When you tuck into your Thanksgiving turkey dinner, you likely have a preference for white meat or dark meat. It's not your imagination that the two varieties of meat have a different texture and flavor from each oher. White meat and dark meat have different chemical compositions and different purposes for the turkey. Turkey meat consists of muscle, which in turn is made from protein fibers. White meat and dark meat contain a mix of protein fibers, but white fibers predominate in white meat while dark meat contains more red fibers.
White Turkey Meat
- White meat is found in the breast and wing muscles of a turkey.
- Turkey can fly, but it is not their main mode of locomotion. Turkeys use their wing muscles when they need a burst of speed to escape predators. These muscles produce a lot of power, but they fatigue quickly.
- Turkey breast and wing muscles consist mainly of white muscle fibers. These fibers contract quickly and split ATP at a fast pace, though they become exhausted quickly, too.
- White fibers are powered by anaerobic respiration so a turkey can move quickly even though its muscles may have exhausted the available oxygen. The tissue contains a large amount of glycogen, which can be used as fast energy source.
Dark Turkey Meat
- Turkey legs and thighs are dark meat.
- Turkey spend a lot of time walking on the ground. Their leg muscles are adapted for regular, continuous use.
- Leg and thigh muscles consist primarily of red muscle fibers. These fibers contract slowly and split ATP for energy at a relatively low rate.
- Red muscle fibers rely on aerobic respiration. The protein uses oxygen to relax/contract so this tissue is rich in capillaries, which give it a deep color and rich flavor. Dark meat contains a lot of myoglobin and is rich in mitochondria, which produce energy for the muscle tissue.
Based on your understanding of white and red muscle fibers, which do you expect to find in the wings and breast of a migratory bird, such as a goose? Since they use their wings for long flights, ducks and geese contain red fibers in their flight muscles. These birds don't have white meat compared with a turkey. You'll also find a difference in the muscle composition of people. For example, a marathon runner would be expected to have a higher percentage of red fibers in his leg muscles compared with the muscles of a sprinter.
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