Question | Answer |
What is another name for the cell membrane? Hint: think of what makes it up. | The phospholipid bilayer. |
Which part of a phospholipid is hydrophobic? Hydrophilic? | The head of a phospholipid is hydrophilic. The fatty acid tails of the phospholipid are hydrophobic. |
Why is the plasma membrane also called a 'fluid mosaic'? | Because it is made up of many different proteins and lipids (mosaic) and it is flexible (fluid). |
What does cholesterol do for the cell membrane? | It provides the cell membrane with some rigidity. Otherwise the membrane would be too flexible. |
What do proteins in the membrane do for the cell? | They can act as enzymes, receive signals, and transport items across the cell membrane. |
What is passive transport? | any form of movement across a membrane that does not require the use of ATP. |
What are some examples of passive transport? | Diffusion, facilitated diffusion, osmosis. |
What is diffusion? | Diffusion is when there is movement of a substance from an area of high concentration of that substance to an area of lower concentration. |
What is osmosis? | Osmosis is the diffusion of water across the membrane from high water concentration to low water concentration. |
What is a concentration gradient? | When there are more molecules of one type on one side of the membrane than the other. |
What is a hypertonic solution? | A solution where the solute is MORE concentrated than another. |
What is a hypotonic solution? | A solution where the solute is LESS concentrated than another. |
What is an isotonic solution? | A solution where the solute is equally concentrated on either side of the membrane. |
What is a solute? A solvent? | A solute is the item that is being dissolved. A solvent is the liquid doing the dissolving. |
What happens to a cell in a hypertonic solution? Why? | The cell will shrink because water is moving out to balance the solution. |
What happens to a cell in a hypotonic solution? Why? | The cell will expand and perhaps even burst because water is moving in to balance the solution. |
What happens to a cell in an isotonic solution? Why? | The cell will stay the same because it is at a state of dynamic equilibrium. Water is moving in and out of the cell at the same rate. |
What is active transport? | transport of a substance across a cell membrane against the concentration gradient; requires ATP (energy). |
What is endocytosis? | It is the process by which cells absorb material from outside the cell by engulfing it with their cell membrane. |
What is exocytosis? | It is the process by which a vesicle fuses with the cell membrane, dumping its contents outside the cell. |
What is phagocytosis? | It is when cells engulf food with their cell membrane and then digest it. |
What is pinocytosis? | It is when cells engulf water by forming vesicles. |
How does molecule size affect diffusion? | The larger the molecule, the less likely it is to cross the membrane. Smaller molecules will diffuse first. |
How does concentration affect diffusion? | The more concentrated the solution, the faster it will diffuse across the membrane. |