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| Answer |
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| passive transport |
process by which some substances can cross the cell membrane without any input of energy by the cell |
| diffusion |
movement of molecules from an area of higher concentration to an area of lower concentration |
| concentration gradient |
difference in the concentration of molecules across a distance |
| equilibrium |
concentration of molecules is the same throughout the space the molecules occupy |
| simple diffusion |
diffusion across a membrane that only allows certain molecules to pass through the membrane |
| osmosis |
process by which water molecules diffuse across a cell membrane from an area of higher concentration to an area of lower concentration |
| hypotonic |
describes a solution whose solute concentration is lower than the solute concentration inside a cell |
| hypertonic |
describes a solution whose solute concentration is higher than the solute concentration inside a cell |
| isotonic |
describes a solution whose solute concentration is equal to the solute concentration inside a cell |
| contractile vacuoles |
organelles that remove water by collecting the excess water and then contracting to pump out the water |
| turgor pressure |
pressure that water molecules exert against the cell wall |
| plasmolysis |
condition in which cells shrink away from the cell walls, and turgor pressure is lost |
| cytolysis |
condition in which a hypotonic environment causes water to diffuse into the cell, making it swell and eventually burst |
| facilitated diffusion |
type of passive transport in which molecules that cannot readily diffuse through cell membranes are assisted by carrier proteins; thus ~ facilitated |
| carrier proteins |
specific proteins in the membrane that assist the movement of molecules in facilitated diffusion |
| ion channels |
type of membrane protein involved in passive transport - diffusion through ion channels |
| active transport |
movement of materials from an area of lower concentration to an area of higher concentration; UP concentration gradient; REQUIRES cell to expend ENERGY |
| sodium-potassium pump |
transports Na+ ions and K+ ions up their concentration gradients |
| endocytosis |
process by which cells ingest external fluid, macromolecules, and large particles, including other cells |
| pinocytosis |
involves transport of solutes or liquids: DRINK |
| phagocytosis |
movement of large particles or whole cells |
| phagocytes |
cells that allow lysosomes to fuse with the vesicles that contain the ingested bacteria and viruses |
| vesicle |
pouch pinched off from the cell membrane, becoming a membrane bound organelle |
| exocytosis |
the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out of the cell |
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