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Ch. 6

Molecular Biology

an organism's metabolism transforms ____ and _____. Matter, energy
The totality of an organism's chemical reactions is called ______. metabolism
In a _____ ________, a specific molecule is altered in a series of defined steps, resulting in a product. metabolic pathway
some metabolic pathways release energy by breaking down complex molecules to simpler compounds. These degradative processes are called breakdown pathways, or _______ _______. catabolic pathways
_______ _______ consume energy to build complicated molecules from simpler ones; they are sometimes called biosynthetic pathways. anabolic pathways
_____ is the study of how energy flows through living organisms. bioenergetics
The study of transformations that occur in a collection of matter is called ____. thermodynamics
Which law states the following? The energy of the universe is constant; energy can be transformed, but cannot be created or destroyed. Also called the "principle of conservation of energy" the first law of thermodynamics
Which law states the following? Every energy transfer or transformation increases the entropy of the universe. the second law of thermodynamics
_____ is a measure of disorder or randomness entropy
a process that can occur without an input of energy is called a ______ _____. spontaneous process
A process that cannot occur on its own is said to be _____; it will happen only if energy is added to the system. nonspontaneous
For a process to occur spontaneously, it must increase the _____ of the universe. entropy
at an organismal level, complex and beautifully ordered structures result from ____ ____ that use simpler starting materials. biological processes
the __-___ change of a reaction tells us whether or not the reaction occurs spontaneously. Free-energy
T or F? Free energy is the portion of a system's energy that can perform work when temperature and pressure are uniform throughout the system, as in a living cell. True
___ _ represents the difference between the free energy of the final state and the free energy of the initial state. delta G
T or F? We can't think of free energy as a measure of a system's instability- it's tendency to change to a more stable state. False
An ___ ____ proceeds with a net release of free energy. exergonic reaction
an ______ reaction is one that absorbs free energy from its surroundings. endergonic
What are the 3 main kinds of work a cell does? chemical work, transport work, mechanical work
the use of an exergonic process to drive an endergonic one is called ____ _____. energy coupling
ATP contains Sugar ribose, nitrogenous base adenine, and a chain of 3 phosphate groups bonded to it.
T or F? Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways. True
T or F? The coupling of ATP hydrolysis to the production of a proton gradient across a membrane by a proton pump is an example of energy transformation. False
T or F? Organisms acquire energy from, and lose energy to, their surroundings. True
consider the growth of a farmer's crop over a season. What would be a possible limitation imposed by the 1st or 2nd law of thermodynamics? to obey the 1st law, the crops must represent an open system.
state the relevance of the 1st law of thermodynamics to biology. energy can be freely transformed among different forms as long as the total energy is conserved.
What is the most abundant form of energy in a cell? chemical energy
T or F? According to the 2nd law of thermodynamics, the decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists. True
if the entropy of a living organism is decreasing, what is most likely to be occurring simultaneously? energy input into the organism must be occurring to drive the decrease in entropy.
which molecule has the most free energy per molecule? a starch olecule
An exergonic (spontaneous) reaction is a chemical reaction that ____. releases energy when proceeding in the forward direction.
T or F? The following reaction is endergonic: glucose + fructose > sucrose True
Molecules A & B contain 110 kcal/mol of free energy & molecules C & D contain 150 kcal/mol of energy. A & B are converted to C & D. What can be concluded? the reaction that proceeds to convert A & B to C & D is endergonic; the products are more organized than the reactants.
What determines the sign of delta G for a reaction? the free energy of the reactants & the free energy of the products.
metabolic pathways in cells are typically far from equilibrium. what process might tend to keep these pathways away from equilibrium? 1) the continuous removal of the products of a pathway to be used in other reactions. 2) an input of free energy from outside the pathway.
T or F? the proton movement against a gradient of protons would be an example of cellular work accomplished with the free energy derived from the hydrolysis of ATP. True
The hydrolysis of ATP drives cellular work by ____. releasing free energy that can be coupled to other reactions.
ATP hydrolysis being used to drive the active transport of an ion into the cell against the ion's concentration gradient is an example of ____ _____. energy coupling
much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. these bonds are unstable because ____. the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP.
when 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. explain this observation. in the cell, the hydrolysis of ATP is couple to other endergonic reactions.
what best characterizes the role of ATP in cellular metabolism? the free energy released by ATP hydrolysis may be coupled to an endergonic prose via the formation of a phosphorylated intermediate.
the formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which reaction or pathway? the hydrolysis of ATP
which functional group is associated with a release of energy when removed from the carbon skeleton with water that cells can harvest to perform many functions? phosphate
a chemical reaction is designated as exergonic rather than endergonic when ____. the potential energy of the products is less than the potential energy of the reactants.
what is changed by the presence of an enzyme in a reaction? the activation energy
what do the sign and magnitude of the delta G of a reaction tell us about the speed of the reaction? neither the sign nor the magnitude of delta G have anything to do with the speed of a reaction.
how do enzymes lower activation energy? by locally concentrating the reactants
T or F? enzymes speed up the rate of the reaction without changing the DG for the reaction. True
Enzymes can lower the ____ ____ of reactions, but they cannot change the equilibrium point because they cannot change the net energy output. activation energy
a plot of activation rate (velocity) against temperature for an enzyme indicates little activity at 10 degrees C & 45 degrees C, with peak activity at 35 degrees C. explain the low velocity at 10 degrees C. There is too little activation energy available
T or F? An enzyme is consumed during the reaction it catalyzes. False
T or F? The active site of an enzyme may resemble a groove or pocket in the surface of a protein into which the substrate fits. True
what is meant by the "induced fit" of an enzyme? the enzyme changes its shape slightly as the substrate binds to it.
T or F? Heat form the environment is necessary for substrates to get over the activation energy barrier. the kinetic energy of the substrates is increased as the amount of heat in the system is increased. True
above a certain substrate concentration, the rate of an enzyme-catalyzed reaction drops as the enzymes become saturated. what would lead to a faster conversion of substrate into product under these saturated conditions? an increase of concentration in enzyme & increasing the temperature by a few degrees.
which of the following actions would NOT affect the rate of an enzyme reaction? heating the enzyme, cooling the enzyme, substrate concentration, pH None of the listed responses are correct
enzyme activity is affected by pH because ______. high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site.
T or F? the action of competitive enzyme inhibitors may be reversible or irreversible. True
the process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of _____. allosteric regulation
T or F? allosteric proteins are sensitive to environmental conditions, are acted on by inhibitors, & exist in active and inactive conformations. True
Created by: KellyClark