A scientist examines a cell using a microscope and notes that the cell has a large number of mitochondria and ribosomes. Within the cell are proteins that can contract. Which of the following is the most likely cell type?

Muscle cells can contract in response to stimuli. Moreover, muscle cells also have a large number of mitochondria and ribosomes for energy requirements and protein synthesis, respectively.

All muscle cells can contract by the interaction of myosin and actin proteins, which form myofibrils, the repeating molecular structure of sarcomeres (the sarcomeres are the functional and structural unit for contraction).  The globular heads of myosin bind to actin filaments, forming cross-bridges that cause the muscle cells to contract and expand.Ribosomes are organelles required for protein synthesis. Muscle cells have a lot of proteins, especially actin and myosin myofibrillar proteins, which are responsible for muscle fiber structure.Mitochondria are the energetic centers of the cell. In consequence, thousands of mitochondria can be observed in cells with high energy requirements such as muscle cells, which release a large amount of energy quickly for movement.Mitochondria, using oxygen available within the cells and metabolize food biomolecules to generate ATP (the energy coin of the cells) that power up the cell.

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Environmental science studies the interactions between the physical, chemical, and biological components of the environment, including their effects on all types of organisms. earth science (also known as geoscience), is an inclusive term for all sciences related to earth (geology, meteorology, oceanogr maphy, etc).  although environmental and earth science cover essentially the same material, environmental science places greater emphasis on the biological realm, while earth science places greater emphasis on the physical realm.    environmental and earth science study the interactions of four major systems or “spheres” (figure 8.6).  the  geosphere  consists of the core, mantle and crust of the earth.the  atmosphere  contains all of the earth’s air and is divided into troposphere, stratosphere, mesosphere, thermosphere and ionosphere.the  hydrosphere  contains all of the solid, liquid and gaseous water on earth, extending from the depths of the sea to the upper reaches of the troposphere where water is found.  ninety-seven percent of the hydrosphere is found in salty oceans, and the remainder is found as vapor or droplets in the atmosphere and as liquid in ground water, lakes, rivers, glaciers and snowfields.  the  biosphere  is the collection of all earth’s life forms, distributed in major life zones known as biomes:   tundra, boreal forest, temperate deciduous forest, temperate grassland, desert, savannah, tropical rainforest, chaparral, freshwater, and marine.although the four systems have their unique identities, there is substantial interaction between them.  environmental scientists study the effects of events in one sphere on the other spheres. for example, a volcanic eruption in the geosphere may cause profound direct and indirect effects on the hydrosphere, atmosphere and biosphere as follows: example 1 (volcano)    on may 18, 1980, mount saint helens, in the state of washington, erupted.  this event altered the surrounding environment, and provided scientists with an opportunity to study the effects of volcanic eruptions on the geosphere, hydrosphere, atmosphere and biosphere.  such studies are vital because volcanic eruptions will continue to occur, and will have increasing impact on humans as people continue to settle lands closer to dormant volcanoes. the following are but a few of the myriad of interactions resulting from a volcanic