Biology 1703 Exam 1 Set 3

False. The fixation of carbon from CO2 occurs independently of light.

(true or false) CO2 gas is fixed in a series of reactions that are light-dependent.

False. Competitive inhibitors bind reversibly to an enzyme's active site.

(true or false) Competitive inhibitors bind irreversibly to the enzyme active site, lowering Vmax.

True

(true or false) During cellular respiration, carbon-containing molecules become successively more oxidized until they reach their most oxidized form, as CO2.

False. An enzyme catalyzes its reaction in both directions, lowering the energy of activation for both the forward and reverse reactions. Enzymes do not affect the free energy of the reactants and products are the same, and thus they do not affect the reaction equilibrium.

(true or false) Enzymes alter the equilibrium point of a reaction.

False. By lowering the energy of activation, enzymes increase the number of molecules in a population that can overcome the activation barrier.

(true or false) Enzymes increase the average energy of reactant molecules.

True

(true or false) Enzymes increase the probability that any given reactant molecule will be converted to product.

True

(true or false) Enzymes lower the activation energy for a specific reaction.

False. Enzymes do not affect the initial energy of the reactants nor the final energy of the products after the reaction is complete, which are the values that determine the change in free energy of a reaction.

(true or false) Enzymes lower the free energy released by the reaction that they facilitate.

False. The most stable form of hydrogen is H2O.

(true or false) H2 is the most stable and abundant form of hydrogen in the environment.

False. Plants, as well as photosynthetic algae and bacteria, perform both photosynthesis and respiration. This means that photosynthetic organisms release both O2 and CO2 into the atmosphere.

(true or false) Photosynthetic organisms release only O2 into the atmosphere, while non photosynthetic organisms release only CO2.

True

(true or false) Sequential pathways can help drive unfavorable reactions by siphoning off the products into the next energetically favorable reactions in the series.

True

(true or false) The cycling of carbon through the biosphere first requires the incorporation of inorganic CO2 into organic molecules.

True

(true or false) The cytosol is densely packed with molecules, creating what is more an aqueous gel than a solution.

False. Small molecules diffuse through the cytosol nearly as rapidly as they diffuse in water.

(true or false) The diffusion rates for smaller molecules in the cytosol are much lower than what is observed for the same molecules in water.

True

(true or false) The oxidation of one molecule is always coupled to the reduction of a second molecule.

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.

(true or false) The second law of thermodynamics states that the total amount of energy in the Universe does not change.

False. The ultimate source of energy for living organisms is sunlight.

(true or false) The ultimate source of energy for living systems is chlorophyll.

False. Initial reaction velocities are measured to determine Vmax.

(true or false) Vmax can be determined by measuring the amount of product accumulated late in the reaction.

False. Even nonspecific interactions between macromolecules can be favorable if there is a large number of water molecules and ions displaced at the interaction interface. This would lead to an overall increase in disorder, even though the two larger molecules become associated and more ordered.

(true or false) When two macromolecules form a complex, the free energy of the system increases because there is a net increase in the amount of order in the cell.

enzymes

A chemical reaction is defined as spontaneous if there is a net loss of free energy during the reaction process. However, spontaneous reactions do not always occur rapidly. Favorable biological reactions require ______________ to selectively speed up reactions and meet the demands of the cell.

enzymes

Catalysts are molecules that lower the activation energy for a given reaction. Cells produce their own catalysts called _____________.

ΔG becomes less negative and ΔG° stays the same.

For the reaction Y!X at standard conditions with [Y] = 1 M and [X] = 1 M, ΔG is initially a large negative number. As the reaction proceeds, [Y] decreases and [X] increases until the system reaches equilibrium. How do the values of ΔG and ΔG° change as the reaction equilibrates?

(a) kon/koff = K and (c) K = [AB]/[A][B]

If proteins A and B have complementary surfaces, they may interact to form the dimeric complex AB. Which of the following is the correct way to calculate the equilibrium constant for the association between A and B?

ΔG° = 1

In the case of a simple conversion reaction such as X!Y, which value of ΔG° is associated with a larger concentration of X than Y at equilibrium? (Hint: How is ΔG° related to K?)

oxidation

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 _____________.

chemical bonds

The energy used by the cell to generate specific biological molecules and highly ordered structures is stored in the form of _____________.

K = [X]/[Y]

The equilibrium constant (K) for the reaction Y!X can be expressed with respect to the concentrations of the reactant and product molecules. Which of the expressions below shows the correct relationship between K, [Y], and [X]?

binding energy

The equilibrium constant for complex formation between molecules A and B will depend on their relative concentrations, as well as the rates at which the molecules associate and dissociate. The association rate will be larger than the dissociation rate when complex formation is favorable. The energy that drives this process is referred to as ___________.

the enzyme-substrate binding affinity

The graph in Figure Q3-52 illustrates the relationship between reaction rates and substrate concentration for an enzyme-catalyzed reaction. What does the Km value indicate with respect to enzyme-substrate interactions?

electrical OR kinetic

In the first stage of photosynthesis, light energy is converted into what other form of energy?

16.98

Isomerization of glucose 1-phosphate to glucose 6-phosphate is energetically favorable. At 37°C, ΔG° = -1.42 log10K. What is the equilibrium constant for this reaction if ΔG° = -1.74 kcal/mole at 37°C?

electrons, proton

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.

ΔG°

ΔG measures the change of free energy in a system as it converts reactant (Y) into product (X). When [Y] =[X], ΔG is equal to _____________.

ATP

Activated carriers are small molecules that can diffuse rapidly and be used to drive biosynthetic reactions in the cell. Their energy is stored in a readily transferable form such as high-energy electrons or chemical groups. Which of the molecules below is the most widely used activated carrier?

heat

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 _____________.

catabolic

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 break down nutrients in food can be described as _____________.

spontaneous

Chemical reactions that lead to a release of free energy are referred to as "energetically favorable." Another way to describe these reactions is:

CO2, H2O

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?

condensation

Energy cannot be created or destroyed, but it can be converted into other types of energy. Cells use potential kinetic energy to generate stored chemical energy in the form of activated carrier molecules, which are often employed to join two molecules together in _____________ reactions.

stable

Even though cellular macromolecules contain a large number of carbon and hydrogen atoms, they are not all spontaneously converted into CO2 and H2O. This absence of spontaneous combustion is due to the fact that biological molecules are relatively __________ and an input of energy is required to reach lower energy states.

unequal sharing electrons across a covalent bond

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?

CO2, photosynthesis

Oxidation is a favorable process in an aerobic environment, which is the reason cells are able to derive energy from the oxidation of macromolecules. Once carbon has been oxidized to _______________, its most stable form, it can only cycle back into the organic portion of the carbon cycle through __________________.

a net loss

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?

The rate of substrate consumption shortly after mixing the enzyme and substrate, for several substrate concentrations

The maximum velocity (Vmax) of an enzymatic reaction is an important piece of information regarding how the enzyme works. What series of measurements can be taken in order to infer the maximum velocity of an enzyme-catalyzed reaction?

slow

The net distance a molecule travels through the cytosol via diffusion is relatively short in comparison with the total distance it may need to travel. This is because movement governed by diffusion alone is a ________________ process that is most effective for the dispersion of small molecules over short distances.

water, hydrolysis.

The potential energy stored in high-energy bonds is commonly harnessed when the bonds are split by the addition of _______________ in a process called _____________.

entropy

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 _____________.

80 seconds

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.

the regulation of the enzyme activity

The study of enzyme kinetics is usually performed with purified components and requires the characterization of several aspects of the reaction, including the rate of association with the substrate, the rate of catalysis, and _____________.

Vmax

The study of enzymes also includes an examination of how the activity is regulated. Molecules that can act as competitive inhibitors for a specific reaction are often similar in shape and size to the enzyme's substrate. Which variable(s) used to describe enzyme activity will remain the same in the presence and absence of a competitive inhibitor?

1/Vmax and 1/Km

What information regarding an enzyme-catalyzed reaction is obtained in a plot of the inverse of the initial velocities against the inverse of the corresponding substrate concentrations?

oxidized

When elemental sodium is added to water, the sodium atoms ionize spontaneously. Uncharged Na becomes Na+. This means that the Na atoms have been _____________.

anabolic

When there is an excess of nutrients available in the human body, insulin is released to stimulate the synthesis of glycogen from glucose. This is a specific example of a(n) __________ process, a general process in which larger molecules are made from smaller molecules.

ΔG° + RT ln [X]/[Y] = 0

Which of the following is true for a reaction at equilibrium?

The concentration of the complex remains lower than the concentration of the unbound components.

Which of the following statements would not be true of a favorable binding equilibrium?

oxidation

Your body extracts energy from the food you ingest by catalyzing reactions that essentially "burn" the food molecules in a stepwise fashion. What is another way to describe this process?