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2024 OFFICIAL GUIDE TO THE MCAT EXAM WITH CORRECT ANSWERS
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2024 OFFICIAL GUIDE TO THE MCAT EXAM WITH CORRECT ANSWERS
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Official Guide to the MCAT ExamStudy online at https://quizlet.com/_88bvyz
1. BB section
2. What is the difference between Understand the difference between Type I
Type I and Type II muscle and Type II Muscle fibers.
fibers?
Type I (slow-twitch) - mitochondria rich,
slow twitch (slow conduction velocity), slow
contraction speed, aerobic, long, low pow-
er, long duration, fatigue-free.
Type II fibers - two types, Type IIA, and Type
IIB. Type IIA are intermediate between I and
IIB.
Type IIB are white, fast contraction
speed, fast-twitch (fast conduction veloci-
ty), anaerobic, short, easily fatigue, power,
ATP from creatine phosphate.
3. QUESTION 1: D. got this wrong because i did not un-
The muscle subtype represent- derstand which culture (A, B or C) related
ed by Culture C is LEAST likely to which muscle type in the table in the
to be characterized by: passage.
A. a fast rate of muscle contrac-
tion. Don't be fooled by this answer choice. Even
B. the ability to engage in ox- though in the "Activity used for" section it
idative and anaerobic respira- states anaerobic. The type IIA muscle fiber
tion. still exhibits "high oxidative capacity" which
C. the presence of medi- means it would be able to perform BOTH
um-sized motor units. anaerobic and aerobic processes.
D. low densities of mitochon- Based on the passage, it can be inferred
dria and capillaries. that Culture B is I, Culture A is Type IIx.
Further, Culture C is then Type IIa. There
are many clues to figure this out. If this is
the case, Type IIa will have HIGH density of
mitochondria for oxidative phosporylation
(which is indicated as being high for IIA).
make sure to look at LEAST likely in the
passage.
, Official Guide to the MCAT Exam
Study online at https://quizlet.com/_88bvyz
4. QUESTION 2: C. got it wrong, chose A, bc did not know
Which steps involved in the that ca reuptake required ATP
contraction of a skeletal mus- Also known as "cross bridge dissociation".
cle require binding and/or hy- This occurs after the power stroke to put the
drolysis of ATP? myosin head into a low energy position II.
I. Dissociation of myosin head Calcium is required to expose the myosin
from actin filament binding sites through the conformational
II. Attachment of myosin head change in tropomyosin III. The conforma-
to actin filament tional change among actin and myosin re-
III. Conformational change that quires the hydrolysis of ATP which is what
moves actin and myosin fila- allows the power stroke a.k.a. the muscle
ments relative to one another contraction caused when myosin pulls actin
IV. Binding of troponin to actin towards the middle of the sarcomere VI.
filament Reuptake of calcium requires ATP because
V. Release of calcium from the the ions are moving against their concen-
sarcoplasmic reticulum tration gradient into the SR
VI. Reuptake of calcium into the
sarcoplasm
A. I, II, and III only
B. II, III, and IV only
C. I, III, and VI only
D. III, IV, and VI only
5. What are the steps for muscle
contraction?
6. QUESTION 3: A. because we know ach causes con-
Does the release of Ach in tractions also according to the passage it
skeletal muscle cells, cause de- states that ach caused a cell culture to
polarization or hyperpolariza- retain contractile activity for longer than 30
tion? mins.
, Official Guide to the MCAT Exam
Study online at https://quizlet.com/_88bvyz
The addition of acetylcholine Acetylcholine is released at the neuromus-
to the medium most likely in- cular junction where it binds to receptors
duced: on the muscle cells and, depending on the
type of muscle cell, causes depolarization
a. depolarization of the cell or hyperpolarization of the cell membrane.
membrane that resulted in con- In skeletal muscles, acetylcholine binds to
traction. its receptors, which leads to depolarization
b. repolarization of the cell of the muscle cell membrane and muscle
membrane that resulted in re- contraction.
laxation.
c. hyperpolarization of the cell
membrane that resulted in con-
traction.
d. depolarization of the cell
membrane that resulted in re-
laxation.
7. QUESTION 4: A.
The terminal electron acceptor I chose C but thats wrong bc NADH re-
in lactic acid fermentation is: duces pyruvate to produce lactate and re-
a. pyruvate. generate NAD+ so glycolysis can continue.
b. oxygen.
c. NAD+. You have to know the key difference be-
d. water. tween fermentation and aerobic respiration
for this question. In aerobic respiration, oxy-
gen is an electron acceptor while in fermen-
tation, pyruvate is an electron acceptor to
regenerate NAD+, so glycolysis can con-
tinue. In this process, NADH reduces pyru-
vate to produce lactate. Therefore, pyruvate
serves as the electron acceptor in produc-
tion of lactate.
Remember, 2 ATP produced in fermenta-
tion process per mol of glucose (which oc-
curs when no O2 present in eukaryotes)!
In glycolysis, however, 32 ATP is produced
per mol of glucose. This is a vast difference.
, Official Guide to the MCAT Exam
Study online at https://quizlet.com/_88bvyz
8. QUESTION 5: A. got this correct but because i guessed.
What control experiment was I did not understand the terminology but
necessary to ensure that the rationalizing it out, if you are trying to test
apparent subcellular locations that the location of MS2 did not affects the
of the cat6xbs and lacY6xbs locations of cat and lac then you must take
transcripts were NOT skewed out cat and lac and see where MS2 is and
by the location preference of then add cat and lac back in and see where
the bound MS2-GFP? it is.
a. Determination of expression
of MS2-GFP in cells that lacked
the 6xbs insertion upstream of
the cat and lacY genes
b. Use of E. coli cells that ex-
pressed only MS2 instead of
the MS2-GFP fusion protein
c. Insertion of the 6xbs region
upstream of both the cat and
lacY genes in the same cells
d. Determination of expression
of both MS2 and GFP as sep-
arate proteins rather than as a
fusion protein
9. QUESTION 6: D. got this correct but because I did was
Which other cellular compo- thinking of cell membrane components but
nents are likely to be locatedneeded to recognize that the passage was
near the lacY6xbs transcript in
about E.coli (a prokaryote).
the cell membrane? The passage states lacY is located near
the cell membrane, so the answer will have
A.Proteins and glycolipids to be the cell components of an E.coli mem-
B. Glycolipids and sterols brane (a prokaryote). E.coli is a gram neg-
C. Sterols and phospholipids ative cell. Gram negative cells have a thin
D. Phospholipids and proteins peptidoglycan layer and a outer cell wall
(which contains LPS). E.coli membranes,
like all cells, have plasma membranes (in-
ner most) and this plasma membrane con-
tains 75% protein, and 25% phospolipids.
Typically, these are the major two compo-
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