Chapter 3
True or false: Enzymes lower the free energy released by the reaction that they facilitate
False.
True or false: The ultimate source of energy for living systems is chlorophyll.
False.
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
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
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
3-15 When 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
3-18 Seed oils are often dehydrogenated and added back into processed foods as partly unsaturated fatty acids. In comparison with the original oil, the new fatty acids have additional double carbon-carbon bonds, replacing what were once single bonds. This process could also be described as _____________. (a) isomerization (b) oxidation (c) reduction (d) protonation
b
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
3-22 Catalysts are molecules that lower the activation energy for a given reaction. Cells produce their own catalysts called _____________. (a) proteins (b) enzymes (c) cofactors (d) complexes
b
3-32 The potential energy stored in high-energy bonds is commonly harnessed when the bonds are split by the addition of _______________ in a process called _____________. (a) ATP, phosphorylation (b) water, hydrolysis (c) hydroxide, hydration (d) acetate, acetylation
b
3-37 The net distance a molecule travels as it diffuses through the cytosol is relatively short in comparison with the total distance it travels. This is because movement governed by diffusion alone is a ________________ process that is most effective for the dispersion of small molecules over short distances. (a) slow (b) random (c) regulated (d) complicated
b
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
3-20 Chemical reactions that lead to a release of free energy are referred to as "energetically favorable." Another common way in which these reactions are described is _____________. (a) uphill (b) uncatalyzed (c) spontaneous (d) activated
c
3-38 The small molecule cyclic AMP (cAMP) takes about 0.2 second to diffuse 10 μm, on average, in a cell. Suppose that cAMP is produced near the plasma membrane on one end of the cell how long will it take for this cAMP to diffuse through the cytosol and reach the opposite end of a very large cell, on average? Assume that the cell is 200 μm in diameter. (a) 4 seconds (b) 16 seconds (c) 80 seconds (d) 200 seconds
c
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
3-21 ΔG° indicates the change in the standard free energy as a reactant is converted to product. Given what you know about these values, which reaction below is the most favorable? (a) ADP + Pi → ATP ΔG° = +7.3 kcal/mole (b) glucose 1-phosphate → glucose 6-phosphate ΔG° = -1.7 kcal/mole (c) glucose + fructose → sucrose ΔG° = +5.5 kcal/mole (d) glucose → CO2 + H2O ΔG° = -686 kcal/mole
d
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
3-53 NADH and NADPH are activated carrier molecules that function in completely different metabolic reactions. Both carry two additional ________ and one additional _____________. This combination can also be referred to as a hydride ion. (a) protons, electron (b) electrons, phosphate (c) hydrogens, electron (d) electrons, proton
d
True or false: The second law of thermodynamics states that the total amount of energy in the Universe does not change
False
True or False: H2 is the most stable and abundant form of hydrogen in the environment.
False
True or false: CO2 gas is fixed in a series of reactions that are light-dependent.
False
True or false: Enzymes increase the probability that any given reactant molecule will be converted to product.
False
True or false: Enzymes increase the average energy of reactant molecules.
True
True or false: Enzymes lower the activation energy for a specific reaction.
True
