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8 Cards in this Set
- Front
- Back
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Describe the structure of the plasma membrane of cells.
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There are two main parts to a plasma membrane: the phospholipid bilayer and proteins that are embedded and floating among the phospholipid molecules. Each phospholipid molecule consists of a hydrophilic head and two hydrophobic tails. The hydrophilic heads are point to the inside and outside of the cell and the hydrophobic fatty acid tails point toward each other.
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The plasma membrane of a cell is selectively permeable. What does that mean?
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The plasma membrane is selectively permeable and therefore allows only certain substances to pass through it and enter the cell.
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What type of molecules can pass directly through the phospholipid bilayer of the plasma membrane of cells?
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Non-polar, uncharged molecules (such as oxygen & carbon dioxide).
It is slightly permeable to small, uncharged polar molecules such as water. It is *impermeable* to ions and large, uncharged polar molecules. |
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Describe how ions and large, uncharged polar molecules are able to pass through a plasma membrane.
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They pass through protein channels that are embedded and floating among the phospholipid molecules.
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Define "concentration gradient."
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A concentration gradient exists when there is a difference in the concentration of a substance on one side of a plasma membrane versus the other side of the plasma membrane. In other words, when the concentration inside of the substance inside of the cell is different than outside the cell.
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Define "electrical gradient."
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An electrical gradient exists when there is difference in the amount of electrical charge (due to ions) on one side of the plasma membrane versus the other side of the membrane.
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Define "diffusion."
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Diffusion is the movement of substance from a place of high concentration to a place of low concentration. When a substance diffuses, it *moves down the concentration gradient.*
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What characteristics do substances possess that must pass through a plasma membrane through the process of facilitated diffusion?
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Solutes that are too polar or highly charged must pass through the plasma membrane through facilitated diffusion.
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