Breath. A cycle of Krebsa

you are: Breath

Enzymes, katalizirujushchie oxidation piruvata to СО2, are in internal kompartmente mitohondry (fig. 5.6). The enzymes oxidising (with simultaneous formation ATR and Н2O) the products of this process restored kofaktory, are localised on an inside mitohondrialnoj membranes. Piruvat at first it is split, losing СО2 (dekar-boksiliruetsja), and the formed acetate (a two-carbon fragment) joins the substance named kofermentom And (SoA). The product of this reaction of joining, Acetyl-soa, is involved directly in a cycle trikarbonovyh acids, or the cycle of Krebsa making the second of three stages of process of breath.

At first the two-carbon fragment is transferred from Acetyl-soa to the four-carbon organic acid playing a role ' of an acceptor ' of this two-carbon fragment. Six-carbon connection - lemon acid is as a result formed. This six-carbon connection, being exposed to a number of consecutive transformations, into which time it gives at first one atom of carbon, and then the second, it is split again before four-carbon connection. Thus, two atoms of carbon involved in a cycle in a kind atsetilnoj of group, are liberated in the form of СО2.

At some stages of these transformations energy is liberated. It or is used directly for synthesis ATR in the corresponding systems connected with a membrane, or spent for restoration of soluble carriers of a respiratory chain. Number of such carriers concern NAD +, restored in NADH, and flavinadenindinukleotid (FAD), restored in FADH2. At these reactions of restoration a proton and elektron arrive from the same atom of hydrogen in a substratum molecule. In other points of a chain of carrying over elektronov restoration is carried out by carrying over of one only elektronov. The proton (N +) if necessary or arrives from the water cellular environment, in which always! There is a surplus of protons, or, on the contrary, passes in it.

The Total result of a cycle of Krebsa is reduced, hence, to that everyone atsetilnaja the group (a two-carbon fragment), formed of piruvata (three-carbon connection), is split to СО2. During this process certain carriers elektronov (NAD + and FAD) are restored and quantity ATR is synthesised also.