|MadSci Network: General Biology|
Dear Mr. Stein, Your question is an interesting one. However, let's clear up a few details. Red Blood Cells(RBCs) have nothing to do with why meat is dark or white. RBCs are part of a wonderful mixture of other proteins, nutrients, and waste particles that flow through your vasculature, otherwise know as "Blood". They deliver oxygen to tissues and take away carbon dioxide, in short. They do not cause the meat in the animal to be a particular color. Now to answer your question, let's consider the color of the meat. This is where it's interesting. There are different "TYPES" of meat, or "Fiber Types." Fibers are the elemental structures that make up which kind of meat your con- sidering. For example, white meat is mostly composed of Fast Twitch Fiber (FTF). Not to get bogged down in cellular details, but this kind is mainly used for heavy lifting, or to develop a bulky appearance. It's primary source of energy is glycogen (glucose). On the other hand, there's a different type of fiber (muscle) that's usually associated with dark meat, called "Slow Twitch Fiber" (STF). It's a group of postural muscles that can be found near areas where an animal bears a lot of body weight, ie., lower back, inner thighs, some parts of the lower leg, etc. Their main source of energy is from oxygen. This meat can be very tough and greasy due to it's metabolism. The dissimiliar structure and vascular supply in FTFs and STFs makes them different in appearance and texture. Hopefully this will give you some new information as you devour your dinner. Just remember, all animals have white meat and dark meat. The difference is in the composition and proportions found in a particular animal's muscle group. Fred Moore Louisville, Ky.
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