Heme Sentence Examples
Using isotopic tracers, it was initially found that N & C atoms of heme are derived from glycine and acetate.
Proteins; Ligands; Heme; ChloroP prediction server ChloroP is a neural network-based method for predicting chloroplast transit peptides and their cleavage sites.
You should then be able to work out whether it is financially beneficial for you to change sc heme.
Heme (component of hemoglobin in red blood cells that carries oxygen throughout the body) is broken down into bilirubin, which moves to the liver where it is processed and added to bile, a digestive fluid.
The porphyrias are disorders in which the body produces too much porphyrin and insufficient heme (an iron-containing nonprotein portion of the hemoglobin molecule).
Porphyrin is a foundation structure for heme and certain enzymes.
Overproduction and overexcretion of porphyrins causes low, unhealthy levels of heme and certain important enzymes, creating various physical symptoms.
Biosynthesis of heme is a multistep process that begins with simple molecules and ends with a large, complex heme molecule.
As a heme precursor molecule moves through each step, an enzyme modifies the precursor in some way.
Owing to a defect in one of the enzymes of the heme biosynthesis pathway, protoporphyrins or porphyrins (heme precursors) are prevented from proceeding further along the pathway.Advertisement
Specific symptoms depend on the point at which heme biosynthesis is blocked and which precursors accumulate.
Heme is produced in several tissues in the body, but its primary biosynthesis sites are the liver and the bone marrow.
Heme synthesis for immature red blood cells, namely the erythroblasts and the reticulocytes, occurs in the bone marrow.
Although production is concentrated in the liver and bone marrow, heme is utilized in various capacities in virtually every tissue in the body.
In most cells, heme is a key building block in the construction of factors that oversee metabolism and transport of oxygen and energy.Advertisement
In the liver, heme is a component of several vital enzymes, particularly cytochrome P450.
In immature red blood cells, heme is the featured component of hemoglobin.
The heme molecule is composed of porphyrin and an iron atom.
Much of the heme biosynthesis pathway is dedicated to constructing the porphyrin molecule.
An iron atom is placed at its center point in the last step of heme biosynthesis.Advertisement
The production of heme may be compared to a factory assembly line.
The control of heme biosynthesis is complex.
For example, one point at which heme biosynthesis may be controlled is at the first step.
When heme levels are low, greater quantities of delta-aminolevulinic acid (ALA) synthase are produced.
As a result, larger quantities of heme precursors are fed into the biosynthesis pathway to step up heme production.Advertisement
Under normal circumstances, when heme concentrations are at an appropriate level, precursor production decreases.
However, a glitch in the biosynthesis pathway-represented by a defective enzyme-means that heme biosynthesis does not reach completion.
Because heme levels remain low, the synthesis pathway continues to churn out precursor molecules in an attempt to correct the heme deficit.
Although there are eight steps in heme biosynthesis, there are only seven types of porphyrias; a defect in ALA synthase activity does not have a corresponding porphyria.
Enzymes involved in heme biosynthesis display subtle, tissue-specific variations; therefore, heme biosynthesis may be impeded in the liver, but normal in the immature red blood cells, or vice versa.
Porphyrias affecting heme biosynthesis in the liver were referred to as hepatic porphyrias.
Porphyrias that affect heme biosynthesis in immature red blood cells were referred to as erythropoietic porphyries.
Hepatoerythopoietic porphyria (HEP) affects heme biosynthesis in both the liver and the bone marrow.
The underlying cause of all porphyrias is a defective enzyme important to the heme biosynthesis pathway.
Owing to deficient ferrochelatase, the last step in the heme biosynthesis pathway-the insertion of an iron atom into a porphyrin molecule-cannot be completed.
If these tests reveal abnormal levels of protoporphyrins, further tests are done to measure heme precursor levels in red blood cells and the stool.
Whether heme precursors occur in the blood, urine, or stool gives some indication of the type of porphyria, but more detailed biochemical testing is required to determine their exact identity.
Making this determination yields a strong indicator of which enzyme in the heme biosynthesis pathway is defective; which, in turn, allows a diagnosis of the particular type of porphyria.
If one of two heme precursors-porphobilinogen or urobilinogen-is present, the sample turns pink or red.
Other biochemical tests rely on the fact that heme precursors become less soluble in water (able to be dissolved in water) as they progress further through the heme biosynthesis pathway.
Hematin seems to work by signaling the pathway of heme biosynthesis to slow production of precursors.
The drug cholestyramine may reduce the skin's sensitivity to sunlight as well as the accumulated heme precursors in the liver.
It causes heme biosynthesis to decrease, preventing the further accumulation of heme precursors.
Protoporphyrin-A kind of porphyrin that links with iron to form the heme of hemoglobin.
Hemoglobin A-Normal adult hemoglobin that contains a heme molecule, two alpha-globin molecules, and two beta-globin molecules.
Hemoglobin consists primarily of iron-bearing proteins called heme groups and moiety globin protein, which together give hemoglobin its ability to carry oxygen.
The heme groups are molecular chains of different types and actually create six different hemoglobins that vary in their amino acid composition and also in the genes that control them.
The genetic defects are subdivided into errors of heme production (porphyria) and those of globin production, known collectively as the hemoglobinopathies.
When examined under a microscope, the RBCs also appear pale or light colored from the absence of heme, the major component of hemoglobin, which is the iron-bearing protein and coloring pigment in RBCs.
Red meat sources reliably replace the heme component of red blood cells, raising hemoglobin levels and helping to correct iron deficiency.
Absorption is best when the food contains heme, just as in human red cells.
Hemoglobin consists of a complex of a protein plus heme.
Heme consists of iron plus protoporphyrin IX.
Normally, during the course of red blood cell formation, protoporphyrin IX acquires iron, to generate heme, and the heme becomes incorporated into hemoglobin.