A microbial species is able to survive in near freezing temperatures. Its cell membrane is able to stay fluid at such temperatures because
it has sterols (like cholesterol) in its membrane
it has a higher amount of protein in its membrane
it has a thicker glycocalyx
it has a thick cell wall
The Correct Answer is A
A. It has sterols (like cholesterol) in its membrane: Sterols insert themselves between phospholipids in the cell membrane, preventing tight packing of fatty acid chains. This helps maintain fluidity even in cold environments, allowing essential processes like transport and signaling to continue.
B. It has a higher amount of protein in its membrane: While membrane proteins are crucial for transport and enzymatic functions, they do not significantly impact the bilayer’s ability to remain fluid in near-freezing temperatures.
C. It has a thicker glycocalyx: The glycocalyx primarily aids in protection, adhesion, and biofilm formation. It does not play a major role in maintaining membrane fluidity under cold stress.
D. It has a thick cell wall: A thick cell wall protects against osmotic lysis and provides shape, but it does not regulate the lipid bilayer’s flexibility or prevent rigidity in freezing conditions.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. protein only: Prions are infectious agents made entirely of misfolded proteins without nucleic acids. They propagate by inducing normal cellular proteins to misfold, leading to neurodegenerative diseases.
B. an RNA surrounded by a protein capsid: This describes a typical RNA virus, not a prion. Viruses contain nucleic acids, while prions lack them completely.
C. circular RNA only: Circular RNA molecules are found in viroids, which infect plants, but prions are distinct as they are composed solely of protein.
D. circular DNA only: Circular DNA is present in some viruses and plasmids, but prions do not contain DNA or any form of nucleic acid.
Correct Answer is C
Explanation
A. Mitochondria: Prokaryotic cells do not contain mitochondria. Instead, they generate energy through processes that occur across the plasma membrane. They are found exclusively in eukaryotic cells and are absent in prokaryotes.
B. Lysosomes: Lysosomes are membrane-bound organelles found only in eukaryotic cells. Prokaryotes lack these structures and instead rely on enzymes within the cytoplasm for breakdown processes.
C. Ribosomes: Ribosomes are present in prokaryotes and eukaryotes, serving as the site of protein synthesis. In prokaryotes, they are smaller (70S type) but functionally equivalent to those in eukaryotes.
D. All of the above: This is incorrect because prokaryotes do not contain mitochondria or lysosomes.
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