Which type of cell junction acts as anchors and distributes tension through a cellular sheet and reduces the chance of tearing when it is subjected to great mechanical stress?
tight junctions
gap junctions
connexons
desmosomes
The Correct Answer is D
A. Tight junctions: Tight junctions form impermeable seals between adjacent cells, preventing leakage of substances across epithelial layers. Their primary role is barrier formation rather than providing strength against mechanical stress.
B. Gap junctions: Gap junctions consist of protein channels that allow ions and small molecules to pass directly between cells. They are important for communication and electrical coupling but do not serve as anchors against mechanical forces.
C. Connexons: Connexons are the protein subunits that form the channels in gap junctions. While essential for intercellular communication, they do not function in distributing mechanical tension or preventing tissue tearing.
D. Desmosomes: Desmosomes are anchoring junctions that attach cells to one another through intermediate filaments. They provide strong mechanical linkage, distribute tension across the tissue, and reduce the risk of tearing under stress.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A. The enzyme will denature and become inactive: Salivary amylase works best at a neutral to slightly basic pH, such as in the mouth. Once it reaches the stomach, the highly acidic environment disrupts its three-dimensional structure, causing denaturation and loss of activity
B. The enzyme will continue to function as it remains unchanged in chemical reactions: While enzymes are not consumed in reactions, their activity depends on pH and temperature. At a gastric pH of 2.5, salivary amylase cannot maintain its shape, so it stops functioning.
C. The enzyme will assume an alternate form and catalyze additional reactions: Enzymes are highly specific to their structure and active site. Once denatured, they do not take on new functional forms or catalyze new reactions.
D. The enzyme will denature but retain its function: Denaturation disrupts the enzyme’s active site, preventing substrate binding. If the enzyme denatures, it loses its catalytic ability entirely and cannot retain its original function.
Correct Answer is C
Explanation
A. Pinocytosis: Pinocytosis is a form of endocytosis where the cell engulfs extracellular fluid and dissolved solutes. This process requires energy in the form of ATP to allow vesicle formation and internalization, so it is restricted by ATP availability.
B. Exocytosis: Exocytosis involves vesicles fusing with the plasma membrane to release substances outside the cell. The vesicle movement and membrane fusion are energy-dependent processes, making ATP essential for this mechanism.
C. Osmosis: Osmosis is the passive movement of water molecules across a selectively permeable membrane, driven by concentration gradients. Since it does not require cellular energy, it is not restricted by ATP levels and can occur even when ATP is depleted.
D. Phagocytosis: Phagocytosis is the engulfment of large particles or pathogens by the cell. This process requires ATP to reorganize the cytoskeleton and form phagosomes, so limited ATP availability would restrict its function.
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