2010 BSC Review Sheet Chapter 8
2010
Metabolism and Enzymes
Summer
Answer the following questions as completely as possible, referring to your class notes and
textbook. They are designed to help you process and review course material. Questions on
quizzes and exams will also deal with these topics, but will be specific and in a M/C and T/F
format. Quiz and exam questions may not be limited to the topics covered here.
1. Explain the terms metabolism, catabolism, and anabolism and how they are related.
Metabolism the totality of an organisms chemical reactions/an emergent property of
life that arises from interactions between molecules within the orderly environment of the
cell.
Catabolism used to breakdown biomolecules / release energy / cellular respiration
Ex. Sugar glucose is broken down in the presence of oxygen into CO2 and
H2O.
Anabolism used to build molecules / require an input of energy / also called
biosynthetic pathways
ex. Synthesis of a protein from an amino acid
They are all related by occur in a metabolic pathway: catabolism (energy released from
downhill reactions of catabolic pathways can be stored and then used to) anabolism
(drive uphill reactions of anabolic pathways)
Bioenergetics the study of how energy flows through living organisms.
2. Explain the first two laws of thermodynamics and how they apply to cells. Why must cells
be open systems?
1st law of thermodynamics energy can be transferred and transformed, but it cannot
be created nor destroyed. (principle of conservation of
energy)
2nd law of thermodynamics every energy transfer or transformation increases the
entropy of the universe.
Cell must be open systems because:
o Energy and matter can be transferred between the system and its surroundings.
3. What is free energy, how what does it have to do with cellular work? How does free energy
change in chemical reactions or processes; how can DG be calculated? What does the sign of
DG (negative/positive) tell you about a reaction or process?
Free energy the portion of a systems energy that can perform work when
temperature and pressure are uniform throughout the system, as in a
living cell.
Delta G (free energy) = Delta H (enthalpy) T(temp) DeltaS (entropy)
Processes that are negative are spontaneous
Processes that are zero or positive are never spontaneous
4. Relate the terms exergonic and endergonic free to energy change. Then explain how the total
energy and the entropy change in an exergonic or an endergonic reaction or process. Apply
the terms favorable/spontaneous and unfavorable/nonspontaneous. Finally, state whether
stability increases/decreases in each case.
Exergonic energy outward / proceeds with a net release of free energy Delta G is
Negative / favorable - spontaneous /
Endergonic energy inward / absorbs free energy from its surroundings / stores free
energy in molecules / Delta G increases. / nonfavorable - nonspontaneous
5. When can an exergonic reaction drive/fuel an endergonic one? What is the specific
exergonic reaction that is commonly coupled to endergonic ones in cells?
Energy coupling ---- Compare Delta G
Delta G +7.3 kcal/mol Delta G -9 kcal/mol has to be bigger
ATP hydrolysis
Energy + ATP + Pi ATP
6. What type of monomer is ATP? List its parts. How is its chemical energy liberated? How
do cells use ATP to drive endergonic reactions? What other function does ATP have in
cells?
ATP is a monomer of the Nucleotide Adenine
o Sugar ribose, nitrogenous base adenine, and chain of three phosphate groups
Drives chemical, transport, and mechanical work.
7. What is the activation energy (EA) of a reaction? How does heat help reactants to overcome
EA? How do enzymes help reactants to overcome EA?
Activation energy (Ea) energy required to contort the reactant molecules so the
bonds can break
8. Why does a substrate bind the active site of an enzyme? How does it bind? Give examples
of what an active site can physically do to substrates to speed up chemical reactions.
9. What is an allosteric site and how does it affect enzyme functioning? Do all enzymes have
allosteric sites? How about active sites?
no
yes
10. Explain how substrate concentration, enzyme concentration, temperature, and pH affect the
rate of an enzyme catalyzed reaction. Which of these are subject to change in cells?
Substrate concentration
Enzyme concentration
Temperature increase
pH increase 6-8
11. Compare and contrast competitive inhibition with noncompetitive inhibition.
Competitive inhibition:
Noncompetitive inhibition:
12. Explain how feedback inhibition regulates the abundance of a given biomolecule?
13. Describe three ways that cells localize their enzymes for more efficient functioning in.
3 ways cells localize:
o