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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 is hominids
Dauba Reply
what is genetics
Musa Reply
what is meiosis?
Musa
list three vertebrate animal and three invertebrate animal
Katie Reply
lizard, goat, frog ,earthworm, housefly, tapeworm
idoko
what is meant by radial symmetry?
Boadi
what is meaning of polysaccharide
mark Reply
water as a function in cell for inorganic substances
chisom Reply
hi john....wat about for mineral salts, its function in a cell and structure
chisom
hi chisom which topic is this
Ezeh
what is sepsis
Dauba
this biology is for which grade?
Janet Reply
A1
Boadi
state any one specialized animal cell and it's function
Pascal Reply
sperm cell: Fertilization
Tshering
Can DNA and RNA be praticalized
Oyewale Reply
you can make models of them and show how they replicate
Oswald
what is dentition
Tisa Reply
Study of teeths and their functions
Stanisla
what are the function
Tisa
it's not teeths. teeth is plural as well as singular noun. the function of the teeth is to cut and grind food for easier swallowing and for increasing the surface area if the fish as the substrate in which digestive enzymes work
Oswald
dentition is not the study of teeth but the arrangement of teeth in the mouth of species or individuals
Oswald
what are the two types of teeth
Tisa
upper lower jaw and upper jaw teeth
Dauba
Function of probosis
Adeola Reply
why do we study biology?
SYDNEY Reply
where biology began
Alhaji
What are chromesome
Talkmore Reply
condensed DNA wrapped with histone
Elias
chromosomes are gins that we take from our parents.when mom get pregnant the baby inside is made up of 23 chromosomes from his dad and 23 chromosomes from his mom.so a baby is made up of totally 46 chromosomes
ezera
chromosome are rod or thread shape body located in the nucleus of a cell.
Alhaji
what are chromosomes
Persiviour
what is chromosome?
Royd Reply
How can a person who has been in the vascular disease repairs his or her DNA
Rabson Reply
i need its explanation sir..pls provid na...🙁
Shaf Reply
Of wat
John
explanation for wat
Christian
Of war na so dat I can provide
John
Is d process which food is converted into substance dat can be utilize by d body
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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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