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MICROBIOLOGY MIDTERM EXAM |ACTUAL
EXAM QUESTIONS & ANSWERS (100%
VERIFIED) |LATEST 2025/2026
Elements that are required in relatively large amounts by microorganisms are called...
A.multivitamins
B. meganurtients
C. macronutrients
D. macromolecules - Correct Ans✓✓ C. macronutrients
When a microorganism is placed in a(n) ________ solution, water will eneter into the cell
and cause it to burst unless something is done to prevent it.
A. hypotonic
B. isotonic
C. hypertonic
D. osomotic - Correct Ans✓✓ A. hypotonic
If cells are grown in media containing amino acids labeled with radioactive nitrogen, most of
the radioactivity will be found in the cells...
A. DNA
B. proteins
C. phospholipids
D. DNA and proteins
E. DNa and phosophlipids - Correct Ans✓✓ D. DNA and proteins
Micooraginams that grow best at temperatures between 45-70 degrees celsius are called:
A. Thermophiles
B. Psycrophiles
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C. Thermophobes
D. Mesophiles - Correct Ans✓✓ A. Thermophiles
Which of the following is an advantage of the standard plate count?
A. can readily count cells that fomr aggregates
B. determines the number of viable cells
C. can be performed on very dilute samples, such as lake water
D. provides immediate results
E. can be used to count heat-sensitive bacteria - Correct Ans✓✓ B. determines the number of
viable cells
The total number of viable microorganisms remains constant in stationary phase because:
A. there is a balance between cell division and cell death
B. there is a cessation of cell division even though the cells may remain metabolically activie
C. either a or b
D. niether a or b - Correct Ans✓✓ C. either a or b
Which of the following is NOT a direct method to measuree microbial growth?
A. direct microscopic count
B. standard plate count
C. filtration on a support membrane followed by incubation on medium
D. metabolic activity
E. most probably number - Correct Ans✓✓ D. metabolic activity
Media counting some ingredients of unknown chemical composition are called ______ media
A. undefined
B. complex
C. defined
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D. synthetic - Correct Ans✓✓ B. Complex
Which of the following is the best definition of generation time?
A. the length of time needed for lag phase
B. the length of time needed for a cell to divide
C. the minimum rate for 10 new cells to form
D. the duration of exponential growth phase
E. the timeneeded for nuclear division - Correct Ans✓✓ B. the length of time needed for a
cell to divide
A gene is best defined as...
A. a segment of DNA
B. three nucleotides that code for an amino acid
C. a sequence of nucleotides in DNA that codes for a functional product
D. a sequence of nucleotides in RNA that codes for a functional product - Correct Ans✓✓ C.
a sequence of nucleotides in DNA that codes for a functional product
How many nucleotide bases are found in the code for each amino acid?
A. 2
B. 3
C. 4
D. varies with the paricular amino acid - Correct Ans✓✓ B. 3
A culture medium which only gram-positive organisms grow, and in which a yellow halo
surrounds Staphylococcus aureus colinies, distinguishing S. aureus from other growing
species, is best described as...
A. a selective, but not differential medium
B. a differential, but not selective medium
C. an enrichment culture
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D. both a selective a differential medium
E. both a differential and enrichment culture - Correct Ans✓✓ D. both a selective and
differential medium
Which of the following is NOT a pyrimidine?
A. adenine
B. cytosine
C. thymine
D. uracil - Correct Ans✓✓ A. adenine
Which nitrogenous case would only be found in RNA?
A. adenine
B. thymine
C. cytosine
D. guanine
E. uracil - Correct Ans✓✓ E. uracil
Synthesis of an enzyme coded by a repressible gene is stopped by the...
A. transformation of the bacteria
B. accumulation of product that the enzyme catalyzes the production of
C. catabolism of the product
D. RNa polymerase binding to the repressor - Correct Ans✓✓ B. accumulation of product
that the enzyme catalyzes the production of
Which of the following is a product of DNA replication?
A. a new strant of DNa
B. rRNa
C. tRNA
MICROBIOLOGY MIDTERM EXAM |ACTUAL
EXAM QUESTIONS & ANSWERS (100%
VERIFIED) |LATEST 2025/2026
Elements that are required in relatively large amounts by microorganisms are called...
A.multivitamins
B. meganurtients
C. macronutrients
D. macromolecules - Correct Ans✓✓ C. macronutrients
When a microorganism is placed in a(n) ________ solution, water will eneter into the cell
and cause it to burst unless something is done to prevent it.
A. hypotonic
B. isotonic
C. hypertonic
D. osomotic - Correct Ans✓✓ A. hypotonic
If cells are grown in media containing amino acids labeled with radioactive nitrogen, most of
the radioactivity will be found in the cells...
A. DNA
B. proteins
C. phospholipids
D. DNA and proteins
E. DNa and phosophlipids - Correct Ans✓✓ D. DNA and proteins
Micooraginams that grow best at temperatures between 45-70 degrees celsius are called:
A. Thermophiles
B. Psycrophiles
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C. Thermophobes
D. Mesophiles - Correct Ans✓✓ A. Thermophiles
Which of the following is an advantage of the standard plate count?
A. can readily count cells that fomr aggregates
B. determines the number of viable cells
C. can be performed on very dilute samples, such as lake water
D. provides immediate results
E. can be used to count heat-sensitive bacteria - Correct Ans✓✓ B. determines the number of
viable cells
The total number of viable microorganisms remains constant in stationary phase because:
A. there is a balance between cell division and cell death
B. there is a cessation of cell division even though the cells may remain metabolically activie
C. either a or b
D. niether a or b - Correct Ans✓✓ C. either a or b
Which of the following is NOT a direct method to measuree microbial growth?
A. direct microscopic count
B. standard plate count
C. filtration on a support membrane followed by incubation on medium
D. metabolic activity
E. most probably number - Correct Ans✓✓ D. metabolic activity
Media counting some ingredients of unknown chemical composition are called ______ media
A. undefined
B. complex
C. defined
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D. synthetic - Correct Ans✓✓ B. Complex
Which of the following is the best definition of generation time?
A. the length of time needed for lag phase
B. the length of time needed for a cell to divide
C. the minimum rate for 10 new cells to form
D. the duration of exponential growth phase
E. the timeneeded for nuclear division - Correct Ans✓✓ B. the length of time needed for a
cell to divide
A gene is best defined as...
A. a segment of DNA
B. three nucleotides that code for an amino acid
C. a sequence of nucleotides in DNA that codes for a functional product
D. a sequence of nucleotides in RNA that codes for a functional product - Correct Ans✓✓ C.
a sequence of nucleotides in DNA that codes for a functional product
How many nucleotide bases are found in the code for each amino acid?
A. 2
B. 3
C. 4
D. varies with the paricular amino acid - Correct Ans✓✓ B. 3
A culture medium which only gram-positive organisms grow, and in which a yellow halo
surrounds Staphylococcus aureus colinies, distinguishing S. aureus from other growing
species, is best described as...
A. a selective, but not differential medium
B. a differential, but not selective medium
C. an enrichment culture
, Page |4
D. both a selective a differential medium
E. both a differential and enrichment culture - Correct Ans✓✓ D. both a selective and
differential medium
Which of the following is NOT a pyrimidine?
A. adenine
B. cytosine
C. thymine
D. uracil - Correct Ans✓✓ A. adenine
Which nitrogenous case would only be found in RNA?
A. adenine
B. thymine
C. cytosine
D. guanine
E. uracil - Correct Ans✓✓ E. uracil
Synthesis of an enzyme coded by a repressible gene is stopped by the...
A. transformation of the bacteria
B. accumulation of product that the enzyme catalyzes the production of
C. catabolism of the product
D. RNa polymerase binding to the repressor - Correct Ans✓✓ B. accumulation of product
that the enzyme catalyzes the production of
Which of the following is a product of DNA replication?
A. a new strant of DNa
B. rRNa
C. tRNA
