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Biology Chapter 5
Structure and Function of Plasma Membrane
| Question | Answer |
|---|---|
| What is the plasma membrane made of? | Made of a phospholipid bilayer often referred to as a fluid mosaic. |
| What is in the plasma membrane? | Phospholipids, integral or peripheral proteins, and carbohydrates. |
| What is a peripheral protein and what does it do? | It is a protein on the plasma membrane's surface either on interior or exterior side. Can serve as enzymes, structural attachments, or as a part of cell's recognition sites. |
| What is an integral protein and what does it do? | It is a protein embedded in the phospholipid bilayer all the way through. Can be used as transport or receptors. |
| What do carbohydrates do? | These are always on the outside of the membrane and are bound to proteins (glycoprotein) or to lipids (glycolipid). Role in cellular recognition. |
| Define glycocalyx. | The carbohydrates on cell's exterior. The glycocalyx is highly hydrophilic and attracts large amounts of water to cell's surface. |
| What does cholesterol do for the plasma membrane? | The cholesterol found in between the phospholipids buffers against harsh temperature changes. |
| What controls fluidity of plasma membrane? | The proportion of unsaturated fatty acids to saturated fatty acids. |
| Define concentration gradient/ | Area of high concentration adjacent to an area of low concentration. |
| What does selective permeability mean? | Allows some substances to pass, but not others. |
| What is passive transport? | This requires no energy from the cell and happens naturally. This always follows the concentration gradient. |
| What is active transport? | This requires energy from the cell, in the form of ATP. Usually goes against the concentration gradient. |
| Define diffusion. | This is a passive transport process. A single substance moves from a high concentration to a lower concentration to make it equal. |
| What factors affect the diffusion rate? | Extent of concentration gradient, mass of molecules diffusion, temperature, solvent density, solubility, surface area and plasma membrane thickness, and distance travelled. |
| Related to diffusion, which membrane will have a better diffusion rate? A smaller membrane or a larger one? | A smaller membrane limits diffusion whereas a bigger membrane encourages diffusion. |
| What substances require a transportation medium to go across the plasma membrane? | Anything that is polar. |
| Describe facilitated transport. | A process by which material moves down a concentration gradient using integral proteins. A certain substance first attaches to protein or glycoprotein receptors, it then is passed to specific integral proteins for passage. |
| What is a channel protein? | A membrane protein that allows a substance to pass through its hollow core across the plasma membrane. These proteins form a tunnel. Can be open or gated. |
| What is an aquaporin? | A channel protein that allows water to pass through the membrane at a very high rate. |
| Define carrier proteins. | Another membrane protein that moves a substance by changing its own shape. These proteins bind substances. |
| What is osmosis? | The passive movement of ONLY water from an area of high concentration to an area of lower concentration. |
| Define tonicity. | Amount of solute in a solution. This shows how an extracellular solution can change a cell's volume by affecting osmosis. |
| Define osmolarity. | The solution's total solute concentration. Low osmolarity means it has a greater number of water molecules relative to the number of solute particles. Vice versa for high osmolarity. |
| What is a hypotonic solution? | A solution where the extracellular fluid lower osmolarity than the fluid inside the cell, therefore water travels INTO the cell and it ruptures. |
| What is a hypertonic solution? | A solution where the extracellular fluid has higher osmolarity than the fluid inside the cell, therefore water travels OUT of the cell and it deflates. |
| What is a isotonic solution? | A solution where the extracellular fluid has the SAME osmolarity as inside the cell. There is no net movement of water. |
| Define plasmolosis. | The detaching of the cell membrane from the cell wall and constricting the cell membrane when a plant cell is in a hypertonic solution. This causes plants to wilt. |
| What is an electrochemical gradient? | A combined electrical and chemical force that produces a gradient. |
| Describe a pump. | An active transport mechanisms that works against the electrochemical gradients. ATP changes the configuration of a carrier protein. |
| What is primary active transport? | This moves ions across a membrane and creates a difference in charge across that membrane and is directly dependent on ATP. |
| What is secondary active transport? | This doesn't directly require ATP. This is the movement of material due to the electrochemical gradient established by primary active transport. |
| Name the three main transporters of active transport. | Uniporter, symporter, and antiporter. |
| Function of the uniporter is____ | To carry one specific ion or molecule in one direction. |
| Function of the symporter is____ | To carry two different ions or molecules in one direction. |
| Function of the antiporter is____ | To carry two different ions or molecules in two different directions. |
| What is endocytosis? | A type of active transport that moves substances, including fluids and particles, into a cell. |
| What is exocytosis? | Process of passing bulk material out of a cell. |
| Define pinocytosis. | A variation of endocytosis that imports macromolecules that the cell needs from the extracellular fluid. |
| Define phagocytosis. | This is the process of when a cell takes in very large particles or even another cell. Means "cell eating." |
| Which plasma membrane component can be found on its surface or embedded in the membrane structure? | Proteins |
| What is the primary function of carbohydrates attached to the exterior of cell membranes? | Identification of the cell. |
| Water moves via osmosis______ | from an area with high concentration to an area of lower concentration. |
| What problem is faced by organisms that life in fresh water? | Their bodies tend to take in too much water. |
| Active transport must function continually because_____ | diffusion is constantly moving solutes in opposite directions. |
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tali_Alley
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