CLARA FRANZINI ARMSTRONG / SCIENCE PHOTO LIBRARY CLARA FRANZINI ARMSTRONG / SCIENCE PHOTO LIBRARY
Muscle cell. Freeze-etched Transmission Electron Micrograph (TEM) of myofibrils (yellow stripes) in a striated (skeletal) muscle cell. Myofibrils con- tain tiny protein filaments that show here as thin black lines running parallel to the direction of the myofibrils. These "myofilaments" consist of two types of protein: actin & myosin. When activated, the actin and myosin filaments slide over each other, overlapping and making the muscle cell contract. Freeze etching involves fracturing deep-frozen cells and then evaporating water from their surface to throw the structure into relief. Magnification unknown.
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