Chapter 8 Mastering biology
Based on the graph, what is the optimal pH for pepsin activity?
A pH of 2.0 demonstrates the peak activity for pepsin.
When properly aligned, the enzyme and substrate from an enzyme-substrate (ES) _____.
complex
An enzyme is_______ when it loses its native conformation and its biological activity.
denatured
AC+BC (reactant~lower on graph) ---> AB+CD (product~higher on graph) This graph illustrates a(n) _____ reaction.
endergonic
The reaction ADP + P --> ATP is a(n) _____ reaction.
endergonic
Which of these reactions requires a net input of energy from its surroundings?
endergonic
"Conservation of energy" refers to the fact that _____.
energy cannot be created or destroyed but can be converted from one form to another
When the noncompetitive inhibitor is bonded to the enzyme, the shape of the _____ is distorted
enzyme
A(n) _____ reaction occurs spontaneously.
exergonic
The energy for an endergonic reaction comes from a(n) _____ reaction.
exergonic
The following reaction A --> B + C + heat is a(n) _____ reaction.
exergonic
Select the INCORRECT association.
exergonic ... uphill
Which of these are by-products of cellular respiration?
heat, carbon dioxide, and water
What type of reaction breaks the bonds that join the phosphate groups in an ATP molecule?
hydrolysis
A(n)______ inhibitor bonds to a site on the enzyme that is not the active site
noncompetitive
Chemical energy is a form of _____ energy.
potential
Look at the graph of reaction rate versus substrate concentration for an enzyme. In which region does the reaction rate remain constant?
region C
Refer again to the graph. In which region is the enzyme saturated with substrate?
region C
An enzyme is considered _______ because of its ability to recognize the shape of a particular molecule.
specific
Enzyme inhibitors disrupt normal interactions between an enzyme and its _____
substrate
In a catalyzed reaction a reactant is often called a ____.
substrate
In this reaction _____. The figure shows a scheme of a chemical reaction. The reactants are two molecules, one of which consists of A and B, the other - of C and D. The products are two molecules, one of which consists of A and C, the other - of B and D. The potential energy of molecules AB and CD is higher than the potential energy of molecules AC and BD.
the products have less potential energy than the reactants
What is energy coupling?
the use of energy released from an exergonic reaction to drive an endergonic reaction
Rank these by reaction rate, as measured by the rate of product formation per unit time, from lowest reaction rate to highest reaction rate. To rank items as equivalent, overlap them.
uncatalyzed reaction (lowest) < reaction catalyzed by enzyme A < reaction catalyzed by enzyme B (highest)
AB+CD (reactant~higher on graph) ---> AC+BD (product~lower on graph) In this reaction _____.
. heat has been released to the environment
Based on the graph, what is the optimal pH for trypsin activity?
8
Which of the following statements about equilibrium of chemical reactions is correct? See Concept 8.2 (Page 147) `
A reaction that is at equilibrium is not capable of doing any work.
What can you do to speed the reaction up again?
Add more substrate; it will outcompete the inhibitor and increase the reaction rate
Can you match these prefixes, suffixes, and word roots with their definitions?
Enzyme: ase Change, turn, move: trop outside of: extra heat: therm milk: lac sweet: glyc moving: kin other: allo across: trans under: sub
Consider a situation in which the enzyme is operating at optimum temperature and pH, and has been saturated with substrate. What is your best option for increasing the rate of the reaction?
Increase the enzyme concentration.
Usually a(n) _____ inhibitor forms a covalent bond with an amino acid side group within the active site, which prevents the substrate from entering the active site or prevents catalyctic activity
Irreversible
What is the fate of the phosphate group that is removed when ATP is converted to ADP?
It is acquired by a reactant in an endergonic reaction.
Using the figure to guide your response, select the best explanation for why natural selection might have resulted in the optimal pH for pepsin.
Natural selection favors enzymatic activity of pepsin at a pH of 2.0 because 2.0 is the pH inside the stomach.
Which of the following statements is most likely to be true in the case of the feedback-regulated enzymatic pathway shown?
P4 binds E1 and deactivates it
A ______, such as a vitamin, binds to an enzyme and plays a role in catalysis.
cofactor
A (n)______ inhibitor has a structure that is so similar to the substrate that it can bond to the enzyme just like the substrate
competitive
Which of the following statements about the combustion of glucose with oxygen to form water and carbon dioxide (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O) is correct? See Concept 8.2 (Page 147)
The entropy of the products is greater than the entropy of the reactants.
What can you do to regain the activity of the enzyme?
The enzyme is inactive at this point. New enzyme must be added to regain enzyme activity.
Which of these is exhibiting kinetic energy?
a space station orbiting Earth
A substrate binds to an enzyme at the _________, where the reaction occurs.
active site
The competitive inhibitor competes with the substrate for the ____ of an enzyme
active site
In cells, what is usually the immediate source of energy for an endergonic reaction?
atp
An enzyme is considered ________ because it speeds up a chemical reaction without being used up.
catalyst
In your body, what process converts the chemical energy found in glucose into the chemical energy found in ATP?
cellular respiration
