Cell Biology Questions
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Energy from exergonic reactions is transferred from place to place in cells via __________.- microscopic channels - energy-carrier molecules such as ATP - glucose - mitochondria
The amino acid threonine is converted to isoleucine by a sequence of five enzymatic reactions. When isoleucine levels are high, the first reaction in this sequence is "turned off." This is an example of _____. - substrate activation - feedback inhibition - competitive inhibition - coenzyme activation
The speed of a reaction is determined mostly by its _____. - temperature - volume - activation energy - potential energy
Which of the following statements is/are correct about how enzymes work? - Enzymes catalyze specific chemical reactions because the shape of their active site allows only certain substrate molecules to enter. - The product(s) enter the enzyme active site in specific orientations. - Enzymes can function over a wide range of temperatures. - The substrate(s) enter the enzyme's allosteric site.
The second law of thermodynamics states that __________. - energy transactions are completely efficient - energy cannot be created or destroyed - disorder tends to increase over time - energy is constantly being created
If all matter tends toward increasing randomness and disorder, how can life exist on Earth? - Living things do not obey the second law of thermodynamics. - There is a constant input of energy from the sun. - Living things do not require energy. - More energy is created to replace the energy destroyed by the disorder.
The most important reason a particular enzyme can function only within certain limits of temperature, salt conditions, and pH is that __________. - changes in temperature, salt, and pH change the shape of an enzyme - changes in temperature, salt, and pH alter the amount of substrates - changes in temperature, salt, and pH alter the amount of enzyme present - changes in temperature, salt, and pH lower the activation energy of a reaction
Which of the following situations illustrate(s) the coupling of exergonic to endergonic reactions in cells? - the breakdown of glucose, producing ATP - the active transport of sodium into the cell - the movement of a muscle powered by the hydrolysis of ATP - the diffusion of oxygen into the cell and carbon dioxide out of the cell - the production of a protein by dehydration synthesis - absorption of water by a root cell
Which of the following is NOT used by an enzyme to promote a reaction?- bond distortion - increased kinetic energy of substrate - temporary chemical bonds - electrical interactions - substrate orientation
Which of the following is NOT true about enzymes? - Enzymes are proteins. - Enzymes are biological catalysts. - Enzymes are very specific for the reactions that they catalyze. - Enzymes, like other reactants, are used up in the reactions that they catalyze.
A substance that is acted on by an enzyme to produce a product is called a(n) _____. - allosteric inhibitor - coenzyme - substrate - electron carrier
The second law of thermodynamics relates the organization of matter to energy. It states that unless additional energy is used, the orderliness of a system tends to _____, whereas entropy _____. - increase, decreases - decrease, increases - stay the same, increases - decrease, stays the same
If the products of a reaction have more energy than the reactants, then we say this is a(n) __________. - exergonic reaction - endergonic reaction - activation energy-requiring reaction - coupled reaction
A coupled reaction is one in which __________. - a couple of reactants are brought together to form a product - one reaction immediately follows another reaction - energy from an exergonic reaction is used to drive an endergonic reaction - a couple of reactions occur close to one another in the cell
Enzymes are a class of proteins that catalyze chemical reactions in cells. Like all other catalysts, they speed up chemical reactions by __________. - lowering the activation energy of the reaction - releasing energy for the reaction - making the reaction endergonic - elevating the activation energy of the reaction
Potential energy represents __________. - the energy of motion - stored energy - newly created energy - energy that is unavailable for use
Why do most reactions occur more rapidly at high temperature? - Molecules move more rapidly at higher temperatures. - Collisions between molecules are more frequent. - Collisions will be hard enough to force electron shells to interact. - Molecules move more rapidly, allowing for more frequent and forceful collisions between electron shells.
__________ will occur spontaneously. - Exergonic reactions - Endergonic reactions - Both exergonic and endergonic reactions - Neither exergonic nor endergonic reactions
How is ATP used in energy metabolism? - ATP synthesis is coupled to the endergonic reactions of glucose synthesis. - The reactions of protein synthesis lead to ATP synthesis. - ATP synthesis is coupled to an exergonic reaction, the breakdown of glucose. - ATP hydrolysis increases entropy.
Lysosomes have an acidic interior (pH = 5), unlike the rest of the cell (pH = 7). Lysosomal enzymes are most active at _____. - pH = 4 - pH = 5 - pH = 7 - pH = 9