Biology chapter 5 question and answers

Which statement best describes phagocytosis?

A cell engulfs a particle by wrapping pseudopodia around it and packaging it within a vacuole

Most cellular work is accomplished by _____ energizing molecules by _____ them.

ATP ... phosphorylating

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.

Which of the following is a difference between active transport and facilitated diffusion?

Active transport requires the expenditure of cellular energy, and facilitated diffusion does not.

Which of the following statements about cell membrane transport is true?

Active transport works with the assistance of proteins to move molecules from areas of low concentration to areas of high concentration.

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.

Cells A and B are the same size and shape, but cell A is metabolically quiet and cell B is actively consuming oxygen. Oxygen will diffuse more quickly into cell _____ because _____.

B ... the diffusion gradient there is steeper

Green olives may be preserved in brine, which is a 20-30% salt solution. How does this method prevent contamination by microorganisms?

Bacteria can't survive in a hypertonic solution because they lose 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 enzyme function is true?

Excessive salt ions can cause an enzyme to denature.

Which of these statements describes what occurs in facilitated diffusion?

Facilitated diffusion of solutes occurs through protein pores in the membrane.

Why doesn't the antibiotic penicillin harm humans?

Human cells do not have cell walls.

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.

Which of the following statements is true about passive transport?

Passive transport requires no expenditure of cellular energy.

Which of these situations accurately represents osmoregulation in organisms?

Plant cells need a hypotonic environment in order to stay turgid.

Which of these statements about enzyme inhibitors is true?

The action of competitive inhibitors may be reversible or irreversible.

Which of the following is an example of the second law of thermodynamics?

The aerobic respiration of glucose generates heat.

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.

The membrane is referred to as a "fluid mosaic" structure. Which of the following statements is true?

The fluid is phospholipid, and the mosaic is protein.

According to the second law of thermodynamics, which of the following is true?

The ordering of one system depends on the disordering of another.

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

Taq polymerase is an enzyme isolated from the organism Thermophilus aquaticus. This organism has been found living in the hot springs of Yellowstone National Park. This enzyme is used to copy human DNA from crime scenes. Most reactions are performed at ranges similar to those of the human body; however, what considerations should be made for optimum use of this enzyme?

The temperature should be raised.

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.

The concentration of solutes in a red blood cell is about 2%. Sucrose cannot pass through the membrane, but water and urea can. Osmosis would cause red blood cells to shrink the most when immersed in which of the following solutions?

a hypertonic sucrose solution

When in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. This occurs regardless of whether the concentration of this molecule is higher inside or outside the cell. Using this information, which transport mechanism is most likely to be responsible for the movement of the molecule across a plasma membrane?

active transport

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

Cellular respiration is an example of _____.

an exergonic reaction

Stability of an animal cell plasma membrane is enhanced by _____.

cholesterol molecules

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

The movement of atoms, ions, or molecules from a region of higher concentration to regions of lower concentration is called _____.

diffusion

The phosphorylation of ADP to form ATP is an _____ reaction that _____ energy.

endergonic ... requires an input of

A nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mother's milk. These molecules probably enter the cells lining the baby's digestive tract via _____.

endocytosis

If the entropy of a system is increasing, this means that _____.

energy input will be needed to maintain organization

The secretion of neurotransmitters out of the nerve cell, from small vesicles at the end of the axon, can be considered an example of _____.

exocytosis

What condition might result from an excess of aquaporins?

fluid retention in pregnant women

Phospholipids are well suited to be the main structural components of membranes because they _____.

form a selectively permeable structure

When considering the formation of membranes, they _____.

form spontaneously in aqueous environments

If the volume of a cell increases when it is placed in an aqueous solution, that solution is said to be _____ to the cell.

hypotonic

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

Which of the following statements is true about diffusion?

it's a passive process

If the tertiary structure of an enzyme is changed, _____.

its substrate may not fit properly in the active site

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

kinetic ... chemical

The mechanism of enzyme action is to _____.

lower the energy of the activation of a reaction

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

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

The diffusion of water across a selectively permeable membrane is called _____.

osmosis

Some liver cells ingest bacteria, a function probably accomplished by _____.

phagocytosis

Which of the following terms specifically refers to the intake of very large particles by cells?

phagocytosis

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

LDLs enter cells by means of _____.

receptor-mediated endocytosis

Which of the following enables a cell to pick up and concentrate a specific kind of molecule?

receptor-mediated endocytosis

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

remain standing upright

Seawater is dangerous to drink because _____.

seawater is hypertonic to your body tissues and drinking it will cause you to lose water by osmosis

The lipids in a cell membrane are arranged _____.

so that the nonpolar parts of two lipids point toward each other

The first law of thermodynamics _____.

states that energy is neither created nor destroyed

Succinylcholine is structurally almost identical to acetylcholine, but if combined with the enzyme that normally hydrolyzes acetylcholine, the enzyme is no longer able to hydrolyze acetylcholine. This suggests that _____.

succinylcholine must be a competitive inhibitor of acetylcholine

Energy is _____.

the capacity to perform work

The transport of molecules of a particular solute from inside an animal cell across the cell membrane to the extracellular fluid always requires energy when _____.

the concentration of the solute is lower inside the cell than outside it

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

A reaction is designated as exergonic rather than endergonic when _____.

the potential energy of the products is less than the potential energy of the reactants

What substance is transported by aquaporins?

water

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

would never associate but instead would remain as individual molecules completely dissolved in the oil