Cell Membrane Structure & Function Chapter 3
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27 terms
Terms | Definitions |
|---|---|
 Active transport | Movement of individual small molecules or ions through membrane-spanning proteins, using cellular energy, usually ATP. Cell uses energy to move substances against a concentration gradient. |
| Aquaporins | Allows water to cross membranes by facilitated diffusion which is faster than simple diffusion. |
| Carrier protein | A passive transport protein that grabs onto a specific molecule on one side of the membrane and carries it through. |
| Cell wall | Plasma membranes in plants, fungi and bacteria. They support/protect fragile cells from gravity/winds. Walls are porous and allow passage of minerals, H2O, CO2, amino acids and sugars. |
| Channel protein | A passive transport protein that forms channels in the lipid bilayer through which certain ions can cross the membrane. |
| Concentration gradient | A difference in concentration from one area to another. |
| Diffusion | Movement of molecules from regions of high concentration to low; "going down" the gradient. The greater the concentration gradient, the faster the rate of diffusion. |
| Endocytosis | Movement of a large particle into a cell, which are engulfed as the plasma membrane forms vesicles (membranous sacs) that enter the cytoplasm. |
| Energy-requiring Transport | Movement across a membrane of substances that travel against a concentration gradient; requires the cell to expend energy such as active, endocytosis or exocytosis. |
| Exocytosis | Movement of unwanted materials (waste of digestion/secrete hormones) out of a cell that get enclosed in a membrane vesicle. |
| Facilitated diffusion | Water-soluble molecules, such as ions (K+, Na+, Ca2+), amino acids, simple sugars cannot pass through the bilayer on their own but rather utilizing the passive transport of channel proteins or carrier proteins. |
| Fluid mosaic | Structure of the membrane in which substances of liquid/gas change shape w/o breaking apart and whose molecules move freely in a lumpy, constantly shifting mosaic of tiles. |
| Hydrophilic | The head of the phospholipid molecule that is attracted to water molecules. |
| Hydrophobic | The tail of the phospholipid molecule that repels water molecules. These tails repel water and "hide" inside the membrane. |
| Osmosis | Movement of water across membranes from areas of high water concentration to low. Pure water has the highest water concentration. |
| Passive transport | Substances move into or out of cells down concentration gradients. Requires no expenditure of energy. |
| Phospholipid bilayer | Double layer of phospholipid. Phospholipids are not bonded to each other. |
| Pinocytosis | Process in which plasma membrane dimples inward and then buds off into the cytoplasm. |
| Phagocytosis | Process to pick up larger particles. The cell extends parts of its surface membrane (pseudopods) that fuse together around the particle and carries it into the cell inside a vesicle. |
| Plasma membrane | The thin layer surrounding a cell's contents. Acts as a gatekeeper, controlling which substances are allowed to pass in or out and transferring chemical messages from the external environment to the cell's interior. |
| Receptor-mediated endocytosis | A type of endocytosis that depends on the many receptor proteins on the outside surface. Each receptor protein has a binding site for a particular molecule. |
| Receptor protein | Membrane protein that delivers chemical messages to the cell. Triggers responses inside the cell when specific molecules outside the cell bind to them. |
| Recognition protein | Membrane protein that serves as identification tags and cell-surface attachment sites. Can distinguish your cells from disease-causing invaders. |
| Selectively permeable | Membranes that allow the passage of some molecules- prevents the passage of others |
| Simple diffusion | A Passive transport in which molecules that dissolve in lipids, like ethyl alcohol & vitamin A easily diffuse across the bilayer as well as water, oxygen and carbon dioxide |
| Transport protein | Membrane protein that allows movement of hydrophilic molecules through the plasma membrane. They allow movement by forming channels through which molecules pass or by grabbing onto molecules and carrying them across the membranes. |
| Vesicle | Membraneous sac pinched off to surround a particle or droplet of fluid in the cytoplasm |
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