Answer the following question given this paragraph: Muscles cannot contract on their own. They need a stimulus from a nerve cell to "tell" them to contract. Let's say you decide to raise your hand in class. Your brain sends electrical messages to nerve cells, called motor neurons, in your arm and shoulder. The motor neurons, in turn, stimulate muscle fibers in your arm and shoulder to contract, causing your arm to rise. Involuntary contractions of cardiac and smooth muscles are also controlled by nerves. Q: What do muscles need to contract? Choices: - stress - tendons - pressures - stimulus A:
stimulus
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Answer the following question given this paragraph: Biochemical reactions are chemical reactions that take place inside living things. Thousands of biochemical reactions continuously take place inside each cell. The sum of all these biochemical reactions is called metabolism. Q: What is the sum of all biochemical reactions in cells called? Choices: - respiration - diffusion - evolution - metabolism A:
metabolism
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Answer the following question given this paragraph: When the maximum amount of solute has been dissolved in a given amount of solvent, we say that the solution is saturated with solute. When less than the maximum amount of solute is dissolved in a given amount of solute, the solution is unsaturated. These terms are also qualitative terms because each solute has its own solubility. A solution of 0.00019 g of AgCl per 100 g of H2O may be saturated, but with so little solute dissolved, it is also rather dilute. A solution of 36.1 g of NaCl in 100 g of H2O is also saturated but rather concentrated. Ideally, we need more precise ways of specifying the amount of solute in a solution. We will introduce such ways in Section 11.2 "Quantitative Units of Concentration". In some circumstances, it is possible to dissolve more than the maximum amount of a solute in a solution. Usually, this happens by heating the solvent, dissolving more solute than would normally dissolve at regular temperatures, and letting the solution cool down slowly and carefully. Such solutions are called supersaturated solutions and are not stable; given an opportunity (such as dropping a crystal of solute in the solution), the excess solute will precipitate from the solution. It should be obvious that some solutes dissolve in certain solvents but not others. NaCl, for example, dissolves in water but not in vegetable oil. Beeswax dissolves in liquid hexane but not water. What is it that makes a solute soluble in some solvents but not others? The answer is intermolecular interactions. The intermolecular interactions include London dispersion forces, dipole-dipole interactions, and hydrogen bonding (as described in Chapter 10 "Solids and Liquids"). From experimental studies, it has been determined that if molecules of a solute experience the Saylor URL: http://www. saylor. org/books. Q: When the maximum amount of solute has been dissolved in a given amount of solvent, we say that the solution is what? Choices: - blended - used - empty - saturated A:
saturated
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Answer the following question given this paragraph: Q: Gene duplications that are able to persist over many generations without causing too much harm to an organism or species can lead to what? Choices: - characteristics - parasites - permutations - mutations A:
mutations
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