False-colour transmission electron micrograph (TEM) of the cytoplasm of a rat spermatocyte, featuring a mitochondrion (right, a yellow, cigar- shaped organelle). Spermatocytes are cells produced as an intermediate stage in spermatogenesis (formation of sperm) which occurs in the seminiferous tubules of the testis. Mitochondria are sites of a cell's energy production, containing ATP & a variety of enzymes. Each is bounded by a double membrane, the inner one being folded inwards to form projections (cristae - orange lines), which partially compartmentalise the mitochondrion. Magnification: x14,700 at 35mm size.
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