chapter 9

Solute

A substance that is dissolved in a solution.

transport protein

A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.

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.

active transport

Energy-requiring process that moves material across a cell membrane against a concentration difference

Why doesn't the antibiotic penicillin harm humans?

Human cells do not have cell walls.

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

facilitated diffusion

Movement of specific molecules across cell membranes through protein channels

exocytosis

Process by which a cell releases large amounts of material

Which of these statements is TRUE with regard to this animation?

Sodium and potassium ions are transported against their concentration gradients.

Lactase is essential for digesting lactose in milk. This enzyme is specific for this sugar. Why?

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

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

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

active transport.

An enzyme is considered a______ it speeds up a chemical reaction without being used up.

catalyst

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

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

denature

A molecule moves down its concentration gradient using a transport protein in the plasma membrane. This is an example of

facilitated diffusion.

Which of these are by-products of cellular respiration?

heat and water

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

hypertonic

There is a net diffusion of water out of an animal cell when it is placed in a- solution.

hypertonic

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

hypotonic

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

What name is given to the process by which water crosses a selectively permeable membrane?

osmosis

Diffusion across a biological membrane is called

passive transport

Facilitated diffusion is a type of _____.

passive transport

Chemical energy is a form of _____ energy.

potential Chemical energy is a form of stored energy.

Endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

In a catalyzed reaction, a reactant is often called a

substrate

You can recognize the process of pinocytosis when _____.

the cell is engulfing extracellular fluid

In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?

cellular respiration

The plasma membrane forms a pocket that pinches inward, forming a vesicle that contains material from outside the cell. This describes the process of

endocytosis

In active transport,

molecules move across the plasma membrane against their concentration gradient.

coenzyme

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

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

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.

Which of these is exhibiting kinetic energy?

a space station orbiting Earth Kinetic energy is energy of motion.

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?

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

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

"Conservation of energy" refers to the fact that _____.

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

The ideal osmotic environment for a plant cell is a- environment.

hypotonic

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

induced fit

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

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

isotonic

The ideal osmotic environment for an animal cell is a - environment.

isotonic

When molecules move down their concentration gradient, they move from where they are - to where they are less -.

more concentrated, less concentrated.

A white blood cell engulfing a bacterium is an example of _____.

phagocytosis

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

Water crosses the plasma membrane

through facilitated diffusion or diffusion.

Aquaporins are proteins that facilitate the transport of __________ across the membrane.

water