Difference between revisions of "Blood clotting cascade"
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| − | A number of | + | A number of [[protein]]s are involved in the series of events that lead to [[vertebrate]] [[blood clotting]]. |
| − | Michael Behe describes it thus: | + | [[Michael Behe]] describes it thus: |
<blockquote> | <blockquote> | ||
| − | When an animal is cut, a protein called Hagemann factor (XII) sticks to the surface of | + | When an animal is cut, a protein called Hagemann factor (XII) sticks to the surface of [[cell]]s near the wound. Bound Hagemann factor is then cleaved by a protein called HMK to yield activated Hagemann factor. Immediately the activated Hagemann factor converts another protein, called prekallikrein, to its active form, kallikrein.<ref>Behe, M. 1996. Darwin's Black Box. New York: The Free Press</ref> |
</blockquote> | </blockquote> | ||
Behe, who is a supporter of [[intelligent design]], argues that all of these components must be in place before the system will work: | Behe, who is a supporter of [[intelligent design]], argues that all of these components must be in place before the system will work: | ||
<blockquote> | <blockquote> | ||
| − | ...none of the cascade proteins are used for anything except controlling the formation of a clot. Yet in the absence of any of the components, blood does not clot, and the system fails. <ref>Behe, M. 1996. Darwin's Black Box, p.86. New York: The Free Press</ref> | + | ...none of the cascade proteins are used for anything except controlling the formation of a clot. Yet in the absence of any of the components, blood does not clot, and the system fails.<ref>Behe, M. 1996. Darwin's Black Box, p.86. New York: The Free Press</ref> |
</blockquote> | </blockquote> | ||
| − | Although, as Behe points out, Factor XII initiates the "cascade of proteins" in vertebrates, | + | Although, as Behe points out, Factor XII initiates the "cascade of proteins" in vertebrates, [[dolphin]]s lack Factor XII <ref>Robinson, A. J., M. Kropatkin, and P. M. Aggeler, 1969. Hagemann Factor (Factor XII) Deficiency in Marine Mammals. Science 166: 1420-1422</ref> and yet their blood is known to clot. Similarly, [[mollusc]]s such as [[snail]]s have only four components in their blood clotting cascade, with a single protease step. This appears to contradict the notion of [[irreducible complexity]] in regard to this process. |
==References== | ==References== | ||
<references/> | <references/> | ||
| − | [[ | + | [[Category:Biology]] |
Latest revision as of 04:14, June 23, 2016
A number of proteins are involved in the series of events that lead to vertebrate blood clotting.
Michael Behe describes it thus:
When an animal is cut, a protein called Hagemann factor (XII) sticks to the surface of cells near the wound. Bound Hagemann factor is then cleaved by a protein called HMK to yield activated Hagemann factor. Immediately the activated Hagemann factor converts another protein, called prekallikrein, to its active form, kallikrein.[1]
Behe, who is a supporter of intelligent design, argues that all of these components must be in place before the system will work:
...none of the cascade proteins are used for anything except controlling the formation of a clot. Yet in the absence of any of the components, blood does not clot, and the system fails.[2]
Although, as Behe points out, Factor XII initiates the "cascade of proteins" in vertebrates, dolphins lack Factor XII [3] and yet their blood is known to clot. Similarly, molluscs such as snails have only four components in their blood clotting cascade, with a single protease step. This appears to contradict the notion of irreducible complexity in regard to this process.