MITOCHONDIA

Under light microscope, mitochondria are linear, granular or short rod shape. Under certain conditions, the morphology of mitochondria in the same cell changes dynamically and reversely. The changes of osmotic pressure, pH and temperature can cause the changes of mitochondrial size.

Under the electron microscope, mitochondria are capsular structures formed by two layers of inner and outer unit membranes, it is mainly composed of outer membrane, inner membrane,  an intermembrane space and a matrix. The intermembrane space is also called the outer chamber, and the matrix is also called the inner chamber

<ul><li><span style="font-size: inherit;">The&nbsp;outer&nbsp;membrane&nbsp;is&nbsp;a&nbsp;unit&nbsp;membrane&nbsp;surrounding&nbsp;the&nbsp;outer&nbsp;surface&nbsp;of&nbsp;mitochondria,&nbsp;with&nbsp;a&nbsp;thickness&nbsp;of&nbsp;6-7&nbsp;nm.&nbsp;Flat&nbsp;and&nbsp;smooth,&nbsp;not&nbsp;connected&nbsp;to&nbsp;the&nbsp;intima.&nbsp;The&nbsp;outer&nbsp;membrane&nbsp;</span><font color="#5c4038" style="font-size: inherit;">contains&nbsp;</font><font color="#a23c73" style="font-size: inherit;">a&nbsp;variety&nbsp;of&nbsp;transport&nbsp;proteins&nbsp;called&nbsp;porins</font><span style="font-size: inherit;">,&nbsp;they&nbsp;constitute&nbsp;water-containing&nbsp;channels&nbsp;through&nbsp;which&nbsp;water-soluble&nbsp;substances&nbsp;can&nbsp;pass&nbsp;in&nbsp;the&nbsp;lipid&nbsp;bilayer.&nbsp; Compared&nbsp;with&nbsp;the&nbsp;inner&nbsp;membrane,&nbsp;the&nbsp;outer&nbsp;membrane&nbsp;is&nbsp;</span><font color="#a23c73" style="font-size: inherit;">rich&nbsp;in&nbsp;cholesterol</font><span style="font-size: inherit;">&nbsp;and&nbsp;phospholipids,&nbsp;and&nbsp;contains&nbsp;</span><font color="#a23c73" style="font-size: inherit;">less&nbsp;protein</font><span style="font-size: inherit;">&nbsp;than&nbsp;the&nbsp;inner&nbsp;membrane.&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; The&nbsp;marker&nbsp;enzyme : monoamine&nbsp;oxidase&nbsp;(monoamine)&nbsp;oxidase).</span></li></ul>

<ul><li>The&nbsp;inner&nbsp;membrane,&nbsp;located&nbsp;on&nbsp;the&nbsp;medial&nbsp;side&nbsp;of&nbsp;the&nbsp;outer&nbsp;membrane,&nbsp;is&nbsp;also&nbsp;composed&nbsp;of&nbsp;a&nbsp;unit&nbsp;membrane,&nbsp;but&nbsp;is&nbsp;slightly&nbsp;thicker&nbsp;than&nbsp;the&nbsp;outer,&nbsp;which&nbsp;is&nbsp;6-8&nbsp;nm&nbsp;thick.&nbsp;The&nbsp;inner&nbsp;membrane&nbsp;is&nbsp;<font color="#a23c73">rich&nbsp;in&nbsp;protein</font>,&nbsp;with&nbsp;a&nbsp;ratio&nbsp;of&nbsp;protein&nbsp;to&nbsp;lipid&nbsp;greater&nbsp;than&nbsp;3:&nbsp;1.&nbsp;also<font color="#a23c73">&nbsp;rich&nbsp;in&nbsp;cardiolipin</font>&nbsp;(up&nbsp;to&nbsp;20%)&nbsp;and&nbsp;<font color="#a23c73">lacking&nbsp;in&nbsp;cholesterol</font>,&nbsp;similar&nbsp;to&nbsp;bacteria.The&nbsp;substance&nbsp;exchange&nbsp;between&nbsp;the&nbsp;martix&nbsp;and&nbsp;the&nbsp;outside&nbsp;world&nbsp;needs&nbsp;to&nbsp;be&nbsp;involved&nbsp;through&nbsp;the&nbsp;translocation&nbsp;enzyme&nbsp;of&nbsp;the&nbsp;endometrium.&nbsp;</li><li>The&nbsp;marker&nbsp;enzyme&nbsp;:&nbsp;cytochrome&nbsp;c&nbsp;oxidase&nbsp;.</li><li>The&nbsp;inner&nbsp;membrane&nbsp;folds&nbsp;into&nbsp;the&nbsp;inner&nbsp;chamber&nbsp;of&nbsp;the&nbsp;mitochondria&nbsp;to&nbsp;form&nbsp;a&nbsp;number&nbsp;of&nbsp;folds&nbsp;or&nbsp;tubular&nbsp;structures&nbsp;called&nbsp;cristae.&nbsp;The&nbsp;formation&nbsp;of&nbsp;the&nbsp;cristae&nbsp;increases&nbsp;the&nbsp;surface&nbsp;area&nbsp;of&nbsp;the&nbsp;inner&nbsp;membrane.</li></ul>

<ul><li>On&nbsp;the&nbsp;inner&nbsp;surface&nbsp;of&nbsp;the&nbsp;inner&nbsp;membrane&nbsp;and&nbsp;the&nbsp;cristae&nbsp;membrane,&nbsp;there&nbsp;are&nbsp;many&nbsp;small&nbsp;spherical&nbsp;particles&nbsp;with&nbsp;stalks&nbsp;towards&nbsp;the&nbsp;inner&nbsp;chamber,&nbsp;called&nbsp;clementaryparticles&nbsp;or&nbsp;F&nbsp;particles&nbsp;(F&nbsp;factor),&nbsp;it&nbsp;is&nbsp;composed&nbsp;of&nbsp;ATP&nbsp;synthase&nbsp;(ATP&nbsp;synthase).&nbsp;ATP&nbsp;synthase&nbsp;is&nbsp;a&nbsp;multicomponent&nbsp;complex&nbsp;with&nbsp;ATP&nbsp;synthase&nbsp;activity&nbsp;in&nbsp;the&nbsp;membrane-bound&nbsp;state&nbsp;and&nbsp;ATP&nbsp;hydrolase&nbsp;activity&nbsp;in&nbsp;the&nbsp;free&nbsp;state.&nbsp;The&nbsp;granulocytes&nbsp;are&nbsp;perpendicular&nbsp;to&nbsp;the&nbsp;inner&nbsp;membrane&nbsp;surface&nbsp;and&nbsp;arranged&nbsp;regularly,&nbsp;and&nbsp;the&nbsp;granulocytes&nbsp;are&nbsp;10&nbsp;nm&nbsp;apart.</li></ul>

<ul><li>Intermembrane&nbsp;space:Between&nbsp;the&nbsp;mitochondria&nbsp;and&nbsp;the&nbsp;adventitia&nbsp;is&nbsp;a&nbsp;closed&nbsp;gap&nbsp;with&nbsp;a&nbsp;width&nbsp;of&nbsp;6&nbsp;to&nbsp;8&nbsp;nm,&nbsp;which&nbsp;is&nbsp;called&nbsp;the&nbsp;membrane space or&nbsp;outer&nbsp;chamber&nbsp;(Chamber),&nbsp;which&nbsp;is&nbsp;filled&nbsp;with&nbsp;amorphous&nbsp;substances&nbsp;and&nbsp;contains&nbsp;various&nbsp;soluble&nbsp;enzymes,&nbsp;substrates&nbsp;and&nbsp;cofactors.&nbsp;The&nbsp;part&nbsp;of&nbsp;the&nbsp;membrane&nbsp;gap&nbsp;that&nbsp;extends&nbsp;to&nbsp;the&nbsp;inside&nbsp;of&nbsp;the&nbsp;kurtosis&nbsp;is&nbsp;called&nbsp;the&nbsp;inside&nbsp;of&nbsp;the&nbsp;kurtosis&nbsp;space).</li></ul>

<ul><li>Inner&nbsp;chamber&nbsp;and&nbsp;martix:The&nbsp;space&nbsp;formed&nbsp;inside&nbsp;the&nbsp;intima&nbsp;is&nbsp;called&nbsp;the&nbsp;inner&nbsp;chamber&nbsp;or&nbsp;intercristal&nbsp;space),&nbsp;which&nbsp;is&nbsp;filled&nbsp;with&nbsp;a&nbsp;relatively&nbsp;dense&nbsp;substance&nbsp;called&nbsp;the&nbsp;mitochondrial&nbsp;matrix.&nbsp;The&nbsp;matrix&nbsp;contains&nbsp;lipids,&nbsp;proteins,&nbsp;enzymes&nbsp;related&nbsp;to&nbsp;triacid&nbsp;cycle,&nbsp;oxidation&nbsp;of&nbsp;pyruvate&nbsp;and&nbsp;fatty&nbsp;acids,&nbsp;amino&nbsp;acid&nbsp;metabolism&nbsp;and&nbsp;mitochondrial&nbsp;protein&nbsp;synthesis,&nbsp;and&nbsp;nucleic&nbsp;acid&nbsp;synthetases.&nbsp;It&nbsp;also&nbsp;contains&nbsp;mitochondrial&nbsp;DNA&nbsp;(mtDNA),&nbsp;mitochondrial&nbsp;mRNA,&nbsp;tRNA&nbsp;and&nbsp;mitochondrial&nbsp;ribosomes.&nbsp;In&nbsp;addition,&nbsp;the&nbsp;matrix&nbsp;contains&nbsp;some&nbsp;relatively&nbsp;large&nbsp;dense&nbsp;particles&nbsp;with&nbsp;diameters&nbsp;of&nbsp;30&nbsp;to&nbsp;50&nbsp;nm,&nbsp;referred&nbsp;to&nbsp;as&nbsp;matrix&nbsp;granule,&nbsp;contains&nbsp;calcium,&nbsp;magnesium,etc.</li></ul>

Mitochondrial&nbsp;proteins&nbsp;are&nbsp;classified&nbsp;into&nbsp;soluble&nbsp;and&nbsp;insoluble&nbsp;proteins.&nbsp;The&nbsp;soluble&nbsp;proteins&nbsp;are&nbsp;mainly&nbsp;the&nbsp;enzymes&nbsp;in&nbsp;the&nbsp;matrix&nbsp;and&nbsp;the&nbsp;peripheral&nbsp;proteins&nbsp;of&nbsp;the&nbsp;membrane,&nbsp;while&nbsp;the&nbsp;insoluble&nbsp;proteins&nbsp;are&nbsp;the&nbsp;mosaic&nbsp;proteins,&nbsp;structural&nbsp;proteins&nbsp;and&nbsp;enzyme&nbsp;proteins&nbsp;of&nbsp;the&nbsp;membrane.

The&nbsp;lipid&nbsp;components&nbsp;in&nbsp;mitochondria&nbsp;vary&nbsp;with&nbsp;different&nbsp;cell&nbsp;types,&nbsp;but&nbsp;most&nbsp;of&nbsp;them&nbsp;are&nbsp;phospholipids,&nbsp;accounting&nbsp;for&nbsp;more&nbsp;than&nbsp;3/4&nbsp;of&nbsp;the&nbsp;total&nbsp;lipid.&nbsp;Among&nbsp;them,&nbsp;phosphatidylcholine&nbsp;(lecithin)&nbsp;and&nbsp;phosphatidylethanolamine&nbsp;(cephalin)&nbsp;accounted&nbsp;for&nbsp;the&nbsp;majority,&nbsp;in&nbsp;addition&nbsp;to&nbsp;a&nbsp;certain&nbsp;amount&nbsp;of&nbsp;cardiolipin&nbsp;and&nbsp;less&nbsp;cholesterol&nbsp;content.

Physical&nbsp;medium&nbsp;

take part in emzymatic reaction

Glycolysis

Acetyl-CoA production

Krebs cycle

Electron&nbsp;transfer&nbsp;coupled&nbsp;oxidative&nbsp;phosphorylation