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MCB 3020 Exam Questions and Answers Latest Update

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Define thermodynamics - Answer-The study of energy transformations that occur in a collection of matter. List the laws of thermodynamic and describe their relevance in the chemical reactions - Answer-First:-energy can be neither created nor destroyed-total energy in universe remains constant-how...

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  • October 9, 2024
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  • 2024/2025
  • Exam (elaborations)
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  • mcb 3020 exam questions and answers latest update
  • define thermodynamics answer the study of energy

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MCB 3020 Exam Questions and Answers
Latest Update 2024-2025
Define thermodynamics - Answer-The study of energy transformations that occur in a
collection of matter.

List the laws of thermodynamic and describe their relevance in the chemical reactions -
Answer-First:-energy can be neither created nor destroyed-total energy in universe
remains constant-however energy may be redistributed either within a system or
between the system and its surroundings
second:-physical and chemical processes proceed in such a way that the disorder of the
universe increases to the maximum possible

Define the standard reduction potential. - Answer-- the tendency of species to be
reduced or to be oxidized
- the emf generated at 25 C and pH 7 by a sample half-cell with respect to a reference
half cell

Why does aerobic growth generate the highest amount of energy (ATP)? How does this
value play a role in the organization of the electron transport system? - Answer-(more
negative E0 = better electron donor, more positive E0 = better electron acceptor)*The
greater the difference between the E0 of the donor and the E0 of the acceptor= the
more neg. the delta G bc more energy is released from redox rxn

Compare E'0 of aerobic and anaerobic respiration. - Answer-OXYGEN HAS
GREATEST E0Anaerobic generally yields less energy because E0 of electron acceptor
is less positive than E0 of O2. Aerobic respiration generates the greatest amount of
energy

True or false: the first electron carrier in the ETC has the most negative E'0? - Answer-
True, In the electron transport chain, electrons move from elcetron carriers with more
negative E0 to electron carriers with a more positive E0

True or false: a redox pair with more negative reduction potential will spontaneously
donate electrons to a pair with more positive potential. - Answer-true

True or False: The more positive the reduction potential, the greater the affinity for
electrons. - Answer-true

True or false: ETC are associated with plasma membranes or mitochondrial/chloroplast
internal membranes. - Answer-True, Eukarya=mitochondira, archaea/bacteria=cell
membrane

,True or false: all molecules found in the ETC are capable of transferring both electrons
and protons. - Answer-False, Electrons are passed down the electron transport chain
and protons are pumped across the membrane creating a PMF.

Describe the flow of electron in fermentation and respiration. What happened to the
electron in fermentation and respiration? - Answer- Respiation: Electrons are passed
down the electron transport chain and protons are pumped across the membrane
creating a PMF. Electrons either accepted by O2 (aerobic) or EXOGENOUS organic
acceptors (anaerobic)
Aerobic-
1. macromolecules broken down into monomers
2. glucose undergoes glycolysis
3. Acetyl-CoA oxidized in Krebs cycle producing lil ATP & a lot of NADH and FADH2.
(these carry electrons to ETC as stated above^)
Fermentation:
-no PMF (use ATP synthase in opposite direction) or ETC or oxi phos.
- electron acceptor is ENDOGENOUS (pyruvate)
(1) NADH is oxidized to NAD+;
(2) O2 is not needed;
(3) the electron acceptor is often either pyruvate or a pyruvate derivative
(4) an ETC is not used to reoxidize NADH, and this reduces the ATP yield per glucose
significantly

Describe how enzymes are involved in chemical reactions: activation energy, lowering
E0. - Answer-**Enzyme lowers Activation Energy and speeds up rate of reaction•carry
out reactions at physiological conditions•Act as Protein catalysts-high specificity for the
reaction catalyzed and the molecules acted on-Increases the rate of a reaction without
being permanently altered•Substrates = reacting molecules•Products = substances
formed by reaction•Some enzymes are composed solely of one or more polypeptides

Define apoenzyme - Answer-protein portion of an enzyme

Define cofactor - Answer-an ion or molecule (nonprotein) that binds to an enzyme
before substrates can bind

Define prosthetic group - Answer-non protein, organic substance; FIRMLY attached
(opposite of coenzyme)

e.g. heme group of hemoglobin

What is the significance of cofactors - Answer--cofactors are neccessary for an enzyme
to function properly

how are enzymatic activities regulated and inhibitted? - Answer--Enzymes have an
optimal pH and temp. range where their activity is highest.-Can be inhibited by changes
in:temp(alters h-bonds)pH(affects ionic properties)

, How does the use of sulfanilamide as a competitive inhibition control enzymes involved
in the synthesis of folic acid? - Answer-a competitive inhibitor is sulfanilamide (a sulfa
drug), which inhibits the enzyme whose normal substrate is para-aminobenzoic acid
(PABA):PABA is an essential nutrient used by many bacteria in the synthesis of folic
acid, a vitamin that fuctions as a coenzyme. When sulfanilamide is administered to
bacteria, the enzyme that normally converts PABA to folic acid combines instead with
sulfanilamide. Folic Acid combines instead with sulfanilamide. Folic Acid is not
synthesized and the bacteria cannot grow.

What is the role of prosthetic groups? - Answer-saturation of the substrate molecule. (as
conc. of subs. inc, saturation of enzymes inc.)

Ribozymes vs enzymes
what are they made of? Describe the role of ribozymes in self-splicing. - Answer-A
ribozyme is a ribonucleic acid (RNA) fragment that can act as an enzyme that catalyzes
a chemical reaction. The ribozyme catalyses specific reactions in a similar way to that of
protein enzymes. RNA Self splicing is a form of RNA processing in which a newly made
precursor messenger RNA transcript is transformed into a mature messenger RNA.
During splicing, introns are removed and exons are joined together.

Enzymes are a globular protein.

Distinguish allosteric regulation and covalent modification - Answer-Allosteric
regulation:a small molecule called an allosteric effector binds reversibly to a regulatory
site away from the catalystic site, causing a conformational change in the enzyme which
could help activate or inhibit enzyme activity.
Covalent modification:chemical groups are added to or removed from the enzyme
(covalent attachment), affecting its activity. ie, phosphorylation and dephosphorylation

list and describe the effects of environmental factors on enzymatic activities. - Answer-
1. Substrate concentration ("puzzle piece" required by enzyme to operate) *more
substrate= inc. in enzyme activity until it reaches the saturation level
2. pH
3. Temperature (affects h-bonds)
Enzyme denatures when temp and pH rise too much above optima causing the
enzyme's structure and activity to lose

What chemical intermediate links pyruvate to TCA? - Answer-Acetyl-COA

Compare respiration and fermentation - Answer-Fermentation is energy being released
from O2 while respiration is cells obtaining energy from food.

Why does anaerobic respiration and fermentation make less ATP than aerobic
respiration? - Answer-Anaerobic respiration produces less ATP than aerobic respiration

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