What structure controls passage of materials into and out of the cell?
Nucleus
Lysosome
Plasma membrane
Cytoplasm
The Correct Answer is C
A. Nucleus: Contains the cell’s genetic material and regulates gene expression and cell activities, but does not act as the selective barrier for material exchange with the external environment.
B. Lysosome: Membrane-bound organelle with hydrolytic enzymes that digests macromolecules and damaged organelles; not responsible for controlling entry/exit of substances.
C. Plasma membrane: A phospholipid bilayer with embedded proteins that provides selective permeability, transport channels, pumps, and mechanisms (endocytosis/exocytosis) controlling passage of materials into and out of the cell.
D. Cytoplasm: The intracellular fluid and organelle-containing matrix where metabolic reactions occur; it does not determine what crosses the cell boundary.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A. Store calcium: Calcium storage is a function of bone (osteocytes/osteoblast activity) rather than a primary role of stem cells.
B. Cause disease: Stem cells do not inherently cause disease; they are undifferentiated cells capable of giving rise to specialised cell types (though malignant transformation is a separate process).
C. Replace/repair damaged cells: Stem cells can divide and differentiate to regenerate or replace damaged or lost cells within tissues.
D. Transmit impulses: Transmitting electrical impulses is a function of neurons (nervous tissue), not a primary role of stem cells.
Correct Answer is B
Explanation
A. Osmosis: Osmosis is the passive diffusion of water across a semipermeable membrane down its concentration gradient.
B. Active transport: Active transport uses cellular energy (usually ATP) to move substances across membranes against their concentration gradients.
C. Diffusion: Diffusion is the passive movement of solutes down their concentration gradient, not against it.
D. Filtration: Filtration is movement of fluid and solutes driven by pressure differences (e.g., blood pressure) and is not specifically transport against a concentration gradient
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