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Which term most precisely describes the cellular process of breaking down large molecules into smaller ones?
catabolism
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Describe how anabolic pathways function
They consume energy to build up polymers from monomers.
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First law of thermodynamics?
Energy cannot be created or destroyed.
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For living organisms, which of the following is an important consequence of the first law of thermodynamics?
The organism ultimately must obtain all of the necessary energy for life from its environment.
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Whenever energy is transformed, there is always an increase in the
entropy of the universe.
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Which types of reactions would decrease the entropy within a cell?
anabolic reactions
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Which of the following is the smallest closed system?
-a cell
-an organism
-an ecosystem
-Earth
-the universe
-the universe
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What is true of metabolism in its entirety in all organisms?
Metabolism consists of all the energy transformation reactions in an organism.
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ΔG =ΔH - TΔS.
What does each symbol mean?
- ΔG = Gibbs' free energy
- ΔH = Enthalpy change
- ΔS = Entropy change
- T = Temperature in Kelvin
- ΔG < 0 , the reaction is spontaneous
- ΔG > 0, the reaction is nonspontaneous
- ΔG = 0, the reaction is at equilibrium
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A system at chemical equilibrium
can do no work.
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What is true for all exergonic reactions?
The reaction proceeds with a net release of free energy.
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Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell?
a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway
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Which of the following shows the correct changes in thermodynamic properties for a chemical reaction in which amino acids are linked to form a protein?
+ΔH, -ΔS, +ΔG
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When glucose monomers are joined together by glycosidic linkages to form a cellulose polymer, the changes in free energy, total energy, and entropy are as follows:
+ΔG, +ΔH, -ΔS.
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A chemical reaction that has a positive ΔG is correctly described as
endergonic
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Why is ATP an important molecule in metabolism?
It provides energy coupling between exergonic and endergonic reactions.
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When 10,000 molecules of ATP are hydrolyzed to ADP and i in a test tube, about twice as much heat is liberated as when a cell hydrolyzes the same amount of ATP. Which of the following is the best explanation for this observation?
Reactant and product concentrations in the test tube are different from those in the cell.
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Which of the following is most similar in structure to ATP?
an RNA nucleotide
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What is true concerning catabolic pathways?
They supply energy, primarily in the form of ATP, for the cell's work.
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When chemical, transport, or mechanical work is done by an organism, what happens to the heat generated?
It is lost to the environment.
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When ATP releases some energy, it also releases inorganic phosphate. What purpose does this serve (if any) in the cell?
The phosphate may be incorporated into any molecule that contains phosphate.
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What is the difference (if any) between the structure of ATP and the structure of the precursor of the A nucleotide in RNA?
There is no difference
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What is true about enzyme-catalyzed reactions?
The reaction is faster than the same reaction in the absence of the enzyme.
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Reactants capable of interacting to form products in a chemical reaction must first overcome a thermodynamic barrier known as the reaction's
activation energy
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A solution of starch at room temperature does not readily decompose to form a solution of simple sugars because
the activation energy barrier for this reaction cannot be surmounted.
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Enzymes increase the rate of a reaction by
lowering the activation energy barrier
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During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the
-20 kcal/mol
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The active site of an enzyme is the region that
is involved in the catalytic reaction of the enzyme.
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According to the induced fit hypothesis of enzyme catalysis
The binding of the substrate changes the shape of the enzyme's active site.
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Mutations that result in single amino acid substitutions in an enzyme
may affect the physicochemical properties of the enzyme such as its optimal temperature and pH.
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Increasing the substrate concentration in an enzymatic reaction could overcome which of the following?
competitive inhibition
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Enzymes increase the rate of chemical reaction by
lowering activation energy barriers.
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Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n)
cofactor necessary for enzyme activity.
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When you have a severe fever, what grave consequence may occur if the fever is not controlled?
change in the tertiary structure of your enzymes
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How does a noncompetitive inhibitor decrease the rate of an enzyme reaction?
by changing the shape of the enzyme's active site
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The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as
feedback inhibition
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Enzyme cooperativity - a substrate molecule bound to an active site of one subunit promotes
substrate binding to the active site of other subunits.
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Allosteric enzyme regulation is usually associated with
an enzyme with more than one subunit
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Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?
localization of enzymes into specific organelles or membranes
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An important group of peripheral membrane proteins are enzymes such as the phospholipases that cleave the head groups of phospholipids. What properties must these enzymes exhibit?
water solubility
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How might an amino acid change at a site distant from the active site of the enzyme alter the enzyme's substrate specificity?
by changing the shape of the protein
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Which curve(s) on the graphs may represent the temperature and pH profiles of an enzyme taken from a bacterium that lives in a mildly alkaline hot springs at temperatures of 70°C or higher?
curves 3 and 5
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Which temperature and pH profile curves
on the graphs were most likely generated from analysis of an enzyme from a
human stomach where conditions are strongly acid?
curves 1 and 4
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Interpret this.
ATP is a molecule that acts as an intermediary to store energy for cellular work.
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How do cells use the ATP cycle shown in the figure?
Cells use the cycle to recycle ADP and phosphate.
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Catabolism is to anabolism as exergonic is to ________.
endergonic
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Most cells cannot harness heat to perform work because
temperature is usually uniform throughout a cell.
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Which of the following metabolic processes can occur without a net influx of energy from some other process?
A) ADP + i → ATP + H2O
B) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
C) 6 CO2 + 6 H2O → C6H12O6 + 6 O2
D) amino acids → protein
E) glucose + fructose → sucrose
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
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If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to
add more of the enzyme.
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Some bacteria are metabolically active in hot springs because
their enzymes have high optimal temperatures.
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If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?
Nothing; the reaction will stay at equilibrium.
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