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exam study
the cell
| Question | Answer |
|---|---|
| Because cell membranes are made up of phospholipids, which are amphipathic (having both hydrophobic and hydrophillic parts), with the interior being the hydrophobic tails, what molecules can easily cross the membrane? | Only certain molecules can easily cross the membrane. Larger molecules or charged molecules must cross the membrane using membrane proteins, and this process is regulated. |
| What is simple diffusion? | Simple diffusion is when molecules move from an area of higher concentration to an area of lower concentration. |
| Does simple diffusion require ATP (energy) or a membrane protein? | No ATP (energy) required. No membrane protein required |
| What substances move by simple diffusion? | Oxygen, carbon dioxide, N₂, glycerol, short-chain fatty acids. |
| What is osmosis? | Osmosis is when water moves from an area of higher water concentration to an area of lower water concentration—no ATP required. |
| Even though water is polar, how can it cross the membrane? | Even though water is polar, it is small enough to cross the membrane without a membrane protein and will move based on the osmotic pressure— |
| Even though water is polar, how can it cross the membrane? (continued) | the concentration of solutes that have a charge or are polar, such as sodium ions. Water can also cross cell membranes through aquaporin proteins. |
| What is a cell’s typical osmotic concentration and NaCl concentration? | A cell has a typical osmotic concentration of approximately 300 mOsmol. A cell typically has 0.9% NaCl—this is “normal saline,” such as contact lens solution. |
| What is a hypertonic solution? | Hypertonic solution has more solute than the cell. Water will move from cell into solution; cell will shrink. |
| What is an isotonic solution? | Isotonic solution has the same concentration of solute as the cell. Water will move equally into and out of cell; cell will stay the same. |
| What is a hypotonic solution? | Hypotonic solution has less solute than the cell. Water will move from solution into cell; cell will swell and could burst. |
| What is facilitated diffusion? | This requires the use of membrane proteins. Each substance has a specific membrane protein. Molecules move down their concentration gradient. ATP is not required. |
| How do channels and carriers function in facilitated diffusion? | Channels generally allow ions to cross the membrane, and they can flow freely as long as the channel is open. Carriers move nutrients such as glucose and amino acids but can also move ions. Carriers can become saturated. |
| What is primary active transport? | This requires the use of membrane protein carriers. Each substance has a specific membrane protein. Molecules move against their concentration gradient. ATP is required. |
| How does the sodium-potassium (Na⁺-K⁺) pump function? | The sodium-potassium (Na⁺-K⁺) pump uses energy, in the form of ATP, to pump 3 Na⁺ out of the cell; and 2 K⁺ into the cell. |
| What is the purpose of the sodium-potassium pump? | Maintain electrical gradient: cells are relatively more negative compared to the extracellular fluid. Maintain chemical gradient: higher sodium outside cells can be used to drive secondary active transport. |
| What is the proton pump? | The proton pump uses energy to pump protons across a membrane. In mitochondria, a proton gradient builds up in the intermembrane space. The result is a concentration gradient favouring the reentry of protons back into the cell. |
| What is the proton pump? (continued) | The only way that protons can cross back into the cell is through channels that generate ATP. This process, known as chemiosmosis, is essential to energy metabolism. |
| What is coupled transport? | Moving two substances across a membrane at the same time. |
| What is symport and antiport? | Symport: substances move in the same direction. Antiport: substances move in opposite directions. |
| What is secondary active transport? | Secondary active transport involves the use of the sodium gradient outside of cells to pull other nutrients such as glucose or amino acids into a cell so that ATP is not required. |
| How are large molecules moved into and out of a cell? | Bulky substances are contained within vesicles as they are moved into and out of a cell. |
| What is endocytosis? | Endocytosis is the engulfing of substances outside of the cell in order to form a vesicle that is brought inside the cell. |
| What is phagocytosis? | Phagocytosis: solids, such as immune cell engulfing pathogens. |
| What is pinocytosis? | Pinocytosis: fluids, such as human egg engulfing fluids with nutrients before fertilization. |
| What is exocytosis? | Exocytosis is the discharge of substances from vesicles at the inner surface of the cell. |
Created by:
oliviavanwort
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