Biochemistry - The Chemical Reactions of Living Cells, Volume 1 - D. Metzler 1980

Location
Eukaryotic cells
Mitochondria and plastids

A characteristic feature of Eukaryotic Cells is the presence of Cell/35.html">Mitochondria—complex double-membrane structures comparable in size to Bacteria (Figs. 1-3 and 1-4). The inner mitochondrial membrane forms numerous deep folds known as cristae (ridge-like projections). While the outer membrane is permeable to low-molecular-weight compounds, The entry of substances into the mitochondrial interior (the matrix) and their exit are strictly regulated by the inner membrane. Although certain oxidation reactions take place in the ER, the primary processes responsible for ENERGY GENERATION AND storage in aerobic organisms are localized within the mitochondria; it is in these Organelles that the bulk of oxygen consumption occurs. At the time, many biochemists were greatly surprised to discover low-molecular-weight circular DNA within mitochondria. It was subsequently found that mitochondria contain Ribosomes similar in size to bacterial ribosomes, though smaller than those attached to the rough ER.

Mitochondria are present in all eukaryotic cells that rely on oxygen for Respiration. The number of mitochondria per cell ranges from 1 (in the smallest trypanosomes) to 3∙105 (in certain oocytes). A typical Liver cell contains over 1,000 mitochondria [21]. New and intriguing insights have emerged from the STUDY OF Yeast mitochondria [22]. Examination of serial sections through a single cell (Box 1-B) revealed that all the mitochondria are interconnected. Thus, the mitochondria in yeast cells are not isolated organelles, but rather a single continuous intracellular network. Whether this holds true for other organisms remains unclear.

Plastids are plant cell organelles that perform a variety of Functions. The most crucial role is played by METABOLISM/14.html">Chloroplasts, chlorophyll-containing structures where Photosynthesis takes place. Much like mitochondria, chloroplasts feature a folded inner membrane and a small amount of low-molecular-weight DNA.



Last update: 06/08/2026

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