What substance move freely in and out of a cell by diffusion?
Proteins
Enzymes
Hormones
Electrolytes
The Correct Answer is C
A) Proteins:
Proteins are generally too large to diffuse freely across the cell membrane. They require specific transport mechanisms, such as endocytosis or transport proteins, to move in and out of cells. The hydrophilic nature of most proteins further complicates their passage across the lipid bilayer.
B) Enzymes:
Like proteins, enzymes are large molecules that do not freely diffuse across cell membranes. Enzymes, being proteins, also need specialized transport mechanisms or need to be secreted or endocytosed to enter or exit cells.
C) Hormones:
Many hormones, particularly lipid-soluble ones like steroid hormones, can diffuse freely across the cell membrane. These hormones pass through the lipid bilayer due to their hydrophobic nature and bind to intracellular receptors, initiating cellular responses. However, water-soluble hormones (e.g., insulin) typically do not diffuse freely but interact with receptors on the cell surface.
D) Electrolytes:
Electrolytes (such as sodium, potassium, calcium, and chloride ions) are charged particles that cannot pass freely through the lipid bilayer due to the hydrophobic interior of the cell membrane. They require specific ion channels or transporters to move in and out of the cell. Diffusion of electrolytes is facilitated through these channels, but it is not a simple diffusion process as seen with small, uncharged molecules.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
A) Parkinson disease is characterized by an imbalance of dopamine and acetylcholine:
The decrease in dopamine results in an imbalance between dopamine and acetylcholine. Normally, dopamine and acetylcholine work in a balanced manner to regulate motor control. As dopamine levels decrease in Parkinson's disease, acetylcholine's effects become more prominent, leading to motor symptoms such as tremors, rigidity, and bradykinesia (slowness of movement).
B) Parkinson disease involves increased dopamine production and decreased acetylcholine:
This statement is incorrect. In Parkinson's disease, there is actually a decrease in dopamine production, not an increase. The disease is characterized by the degeneration of dopamine-producing neurons, leading to the motor symptoms typical of Parkinsonism. The imbalance in Parkinson's disease is primarily one of decreased dopamine and relatively increased acetylcholine activity.
C) Alzheimer disease is caused by decreased amounts of dopamine and degeneration of cholinergic neurons:
While Alzheimer's disease does involve a degeneration of cholinergic neurons (specifically those that release acetylcholine), the primary pathology is related to the accumulation of amyloid plaques and tau tangles, not primarily a decrease in dopamine. Alzheimer's disease is primarily associated with a deficiency in acetylcholine, not dopamine, leading to cognitive impairments, rather than motor deficits.
D) Alzheimer disease involves a possible excess of acetylcholine and neuritic plaques:
This statement is incorrect. Alzheimer's disease is characterized by a deficiency of acetylcholine, which plays a crucial role in memory and cognitive function. The hallmark pathologic features of Alzheimer's disease include the presence of neuritic plaques (formed from amyloid beta) and neurofibrillary tangles (composed of tau protein), not an excess of acetylcholine.
Correct Answer is C
Explanation
A) Hypothalamus and the medulla: While the hypothalamus and medulla play critical roles in regulating autonomic functions and overall sympathetic nervous system activity, the primary origin of the sympathetic nervous system's neural impulses comes from the spinal cord, specifically in the thoracic and lumbar regions. The hypothalamus and medulla are involved in coordinating and regulating sympathetic activity rather than being the origin of the impulses themselves.
B) Cranium and sacral area of the spinal cord: The cranium and sacral regions are primarily associated with the parasympathetic nervous system, not the sympathetic nervous system. The parasympathetic nervous system's nerve fibers arise from the brainstem and the sacral region, while the sympathetic fibers originate from the thoracic and lumbar areas.
C) Thoracic and lumbar section of the spinal cord: The sympathetic nervous system originates in the thoracolumbar region of the spinal cord, which includes the thoracic and lumbar segments (T1-L2). These regions house the preganglionic neurons whose axons exit the spinal cord and synapse in sympathetic ganglia, leading to the sympathetic effects on organs and tissues. This makes the thoracic and lumbar sections the correct location for the origin of SNS impulses.
D) Nerve membrane: The nerve membrane, or the cellular membrane of individual neurons, is not the location where impulses originate. The origin of the impulses is in the central nervous system (CNS), specifically in the spinal cord for the sympathetic system, not at the level of the individual nerve membranes.
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