OFFICIAL GUIDE TO THE MCAT EXAM OFFICIAL GUIDE TO THE MCAT EXAM (2025 EDITION
COMPLETE AAMC-ALIGNED REVIEW, STRATEGIES, AND HIGH-YIELD PRACTICE
Study online at https://quizlet.com/_88bvyz
1. BB section:
2. What is the difference between Type I and Type II muscle fibers?: Understand the
ditterence between Type I and Type II Muscle fibers.
Type I (slow-twitch) - mitochondria rich, slow twitch (slow conduction velocity), slow contraction speed, aerobic, long,
low power, 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 velocity), anaerobic, short, easily fatigue, power,
ATP from creatine phosphate.
3. QUESTION 1:
The muscle subtype represented by Culture C is LEAST likely to be characterized
by:
A. a fast rate of muscle contraction.
B. the ability to engage in oxidative and anaerobic respiration.
C. the presence of medium-sized motor units.
D. low densities of mitochondria and capillaries.: D. got this wrong becaus e i did not under-
stand which culture (A, B or C) related to which muscle type in the table in the passage.
Don't be fooled by this answer choice. Even though in the "Activity used for" section it states anaerobic. The type IIA
muscle fiber still exhibits "high oxidative capacity" which means it would be able to perform BOTH anaerobic and
aerobic processes.
Based on the passage, it can be inferred 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.
4. QUESTION 2:
Which steps involved in the contraction of a skeletal muscle require binding
and/or hydrolysis of ATP?
I. Dissociation of myosin head from actin filament
II. Attachment of myosin head to actin filament
III. Conformational change that moves actin and myosin filaments relative to
one another
, OFFICIAL GUIDE TO THE MCAT EXAM OFFICIAL GUIDE TO THE MCAT EXAM (2025 EDITION
COMPLETE AAMC-ALIGNED REVIEW, STRATEGIES, AND HIGH-YIELD PRACTICE
Study online at https://quizlet.com/_88bvyz
IV. Binding of troponin to actin filament
V. Release of calcium from the sarcoplasmic reticulum
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: C. got it wrong, chose A, bc did not know that ca reuptake required ATP
Also known as "cross bridge dissociation". This occurs after the power stroke to put the myosin head into a low energy
position II. Calcium is required to expose the myosin binding sites through the conformational change in tropomyosin
III. The conformational change among actin and myosin requires the hydrolysis of ATP which is what allows the power
stroke a.k.a. the muscle contraction caused when myosin pulls actin towards the middle of the sarcomere VI. Reuptake
of calcium requires ATP because the ions are moving against their concentration gradient into the SR
5. What are the steps for muscle contraction?:
6. QUESTION 3:
Does the release of Ach in skeletal muscle cells, cause depolarization or hyper-
polarization?
The addition of acetylcholine to the medium most likely induced:
a. depolarization of the cell membrane that resulted in contraction.
b. repolarization of the cell membrane that resulted in relaxation.
c. hyperpolarization of the cell membrane that resulted in contraction.
d. depolarization of the cell membrane that resulted in relaxation.: A. because we
know ach causes contractions also according to the passage it states that ach caused a cell culture to retain contractile
activity for longer than 30 mins.
Acetylcholine is released at the neuromuscular junction where it binds to receptors on the muscle cells and, depending
, OFFICIAL GUIDE TO THE MCAT EXAM OFFICIAL GUIDE TO THE MCAT EXAM (2025 EDITION
COMPLETE AAMC-ALIGNED REVIEW, STRATEGIES, AND HIGH-YIELD PRACTICE
Study online at https://quizlet.com/_88bvyz
on the type of muscle cell, causes depolarization or hyperpolarization of the cell membrane. In skeletal muscles,
acetylcholine binds to its receptors, which leads to depolarization of the muscle cell membrane and muscle contraction.
7. QUESTION 4:
The terminal electron acceptor in lactic acid fermentation is:
a. pyruvate.
b. oxygen.
c. NAD+.
d. water.: A.
I chose C but thats wrong bc NADH reduces pyruvate to produce lactate and regenerate NAD+ so glycolysis can
continue.
You have to know the key ditterence between fermentation and aerobic respiration for this question. In aerobic
respiration, oxygen is an electron acceptor while in fermentation, pyruvate is an electron acceptor to regenerate NAD+,
so glycolysis can continue. In this process, NADH reduces pyruvate to produce lactate. Therefore, pyruvate serves as the
electron acceptor in production of lactate.
Remember, 2 ATP produced in fermentation process per mol of glucose (which occurs when no O2 present in
eukaryotes)! In glycolysis, however, 32 ATP is produced per mol of glucose. This is a vast ditterence.
8. QUESTION 5:
What control experiment was necessary to ensure that the apparent subcellu-
lar locations of the cat6xbs and lacY6xbs transcripts were NOT skewed by the
location preference of the bound MS2-GFP?
a. Determination of expression of MS2-GFP in cells that lacked the 6xbs inser-
tion upstream of the cat and lacY genes
b. Use of E. coli cells that expressed 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 separate proteins
rather than as a fusion protein: A. got this correct but because i guessed. I did not understand the
, OFFICIAL GUIDE TO THE MCAT EXAM OFFICIAL GUIDE TO THE MCAT EXAM (2025 EDITION
COMPLETE AAMC-ALIGNED REVIEW, STRATEGIES, AND HIGH-YIELD PRACTICE
Study online at https://quizlet.com/_88bvyz
terminology but rationalizing it out, if you are trying to test that the location of MS2 did not attects the locations of cat
and lac then you must take out cat and lac and see where MS2 is and then add cat and lac back in and see where it is.
9. QUESTION 6:
Which other cellular components are likely to be located near the lacY6xbs
transcript in the cell membrane?
A. Proteins and glycolipids
B. Glycolipids and sterols
C. Sterols and phospholipids
D. Phospholipids and proteins: D. got this correct but because I did was thinking of cell membrane
components but needed to recognize that the passage was about E.coli (a prokaryote).
The passage states lacY is located near the cell membrane, so the answer will have to be the cell components of an
E.coli membrane (a prokaryote). E.coli is a gram negative cell. Gram negative cells have a thin peptidoglycan layer and
a outer cell wall (which contains LPS). E.coli membranes, like all cells, have plasma membranes (inner most) and this
plasma membrane contains 75% protein, and 25% phospolipids. Typically, these are the major two components of all
cell membranes
Prokaryotes CM: do not contain sterols, glycolipids or glycoproteins do have phospholipids, proteins, sphinglolipids
(see below in extra info)
Eukaryotes CM: contain sterols (cholesterol for fluidity), glycolipids and glycoproteins (serve as recognition molecules)
Extra Info: Most prokaryotes cell membranes also do contain include spingolipids (which can be a phospolipid when
head group contain a phosphates - this is then called a spingomyelin. The other types of spingolipids are eramide (OH
head group), or glycolipids (sugar head group) such as cereboside (one sugar), globoside (2+ sugar), and ganglisoide
(oligosacharide with NANA/Salic acid)
10. QUESTION 7:
Using knowledge of Michaelis-Menten kinetics, what effect would the addition
of chloramphenicol have on the kinetics of its target enzyme?
a. Vmax decreases, and KM increases.
b. Vmax decreases, and KM remains unchanged.
c. Vmax remains unchanged, and KM increases.
COMPLETE AAMC-ALIGNED REVIEW, STRATEGIES, AND HIGH-YIELD PRACTICE
Study online at https://quizlet.com/_88bvyz
1. BB section:
2. What is the difference between Type I and Type II muscle fibers?: Understand the
ditterence between Type I and Type II Muscle fibers.
Type I (slow-twitch) - mitochondria rich, slow twitch (slow conduction velocity), slow contraction speed, aerobic, long,
low power, 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 velocity), anaerobic, short, easily fatigue, power,
ATP from creatine phosphate.
3. QUESTION 1:
The muscle subtype represented by Culture C is LEAST likely to be characterized
by:
A. a fast rate of muscle contraction.
B. the ability to engage in oxidative and anaerobic respiration.
C. the presence of medium-sized motor units.
D. low densities of mitochondria and capillaries.: D. got this wrong becaus e i did not under-
stand which culture (A, B or C) related to which muscle type in the table in the passage.
Don't be fooled by this answer choice. Even though in the "Activity used for" section it states anaerobic. The type IIA
muscle fiber still exhibits "high oxidative capacity" which means it would be able to perform BOTH anaerobic and
aerobic processes.
Based on the passage, it can be inferred 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.
4. QUESTION 2:
Which steps involved in the contraction of a skeletal muscle require binding
and/or hydrolysis of ATP?
I. Dissociation of myosin head from actin filament
II. Attachment of myosin head to actin filament
III. Conformational change that moves actin and myosin filaments relative to
one another
, OFFICIAL GUIDE TO THE MCAT EXAM OFFICIAL GUIDE TO THE MCAT EXAM (2025 EDITION
COMPLETE AAMC-ALIGNED REVIEW, STRATEGIES, AND HIGH-YIELD PRACTICE
Study online at https://quizlet.com/_88bvyz
IV. Binding of troponin to actin filament
V. Release of calcium from the sarcoplasmic reticulum
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: C. got it wrong, chose A, bc did not know that ca reuptake required ATP
Also known as "cross bridge dissociation". This occurs after the power stroke to put the myosin head into a low energy
position II. Calcium is required to expose the myosin binding sites through the conformational change in tropomyosin
III. The conformational change among actin and myosin requires the hydrolysis of ATP which is what allows the power
stroke a.k.a. the muscle contraction caused when myosin pulls actin towards the middle of the sarcomere VI. Reuptake
of calcium requires ATP because the ions are moving against their concentration gradient into the SR
5. What are the steps for muscle contraction?:
6. QUESTION 3:
Does the release of Ach in skeletal muscle cells, cause depolarization or hyper-
polarization?
The addition of acetylcholine to the medium most likely induced:
a. depolarization of the cell membrane that resulted in contraction.
b. repolarization of the cell membrane that resulted in relaxation.
c. hyperpolarization of the cell membrane that resulted in contraction.
d. depolarization of the cell membrane that resulted in relaxation.: A. because we
know ach causes contractions also according to the passage it states that ach caused a cell culture to retain contractile
activity for longer than 30 mins.
Acetylcholine is released at the neuromuscular junction where it binds to receptors on the muscle cells and, depending
, OFFICIAL GUIDE TO THE MCAT EXAM OFFICIAL GUIDE TO THE MCAT EXAM (2025 EDITION
COMPLETE AAMC-ALIGNED REVIEW, STRATEGIES, AND HIGH-YIELD PRACTICE
Study online at https://quizlet.com/_88bvyz
on the type of muscle cell, causes depolarization or hyperpolarization of the cell membrane. In skeletal muscles,
acetylcholine binds to its receptors, which leads to depolarization of the muscle cell membrane and muscle contraction.
7. QUESTION 4:
The terminal electron acceptor in lactic acid fermentation is:
a. pyruvate.
b. oxygen.
c. NAD+.
d. water.: A.
I chose C but thats wrong bc NADH reduces pyruvate to produce lactate and regenerate NAD+ so glycolysis can
continue.
You have to know the key ditterence between fermentation and aerobic respiration for this question. In aerobic
respiration, oxygen is an electron acceptor while in fermentation, pyruvate is an electron acceptor to regenerate NAD+,
so glycolysis can continue. In this process, NADH reduces pyruvate to produce lactate. Therefore, pyruvate serves as the
electron acceptor in production of lactate.
Remember, 2 ATP produced in fermentation process per mol of glucose (which occurs when no O2 present in
eukaryotes)! In glycolysis, however, 32 ATP is produced per mol of glucose. This is a vast ditterence.
8. QUESTION 5:
What control experiment was necessary to ensure that the apparent subcellu-
lar locations of the cat6xbs and lacY6xbs transcripts were NOT skewed by the
location preference of the bound MS2-GFP?
a. Determination of expression of MS2-GFP in cells that lacked the 6xbs inser-
tion upstream of the cat and lacY genes
b. Use of E. coli cells that expressed 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 separate proteins
rather than as a fusion protein: A. got this correct but because i guessed. I did not understand the
, OFFICIAL GUIDE TO THE MCAT EXAM OFFICIAL GUIDE TO THE MCAT EXAM (2025 EDITION
COMPLETE AAMC-ALIGNED REVIEW, STRATEGIES, AND HIGH-YIELD PRACTICE
Study online at https://quizlet.com/_88bvyz
terminology but rationalizing it out, if you are trying to test that the location of MS2 did not attects the locations of cat
and lac then you must take out cat and lac and see where MS2 is and then add cat and lac back in and see where it is.
9. QUESTION 6:
Which other cellular components are likely to be located near the lacY6xbs
transcript in the cell membrane?
A. Proteins and glycolipids
B. Glycolipids and sterols
C. Sterols and phospholipids
D. Phospholipids and proteins: D. got this correct but because I did was thinking of cell membrane
components but needed to recognize that the passage was about E.coli (a prokaryote).
The passage states lacY is located near the cell membrane, so the answer will have to be the cell components of an
E.coli membrane (a prokaryote). E.coli is a gram negative cell. Gram negative cells have a thin peptidoglycan layer and
a outer cell wall (which contains LPS). E.coli membranes, like all cells, have plasma membranes (inner most) and this
plasma membrane contains 75% protein, and 25% phospolipids. Typically, these are the major two components of all
cell membranes
Prokaryotes CM: do not contain sterols, glycolipids or glycoproteins do have phospholipids, proteins, sphinglolipids
(see below in extra info)
Eukaryotes CM: contain sterols (cholesterol for fluidity), glycolipids and glycoproteins (serve as recognition molecules)
Extra Info: Most prokaryotes cell membranes also do contain include spingolipids (which can be a phospolipid when
head group contain a phosphates - this is then called a spingomyelin. The other types of spingolipids are eramide (OH
head group), or glycolipids (sugar head group) such as cereboside (one sugar), globoside (2+ sugar), and ganglisoide
(oligosacharide with NANA/Salic acid)
10. QUESTION 7:
Using knowledge of Michaelis-Menten kinetics, what effect would the addition
of chloramphenicol have on the kinetics of its target enzyme?
a. Vmax decreases, and KM increases.
b. Vmax decreases, and KM remains unchanged.
c. Vmax remains unchanged, and KM increases.
