Bio 101 Exam 1 Questions & Answers(SCORED A+)

Sweating has a cooling effect because of water's high __________. -ANSWER heat of vaporization (Water's high heat of vaporization results in evaporative cooling b/c when water evaporates, the surface of the water cools down) Because molecules of water are farther apart in ice than in liquid water, _____. -ANSWER ice floats on liquid water (B/c water molecules in ice are farther apart than in liquid water, ice is less dense and floats) Water is a very versatile solvent because water molecules are -ANSWER polar (b/c molecules of polar solvents have a positive and a negative pole, polar solvents are excellent solvents for ions and for the other polar materials) How does the polarity of water contribute to its ability to dissolve so many substances? -ANSWER b/c it is polar, water's oppositely charged ends are attracted to positively and negatively charged ions and molecules. Water molecules form a hydration shell around oppositely charged particles. (Polar water molecules surround the individual ions or charged molecules, separating and shielding the ions or molecules from one another) Nonpolar molecules that cluster away from water molecules are called __________ molecules. -ANSWER hydrophobic (substances that are nonionic and nonpolar repel water) A molecule that has all nonpolar covalent bonds would be __________ -ANSWER hydrophobic (ex.: the hydrophobic behavior of oil molecules results from a prevalence of nonpolar covalent bonds. Nonpolar molecules do not have an affinity for water or other polar molecules) Hydrophobic molecules are _______ water -ANSWER unable to interact with (substances that are nonionic and nonpolar have no way to interact with it and thus stand apart from it) Why are cell membranes composed primarily of hydrophobic molecules? -ANSWER In order to perform their function of separating the aqueous solutions outside of cells from the aqueous solutions inside of cells, cell membranes cannot be soluble in water. (If cell membranes were hydrophilic, they would break-down and dissolve in the presence of water, rendering them useless as a barrier) Hydrophilic substances, unlike hydrophobic substances, -ANSWER have charges and/or partial charges to which water molecules can adhere (hydrophilic substances are water-loving and have an affinity for water. There is an unequal sharing of electrons resulting in a polar molecule, or there is the gain or loss of an electron/s resulting in the formation of negatively and positively charged ions) Some substances, such as oil and gasoline, will not dissolve in water because _____. -ANSWER their molecules have no charges of partial charges to which water molecules can adhere (the hydrophobic behavior of oil and gasoline molecules results from a prevalence of nonpolar covalent bonds between carbon and hydrogen) A mole of ethyl alcohol weighs 46 g. How many grams of ethyl alcohol are needed to produce 1 L of a 2-millimolar (2 mM) solution? -ANSWER 0.092 g (This would produce a 0.002 M or a 2 mM solution) An acid is________ -ANSWER a compound that donates hydrogen ions to a solution (an acid donates hydrogen ions to a solution) Adding acid tends to __________ of a solution. -ANSWER increase the hydrogen ion concentration and lower the pH Which describes the dissociation of an acid? -ANSWER HF--H(+)+ F(-) (Hydrofluoric acid (HF) dissociates into a hydrogen ion and a fluoride ion) A glass of grapefruit juice, at pH 3, contains _______ H+ as a glass of tomato juice, at pH4 -ANSWER ten times as much (The pH scale is a base-10 logarithmic scale. The change from any pH value to the next smaller value represents a tenfold increase in the hydrogen ion concentration) A solution at pH6 contains __________ than the same amount of solution at pH8 -ANSWER 100 times more H+ (Each pH unit change presents a tenfold difference in the hydrogen ion concentration; thus 10x10=100) Adding a base -ANSWER lower the hydrogen ion concentration and increase the pH (A substance that reduces the hydrogen ion concentration is a base. Reducing the hydrogen ion concentration increases pH) When the pH of a solution shifts from 7 to 3, how has the hydrogen ion concentration changed? -ANSWER It has increased by 10,000 (equation: 7-3=10x10x10x10= 10,000) (because the pH # is the negative log of the hydrogen ion concentration, a change from pH of 7 to a pH of 3 increases the hydrogen ion concentration by 10,000x) A substance that minimizes changes in the concentration of H+ and OH in a solution is a _________ -ANSWER buffer (buffers are substances that minimize changes in the concentration of hydrogen ions and hydroxide ions in a solution, therefore, buffers maintain a relatively constant pH) Sucrose has a molecular mass of 342 daltons. To make a 2-molar (2 M) solution of sucrose, _____. -ANSWER stir 342 g of sucrose in water to dissolve the sugar, and then add enough water to bring the total volume of solution up to 0.5L (or you could stir 684 g of sucrose in water to dissolve the sugar, and then add enough water to bring the total volume of the solution up to 1 L) Why would more carbon dioxide taking up the oceans cause for concern? -ANSWER more carbon dioxide causes an increase in carbonic acid (H2CO3), which leads to a decrease in the concentration of carbonate ion (CO3(2)-) (as seawater becomes more acidic, carbonate ion concentration decreases. The decrease in the availability of carbonate ion makes it more difficult for marine organisms to secrete calcium carbonate shells) What is the term for a group of individuals from one species living within a defined area? -ANSWER population (only the organisms of a given species that have the opportunity to interact with one another are considered )to be within the same population) Which gives the correct sequence of biological organization, from simplest to most complex? -ANSWER cell, tissue, organ, organisms, population, community (Order of increasing complexity) Emergent properties of living systems are defined as properties that_________ -ANSWER are due to the arrangement and interactions of parts as complexity increases (emergent properties are novel properties not present at the level of biological organization just below. emergent properties arise from the arrangement and interactions of parts as complexity increases) Which can be considered a biological system? -ANSWER All of the above; a pond, biosphere, salmon's cardiovascular system, a single liver cell (a system is a combo of components that function together. It can be defined at any scale) Sequencing a protein to discover the order of the amino acids that make it up is an example of ________. Understanding how that protein works with other proteins in a cell is an example of _____________. -ANSWER reductionism...systems biology (Reductionism seeks to reduce complex systems to simpler, more manageable components. Systems biology seeks to understand how all the parts function together) In an ecosystem, nutrients________ and ene