Term
|
Definition
Isolate, organize, and protect contents from the external environment.
Move materials in an out.
Convert energy to a usefull form.
Detect stimuli.
Provide for cell-to-cell communication. |
|
|
Term
|
Definition
| Two layers of phospholipids that are held together by the hydrophobic interactions of the fatty acids. |
|
|
Term
|
Definition
Phospholipids exhibit lateral and flip-flop (initiated by enzymes called flippases) movement. Fluidity of membranes is influenced by the number of saturated and unsaterated fatty acids in the membrane. To offset the effects of high/low temperatures the cell will increase/decrease the length of the fatty acids and decrease/increase the proportion of unsaterated fatty acids. Cholestral can also stabilize membranes.
|
|
|
Term
|
Definition
| Single chain that links the surfaces of the membrane (present in many members of the kingdom Archae). |
|
|
Term
|
Definition
Membranes contain a variety of proteins that can move fluidly around the membrane.
- Integral (intrensic) Proteins: Have a region that is in contact with the environment and a region that is in contact with the fatty acids.
- Peripheral (extrensic) Proteins: Are on the surface of the membrane.
|
|
|
Term
|
Definition
| Have a hydrophilic and a hydrophobic region. Some are "transmembrane proteins" and span the membrane. |
|
|
Term
|
Definition
| Carbohydrates that are combined with either membrane lipids or proteins (are recognition molecules in man). |
|
|
Term
| Movement Through Phospholipid Bilayer |
|
Definition
| Membranes will allow gases, hydrophobic molecules, and small polar molecules to pass through, but large polar molecules and charged molecules cannot pass through. |
|
|
Term
|
Definition
| Transmembrane protein that only allows water to pass through. |
|
|
Term
| Mechanisms for Crossing Membranes |
|
Definition
Passive Transport
- Osmosis: movement of water.
- Diffusion: Movement of solute.
- Facilitated Diffusion
Active transport: Requires energy.
Bulk Trasnport: Transports large molecules. |
|
|
Term
|
Definition
| Molecules move from regions of higher concentration to regions of lower concentration (move down the "concentration gradient"). The greater the gradient the faster the molecules move. Molecules move independently of each other and stop moving whtn equilibrium is reached. |
|
|
Term
|
Definition
Results in equalization of concentration and changes in volumes. THe presence of charged solutes will reduce the rate of osmosis. Three types of environments:
Hypertonic (higher concentration than cell)
Isotonic (same concentration than cell)
Hypotonic (lower concentration than cell)
|
|
|
Term
|
Definition
Movement is still down a concentration gradient but proteins are increasing the rate of diffusion (facilitated is min. 1000 times faster than passive). Two types of proteins involved:
Carrier Proteins: Undergo changes in shape to carry solute.
Channel Proteins: Posses central pore for passage of solute (Gated Channels are channel proteins that can open and close via a stimulus). |
|
|
Term
|
Definition
| One of the most important proteins in facilitated transport. Uses the diffusion of protons to sythesize ATP. |
|
|
Term
|
Definition
| When protein has reached the max. rate of facilitated diffusion. |
|
|
Term
|
Definition
| Moving molecules from low to high concentration via the use of energy. Direct active transport uses ATP and indirect active trasport uses other energy sources. |
|
|
Term
|
Definition
| Active trasnport proein that moves two different substances in opposite directions (known as an antiporter). Process changes the membrane potential (and is thus electrogenic). |
|
|
Term
| Indirect Active Transport |
|
Definition
| Most use an ion gradient that is estiblished by active trasnport as their energy source. Most indirect transport systems are "coupled" with active transport systems. |
|
|
Term
|
Definition
| Inderect active transport system that uses a proton gradient that is established by a proton pump as its energy source. THe protons re-enter the cell by facilitated diffusion causing the protein to import sucrose. |
|
|
Term
|
Definition
| Moves one substance in one direction (proton pump). |
|
|
Term
|
Definition
| Moves two different subtances in the same direction (sucrose transport). |
|
|
Term
|
Definition
| Moves two different substances in opposite directions (sodium-potassium pump). |
|
|
Term
|
Definition
Moves large particles across a membrane.
Endocytosis: movement into cell
Exocytosis: movement out of cell (material is packaged into vesicles, the vesicles then fuse with the cell wall and release their contents outside of the cell). |
|
|
Term
|
Definition
Devided into:
Phagocytosis
Pinocytosis
Receptor-Mediated Endocytosis |
|
|
Term
|
Definition
| Non-specific mechanism that brings large particles into the cell. The cell extends pseudopodia which surround and enclose particles in a vacuole. |
|
|
Term
|
Definition
| Non-specific mechanism that brings dissolves molecules into the cell through invagination. |
|
|
Term
| Receptor-Mediated Endocytosis |
|
Definition
| Mechanism only brings specific dissolved substances into the cell. When a substance binds to certain recptors the protein clathrin binds to the inner region of those receptors. THe clathrin causes the membrane to pull in, forming a "coated pit", and eventually a "coated vesicle". |
|
|
