In gram-negative bacteria, the cell envelope includes an inner membrane, a periplasmic space, and an outer membrane.
True
False
The Correct Answer is A
Gram-negative bacteria have a distinctive cell envelope composed of three key layers. The innermost layer is the cytoplasmic (inner) membrane, which regulates transport and maintains cellular integrity. Outside this is the periplasmic space, a gel-like area containing enzymes and proteins involved in nutrient processing and defense. The outermost layer is the outer membrane, which contains lipopolysaccharides (LPS) that contribute to the structural barrier, immune evasion, and pathogenicity. This multilayered structure differentiates gram-negative bacteria from gram-positive bacteria, which lack an outer membrane and have a much thicker peptidoglycan layer.
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Related Questions
Correct Answer is B
Explanation
A. Nucleus: The nucleus contains the cell’s genetic material and controls transcription and replication. While nuclear damage can affect gene expression and cell survival, it does not directly explain the acute loss of ion gradients and cellular lysis caused by disruption of membrane integrity.
B. Cell membrane: The cell membrane, composed of a phospholipid bilayer with embedded proteins, maintains selective permeability, ion gradients, and cellular homeostasis. Disruption of the membrane compromises the barrier between intracellular and extracellular environments, causing uncontrolled ion flux, osmotic imbalance, and eventual cell lysis.
C. Ribosome: Ribosomes are responsible for protein synthesis, translating mRNA into polypeptides. Impaired ribosomal function affects protein production but does not immediately cause loss of ion gradients or membrane rupture.
D. Cytoskeleton: The cytoskeleton provides structural support, intracellular transport, and shape maintenance. While damage to cytoskeletal elements can affect cell morphology and motility, it does not directly cause ion imbalance or lysis due to phospholipid bilayer disruption.
E. Golgi apparatus: The Golgi apparatus modifies, sorts, and packages proteins and lipids for secretion or intracellular use. Dysfunction here affects protein processing and trafficking but does not directly compromise membrane integrity or lead to immediate lysis.
Correct Answer is A
Explanation
RNA viruses are categorized based on the structure and polarity of their RNA genome. Positive-sense RNA can act directly as messenger RNA and be translated by host ribosomes. Negative-sense RNA must first be transcribed into complementary mRNA by viral RNA-dependent RNA polymerase. Some RNA viruses possess double-stranded RNA genomes, which also require specialized replication mechanisms inside the host cell.
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