General Biology - Campbell Ch 8

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Difference between anabolic and catabolic pathways

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

What situation does not represent an energy transformation?

the coupling of ATP hydrolysis to the production of a proton gradient across a membrane by a proton pump.

Organisms are described as thermodynamically open systems. What statement is consistent with this?

Organisms acquire energy from, and lose energy to, their surroundings.

Consider the growth of a farmer's crop over a season.

To obey the first law, the crops must represent an open system.

What states the relevance of the first law of thermodynamics of 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

What is an example of the second law of thermodynamics as it applies to biological reactions?

The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.

What is true according to the second law of thermodynamics?

The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists.

If the entropy of a living organism is decreasing, what is most likely to occur simultaneously?

Energy input into the organism must be occuriring to drive the decrease in entropy.

What has the most free energy per molecule?

starch

The electronic arrangement in what molecule means that this molecule has greater free energy than others...

methane

What part of the equation (delta)G = (delta)H - T(delta)S tells you if a process is spontaneous?

(delta) G

If, during the process, the system becomes more ordered, then ....

(delta) S is negative

When one molecule is broken down into six component molecules, what will always be true?

(delta) S is positive

An exergonic (spontaneous) reaction is a chemical reaction that ...

releases energy when proceeding in the forward direction.

An example of a endergonic reaction

glucose + fructose --> sucrose

Molecules A and B contain 110kcal/mol of free energy and molecules B and C contain 150kcal/mol of energy. A and B are converted to C and D. What can be concluded?

The reaction that proceeds to convert A andB to C and D is endergonic, the products are more organized than the reactants.

What is an example of the cellular work accomplished with the free energy derived from the hydrolysis of ATP, involved in the production of electrochemical gradients?

proton movement against a gradient of protons

In general, the hydrolysis of ATP drives cellular work by ...

releasing free energy that can be couples to other reactions

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. Why would this be?

In the cell, the hydrolysis of ATP is coupled to other endergonic reactions

What best characterizes the role of ATP in cellular metabolism?

The free enegy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to what reaction/pathway?

the hydrolysis of ATP

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 do the sign and magnitude of the (delta) G of a reaction tell us about the speed of the reaction?

Neither the sign nor 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

What is meant by the "induced fit" of an enzyme?

The enzyme changes its shape slightly as the substrate binds to it.

Enzyme activity is affected by pH because...

high or low pH may disrupt the hydrogen bonding or ionic interactions and thus change the shape of the active site.

Enzyme inhibitors...

the action of competitive inhibitors may be reversible or irreversible.

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

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. What explains this decrease?

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from the binding at the active site.

Under most conditions, the supply of energy by catabolic pathways is regulated by the demand for energy by anabolic pathways. Considering the role of ATP formation and hydrolysis in energy coupling of anabolic and catabolic pathways, what statement...

high levels of ADP act as an allosteric activator of catabolic pathways

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