Cell Energetics

First Law of Thermodynamics

Energy cannot be created or destroyed.

Which of the following terms best describes a chemical reaction for which delta G is positive? 

Endergonic

 Which of the following statements best describes the central role that ATP plays in cellular metabolism?

ATP provides energy coupling between exergonic and endergonic reactions.

 When chemical, transport, or mechanical work is performed by an organism, what happens to the heat that is generated 

It is lost to the environment

 Which of the following statements describes an enzyme function?

Enzymes increase the rate of chemical reactions by lowering activation energy barriers 

A clasping handshake may be used as an analogy for an enzyme-catalyzed reaction because it represents the specific manner in which an enzyme?

Binds substrate

What is the name of the barrier that must be overcome before products are formed in a spontaneous reaction?

Activation energy

 Disruption of the active site of an enzyme would most likely result in which of the following? 

Decreased ability of enzymes to bind substrates.

 Which temperature and pH profile curves on the graphs are most likely associated with an enzyme isolated from a human stomach where conditions are strongly acidic? 

1 and 4

Which of the summary statements below best describes the results of the following reaction?

6co2, 2 pyruvate, and 2 ATP

Glycolysis results in the net production of which of the following sets of molecules per glucose molecule?

2 NADH, 2 pyruvate, and 2 ATP

Which of the following statements best summarizes ATP use and production in the catabolism of each glucose molecule in glycolysis?

2 molecules of ATP are used and 4 molecules of ATP are produced

Which of the following reactions produces the majority of the C02 released by the complete oxidation of glucose?

citric acid cycle

Upon completion of the citric acid cycle, most of the energy originally stored in each glucose molecule catabolized by cellular respiration is stored in which of the following molecules?

NADH

If pyruvate oxidation is blocked, what is the most likely effect on the levels of oxaloacetate and citrate in the citric acid cycle shown in the accompanying figure?

Oxaloacetate will accumulate and citrate will decrease.

Which of the following products result from the oxidation of pyruvate to acetyl-CoA?

NADH and CO2

Which of the following events takes place in the electron transport chain?

Harnessing of energy from redox reactions to generate a proton gradient.

Which of the following processes is driven by chemiosmosis

Oxidative phosphorylation

Which of the following sequences describes the path by which electrons move from high-energy to lower-energy molecules in aerobic respiration?

Glucose → NADH → electron transport chain → oxygen

If the proteins of the electron transport chain were labeled with a fluorescent tag, the fluorescence observed by microscopy will be localized to which of the following regions of the mitochondria?

inner membrane

Which of the following statements best describes the primary role played by oxygen in cellular respiration?

Oxygen serves as the final acceptor for electrons from the electron transport chain.

When a cell is deprived of oxygen, which of the following processes will be inhibited first?

The electron transport chain

In liver cells, the inner mitochondrial membranes contain about five times the surface area of the outer mitochondrial membranes, which allows for increased rates of which process below?

Oxidative phosphorylation

Which of the following metabolic processes normally occurs in most cells regardless of oxygen (O2) availability? 

Glycolysis

In the absence of oxygen, yeast cells can obtain energy from fermentation, which results in the net production of which of the following sets of molecules? 

ATP, CO2, and ethanol.

Which of the following statements best describes the relationship between autotrophs and heterotrophs?

Autotrophs produce organic molecules from CO2 and other inorganic molecules, while heterotrophs obtain organic molecules made by other organisms.

Which of the following statements best describes the conditions under which the Calvin cycle and cellular respiration occur in plants?

Both occur in dark and light

Which of the following statements best describes the relationship between photosynthesis and cellular respiration? 

Photosynthesis stores energy in complex organic molecules; cellular respiration releases energy from complex organic molecules

Lab students placed ten spinach leaf disks in each of three test tubes containing a baking soda solution and a control tube without baking soda. The volume of liquid in each tube and the temperature of the solutions were held constant. All tubes were placed an equal distance from the light source indicated in the accompanying table. After 10 minutes, the amount of oxygen present in each sample was measured. 

Test Tube	Grams of Baking Soda  (CO2 source)	Wattage of Light Bulb
1	0.5	25
2	0.5	50
3	0.5	75
4	0	75

Which tube is expected to produce the least amount of oxygen?

Tube 4

Which of the following processes would be most directly affected if a thylakoid membrane is punctured so that the interior of the thylakoid is no longer separated from the stroma?

Synthesis of ATP

Which of the following events are associated with chemiosmosis in chloroplasts? 

The pH of the thylakoid space increases and ATP is synthesized 

P680+ is said to be the strongest biological oxidizing agent. The strong oxidizing potential of P680+ is essential for its functions because it_____

obtains electrons from the oxygen atom in a water molecule.

 In a plant, which of the following reactions produce molecular oxygen (O2)?

The light reactions alone

The oxygen released by photosynthesis is produced by which of the following processes?

Splitting water molecules.

Based on the accompanying figure, which of the following wavelengths of light is most effective in driving photosynthesis?

440 nm

On the spaceship designed to support a multiyear voyage to the outer planets of the solar system, plants will be grown to provide oxygen and to recycle carbon dioxide. Because the spaceship will be so far from the sun, an artificial light source will be needed to support photosynthesis. Which of the following wavelengths of light should be used to maximize plant growth?

A mixture of blue and red light

In autumn, chlorophyll is degraded in the leaves of deciduous trees. Which of the following statements best explains the change in color from green to shades of yellow, orange, or red?

Other pigments such as carotenoids remain in the leaves after the chlorophyll is degraded

Which of the following molecules will accumulate if light reactions occur normally, but the Calvin Cycle is inhibited?

ATP and NADPH will accumulate.

In which cellular structure are the enzymes of the Calvin cycle localized?

Stroma of chloroplasts.

Which of the following processes occurs in the Calvin cycle?

Reduction of CO2.