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Biological Sciences

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Plasma Membrane and Transport

Question
7 out of 7
 

A single celled microorganism isolated from the Atlantic ocean was accidentally cultured in a medium formulated for fresh water microorganism. What probably happened to the organism?

A The cell shriveled up and died due to exocitosis of salt.
B The cell swelled and burst due to osmosis of water.
C The cell died because the membrane transport proteins would not function properly in the new environment.
D The cell would try to take up as much sodium as possible via endocytosis from the medium.
Ans. B

The microorganism is adapted to life in a high salt environment. Remember that water can freely diffuse across cell membranes. Therefore, the tonicity of the organism was probably well suited to its environment. Placing the cell in the fresh water medium, which was hypotonic to the cell, would have caused water to rush into the cell,

thereby lysing it.

Plasma Membrane and Transport Flashcard List

7 flashcards
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The sodium-potassium (Na+/K+) pump is a critical element for many processes of the cell. For example, it is responsible for a neuron’s ability to transmit messages. The pump transports sodium out of the cell using energy from ATP (the extracellular matrix has a higher concentration of sodium than the intracellular space). The pump also imports potassium, which is more highly concentrated inside the cell than outside. The pump is an example of a cotransport system. Sodium binds to the transport protein and is exported. Once the sodium ion is released, a potassium ion binds and is transported into the cell (actually, for every three sodium ions pumped out of the cell, two potassium ions are pumped in). Thus, a sodium and potassium gradient are established and maintained across the membrane. Since the ions are being transported in opposite directions, this type of pump is called antiport. The sodium gradient established by the Na+/K+ pump can be used in many ways. Another cotransport system, the Na+/glucose pump, is active in human gut epithelial cells, and results in the uptake of glucose. Due to its concentration gradient, sodium diffuses into the cells through the Na+/glucose pump and transports glucose with it (this is called symport). The glucose is processed by the cells and can be used to generate energy. If a sodium gradient is formed, whereby there is a vast excess of sodium outside the cell, which is the most likely result?A An electrical gradient is also formed.B A magnetic gradient is also formed.C Other positively charged ions will enter the cell.D Negatively charged ions will enter the cell.
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The sodium-potassium (Na+/K+) pump is a critical element for many processes of the cell. For example, it is responsible for a neuron’s ability to transmit messages. The pump transports sodium out of the cell using energy from ATP (the extracellular matrix has a higher concentration of sodium than the intracellular space). The pump also imports potassium, which is more highly concentrated inside the cell than outside. The pump is an example of a cotransport system. Sodium binds to the transport protein and is exported. Once the sodium ion is released, a potassium ion binds and is transported into the cell (actually, for every three sodium ions pumped out of the cell, two potassium ions are pumped in). Thus, a sodium and potassium gradient are established and maintained across the membrane. Since the ions are being transported in opposite directions, this type of pump is called antiport. The sodium gradient established by the Na+/K+ pump can be used in many ways. Another cotransport system, the Na+/glucose pump, is active in human gut epithelial cells, and results in the uptake of glucose. Due to its concentration gradient, sodium diffuses into the cells through the Na+/glucose pump and transports glucose with it (this is called symport). The glucose is processed by the cells and can be used to generate energy. A poison was found that prevents binding of sodium to the Na+/K+ pump. What would be the most likely consequence of this poison? I. Potassium would not be pumped into the cell II. Glucose would not be pumped into the cell III. Nerve impulses would not be transmittedA I onlyB III onlyC I and IID I, II and III
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