hemoglobin

noun

he·​mo·​glo·​bin ˈhē-mə-ˌglō-bən 

1

: an iron-containing respiratory pigment of vertebrate red blood cells that consists of a globin composed of four subunits each of which is linked to a heme molecule, that functions in oxygen transport to the tissues after conversion to oxygenated form in the gills or lungs, and that assists in carbon dioxide transport back to the gills or lungs after surrender of its oxygen

2

: any of numerous iron-containing respiratory pigments of various organisms (such as invertebrates and yeasts)

Did you know?

When filled with oxygen, the hemoglobin in your blood is bright red; returning to the lungs without its oxygen, it loses its brightness and becomes somewhat bluish. Hemoglobin levels can change from day to day, and may be affected by such factors as a lack of iron in the diet, a recent loss of blood, and being pregnant. When you give blood, a nurse first pricks your finger to test your hemoglobin level; a low hemoglobin count indicates anemia and may mean that you shouldn't give blood that day. Mild anemia is generally of little importance, but some types can be very serious.

Examples of hemoglobin in a Sentence

Recent Examples on the Web

Iron is a mineral essential for maintaining many of the body’s functions and development, and the body uses iron to make a protein in red blood cells called hemoglobin. —Jacqueline Howard, CNN, 27 Sep. 2024

Most of them showed an increasing trend in blood levels of hemoglobin—an oxygen-carrying protein in red blood cells that can only be formed with iron—and four of the studies reported a significant change. —Audrey Bruno, SELF, 12 Sep. 2024

Unlike sickle cell disease, a severe illness patient has two genes that cause the production of abnormal hemoglobin (the substance in red blood cells that helps carry oxygen). —Dominique Fluker, Essence, 19 Sep. 2024

Hundreds of millions of hemoglobin molecules are packed into each red blood cell. —Maryn McKenna, Scientific American, 17 Sep. 2024

Word History

Etymology

International Scientific Vocabulary, short for earlier hematoglobulin

First Known Use

1869, in the meaning defined at sense 1

Phrases Containing hemoglobin

• fetal hemoglobin
• glycated hemoglobin
• glycosylated hemoglobin
• hemoglobin A
• hemoglobin A1c
• hemoglobin S

Kids Definition

hemoglobin

noun

he·​mo·​glo·​bin ˈhē-mə-ˌglō-bən 

: a protein that contains iron, is the chief means of transporting oxygen in the body of vertebrate animals, occurs in the red blood cells, and is able to combine loosely with oxygen in regions (as the lungs) where it is in high concentration and release it in regions (as the tissues of the internal organs) where it is in low concentration

Medical Definition

hemoglobin

noun

he·​mo·​glo·​bin

variants or chiefly British haemoglobin

ˈhē-mə-ˌglō-bən 

1

: an iron-containing respiratory pigment of vertebrate red blood cells that functions primarily in the transport of oxygen from the lungs to the tissues of the body, that consists of four polypeptide chains of which two are of the type designated alpha and two are of one of the types designated beta, gamma, or delta and each of which is linked to a heme molecule, that combines loosely and reversibly with oxygen in the lungs or gills to form oxyhemoglobin and with carbon dioxide in the tissues to form carbaminohemoglobin, that in humans is present normally in blood to the extent of 14 to 16 grams in 100 milliliters expressed sometimes on a scale of 0 to 100 with an average normal value (as 15 grams) taken as 100, and that is determined in blood either colorimetrically or by quantitative estimation of the iron present see fetal hemoglobin, hemoglobin a compare carboxyhemoglobin, methemoglobin

2

: any of numerous iron-containing respiratory pigments of various organisms (as invertebrates and yeasts)

hemoglobinic adjective

or chiefly British haemoglobinic

ˌhē-mə-glō-ˈbin-ik 

hemoglobinous adjective

or chiefly British haemoglobinous

-ˈglō-bə-nəs