[ 271 ] Life Science GED ® TEST SCIENCE FLASH REVIEW • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Refer to the following passage to answer the next nine questions. Anatomy of Muscles Muscles are made of bundles of cells wrapped in connective tissue called fascicles. Each bundle contains many cylindrical muscle cells or muscle fibers. Like other cells, muscle fibers have mitochondria that provide energy, a plasma membrane that separates the inside and outside of the cell, and endoplasmic reticulum, where proteins are made. However, muscle cells are different from other cells in several ways. First, muscle cells have more than one nucleus. Second, the muscle cell’s plasma membrane surrounds bundles of cylindrical myofibrils that contain protein filaments and regularly folds into the deep parts of the fiber to form a transverse tubule or T-tubule. Third, the muscle cell’s endoplasmic reticulum is called sarcoplasmic reticulum; it is regularly structured, envelops the myofibrils, and ends near the T-tubule in sacs called terminal cisternae. Look at the title of the passage. The title often previews what the reading will be about. What does this title reveal about the passage? Look at each sentence in the passage. Look at the subject of each sentence (we are showing the parts of each one, not the whole): 1. Muscles are made of bundles of cells. . . . 2. Each bundle contains many cylindrical muscle cells. . . . 3. Muscle fibers have mitochondria . . . , plasma membrane . . . , and endoplasmic reticulum. . . . 4. Muscle cells are different from other cells in several ways. 5. Muscle cells have more than one nucleus. 6. The muscle cell’s plasma membrane surrounds bundles of. . . . 7. The muscle cell’s endoplasmic reticulum is called sarcoplasmic reticulum. . . . What do the subjects of the sentences have in common?