BIO 252 EXAM 2 QUESTIONS AND CORRECT ANSWERS

1. Myocyte Muscle cell 2. Sarcolemma Plasma membrane of myocyte 3. Sarcoplasm Cytoplasm of myocyte 4. Myofibril Tightly packed filament bundles found within skeletal muscle fibers. Contractional unit of a muscle cell. 5. Sarcoplasmic reticulum Site of calcium storage in a muscle cell. Surrounds the myofibrils 6. Transverse tubules (T-tubule) Inward extensions of the sarcolemma that dive into the muscle fiber and surround each myofibril to form a tunnel- like network within the muscle fiber 7. Terminal cisternae Enlarged portions of the sarcoplasmic reticulum that flank each side of a T-tubule 8. Triad Combination of a T-tubule and it's two terminal cisternae on either side 9. Organization of muscles and muscle cells Muscle (organ) -- fascicle -- myocyte (cell) -- myofibril (organelle) 10. Myofilament Collection of myofibrils; protein bundles 11. Endomysium Connective tissue over the myocytes 12. Proteins found in myofilaments Contractile proteins Regulatory proteins Structural proteins 13. Contractile proteins Produce tension 14. Regulatory proteins Control when the muscle fiber can contract 1 / 33 BIOL 252 Exam 2 15. Structural proteins Hold the myofilaments in their proper places and ensure the structural stability of the myofibril and the muscle fiber 16. Three types of myofilaments Thick filaments Thin filaments Elastic filaments 17. Thick filaments - largest diameter - many units of myosin - contractile protein 18. Myosin Motor protein for muscle contraction 19. Thin filaments - made up of contractile and regulatory proteins - contains actin, tropomyosin, and troponin 20. Actin Bead-shaped protein with an area called the active site that binds to a myosin head - strung together like beads on a necklace to form the largest part of the thin filament - appears as two