Mitochondrion

 

A round to oval-shaped organelle found in the cells of almost all eukaryotic organisms, range in size from 0.5 to 10 μm. It produces energy, store calcium for cell signaling activities, generate heat, and mediate cell growth and death. Known as the “powerhouses of the cell,” mitochondria produce the energy necessary for the cell’s survival and functioning. Through a series of chemical reactions, mitochondria break down glucose into an energy molecule known as adenosine triphosphate (ATP), which is used to fuel various other cellular processes.

The outer mitochondrial membrane is freely permeable to small molecules and contains special channels capable of transporting large molecules. In contrast, the inner membrane is far less permeable, allowing only very small molecules to cross into the gel-like matrix that makes up the organelle’s central mass. The matrix contains the deoxyribonucleic acid (DNA) of the mitochondrial genome and the enzymes of the tricarboxylic acid (TCA) cycle (also known as the citric acid cycle, or Krebs cycle), which metabolizes nutrients into by-products the mitochondrion can use for energy production.

The processes that convert these by-products into energy occur primarily on the inner membrane, which is bent into folds known as cristae that house the protein components of the main energy-generating system of cells, the ETC. The ETC uses a series of oxidation-reduction reactions to move electrons from one protein component to the next, ultimately producing free energy that is harnessed to drive the phosphorylation of ADP (adenosine diphosphate) to ATP. This process, known as chemiosmotic coupling of oxidative phosphorylation, powers nearly all cellular activities, including those that generate muscle movement and fuel brain functions.

coupling = connection

permeable = allowing liquids or gases to pass through

harnessed to drive = ready to move

❗️Pay Attention To Pronunciation

mitochondrion (pl mitochondria) [maɪtəʊˈkɒndrɪən]

eukaryotic [juːkərɪˈɒtɪk]

permeable [ˈpɚmijəbəl]

deoxyribonucleic [diˌɒksiːˌraɪbəʊnjuːˈkleɪɪk]

chemiosmotic [ˌkɛmiɑzˈmɑdɪk]