Key for Unit 2 review questions found at the end of the chapters
The answers to a selection of the review questions are given below.
This value, together with the concentrations of the A and B dictate the rate of the
(choose one from a, b, c, d, or e above).
What is the name for
B or C (energy of activation of the forward reaction, either with or
without the enzyme).
This value is unaffected by heat or the presence of a catalyst (choose one from a, b,
c, d, or e above).
What is its name?
D (change in free energy, or
At equilibrium this value dictates the value of the ratio
([A] x [B]) /
([C] x [D])
(choose one from
a, b, c, d, or e above)
D (change in free energy determines
whether reactants or products are energetically favored)
Explain the lock and key model of enzyme function, including the role played by the
active site of the enzyme.
The active site of an enzyme provides a 2- or 3-dimensional surface, or pocket, that fits
the shape of the substrate rather like a key fits into a lock.
The active site positions the
substrate so that it is more likely to react, and may interact with the substrate to tweak its
bonds, add or subtract electrons from the substrate, and otherwise lower the energy
required for the substrate to reach the transition state energy level.
Draw an energy profile (like that shown in the figure for question 1) for an endergonic
Alter the profile to show the affect of an enzyme.
Label energy of activation,
transition state, products, reactants, and
It’s essentially the diagram above, but
flipped horizontally so that reactants have less energy and products more.
In other words,
run the reaction above in reverse to get the answer to this question.
Metabolism / Chemistry basics
When a chemistry book presents electron shells, it generally emphasizes that shells
represent distinct energy levels.
Electron shells are also said to represent distance
from the positive charges in the nucleus.
Are these two viewpoints contradictory?
Why or why not?
The two viewpoints are not contradictory.
Electrons that are further from the nucleus
have more energy.
This is because electrons are attracted to protons, and forcing
electrons further from the protons thus requires an input of energy (or an opposing force,
such as negatively charged electrons that have all ready occupied the shells closer to the
2. Refer to
the figure to answer the following questions.
Is the forward reaction
(releasing energy overall) or endergonic
(requiring net energy input)?