what are the differences between oxidation of heme in globin and cytochrome C?

Answer 1

The main difference is that oxidation of the heme group in haemoglobin is irreversible and destroys its function, while for cytochrome C it is reversible and essential for its role as an electron carrier in the electron transport chain.

The Fe+2 in the heme of haemoglobin binds O2 (complex formation; co-ordination bond), but because of a histidine of the globin, O2 cannot get close enough to oxidize Fe+2 to Fe+3.
Remove that residue (e.g. a pure heme) and you get oxidation and loss of the ability to co-ordinate and release oxygen.

Answer 2

Heme And Globin

Answer 3

hold on i'm smoking a blunt. now what was that question again?

Answer 4

Cytochrome c, or cyt c (horse heart: PDB 1HRC) is a small heme protein found loosely associated with the inner membrane of the mitochondrion. It is a soluble protein, unlike other cytochromes, and is an essential component of the electron transfer chain. It is capable of undergoing oxidation and reduction, but does not bind oxygen. It transfers electrons between Complexes III and IV.

Cytochrome c is a highly conserved protein across the spectrum of species, found in plants, animals, and many unicellular organisms. This, along with its small size (molecular weight about 12,000 daltons), makes it useful in studies of evolutionary divergence. It consists of a chain of about 100 amino acids. Cytochrome c can oxidize several reactions such as hydroxylation and aromatic oxidation and shows peroxidase activity by oxidation of various electron donors such as 2,2-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS), 2-keto-4-thiomethyl butyric acid and 4-aminoantipyrine. Cytochrome c is also suspected to be the functional complex in so called LLLT: Low Level Laser Therapy. In LLLT laser light on the wavelength of 670 nanometer penetrates wounded and scarred tissue in order to increase cellular regeneration. Light of this wavelength appears capable of increasing activity of cytochrome c, thus increasing metabolic activity and freeing up more energy for the cells to repair the tissue.

Cytochrome c is also an intermediate in apoptosis, a controlled form of cell death used to kill cells in the process of development or in response to infection or DNA damage. Cytochrome c was identified in 1996 by Xiaodong Wang and coworkers as a critical protein in the apoptotic pathway. Cytochrome c is released by the mitochondria in response to pro-apoptotic stimuli. The sustained elevation in calcium levels precedes cyt c release from the mitochondria. The release of small amounts of cyt c leads to an interaction with the IP3 receptor (IP3R) on the endoplasmic reticulum (ER), preventing calcium inhibition of ER calcium release. The overall increase in calcium triggers a massive release of cyt c, which then acts in the positive feedback loop to maintain ER calcium release through the IP3Rs. This explains how the ER calcium release can reach pathologic levels. This release in turn activates caspase 9, a cysteine protease. Caspase 9 can then go on to activate caspases 3 and 7, which are responsible for destroying the cell from within
Hemoglobin or haemoglobin (frequently abbreviated as Hb) is the iron-containing oxygen-transport metalloprotein in the red cells of the blood in mammals and other animals. Hemoglobin in vertebrates transports oxygen from the lungs to the rest of the body, such as to the muscles, where it releases the oxygen load. Hemoglobin also has a variety of other gas-transport and effect-modulation duties, which vary from species to species, and which in invertebrates may be quite diverse.

The name hemoglobin is the concatenation of heme and globin, reflecting the fact that each subunit of hemoglobin is a globular protein with an embedded heme (or haem) group; each heme group contains an iron atom, and this is responsible for the binding of oxygen. The most common types of hemoglobin contains four such subunits, each with one heme group.

Mutations in the genes for the hemoglobin protein in humans result in a group of hereditary diseases termed the hemoglobinopathies, the most common members of which are sickle-cell disease and thalassemia. Historically in human medicine, hemaglobinopathies were the first diseases to be understood in mechanism of dysfunction, down to the molecular level.


A heme group consists of an iron atom held in a heterocyclic ring, known as a porphyrin. This iron atom is the site of oxygen binding. The iron atom is bonded equally to all four nitrogens in the center of the ring, which lie in one plane. Two additional bonds perpendicular to the plane on each side can be formed with the iron to a fifth and sixth bonding position, one connected strongly to the protein, the other available for binding of an oxygen molecule. The iron atom may either be in the Fe2+ or Fe3+ state, but ferrihemoglobin (methemoglobin) (Fe3+) cannot bind oxygen.

The Fe2+ in hemoglobin may exist in either a high-spin (deoxygenated) or low-spin (oxygenated) state, according to population of the iron (II) d-orbital structure with its 6 available d electrons, as understood in crystal field theory. With the binding of an oxygen molecule as a sixth ligand to iron, the iron (II) atom finds itself in a octahedral field (defined by the six ligand points of the four porphyrin ring nitrogens, the histamine nitrogen, and the O2). In these circumstances, with strong-field ligands, the five d-orbitals (these are the “3d” orbitals of the iron) undergo a splitting in energy between two of the d-orbitals which point directly in the direction of the ligands (dz2 and dx2-y2 orbitals, hybridized in these circumstances into two eg orbitals), and three of the d-orbitals which are pointed in off-directions (the dxy ,dxz, and dyz, hybridized in these circumstances into three t2g orbitals).

When oxygen is bound to Fe2+ in heme, all 6 d-electrons of the iron atom are forced into the three lower-energy t2g orbitals, where they must all be paired (see crystal field theory for diagram). This produces the “low-spin” state of oxyhemoglobin. The sharp high-energy of transition between the t2g and empty eg states of d-orbital electrons in oxyhemoglobin is responsible for the bright red color of the substance. When oxygen leaves, the Fe2+ is allowed to move out of the porphyrin ring plane, away from its five ligands toward the empty space formerly occupied by the O2, and in these circumstances eg orbital energies drop and t2g electrons move into them. This causes the iron atom to expand and increase its net spin, as d-orbitals become populated with unpaired electrons. In these circumstances, the absorption spectrum becomes broader, with smaller transition levels, producing the dark color of deoxyhemoglobin.

In adult humans, the most common hemoglobin type is a tetramer (which contains 4 subunit proteins) called hemoglobin A, consisting of two α and two β subunits non-covalently bound, each made of 141 and 146 amino acid residues, respectively. This is denoted as α2β2. The subunits are structurally similar and about the same size. Each subunit has a molecular weight of about 16,000 daltons, for a total molecular weight of the tetramer of about 64,000 daltons. Haemoglobin A is the most intensively studied of the haemoglobin molecules.

The four polypeptide chains are bound to each other by salt bridges, hydrogen bonds and hydrophobic interaction. There are two kinds of contacts between the α and β chains: α1β1 and α1β2.