hemoglobin

(noun)

iron-containing substance in red blood cells that transports oxygen from the lungs to the rest of the body; it consists of a protein (globulin) and heme (a porphyrin ring with iron at its center)

Related Terms

Examples of hemoglobin in the following topics:

  • Transport of Oxygen in the Blood

    • The majority of oxygen in the body is transported by hemoglobin, which is found inside red blood cells.
    • Most oxygen, 98.5 percent, is bound to a protein called hemoglobin and carried to the tissues.
    • Hemoglobin is made up of four symmetrical subunits and four heme groups.
    • It is the iron in hemoglobin that gives blood its red color.
    • Describe how oxygen is bound to hemoglobin and transported to body tissues

  • Transport of Carbon Dioxide in the Blood

    • Binding of carbon dioxide to hemoglobin is reversible.
    • However, hemoglobin binds to the free H+ ions, limiting shifts in pH.
    • The H+ ion dissociates from the hemoglobin and binds to the bicarbonate ion.
    • Carbon monoxide has a greater affinity for hemoglobin than does oxygen.
    • When carbon monoxide (CO) in the body increases, the oxygen saturation of hemoglobin decreases since hemoglobin will bind more readily to CO than to oxygen.

  • Red Blood Cells

    • Hemoglobin is packed into red blood cells at a rate of about 250 million molecules of hemoglobin per cell.
    • In mammals, the lack of organelles in erythrocytes leaves more room for the hemoglobin molecules.
    • Not all organisms use hemoglobin as the method of oxygen transport.
    • Studies have found that hemoglobin also binds nitrous oxide (NO).
    • Unlike hemoglobin, hemolymph is not carried in blood cells, but floats free in the hemolymph.

  • Types and Functions of Proteins

    • For example, hemoglobin is a globular protein, which means it folds into a compact globe-like structure, but collagen, found in our skin, is a fibrous protein, which means it folds into a long extended fiber-like chain.
    • In the respiratory system, hemoglobin (composed of four protein subunits) transports oxygen for use in cellular metabolism.
    • Structure of human hemoglobin.

  • Protein Structure

    • The oxygen-transport protein hemoglobin consists of four polypeptide chains, two identical α chains and two identical β chains.
    • In sickle cell anemia, a single amino substitution in the hemoglobin β chain causes a change the structure of the entire protein.
    • When the amino acid glutamic acid is replaced by valine in the β chain, the polypeptide folds into an slightly-different shape that creates a dysfunctional hemoglobin protein.
    • These dysfunctional hemoglobin proteins, under low-oxygen conditions, start associating with one another, forming long fibers made from millions of aggregated hemoglobins that distort the red blood cells into crescent or "sickle" shapes, which clog arteries .

  • Gas Exchange across the Alveoli

    • Oxygen (about 98 percent) binds reversibly to the respiratory pigment hemoglobin found in red blood cells.
    • These red blood cells carry oxygen to the tissues where oxygen dissociates from the hemoglobin, diffusing into the cells of the tissues.
    • Since this pressure gradient exists, oxygen can diffuse down its pressure gradient, moving out of the alveoli and entering the blood of the capillaries where O2 binds to hemoglobin.

  • The Role of Blood in the Body

    • Supplying oxygen to tissues (bound to hemoglobin, which is carried in red cells)

  • White Blood Cells

    • They have nuclei and do not contain hemoglobin.

  • Electron Transport Chain

    • The heme molecule is similar to the heme in hemoglobin, but it carries electrons, not oxygen.

  • Constructing an Animal Phylogenetic Tree

    • The hemoglobin B genes in humans and in mice are orthologous.