Term
| 5 Functions of the Plasma Membrane |
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Definition
| Isolate the cell's contents from the external environment, regulate the exchange of essential substances between the cell and extracellular fluid, allows communication between cells, create attachments within and between cells, and regulates many biochemical reactions. |
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Term
| Why is the cell membrane considered to be a fluid mosaic? |
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Definition
| Cell membranes consist of a mosaic or "patchwork" of different proteins that constantly shift and flow within a viscous fluid formed by a double layer of phospholipids. |
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Term
| What is the general function of PHOSPHOLIPIDS and PROTEINS within the cell membrane? |
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Definition
| Phospholipids make a fluid bilayer which helps protect the cell by blocking unwanted materials from entering. They also allow materials to enter and exit the cell. Proteins help aid with this. |
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Term
| Components of a Phospholipid |
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Definition
| Polar "head" and fatty acid "tails" that are nonpolar |
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Term
| Why do phospholipids form a bilayer in the membrane? |
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Definition
| Hydrogen bonds form between water and the hydrophilic phospholipic heads causing the heads to orient outwards toward the water on either side of the membrane. Pairs of these phospholipids are paired up, fatty acid tails on the inside, heads on the outside. |
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Term
| Which type of fatty acid tails would you expect to find an abundance in organisms that live in cold conditions? |
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Definition
| Unsaturated phospholipids because their kinky tails allow the membrane to retain necessary fluidity. |
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Term
| Which types of molecules do NOT easily cross the plasma membrane? Why? |
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Definition
| Biological molecules such as salts, animo acids, and sugars are hydrophilic and polar, and they do not easily cross the plasma membrane because the phospholipid bilayer is nonpolar. |
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Term
| What function does CHOLESTEROL serve in the plasma membrane? |
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Definition
| It stabilizes the lipid bilayer, making it less fluid at higher temperatures, less solid at lower temperatures, and less permeable to water-soluble substances such as ions or monosaccharides. |
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Term
| Why is it important that the cell membrane is fluid and flexible? |
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Definition
| Cells in your body change shape as you move. If they were stiff, cells would break open and die. |
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Term
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Definition
| Proteins to which a carbohydrate is attached. |
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Term
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Definition
| Proteins located in a membrane or the cytoplasm of a cell that bind to SPECIFIC molecules triggering a response in the cell, such as endycotysis, and changes in metabolic rate, cell division, or electrical changes. |
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Term
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Definition
| Proteins or glycoproteins protruding from the outside surface of a plasma membrane that identifies a cell as belonging to a particular species, to a specific individual of that species, and in many cases, to one specific organ within the individual. |
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Definition
| A protein that speeds up the rate of specific biological reactions. |
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Term
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Definition
| Proteins in the plasma membrane of a cell that attaches either to the cytoskeleton inside the cell, or other cells, or to the extracellular matrix. |
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Definition
| Proteins that regulate the movement of water-soluble molecules through the plasma membrane. |
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Term
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Definition
| The difference in concentration of a substance between two parts of a fluid across a barrier such as a membrane. Takes no energy from the cell. |
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Term
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Definition
| The net movement of particles from a region of high concentration of that particle to a region of low concentration, driven by the concentration gradient, may occur entirely within a fluid or across a barrier such as a membrane. |
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Term
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Definition
| The condition in which all acting influences or balanced or canceled by equal opposing forces, the state of being balanced. |
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Term
| What relationship exists between the size of the concentration gradient and the rate of diffusion? |
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Definition
| The greater the concentration gradient, the faster the rate of diffusion. |
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Term
| What is a limitation of diffusion? |
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Definition
| A limitation is the exchange of gases. |
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Term
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Definition
| Only allows certain things pass through. |
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Term
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Definition
The net movement of molecules down a gradient from high to low concentration.
They diffuse directly across the phospholipid bilayer down their concentration gradients.
Ex of substances: water, oxygen, and carbon dioxide. |
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Term
| Facilitated Diffusion (chart) |
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Definition
Diffusion of water, ions, or water-soluble molecules through a membrane via a channel or carrier protein.
Transport proteins aid this, channel proteins form pores in the lipid bilayer through which ions or water can flow down their concentration gradients. Through aquaporons.
Ex of substances: monosaccarides, larger ions/molecules with hydrogen bonds. |
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Term
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Definition
Diffusion of water across the selectively permeable membrane from a region of higher free water concentration to a region of lower free water concentration. High => low.
May occur directly or through aquaporins-channels composed of membrane-spanning proteins.
Ex of substances: water |
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Term
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Definition
| Solutions with equal concentration of solute (and water) concentration of water is equal in the cell as in the environment. Water moves in and out of cell; no change in size. |
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Term
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Definition
| The solution that contains a greater concentration of a solute when a membrane selectively permeable to water separates solutions with different concentrations of a solute. Water moves out of the cell and the cell shrinks. |
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Term
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Definition
| Th solution that contains a lesser concentration of a solute when a membrane selectively permeable to water separates solutions with different concentrations of a solute. Water moves into the cell and the cell swells. |
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Term
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Definition
| Cell death to excessive water loss. |
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Term
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Definition
| Cell death due to excessive water gain. |
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Term
| How do plant and animal cells avoid cytolysis? |
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Definition
| Plant cells resist this by having the cell wall and the central vacuole which stores excess water. Some animal cells have a contractile vacuole that pumps out excess water. |
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Term
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Definition
| The water pressure within a cell/vacuole as a result of osmotic water entry. It gives the cell shape in a plant cell. |
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Term
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Definition
| The movement of materials across a membrane through the use of cellular energy, normally against the concentration gradient. It is important because all cells require some nutrients that are less concentrated in the environment than in the cells cytoplasm. |
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Term
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Definition
| The process in which the plasma membrane engulfs extracellular material, forming membrane-bound sacs that enter the cytoplasm and thereby move material into the cell. |
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Term
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Definition
| The nonselectivae movement of extracellular fluid, enclosed within a vesicle formed from the plasma membrane, into a cell. |
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Term
| Receptor-mediated Endocytosis |
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Definition
| The selective uptake of molecules from the extracellular fluid by binding to a receptor located at a coated pit on the plasma membrane and pinching off the coated pit into a vesicle that moves into the cytoplasm. |
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Term
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Definition
| A type of endocytosis in which extensions of a plasma membrane engulf extracellular particles, enclose them in a membrane-bound sac, and transport them into the interior of the cell. |
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Term
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Definition
| The process in which intracellular material is enclosed within a membrane-bound sac that moves to the plasma membrane and fuses with it, releasing the materials outside the cell. |
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Term
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Definition
| Microscopic projections of the plasma membrane that increases the surface area of a cell. They help absorb and digest food. |
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Definition
Surface structure that link adjacent cells. They are located throughout your body, especially on the small intestine.
Animal |
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Term
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Definition
Cell surface structure; cell-to-cell junction that prevents movement of molecules through the spaces between cells.
Bladder/skin
Animals |
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Term
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Definition
Cell-to-cell junctions where channels connect the cytoplasm of adjacent cells.
Throughout body, liver
Animals |
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Term
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Definition
Holes in the walls of adjacent plant cells that link the insides of adjacent cells.
Throughout plant roots
Plant |
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Term
| SEE QUESTIONS __, __, __, __, __, AND __ ON THE STUDY GUIDE!!!! |
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Definition
| 12, 17, 25, 27, 28, and 31 |
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