BIOL 1030 Chapter 5 homework questions

Which statements about the fluid mosaic structure of a membrane are correct? Select the three correct statements. A) Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane. B) The diverse proteins found in and attached to membranes perform many important functions. C) The kinky tails of some proteins help keep the membrane fluid by preventing the component molecules from packing solidly together. D) Membranes include a mosaic, or mix, of carbohydrates embedded in a phospholipid bilayer. E) The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center.

A B E

Which of the following is a difference between active transport and facilitated diffusion? A) Facilitated diffusion involves transport proteins, and active transport does not. B) Facilitated diffusion can move solutes against a concentration gradient, and active transport cannot. C) Active transport requires the expenditure of cellular energy, and facilitated diffusion does not. D) Active transport involves transport proteins, and facilitated diffusion does not.

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

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 _____. View Available Hint(s) 1) B ... the diffusion gradient there is steeper 2) A ... the diffusion gradient there is shallower 3) A ... its membrane transport proteins will not be saturated 4) B ... the oxygen molecules inside cell B have a higher kinetic energy

B ... the diffusion gradient there is steeper

Why doesn't the antibiotic penicillin harm humans? Penicillin attacks the nervous system. Penicillin attacks plasma membranes. Human cells do not have cell walls. The dosage given to kill bacteria is too low to harm humans.

Human cells do not have cell walls.

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. The pH should be decreased. Nothing should be altered. The enzyme will not work on human DNA.

The temperature should be raised.

Lactase is essential for digesting lactose in milk. This enzyme is specific for this sugar. Why? A) Specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed. B) Molecules and active sites vary in size; only properly sized molecules can fit. C) There is a precise compatibility between the active site and the lactose molecule. D) Reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.

There is a precise compatibility between the active site and the lactose molecule.

Which of these is exhibiting kinetic energy? a rock on a mountain ledge a space station orbiting Earth the high-energy phosphate bonds of a molecule of ATP a person sitting on a couch while watching TV an archer with a flexed bow

a space station orbiting Earth

An enzyme speeds up reactions by lowering the

activation energy

An enzyme is specific because the shape of its ___ matches only particular reactants.

active site

When in solution, a molecule that moves slowly across an artificial membrane moves rapidly across a plasma membrane. This molecule rapidly enters the cell regardless of whether its concentration 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? A) active transport B) exocytosis C) passive transport D) phagocytosis

active transport

The sodium-potassium pump uses energy from ATP to move sodium ions out of the cell, and potassium ions into the cell. This is an example of A) active transport. B) exocytosis. C) diffusion. D) passive transport. E) facilitated diffusion.

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 _____. A) actively pump water back into their cells to counter its loss due to osmosis B) actively pump salt back out of their cells to counter its inflow due to osmosis C) actively pump water back out of their cells to counter its inflow due to osmosis D) synthesize membranes that are impermeable to substances that upset osmotic balance

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

An enzyme is considered a(n) ___ because it speeds up a chemical reaction without being used up.

catalyst

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP? anabolism potentiation redox digestion cellular respiration

cellular respiration

an ___ which is often a vitamin, binds to an enzyme and plays a role in catalysis.

coenzyme

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 feedback inhibition noncompetitive inhibition mixed inhibition

competitive inhibition AZT and the nucleotide compete for the active binding site. When AZT binds to an enzyme known as reverse transcriptase, it blocks the replication of the genetic material of HIV.

High temperatures or changes in pH can ___ an enzyme, causing it to lose its shape and biological activity.

denature

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 __________ active transport osmosis endocytosis passive transport

endocytosis

The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of A) endocytosis. B) diffusion. C) passive transport. D) active transport. E) exocytosis.

endocytosis.

"Conservation of energy" refers to the fact that _____. A) if you conserve energy you will not be as tired B) energy cannot be created or destroyed but can be converted from one form to another C) the entropy of the universe is always increasing D) the net amount of disorder is always increasing E) no chemical reaction is 100 percent efficient

energy cannot be created or destroyed but can be converted from one form to another

A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of A) endocytosis. B) exocytosis. C) active transport. D) facilitated diffusion. E) diffusion.

facilitated diffusion.

Which of these are by-products of cellular respiration? ATP and water water heat and water glucose and water ATP

heat and water

A plant cell placed in a ___ solution will lose water and plasmolyze.

hypertonic

more molecules outside the cell (less free water molecules) more free water molecules in the cell TO water molecules leaving the cell A) isotonic B) hypotonic and isotonic C) hypertonic or isotonic D) hypotonic E) hypertonic

hypertonic

There is a net diffusion of water out of an animal cell when it is placed in a ___

hypertonic solution

An animal cell placed in a ___ solution will gain water, swell, and possibly burst.

hypotonic

more molecules in the cell (less free water molecules) and less free water molecules outside the cell TO free water molecules moving into the cell A) hypotonic ... swelled B) hypertonic ... lost water C) hypertonic ... gained water D) isotonic ... neither lost nor gained water E) hypotonic ... shrunk

hypotonic ... swelled

The ideal osmotic environment for a plant cell is a ___

hypotonic environment

the __ between an active site and its substrate often strains bonds and helps the reaction proceed.

induced fit

Endocytosis moves materials _____ a cell via _____. out of ... membranous vesicles into ... membranous vesicles into ... facilitated diffusion into ... a transport protein out of ... diffusion

into ... membranous vesicles

A plant cell surrounded by a(n) ___ solution will be flaccid (limp).

isotonic

The ideal osmotic environment for an animal cell is a

isotonic environment

in active transport, A) molecules move across the plasma membrane by crossing the lipid bilayer directly, rather than by using a transport protein. B) the plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. C) no energy input is required from the cell. D) a vesicle inside the cell fuses with the plasma membrane and releases its contents outside the cell. E) molecules move across the plasma membrane against their concentration gradient.

molecules move across the plasma membrane against their concentration gradient.

When molecules move down their concentration gradient, they move from where they are ___ concentrated to where they are ____ concentrated.

more to less

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. catalyst competitive inhibitor substrate noncompetitive inhibitor

noncompetitive inhibitor Because the product of the pathway and the substrate of the early-acting enzyme are very different in structure, competitive inhibition is unlikely as this involves binding of an inhibitor to the active site. Much more plausible is noncompetitive inhibition in which the inhibitor binds to a site on the enzyme that is different from the active site.

What name is given to the process by which water crosses a selectively permeable membrane? A) pinocytosis B) phagocytosis C) passive transport D) osmosis E) diffusion

osmosis

Diffusion across a biological membrane is called

passive transport

Facilitated diffusion is a type of _____. A) passive transport B) phagocytosis C) pinocytosis D) active transport

passive transport

A white blood cell engulfing a bacterium is an example of _____. exocytosis facilitated diffusion phagocytosis pinocytosis receptor-mediated endocytosis

phagocytosis

Chemical energy is a form of _____ energy. heat motion kinetic potential entropic

potential

In a catalyzed reaction, a reactant is often called a___

substrate

You can recognize the process of pinocytosis when ____ the cell is engulfing a large particle the cell is engulfing extracellular fluid a receptor protein is involved

the cell is engulfing extracellular fluid

Osmosis is often viewed incorrectly as a process driven directly by differences in solute concentration across a selectively permeable membrane. What really drives osmosis? A) the first law of thermodynamics B) the difference in the height of water columns on either side of a selectively permeable membrane C) the difference in sugar or ion concentration across a selectively permeable membrane D) the difference in water concentration across a selectively permeable membrane

the difference in water concentration across a selectively permeable membrane

You are working on a team that is designing a new drug. For this drug to work, it must enter the cytoplasm of specific target cells. Which of the following would be a factor that determines whether the molecule selectively enters the target cells? A) the phospholipid composition of the target cells' plasma membrane B) the nonpolar, hydrophobic nature of the drug molecule C) the similarity of the drug molecule to other molecules that are transported into the target cells D) the concentration of the drug molecule that is transported in the blood

the similarity of the drug molecule to other molecules that are transported into the target cells

Water crosses the plasma membrane A) through facilitated diffusion or diffusion. B) through active transport. C) against its concentration gradient. D) using a process that requires energy from the cell. E) through cotransport.

through facilitated diffusion or diffusion.

Aquaporins are proteins that facilitate the transport of __________ across the membrane. A) salt B) urine C) proteins D) water

water

in a water filled bubble made of phospholipids, working from the inside out, what would be the order of components observed? A) hydrophobic tail, water, hydrophilic head, hydrophilic head, water, hydrophobic tail B) water, hydrophilic head, hydrophobic tail, hydrophobic tail, hydrophilic head, water C) water, hydrophilic tail, hydrophobic head, hydrophobic head, hydrophilic tail, water D) water, hydrophobic tail, hydrophilic head, hydrophilic head, hydrophobic tail, water

water, hydrophilic head, hydrophobic tail, hydrophobic tail, hydrophilic head, water