Which of the following is a membrane protein that permits ion passage into or out of a cell?
Vesicle
Enzyme
Channel
Lysosome
The Correct Answer is C
A. A vesicle is involved in the transport of substances within or out of the cell via processes like endocytosis or exocytosis but does not directly permit ion passage across the membrane.
B. An enzyme catalyzes chemical reactions and is not directly involved in the transport of ions across the cell membrane.
C. A channel protein facilitates the passage of ions across the cell membrane, allowing specific ions to move in and out of the cell based on concentration gradients.
D. A lysosome is an organelle responsible for digesting and breaking down waste materials within the cell, not for ion transport across the membrane.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
A. Respiratory bronchioles are part of the lower respiratory tract and lead to alveolar sacs, but they themselves are not primarily responsible for gas exchange. Their role is in the conduction of air.
B. Alveolar sacs are the primary site of gas exchange in the lungs. These sacs contain alveoli, where oxygen and carbon dioxide are exchanged between the air and the blood. This is the correct answer.
C. The pleura are double-layered membranes surrounding the lungs and do not play a direct role in gas exchange. They reduce friction and allow for smooth lung expansion.
D. Pulmonary veins carry oxygenated blood from the lungs back to the heart, but gas exchange occurs in the alveolar sacs, not the veins.
Correct Answer is B
Explanation
A. Vitamin B12 is not synthesized in the skin. It is primarily absorbed through the digestive system from dietary sources such as meat and dairy products.
B. Vitamin D is synthesized in the skin when exposed to sunlight, specifically ultraviolet B (UVB) radiation, which triggers the production of vitamin D3, a precursor to the active form of vitamin D.
C. Vitamin A is obtained from dietary sources, such as fruits and vegetables, and is not synthesized in the skin.
D. Vitamin K is primarily absorbed from food and produced by bacteria in the intestines, not synthesized in the skin.
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