BSC 215 Lecture Notes - Lecture 42: Doughnut, Carbonic Anhydrase, Red Blood Cell
11 Jun 2018
School
Department
Course
Professor
The Blood
The blood consists of cells and cell fragments, called formed elements, and water with dissolved
molecules, called blood plasma.
Eyrthrocytes
Erythrocytes, or red blood cells (RBCs), transport oxygen (O 2) and carbon dioxide
(CO 2) in the blood. Erythrocytes contain the protein hemoglobin to which both O 2 and
CO 2 attach.
Mature erythrocytes lack a nucleus and most cellular organelles, thereby
maximizing the cell's volume and thus its ability to carry hemoglobin and
transport O 2.
Erythrocytes are shaped like flattened donuts with a depressed center
(rather than a donut hole). Their flattened shape maximizes surface area for
the exchange of O 2 and CO 2 and allows flexibility that permits their passage
through narrow capillaries.
Hemoglobin contains both a protein portion, called globin, and nonprotein
heme groups. Globin consists of four polypeptide chains, each of which
contains a heme group. The heme group is a red pigment that contains a
single iron atom surrounded by a ring of nitrogen‐containing carbon rings.
One oxygen atom attaches to the iron of each heme group, allowing a single
hemoglobin molecule to carry four oxygen atoms. Each erythrocyte contains
about 250 million hemoglobin molecules.
Oxyhemoglobin (HbO 2 ) forms in the lungs when erythrocytes are exposed to
oxygen as they pass through the lungs. Deoxyhemoglobin (Hb) forms when
oxygen detaches from the iron and diffuses into surrounding tissues.
Carbaminohemoglobin (HbCO 2 ) forms when CO 2 attaches to amino acids of
the globin part of the hemoglobin molecule. About 20–25 percent of the
CO 2 transported from tissues to lungs is in this form.
Carbonic anhydrase, an enzyme in erythrocytes, converts CO 2 and H 2O in
the cells to H + and HCO 3–. About 70 percent of the CO 2 collected from
tissues travels in the erythrocytes as HCO 3–. About 10 percent of the carbon
dioxide stays in the plasma and is transported in the circulatory system as
the bicarbonate ion.
Because they lack cellular organelles and thus the physiology to maintain
themselves, erythrocytes survive for only about 120 days. Degenerated
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The blood consists of cells and cell fragments, called formed elements, and water with dissolved molecules, called blood plasma. Erythrocytes, or red blood cells (rbcs), transport oxygen (o 2) and carbon dioxide (co 2) in the blood. Erythrocytes contain the protein hemoglobin to which both o 2 and. Mature erythrocytes lack a nucleus and most cellular organelles, thereby maximizing the cell"s volume and thus its ability to carry hemoglobin and transport o 2. Erythrocytes are shaped like flattened donuts with a depressed center (rather than a donut hole). Their flattened shape maximizes surface area for the exchange of o 2 and co 2 and allows flexibility that permits their passage through narrow capillaries. Hemoglobin contains both a protein portion, called globin, and nonprotein heme groups. Globin consists of four polypeptide chains, each of which contains a heme group. The heme group is a red pigment that contains a single iron atom surrounded by a ring of nitrogen containing carbon rings.
