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Phys Ch. 4.1
| Question | Answer |
|---|---|
| Lipids that forms bilayers of the plasma membrane. | phospholipids |
| Type of steroid found in the plasma membrane. | cholesterol |
| Lipid with an attached carbohydrate group found on the extracellular side of the plasma membrane. | glycolipid |
| Filamentous coating on the apical surface of certain types of cells. "Coating of sugar." | glycocalyx |
| Most of the plasma membrane lipids are __. A "balloon with two tails." The balloonlike "head" is polar and hydrophilic and the two "tails" are nonpolar and hydrophobic. | phospholipids |
| The phospholipid bilayer ensures that __ remains inside the cell and __ __ (the fluid that surrounds cells) remains outside. | cytosol, interstitial fluid |
| __ is scattered within the hydrophobic regions of the phospholipid bilayer. It strengthens the membrane and stabilizes it at temperature extremes. | cholesterol |
| __ are lipids with attached carbohydrate groups. They are located only on the outer phospholipid layer of the membrane, where they are exposed to the interstitial fluid. | glycolipids |
| Together, the carbohydrate portion of the glycolipid molecules and the glycoprotein molecules help to form the __. | glycocalyx |
| The lipid portion of the plasma membrane is __ in water, which ensures that the plasma membrane will not simply dissolve when it comes into contact with water. | insoluble |
| Membrane proteins are classified as one of two structural types: __ or __. | integral or peripheral |
| __ proteins are embedded w/in, & extend across the phospholipid bilayer. Hydrophobic regions interact w/the hydrophobic interior of the membrane. The hydrophillic regions are exposed to the aqueous environments on either side of the membrane. | integral |
| Many integral membrane proteins are __ that have carbohydrates exposed to the interstitial fluid | glycoproteins |
| __ proteins are not embedded within the lipid bilayer. They are attached loosely to either the external or internal surfaces of the membrane and are often “anchored” to the exposed parts of an integral protein. | peripheral |
| Protein that bonds to a molecule then alters its shape in order to transport the molecule across the plasma membrane. | carrier |
| Chemical released from one cell that binds to receptors on another cell. | ligands |
| Protein that catalyzes a chemical reaction by lowering the activation energy. | enzyme |
| One important function of the __ __ is to to regulate the movement of materials into and out of a cell. | plasma membrane |
| Obtaining and eliminating substances across the plasma membrane occur through the processes of membrane __. These processes are organized into two major categories based on the requirement for expending cellular energy: __ and __ processes. | transport, passive and active |
| __ processes do not require energy expenditure. Instead they simply depend upon the kinetic energy inherent within a substance as it moves down its concentration gradient (i.e., from where there is more of a substance to where there is less). | passive |
| __ processes differ b/c they require cells to expend energy. This involves either the movement of a substance up its concentration gradient (lower concentration to high concentration) or the release (or formation) of a membrane-bound vesicle. | active |
| Random movement of molecules or particles down their concentration gradient. | diffusion |
| The net movement of a substance from where it is more concentrated to where it is less concentrated is called __. | diffusion |
| Diffusion, if unopposed, occurs until the substance reaches __ (i.e., the molecules become evenly distributed throughout a given area(s)). | equilibrium |
| Solutes that are small and nonpolar move into or out of a cell down their concentration gradient by __ __. These molecules do not require a transport protein. They simply pass between the phospholipid molecules that form the plasma membrane. | simple diffusion |
| Passive transport process used when a chemical slips between plasma membrane phospholipids to enter or leave a cell. | simple diffusion |
| Materials that move via simple diffusion include: | respiratory gases (O2 and CO2), small nonpolar fatty acids, ethanol, and urea (a nitrogenous waste produced from amino acids) |
| The plasma membrane cannot regulate simple diffusion—rather, the movement of these substances is dependent only upon the __ __. The substance continues to move across the plasma membrane as long as this exists. | concentration gradient |
| Small solutes that are charged or polar are effectively blocked from entry into the cell by the nonpolar phospholipid bilayer. Their transport into the cell must be assisted by plasma membrane proteins in a process called __ __. | facilitated diffusion |
| What are the two types of facilitated diffusion that are distinguished by the type of transport protein used to move the substance across the membrane? | channel-mediated diffusion and carrier-mediated diffusion |
| Passive transport process using carrier proteins or channel proteins to move a chemical across the plasma membrane. | facilitated diffusion |
| __-__ diffusion is the movement of small ions across the plasma membrane through water-filled protein channels. | channel mediated |
| Every channel is typically specific for one type of ion. The channel is either a __ channel, which is continuously open, or a __ channel, which is usually closed, and opens only in response to a stimulus (e.g., chemical, light, voltage change). | leak, gated |
| __-__ diffusion is the movement of small, polar molecules, such as simple sugars or amino acids. They are assisted across the plasma membrane by a __ protein. | carrier-mediated, carrier |
| __ proteins transport substances such as glucose. The binding of the substance induces the carrier protein to change shape and move it to the other side of the membrane. Like channels, a carrier moves a substance down its gradient. | carrier |
| A carrier that transports only one substance is called a __. Glucose carriers are __ that normally prevent the loss of glucose in the urine. | uniporters |
| The number of channels and carriers in a plasma membrane determines the maximum rate at which a substance can be transported. The rate of facilitated diffusion is __ (faster/slower) when there are a greater number of these transport proteins. | faster |
| __ is unlike the other types of passive membrane transport, because it involves water movement and phospholipid bilayer prevents the movement of solutes. | osmosis |
| Osmosis is the passive movement of water through a __ __ (or semipermeable) membrane. This movement occurs in response to a difference in relative concentration of water on either side of a membrane. | selectively permeable |
| Process by which water moves through a semipermeable membrane from a hypotonic solution to a hypertonic one. | osmosis |
| Water molecules cross the plasma membrane in one of two ways: They either “slip between” the molecules of the phospholipid bilayer (limited amounts) or they move through integral protein water channels called __. | aquaporins |
| Protein channels in the plasma membrane allowing the passage of water. | aquaporins |
| In the context of osmosis, solutes are classified into two categories based upon whether their passage across the plasma membrane is prevented by the phospholipid bilayer: __ or __. | permeable or nonpermeable |
| __ (permeability) solutes (e.g., small and nonpolar solutes such as oxygen, carbon dioxide, and urea) pass through the bilayer. | permeable |
| __ (permeability) solutes (e.g., charged, polar, or large solutes such as ions, glucose, and proteins) are prevented from crossing the bilayer. | nonpermeable |
| During osmosis observe that water moves toward the solution with the __ (greater/lower) water concentration (or stated another way, water moves toward the solution with the __ (lower/greater) solute concentration). | lower, greater |
| Pressure exerted by the movement of water across a semipermeable membrane as it moves toward an area of lower water concentration. The steeper the gradient, the greater the amount of water moved by osmosis and the higher the pressure. | osmotic pressure |
| __ pressure is the pressure exerted by a fluid on the inside wall of its container. | hydrostatic |
| The ability of a solution to change the volume or pressure (or the “tone”) of the cell by osmosis is called __. It is a measure of the solute concentration of fluid surrounding a cell relative to the fluid within a cell. | tonicity |
| In a(n) __ solution, both the cytosol and the solution have the same relative concentration of solutes. The solute concentration of cytosol and the fluid outside the cell are equal and there is no net movement of water. | isotonic |
| In a __ solution, the solution has a lower concentration of solutes, and there is a higher concentration of water than in the cytosol so water moves into the cell. | hypotonic |
| In a hypotonic solution, __ (or rupture) of the cell can occur if the difference in concentration is large enough. __ is the specific term for rupturing red blood cells. | lysis, hemolysis |
| A __ solution has a higher concentration of solutes, and thus a lower concentration of water than does the cytosol so water moves out the cell. | hypertonic |
Created by:
khinson