Sperm mitochondria

Sutovsky, P., Moreno, R. D., Ramalho-Santos, J., Dominko, T., Simerly, C., and Schatten, G., Ubiquitinated sperm mitochondria, selective proteolysis, and the regulation of mitochondrial inheritance in mammalian embryos. Biol. Reprod. 63, 582—590 (2000). 

As far as the mitochondria go, the most significant difference between the male and female is that the male mitochondria have to produce a lot of ATP to propel the sperm as quickly as possible towards the egg, and the female mitochondria do not really have to do much at all. If free radicals generated by an active electron transport chain are responsible for damage to mitochondrial DNA, then it is reasonable to assume that sperm mitochondria are likely to be more damaged than those in the egg. To take this idea one step further, perhaps the mitochondria in the egg cells are prevented from carrying out oxidative phosphorylation at all, in order to preserve as accurate a copy as possible of the DNA to pass to the offspring. 

Mitochondria are present in all eukaryotic cells that use oxygen in respiration, but the number per cell and the form and size vary.1-4 Certain tiny trypanosomes have just one mitochondrion but some oocytes have as many as 3 x 105. Mammalian cells typically contain several hundred mitochondria and liver cells5 more than 1000. Mammalian sperm cells may contain 50-75 mitochondria,6 but in some organisms only one very large helical mitochondrion, formed by the fusion of many individual mitochondria, wraps around the base of the tail. Typical mitochondria appear to be about the size of cells of E. coli. However, study of ultrathin serial sections of a single yeast cell by electron microscopy has shown that, under some growth conditions, all of the mitochondria are interconnected.7... 

Figure 3. (Upper Panel). Scanning electron micrograph of an H. rufescens spermatozoon. The sperm head, from mitochondrion (M) to tip of the acrosome vesicle (granule AV) is 7 pm. The width of the nucleus (N) is 1 pm. (Lower Panel). Transmission electron micrograph of the acrosomal vesicle showing it attached to the nucleus (NF) by the rod of actin filaments (AF). The darker material labelled 1 shows the location of the 18K protein and 2 shows the location of lysin (from Lewis et al., 1980).

Figure 4. Scheme showing sperm-egg interaction in the abalone. 1. The sperm binds to the egg VE by the plasma membrane at the tip of the AV (AG), (F, flagellum M, mitochondrion N, nucleus). 2. The sperm acrosome reacts releasing lysin and the 18K protein from its anterior tip. 3. Lysin disrupts the fibers of the VE and the 18K coats the extending acrosome process as it extends. 4. The sperm passes through the hole in the VE and the membrane covering the tip of the acrosomal process fuses with the egg (from Vacquier and Lee, 1993). 

Mitochondria are present in all eukaryotic cells that use oxygen in respiration, but the number per cell and the form and size vary. Certain tiny trypanosomes have just one mitochondrion but some oocytes have as many as 3 x 10 . Mammalian cells typically contain several himdred mitochondria and liver cells more than 1000. Mammalian sperm cells may contain... 

Less than 0.1% of the total DNA in a cell is present in mitochondria. The genetic information in a mitochondrion is encoded in less than 20,000 base pairs of DNA the information in a human haploid nucleus (i.e., an egg or a sperm cell) is encoded in approximately 3 X 10 (3 billion) base pairs. The DNA and protein synthesizing systems in mitochondria more closely resemble the systems in bacteria, which do... 

Mitochondria are intracellular organelles with a double-membrane structure. Both the number and size of mitochondria vary in different cells - for example, a liver cell contains some 800 mitochondria, a renal tubule cell some 300 and a sperm about 20. The outer mitochondrial membrane is permeable to a great many substrates, while the inner membrane provides a barrier to regulate the uptake of substrates and output of products (see, for example, the regulation of palmitoyl CoA uptake into the mitochondrion for oxidation in section 5.5.1). 

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