BIO Practice Test #2

In simple summary form, the input of the Calvin cycle for every product is __________, and the output is __________ used for glucose synthesis.

3 CO2 ...; a three-carbon molecule

Which of the following is an accurate comparison of active transport and facilitated diffusion?

Active transport moves solutes against their concentration gradient; facilitated diffusion moves substances down their concentration gradient.

Antibiotics—for example, penicillin—cannot be used to treat viral infections, such as the common cold. Why?

Antibiotics inhibit enzymes that are essential to the survival of bacteria only.

Which gas contributes to both global warming and the deterioration of the ozone layer?

CFCs

CAM plants have adapted to arid environments by closing their stomata during the day. However, photosynthesis still occurs. This is because __________.

CO2 is fixed at night when the stomata are open

Which of the following statements regarding the reduction of CO2 to sugar during photosynthesis is true?

Electrons (with accompanying protons) are added to CO2 during photosynthesis.

Which statement regarding enzyme function is true?

Excessive salt ions can cause an enzyme to denature.

Current evidence indicates that the process of photosynthesis arose more than three billion years ago. Its origin had a huge impact on existing organisms and on the physical characteristics of the biosphere. Which major physical change could be attributed to photosynthesis?

Photosynthesis drastically increased the oxygen content of the atmosphere.

Hydrogen is a likely candidate in the search for a replacement for petroleum. However, removing hydrogen from water requires the investment of a great deal of energy. Why are plants considered to be one step ahead in the utilization of hydrogen as an alternative fuel source?

Plant cells possess water-splitting enzymes.

The hydrolysis of DNA into nucleotides constitutes an exergonic reaction. Yet, DNA is quite stable. Why is this the case?

The activation energy required to initiate this reaction is seldom reached.

The eukaryotic cell has multiple membrane-enclosed compartments. This evolutionary innovation provides what advantage to the cell?

The different membrane-enclosed spaces allow different parts of the cell to perform specific functions.

What happens to the chemical energy that is extracted from molecules by cellular activities but that is not used for cellular work?

The energy contributes to the entropy of the system.

Cells store energy that they use for work in the _____.

arrangement of atoms within molecules

Recent data suggests that heat-generating brown fat is most active in __________.

babies

The conversion of NADP+ to NADPH occurs with the assistance of __________.

electrons from water and energy from sunlight

You're on the pilot episode of a new reality show called "The Transport Factor." The host hands you three different amino acids, four different sugars, and two different ions. Then the host shouts, "How many different proteins does the cell need to move these molecules across the plasma membrane using facilitated transport?" Quickly, you correctly respond: _____.

nine

Overall, membranes seem to have a great deal in common, but on closer inspection it is revealed that membranes of different cells have unique properties. What is the primary component of membranes that gives membranes cell-specific properties?

proteins

In oxidative phosphorylation, electrons are passed from one electron carrier to another. The energy released is used to _____.

pump protons (H+) across the mitochondrial membrane

How many turns of the Calvin cycle are required to produce one molecule of glucose?

six

Osmosis is often viewed incorrectly as a process driven directly by differences in solute concentration across a selectively permeable membrane. What really drives osmosis?

the difference in water concentration across a selectively permeable membrane

What controls the direction of a molecule, such as oxygen, involved in passive transport?

the direction of the oxygen concentration gradient

What substance is transported by aquaporins?

water

In plant cells, carbon dioxide and water are joined to form carbohydrates. Plant cells can also break down carbohydrates such as glucose, releasing carbon dioxide, water, and energy. No one has ever observed such reactions between water and carbon dioxide outside of living cells. What allows simple molecules to assemble into more complex molecules, and also disassemble, in cells but not in other, nonbiological environments?

Cells couple energy-releasing reactions to energy-requiring reactions.

Frequently, transplanted organs are rejected by the recipient's body. How is this reaction related to plasma membranes?

Each person has a unique set of carbohydrate chains attached to his or her plasma membranes.

Which statement regarding the light reactions is true?

Electrons are supplied to chlorophyll P680 as it reduces the primary electron acceptor.

We inhale O2 and we exhale CO2. Carbon dioxide is produced _____.

In the reaction that creates acetyl CoA (coenzyme A) from pyruvate

In a theoretical world where all things are possible, how could you increase the amount of energy that could be stored in a molecule of ATP?

Increase the negative charge of each phosphate group.

Macrophages are white blood cells that roam the body searching for invading microbes. Inside macrophage vacuoles these invaders are destroyed. How do the microbes get inside the macrophages?

Microbes are engulfed into the macrophage via phagocytosis.

Given the relatively modest number of calories burned by anything but the most vigorous activities, why can people consume over 2,000 kilocalories a day, yet maintain a healthy body weight?

Most of the energy consumed in food is spent maintaining the body's functions, so only a fraction of food energy needs to be burned in exercise.

During fermentation, __________ that was produced during glycolysis is converted back to __________.

NADH; NAD+

A large research project was carried out in the oceans surrounding Antarctica to learn whether adding iron-containing compounds to the iron-limited polar sea would enhance the growth of phytoplankton (small, free-floating photosynthetic organisms). This project was performed with the hope that if plankton growth were significantly increased over large areas, it might slow global warming. What is the basis for such an expectation?

The increased biomass will act as a sponge (a carbon sink) for atmospheric carbon dioxide.

Table sugar, or sucrose, is quite stable, and left on its own at room or even human body temperature, breakdown occurs very slowly. The breakdown of sucrose into the simple sugars fructose and glucose is an exergonic reaction. Sucrase, an enzyme, can increase the reaction rate at least one-million-fold. How does the net amount of energy released during the breakdown of sucrose compare between a spontaneous reaction and one catalyzed by sucrase?

The sucrase-catalyzed reaction releases the same amount of energy as the spontaneous reaction.

A pharmaceutical company wishes to focus on an enzyme to develop new medications. What type of study would be of the greatest benefit?

Understanding the enzyme's structure would help pharmaceutical companies design molecules that fit to the binding site and alter activity.

Utah's Great Salt Lake has an average salinity seven times higher than that of the oceans. Very few multicellular organisms live in this harsh environment. An example is the brine shrimp, which must devote a large portion of its metabolic energy to osmoregulation. These brine shrimp must _____.

actively pump water back into their cells to counter its loss due to osmosis

Azidothymidine (AZT) is an antiretroviral drug used in the treatment of HIV. It shares a structural similarity to a nucleotide. What might be the mode of action for this drug?

competitive inhibition

Which of the following are photoautotrophs?

corn stalks just before harvest

Each turn of the citric acid cycle generates one ATP and ___ additional energy-rich molecules: __________.

four; 3 NADH and 1 FADH2

Light is _____ energy, which is converted by plants into molecules, which possess _____ energy.

kinetic ... chemical

In cellular respiration, glucose _____ electrons, whereas _____ electrons.

loses ... oxygen gains

Lungs are to breathing as _____ are to cellular respiration.

mitochondria

The synthesis of an amino acid follows this pathway: precursor A → intermediate B → amino acid C. Each reaction is catalyzed by a different enzyme. This metabolic pathway is controlled by feedback inhibition with amino acid C inhibiting the conversion of precursor A to intermediate B. Amino acid C acts as a _____ of the first enzyme in the pathway.

noncompetitive inhibitor

Some human cells, such as nerve cells, are restricted to aerobic respiration to recycle NADH and FADH2. If these cells are deprived of oxygen, then _____.

oxidative phosphorylation would come to a halt because there wouldn't be any oxygen to "pull" the electrons down the transport chain

The light reactions of photosynthesis include __________.

reduction of NADP+

When placed in a hypotonic environment, where the solute concentration is below that of the cell, a houseplant will _____.

remain standing upright

Sunlight is essential for the varied life on Earth. Sunlight provides energy to photosynthetic organisms by providing __________.

the energy necessary to power the rearrangement of chemical bonds in H2O and CO2

Oxidative phosphorylation could not occur without glycolysis and the citric acid cycle, because _____.

these two stages supply the electrons needed for the electron transport chain

Chlorophyll is found in the __________ of chloroplasts

thylakoid membranes

What is the potential benefit of photorespiration in plants?

It allows plant cells to reduce the buildup of oxygen gas without opening stomata.

Oxygen is the final electron acceptor for cellular respiration. What is the final electron acceptor in the light reactions of photosynthesis?

NADP+

Which of the following colors of light are useful during the process of photosynthesis?

blue, red, and violet

Using the ATP generated during cellular respiration, the intermediates of glycolysis and the citric acid cycle, such as pyruvate and acetyl CoA, can be siphoned off and used to __________.

build amino acids, fats, and sugars

The primary function of light absorption by photosystems I and II is to produce __________.

free, energized electrons

New drugs are being developed to lower levels of circulating cholesterol. A successful drug would be one that _____.

increases the rate of LDL receptor-mediated endocytosis

When a car engine burns gasoline, the results of the reaction are similar to when cells burn glucose. Both reactions release carbon dioxide and water. In cells, the chemical energy in food is converted to ATP and heat. In a moving car, the chemical energy in gasoline is converted to _____.

kinetic energy and heat

A molecule that functions as the electron donor in a redox reaction __________.

loses electrons and becomes oxidized

A scientist wants to study the enzymes of the citric acid cycle in eukaryotic cells. What part of the cell would she use as a source of these enzymes?

mitochondrial matrix

Glycolysis is the only stage of cellular respiration that _____.

requires ATP to make ATP

Fat is the most efficient molecule for long-term energy storage even compared to carbohydrates because _____.

with their numerous hydrogen atoms, fats provide an abundant source of high-energy electrons

In an oil-based, nonpolar environment, phospholipids would arrange themselves so that they __________.

would stay together but in a reverse orientation, with their tails projecting outward