GCSU (BACHOON) MICROBIOLOGY TEST 2
EXAM WITH CORRECT ACTUAL
QUESTIONS AND CORRECTLY WELL
DEFINED ANSWERS LATEST ALREADY
GRADED A+ 2025 – 2026
how many possible codons are there? - ANSWERS-- 64
possible codons (4^3)
what determines the protein sequence? - ANSWERS-- the
sequence of mRNA
what is the genetic code? - ANSWERS-- the mRNA codons
and the amino acids they encode
1) the code is degenerated = several codons for a specific
amino acid
2) 61 sense codons (codes for an amino acid) 3 nonsense
codons, stop codons (UAA, UGA, UAG)
,- nonsense codons causes termination of translation, ending
polypeptide chain synthesis
3) the code is universal
what is mRNA read by? - ANSWERS-- ribosomes
ribosomes have 2 subunits
what brings the amino acids to the ribosomes? - ANSWERS--
tRNA (has an anticodon = a sequence of 3 bases that is
complementary to a codon)
In prokaryotes: - ANSWERS-- transcription and translation
can take place at the same time
- 60% - 80% constitutive (not regulated.. ON)
- 40% - 20% regulated
mesophiles - ANSWERS-- moderate temperature loving
microbes, most common type
- (25 deg. C - 40 deg. C)
- these are human pathogens also include most of the
common spoilage and disease organisms.
,- ex: 37 deg. C (the optimum temp. for many pathogenic
bacteria)
thermophiles - ANSWERS-- heat loving microbes
- (40 deg. C - 70 deg. C)
- many can't grow at temps below 45 deg. C
- hyperthermophiles = (70 deg. C - 110 deg. C)
what temperature do pathogens grow at? - ANSWERS--
human body temp. (37 degrees celsius)
what pH range do most bacteria grow best in? - ANSWERS--
a narrow pH range
- neutral (6.5 - 7.5)
- very few grow below pH 4
- foods with low pH (cheese, pickles..) don't spoil easily)
What are some examples of bacteria that grow below pH 4?
- ANSWERS-- sulfur oxidizers
- H. pylori
, ____ have more H+ than ______ - ANSWERS-acids, bases
what is the osmotic pressure inside bacterial cells in an
isotonic solution? - ANSWERS-- 0.85% NaCl
What type of solution inhibits bacterial growth? -
ANSWERS-- hypertonic solutions (solutes are higher outside
the cell)
- water leaves the cell
what is plasmolysis? - ANSWERS-- the osmotic loss of water
from the cell in a hypertonic environment
- shrinkage of the cell plasma membrane - die
What causes high osmotic pressure and can be used to
preserve food? - ANSWERS-- salt or sugar
- causes plasmolysis
ex: salted meat, jams, jelly
What percentage of salt and sugar are solutions that restrict
growth? - ANSWERS-solutions that restrict growth are:
> 5% salt
EXAM WITH CORRECT ACTUAL
QUESTIONS AND CORRECTLY WELL
DEFINED ANSWERS LATEST ALREADY
GRADED A+ 2025 – 2026
how many possible codons are there? - ANSWERS-- 64
possible codons (4^3)
what determines the protein sequence? - ANSWERS-- the
sequence of mRNA
what is the genetic code? - ANSWERS-- the mRNA codons
and the amino acids they encode
1) the code is degenerated = several codons for a specific
amino acid
2) 61 sense codons (codes for an amino acid) 3 nonsense
codons, stop codons (UAA, UGA, UAG)
,- nonsense codons causes termination of translation, ending
polypeptide chain synthesis
3) the code is universal
what is mRNA read by? - ANSWERS-- ribosomes
ribosomes have 2 subunits
what brings the amino acids to the ribosomes? - ANSWERS--
tRNA (has an anticodon = a sequence of 3 bases that is
complementary to a codon)
In prokaryotes: - ANSWERS-- transcription and translation
can take place at the same time
- 60% - 80% constitutive (not regulated.. ON)
- 40% - 20% regulated
mesophiles - ANSWERS-- moderate temperature loving
microbes, most common type
- (25 deg. C - 40 deg. C)
- these are human pathogens also include most of the
common spoilage and disease organisms.
,- ex: 37 deg. C (the optimum temp. for many pathogenic
bacteria)
thermophiles - ANSWERS-- heat loving microbes
- (40 deg. C - 70 deg. C)
- many can't grow at temps below 45 deg. C
- hyperthermophiles = (70 deg. C - 110 deg. C)
what temperature do pathogens grow at? - ANSWERS--
human body temp. (37 degrees celsius)
what pH range do most bacteria grow best in? - ANSWERS--
a narrow pH range
- neutral (6.5 - 7.5)
- very few grow below pH 4
- foods with low pH (cheese, pickles..) don't spoil easily)
What are some examples of bacteria that grow below pH 4?
- ANSWERS-- sulfur oxidizers
- H. pylori
, ____ have more H+ than ______ - ANSWERS-acids, bases
what is the osmotic pressure inside bacterial cells in an
isotonic solution? - ANSWERS-- 0.85% NaCl
What type of solution inhibits bacterial growth? -
ANSWERS-- hypertonic solutions (solutes are higher outside
the cell)
- water leaves the cell
what is plasmolysis? - ANSWERS-- the osmotic loss of water
from the cell in a hypertonic environment
- shrinkage of the cell plasma membrane - die
What causes high osmotic pressure and can be used to
preserve food? - ANSWERS-- salt or sugar
- causes plasmolysis
ex: salted meat, jams, jelly
What percentage of salt and sugar are solutions that restrict
growth? - ANSWERS-solutions that restrict growth are:
> 5% salt
