REA MCAT MULTIPLE CHOICE
QUESTIONS WITH 100% CORRECT
ANSWERS LATEST VERSION 2025/2026.
Enzymes are:
a. proteins
b. catalysts
c. carbohydrates
d. both proteins and catalysts - ANS D. Enzymes are proteins that act as catalysts.
Carbohydrates are not proteins, and therefore cannot be enzymes.
Organisms can control all of the following EXCEPT:
a. location of enzymes
b. type of enzymes
c. amount of enzymes
d. activity of enzymes - ANS B. Organisms control the activity of enzymes by changing or
blocking active sites. Location and amount of enzymes may be controlled through feedback.
Types of enzymes are determined genetically and cannot be altered.
In feedback inhibition of metabolic pathways, which are controlled directly?
a. end pdts
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,b. metabolites
c. enzymes
d. precursor molecules - ANS C. In feedback inhibition the flow of metabolites is often
regulated by controlling the activity of key enzymes in a pathway. Usually, the first enzyme in a
metabolic pathway is controlled by the end product of the pathway.
Glycolysis does NOT:
a. occur in the cytoplasm
b. require oxygen
c. produce ATP
d. break down glucose - ANS B. Glycolysis is the series of metabolic reactions by which
glucose is converted to pyruvate (a 3-C sugar) with the concurrent formation of ATP. Glycolysis
occurs in the cytoplasm of the cell and for this process the presence of oxygen is unnecessary.
In the Krebs Cycle, all of the following occur EXCEPT:
a. oxidation of succinate
b. formation of FADH2
c. formation of NADH
d. transformation of NADH to NAD - ANS D. NADH is converted to NAD during oxidative
phosphorylation, which yields 3 ATP.
The ratio of ATP produced aerobically to anaerobically by the oxidation of one molecule of
glucose is
a. 2:1
b. 1:2
c. 1:18
d. 18:1 - ANS D. The aerobic production of ATP involves the Krebs cycle and the oxidation of
glucose. The anaerobic production of ATP takes place during glycolysis. The citric acid cycle
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, produces 34 ATP's and the oxidation of glucose produces 2. This makes the total number of
ATP's produced during aerobic processes 36. Glycolysis yields 2 ATP's. The net ratio of aerobic
ATP to anaerobic ATP is 36:2, which reduces to 18:1.
Nitrous acid converts cytosine to uracil by deamination. This type of conversion in one DNA
strand would lead to a change in the complementary base in the other strand to
a. adenine
b. cytosine
c. thymine
d. guanine - ANS A. Cytosine normally binds to guanine and uracil normally binds to adenine.
A conversion of cytosine to uracil would lead to a conversion of guanine to adenine in the
complementary strand. Thus a CG to AU event has occurred.
Viruses differ from living organisms because
a. viruses possess no bounding membrane
b. viruses lack all metabolic machinery
c. viruses lack all reproductive machinery
d. all of the above - ANS D. Viruses do not have any membranes because they have no need
to take in or expel material. Viruses lack all metabolic machinery and do not produce ATP
because they do not perform energy requiring processes. Viruses do possess either DNA or
RNA, but cannot independently reproduce. They must rely on host cells for reproductive
machinery and components.
Moderate viruses may
a. replace DNA only when the host replicates
b. induce tumors
c. cause immediate lysis of infected bacteria
d. have both DNA and RNA - ANS A. In moderate viruses the phage DNA is incorporated
directly into the host chromosome, and thus replicates only when the host does. RNA
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
QUESTIONS WITH 100% CORRECT
ANSWERS LATEST VERSION 2025/2026.
Enzymes are:
a. proteins
b. catalysts
c. carbohydrates
d. both proteins and catalysts - ANS D. Enzymes are proteins that act as catalysts.
Carbohydrates are not proteins, and therefore cannot be enzymes.
Organisms can control all of the following EXCEPT:
a. location of enzymes
b. type of enzymes
c. amount of enzymes
d. activity of enzymes - ANS B. Organisms control the activity of enzymes by changing or
blocking active sites. Location and amount of enzymes may be controlled through feedback.
Types of enzymes are determined genetically and cannot be altered.
In feedback inhibition of metabolic pathways, which are controlled directly?
a. end pdts
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,b. metabolites
c. enzymes
d. precursor molecules - ANS C. In feedback inhibition the flow of metabolites is often
regulated by controlling the activity of key enzymes in a pathway. Usually, the first enzyme in a
metabolic pathway is controlled by the end product of the pathway.
Glycolysis does NOT:
a. occur in the cytoplasm
b. require oxygen
c. produce ATP
d. break down glucose - ANS B. Glycolysis is the series of metabolic reactions by which
glucose is converted to pyruvate (a 3-C sugar) with the concurrent formation of ATP. Glycolysis
occurs in the cytoplasm of the cell and for this process the presence of oxygen is unnecessary.
In the Krebs Cycle, all of the following occur EXCEPT:
a. oxidation of succinate
b. formation of FADH2
c. formation of NADH
d. transformation of NADH to NAD - ANS D. NADH is converted to NAD during oxidative
phosphorylation, which yields 3 ATP.
The ratio of ATP produced aerobically to anaerobically by the oxidation of one molecule of
glucose is
a. 2:1
b. 1:2
c. 1:18
d. 18:1 - ANS D. The aerobic production of ATP involves the Krebs cycle and the oxidation of
glucose. The anaerobic production of ATP takes place during glycolysis. The citric acid cycle
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, produces 34 ATP's and the oxidation of glucose produces 2. This makes the total number of
ATP's produced during aerobic processes 36. Glycolysis yields 2 ATP's. The net ratio of aerobic
ATP to anaerobic ATP is 36:2, which reduces to 18:1.
Nitrous acid converts cytosine to uracil by deamination. This type of conversion in one DNA
strand would lead to a change in the complementary base in the other strand to
a. adenine
b. cytosine
c. thymine
d. guanine - ANS A. Cytosine normally binds to guanine and uracil normally binds to adenine.
A conversion of cytosine to uracil would lead to a conversion of guanine to adenine in the
complementary strand. Thus a CG to AU event has occurred.
Viruses differ from living organisms because
a. viruses possess no bounding membrane
b. viruses lack all metabolic machinery
c. viruses lack all reproductive machinery
d. all of the above - ANS D. Viruses do not have any membranes because they have no need
to take in or expel material. Viruses lack all metabolic machinery and do not produce ATP
because they do not perform energy requiring processes. Viruses do possess either DNA or
RNA, but cannot independently reproduce. They must rely on host cells for reproductive
machinery and components.
Moderate viruses may
a. replace DNA only when the host replicates
b. induce tumors
c. cause immediate lysis of infected bacteria
d. have both DNA and RNA - ANS A. In moderate viruses the phage DNA is incorporated
directly into the host chromosome, and thus replicates only when the host does. RNA
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
