Term
| What does a plasma membrane do? |
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Definition
| isolates the cell's contents from the external environment |
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Term
| What is the structure of the plasma membrane? |
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Definition
| Proteins floating in a double layer of lipids. |
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Definition
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Term
| What is the fluid portion of the membrane? |
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Definition
| The phospholipid bilayer composed of a polar, hydrophilic head and a pair of nonpolar hydrophobic tails. |
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Term
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Definition
| attracted to water molecules and tend to dissolve in water |
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Term
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Definition
| repel water and "hide"inside the membrane (the phospholipid tail of a membrane) |
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Term
| What is embedded in the membrane of a cell? |
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Definition
| Thousands of different proteins. These proteins are responsible for moving substances across the membrane and for communicating with other cells. |
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Term
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Definition
| blocks the passage of most molecules. very small molecules such as water and uncharged lipid soluble molecules can pass |
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Term
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Definition
| allow movement of hydrophilic (water soluble) molecules through the plasma membrane by forming channels or by carring molecules across the membrane. |
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Definition
| deliver chemical messages to the cell. They trigger responses inside the cell when specific molecules outside the cell, such as hormones or nutrients, bind to them. |
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Definition
| movement of molecules from regions of high concentration to regions of low concentration. |
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Term
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Definition
| a difference in concentration between one region and another. |
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Definition
| the movement of water across membranes from areas of high water concentration to areas of low water concentraton. |
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Definition
| movement of substances accross a membrane by traveling down a concentration, pressure or electrical charge gradient. Does not require the cell to expend energy. |
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Definition
| diffusion of water, dissolved gases, or lipid soluble molecules through the phospholipid bilayer. |
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Term
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Definition
| diffusion of (normally water-soluble) molecules through a channel or carrier protein. |
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Term
| Energy-requiring transport |
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Definition
| movement across a membrane of substances that travel against a concentration gradient. Requires the cell to expend energy. |
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Term
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Definition
| movement of individual small molecules or ions through membrane-spanning proteins, using cellular energy, normally ATP. |
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Definition
| Movement INTO a cell of large particles that are engulfed as the plasma membrane forms sacs that enter the cytoplasm. |
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Definition
| Movement OUT of a cell of materials that are enclosed in a membranous sacs that moves to the cell surface, fuses with the plasma membrane, and opens to the outside, allowing its contents to diffuse away. |
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Term
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Definition
| same concentration of dissolved substances (salt) no movement of water across the membrane. |
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Term
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Definition
| too much salt(thus less pure water), causes water to leave the cells and enter the salt solution, shriveling them up |
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Term
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Definition
| with less salt than is in the cells (thus more pure water in the solution), causes water to enter the cells and the cells swell. |
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Term
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Definition
| the plasma membrances of plants, fungi and many types of bacteria lie inside stiff coatings called cell walls. (normally porous) |
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