細(xì)胞生物學(xué)雙語(yǔ)教案3(線粒體結(jié)構(gòu)與功能)-資料下載頁(yè)
2025-04-17 08:45本頁(yè)面
【正文】 adient needed to drive the pump. When the discussion focuses on how mitochondria move proteins into the matrix, you will see another reason why this hydrogen ion (proton) gradient is so important! As shown in the above cartoons, the molecules in the electron transport chain are found as a cluster organized in the cristae. These membrane shelves may be more numerous in mitochondria that are more active in the production of ATP. Thus, they may increase the density of these membranes as the need arises. The flight muscle of a hummingbird has many cristae in each mitochondrion, because the need is so great. Structure and function of the inner membrane and elementary particles .Mitochondria can be separated and the inner and outer membrane can be dissociated. This will result in a fraction containing only the inner membrane and the matrix. These have been called mitoplasts. They are functional and have helped us learn more about the partmentation of mitochondria. One can open mitoplasts and view the inside membrane surface after negatively staining the membranes. This deposits stain around any surface projections. With this method, one can see the elementary particles projecting from the inner surface of the cristae. These are the ATP synthase molecules (or elementary particles) discussed in the previous section. The cartoons in the previous section showed cytochrome C lying just outside the inner membrane. It is a loosely attached peripheral protein lying in the space contained by the cristae. In fact, if the outer membrane is removed, often the cytochrome C is lost and must be replaced to promote function of the mitoplast. How do cytochemists know that cytochrome C is on the inner membrane? We can do cytochemical tests for this cytochrome and the results are shown in this figure. Note that the enzyme reaction product is confined to the cristae and in fact delineates the cristae. Unfortunately, as is the case with most enzyme cytochemistry, the reaction product spreads and it looks like it fills the intermembrane space. This reflects the orientation of cytochrome C. It is found in space inbetween cristae membranes which suggests it is next to the outer leaflet of the cristae membrane, rather than the inner leaflet (opposite to that of the elementary particles, or ATP synthetase).8 /
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