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Chapter 5: The Working Cell
This activity contains 10 questions.
The plasma membrane is selectively permeable. Which of the following can pass freely through the membrane with no assistance?
glucose and lactose
sodium and hydrogen ions
starch and cellulose
oxygen and carbon dioxide
bacteria and viruses
In oil-based liquids, phospholipids are arranged so that their _____ face outward and their _____ are orientated inward.
hydrophobic heads … hydrophilic tails
hydrophilic heads … hydrophobic tails
nonpolar heads … polar tails
hydrophobic tails … hydrophilic heads
hydrophilic tails … hydrophobic heads
The movement of molecules from an area of higher concentration to an area of lower concentration is called _____.
When water moves toward the solution with the _____ solute concentration, the solution is _____.
greater … isotonic
greater … hypertonic
lesser … hypertonic
greater … hypotonic
lesser … hypotonic
Our cells require glucose to produce energy. Consider a cell where the external concentration of glucose has dropped to 5%, but the internal concentration is at 20%. How does the cell obtain more glucose?
Energy can be classified as either potential or kinetic. Which of the following is an example of kinetic energy?
a hot cup of coffee
a bowling ball placed on the top shelf of a closet
the mercury within a thermometer
a car parked by the side of the road
Reactions can be exergonic or endergonic. Which of these reactions is endergonic?
the heating that results when water mixes with sodium hydroxide
the burning of wood
the generation of light by fireflies
hydrolysis of ATP (ATP → ADP + P)
Through an _____ reaction, ATP is hydrolyzed into ADP by _____ and _____ energy.
endergonic … losing a phosphate group … requiring
exergonic … gaining a phosphate group … releasing
endergonic … gaining a phosphate group … releasing
exergonic … losing a phosphate group … releasing
exergonic … losing a phosphate group … requiring
During enzymatic reactions, substrates are converted to products. A property of enzymes that facilitates this reaction is that they are catalysts and therefore _____.
provide activation energy for the reactions they facilitate
change the rate of a reaction without being consumed by the reaction
can make an endergonic reaction exergonic
elevate the activation energy barrier so the molecules will not spontaneously degrade
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.
Specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.
Molecules and active sites vary in size; only properly sized molecules can fit.
Reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.
It is because of polarity compatibilities. Active sites contain electronegative atoms, whereas substrates tend to carry slight positive charges.
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