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05: The Working Cell
This activity contains 28 questions.
growth of a single cell on a tiny wafer
understanding of movement of materials across a membrane
study of energy-deriving metabolic pathways
manipulation of materials at the molecular level
measurement of ATP activity in a test tube
Which is the best definition of energy?
the conversion of one form of chemical energy to another form of chemical energy
the conversion of light energy to chemical energy
the capacity to do work
the bonding of two compounds when it is accompanied by the removal of one molecule of water
Which one of the following statements about energy is correct?
A leaf falling from a tree represents potential energy.
Energy cannot be created or destroyed.
We convert about 99% of our food energy to useful work.
Chemical energy is a form of kinetic energy.
Entropy is the movement of molecules from areas of higher concentration to areas of lower concentration.
Energy is observed in two basic forms: potential and kinetic. Which of the following is an example of potential energy?
the mercury rising within a thermometer
a bowling ball placed on the top shelf of a closet
a hot cup of coffee
waves crashing against the shoreline
a car rolling downhill
Entropy means that __________.
the quantity of usable energy declines with each energy transformation
it is not possible to observe an increase in molecular organization
the quality of energy in the universe is constant
life should be impossible
energy can neither be created nor destroyed
Molecules of food have a special form of potential energy called _____.
Calories are units of _____.
The molecule most directly involved in energy transfer within cells is _____.
Which are materials found in a molecule of ATP?
an organic molecule called adenosine plus three phosphate groups
amino acids in a precise sequence
an organic molecule called adenosine plus two phosphate groups
phosphates attached to deoxyribose
an organic molecule called cytosine plus three phosphate groups
ATP drives work in cells by __________ to other molecules.
preventing phosphate transfer
transmitting brain signals
blocking adenosine transfer
Which is a true statement about the ATP cycle?
About 100 ATP molecules are regenerated per second per cell.
The ATP cycle can operate independently of enzyme help.
The ATP cycle does not involve ADP.
All three phosphates in ATP are involved in muscle contraction.
A single muscle cell only needs about one minute to recycle all of its ATP.
An enzyme is a protein that __________.
changes the rate of a metabolic reaction without being consumed by the reaction
elevates the activation energy of a reaction
can catalyze many different reactions
has only primary structure
provides activation energy for the reactions it facilitates
Activation energy can be described as __________.
energy released by a chemical reaction
energy needed to activate an enzyme
energy needed to activate the reactants and trigger a chemical reaction
Which choice describes the process scientists use to mimic a natural genetic process of cells?
What best explains the observation that an enzyme is selective in the reaction it catalyzes?
Molecules and active sites vary in size; only properly sized molecules can fit.
There is a precise compatibility between an enzyme's active site and the substrate molecule.
Specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.
Active sites carry slight negative charges, and substrates tend to carry slight positive charges.
Reaction-specific enzymes assume a fit by "folding around" the substrate molecules.
Many metabolic pathways are slowed by inhibiting an enzyme required for a particular product. What is this process called?
A primary function of the cell membrane is to __________.
house genetic information
regulate the passage of materials into and out of the cell
digest waste material for disposal
provide a cell skeleton
The passive movement of molecules from an area of higher concentration to an area of lower concentration is called _____.
An animal cell placed in a hypertonic solution will __________.
gain water by osmosis and lyse
experience neither a net gain nor a net loss of water
lose water by osmosis and shrivel
gain water by pinocytosis and lyse
lose water by active transport and shrivel
In osmosis, water always moves toward the _____ solution, that is, toward the solution with the _____ solute concentration.
hypotonic ... lesser
isotonic ... greater
hypertonic ... greater
hypotonic ... greater
hypertonic ... lesser
Which one of the following is an example of osmosis?
food in the refrigerator starting to taste like onions because the onions in the vegetable bin have been stored unwrapped
the distant sound of church bells ringing
the smell of freshly baked pie spreading throughout a house
the smell of a backed-up sewer coming from a bathroom
the movement of a drink of water eventually into the cells lining the small intestine
Which term is used to describe an animal's ability to survive if the cells are exposed to a hypotonic or hypertonic environment?
Plant cells can better tolerate exposure to hypotonic solutions than can animal cells. Which one of the following helps to best explain why plant cells can better tolerate hypotonic solutions?
Chloroplasts consume the extra water in photosynthesis, decreasing the swelling.
The veins in plants drain away the extra water from the plant cells.
The hot sun on plant cells causes any extra water to evaporate.
The rigid cell walls limit how far plant cells can expand and exert a back pressure to limit further water uptake.
Stomata in plant cell leaves quickly drain excess water from the cells.
The concentration of calcium in a cell is 0.3%. The concentration of calcium in the surrounding fluid is 0.1%. How could the cell obtain more calcium?
conservation of energy
The use of energy to move molecules across a membrane defines _____.
Which one of the following terms is sometimes called "cell eating"?
A cell may receive a stimulus from the outside environment or from a signaling molecule __________.
by receptor-mediated endocytosis
through a receptor protein in the plasma membrane
through active transport
A characteristic of phospholipids that makes them a candidate for the first organic compounds on Earth to be related to life is their ability to __________.
self-assemble into simple membranes
mix freely with water
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