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16 Cards in this Set
- Front
- Back
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What helps to keep a cell intact?
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Plasma membrane
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What is known as the gate keeper of the cell?
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plasma membrane
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Why is the plasma membrane said to be selectively permable?
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It allows only certain molecules and ions to enter and exit the cytoplasm freely.
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what pass across the membrane easily?
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small molecules that are lipid soluble, such as oxygen and carbon dioxide.
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Because water is polar, how does it pass through the non polar core of the plasma membrane bilayer?
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by utilizing protein channels called "aquaporins"
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what are aquaporins?
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allows water molecules to freely cross the membrane, if the structure were not present, the water molecules would be unable to pass because of the non polar characteristic of the core of the plasma membrane.
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What are some examples of lipid soluble molecules?
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oxygen, carbon dioxide
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What allows water molecules to freely cross the membrane?
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aquaporins
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What cannot cross the membrane without more direct assistance?
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ions and large molecules
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What is the random movement of molecules from the area of higher concentration to the area of lower concentration, until they are equally distributed? What is another name for random movement of molecules?
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Diffusion, Brownian motion
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what is a passive way for molecules to enter or exit a cell?
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diffusion
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what does it mean by diffusion is a passive way for molecules to enter or exit a cell?
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NO cellular energy is needed to bring it about.
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What is a good example of diffusion?
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cube of sugar in a glass of iced tea. Sugar soon diffuses away from the cube until it is equally dispersed throughout the glass of iced tea and the cube disappears.
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When molecules cross the plasma membrane, which way will they go?
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The molecules move in both directions, but the net movement will be from the region of higher concentrations to the region of lower concentration, until equilibrium is achieved.
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When equilibrium is reached, which way do molecules go?
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As many molecules of the substance enter as leave the cell--equally in both directions
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When oxygen diffuses across the plasma membrane, where is the net movement? Why?
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Toward the inside of the cell, because the cell uses oxygen when it produces ATP molecules for energy purposes.
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