I have gotten it
Dickens
locomotion as an art student is the ability to move from on place to another
John
muscles that are concerned with locomotion
John
Anatomy deals with the study of internal structures of an organism
Osei
The ability of cells or organisms to move and propel itself from place to place. supplement. locomotion in biology pertains to the various movements of organisms (single-celled or multicellular organisms) to propel themselves from one place to another.
garnhial
Anatomy is the branch of biology concerned with structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structure organization of living things - human anatomy is one of the essential basic sciences that are applied in medicine
garnhial
what is multicellular organisms
Massa
multicellular organisms these are living things which have more than one cell
John
what are the theory if cells
Julius Reply
What's the function of epiglottis
Ugo Reply
What Is The Other Name For Intestinal Juice?
Justin Reply
what is the largestest planet of the universe
rick Reply
what are the types of cell
Bernard Reply
prokaryotic and eukaryotic
Yazi
prokaryotic cell and eukaryotic cell
Grace

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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