Bio2 Chapter 3 ENERGY, CATALYSIS, AND BIOSYNTHESIS

3-14 Oxidation is the process by which oxygen atoms are added to a target molecule. Generally, the atom that is oxidized will experience which of the following with respect to the electrons in its outer shell? (a) a net gain (b) a net loss (c) no change (d) an equal sharing

(b) a net loss

3-1 Chemical reactions carried out by living systems depend on the ability of some organisms to capture and use atoms from nonliving sources in the environment. The specific subset of these reactions that breakdown nutrients in food can be described as _____________. (a) metabolic (b) catabolic (c) anabolic (d) biosynthetic

(b) catabolic

3-2 The second law of thermodynamics states that the disorder in any system is always increasing. In simple terms, you can think about dropping NaCl crystals into a glass of water. The solvation and diffusion of ions is favored because there is an increase in _____________. (a) pH (b) entropy (c) ionic structure (d) stored energy

(b) entropy

3-15When elemental sodium is added to water, the sodium atoms ionize spontaneously. Uncharged Na becomes Na+. This means that the Na atoms have been _____________. (a) protonated (b) oxidized (c) hydrogenated (d) reduced

(b) oxidized

3-4 At first glance, it may seem that living systems are able to defy the second law of thermodynamics. However, on closer examination it becomes clear that although cells create organization from raw materials in the environment, they also contribute to disorder in the environment by releasing _____________. (a) water (b) radiation (c) heat (d) proteins

(c) heat

3-17 Oxidation and reduction states are relatively easy to determine for metal ions, because there is a measurable net charge. In the case of carbon compounds, oxidation and reduction depend on the nature of polar covalent bonds. Which of the following is the best way to describe these types of bond? (a) hydrogen bonds in a nonpolar solution (b) covalent bonds in an aqueous solution (c) unequal sharing of electrons across a covalent bond (d) equal sharing of electrons across a covalent bond

(c) unequal sharing of electrons across a covalent bond

3-3 The energy used by the cell to generate specific biological molecules and highly ordered structures is stored in the form of _____________. (a) Brownian motion (b) heat (c) light waves (d) chemical bonds

(d) chemical bonds

3-10 During respiration, energy is retrieved from the high-energy bonds found in certain organic molecules. Which of the following, in addition to energy, are the ultimate products of respiration? (a) CO2, H2O (b) CH3, H2O (c) CH2OH, O2 (d) CO2, O2

(a) CO2, H2O

3-9 Fill in the blanks, selecting from the choices below. Light + _________ + _________ --> ___________+ heat+ sugar CO, CO2, O2, H2, H2O, N2, NO

Light + H2O + CO2 --> O2 + heat + sugars

3-16 Arrange the following molecules in order with respect to their relative levels of oxidation (assign 5 to the most oxidized and 1 to the most reduced). _______ CH2O (formaldehyde) _______ CH4 (methane) _______ CHOOH (formic acid) _______ CH3OH (methanol) _______ CO2 (carbon dioxide)

__3__ CH2O (formaldehyde) __1__ CH4 (methane) __4__ CHOOH (formic acid) __2__ CH3OH (methanol) __5__ CO2 (carbon dioxide)

3-6 Which of the following statements are true or false? If a statement is false, explain why it is false. A. The second law of thermodynamics states that the total amount of energy in the Universe does not change. B. The ultimate source of energy for living systems is chlorophyll. C. CO2 gas is fixed in a series of reactions that are light-dependent. D. H2 is the most stable and abundant form of hydrogen in the environment.

A. False. The second law of thermodynamics states that components of any system move toward greater disorder. It is the first law of thermodynamics that states that energy is neither created nor destroyed. B. False. The ultimate source of energy for living organisms is sunlight. C. False. The fixation of carbon from CO2 occurs independently of light. D. False. The most stable form of hydrogen is H2O.

3-8 Assume that the average human adult requires 2000 kilocalories per day to sustain all normal processes and maintain a constant weight. If manufactured solar panels could somehow provide power directly to the human body, what size solar panel would be required (in cm2)? Assume there are 10 hours of sunlight per day, and that the usable energy output for a typical solar panel is 850 kJ/ft2 per hour. Note: 1 kcal = 4.184 kJ 1 ft2 = 929.03 cm2

Conversion factors: 1 kcal = 4.184 kJ 1 ft2 = 929.03 cm2 If there are 10 hours of sunlight each day hitting the solar panel, there are 8500 kJ/ft2 produced per day. The average adult human requires 8368 kJ per day; thus with a conventional solar panel, we would require a surface area of about a square foot, or more precisely in cm2: 8368 kJ/X = 8500 kJ/929.03 cm2 929.03 × 8368/8500 = X X = 914.57 cm2

3-5 If you weigh yourself on a scale one morning then eat four pounds of food during the day, will you weigh four pounds more the next morning? Why or why not? Hint: What happens to the atoms contained in the food as useful energy is derived from metabolizing the food molecules?

No, you will not weigh four pounds more the next morning because only a small portion of the mass of the food will form components of the body. Much of the mass of food is either released as CO2 and H2O that are breathed out into the atmosphere or converted into materials excreted as waste products.

3-7 Two college roommates do not agree on the best way to handle the clutter piled up in your dorm room. Roommate 1 explains that chaos is inevitable, so why fight it? Roommate 2 counters that maintaining an organized environment makes life easier in many ways, and that chaos is not inevitable. What law of thermodynamics drives the thinking of roommate 1? What thermodynamic argument can be used to support roommate 2?

The second law of thermodynamics supports roommate 1's view. It is favorable for a system to become less ordered, However, if the energy used to create an ordered environment in the room is accompanied by enough release of heat, the Universe will become more disordered as the room becomes more organized. Thus, while increasing chaos is inevitable, the room—like a cell—can be kept highly organized.