Membrane Structure and Function: Chp 7 Flashcards
plasma membrane
is selectively permeable and allows some substances to cross it more easily than others
fluid mosaic model
describes the membrane as fluid, with proteins embedded in or associated with the phospholipid bilayer
phospholipids
present in the membrane and provide a hydrophbic barrier that separates the cell from its liquid environment. Hydrophilic molecules cannot easily enter the cell, but hydrophobic molecules can enter much more easily
integral proteins
are completely embedded in the membrane, some of which are transmembrane proteins that span the membrane completely
peripheral proteins
are loosely bound to the membrane’s surface
carbohydrates
on the membrane are crucial in cell-cell recognition (which is necessary for proper immune function) and in developing organisms ( for tissue differentiation). Cell-surface carbohydrates varyfromspecies to species and are the reason that blood transfusions much be type-specific
nonpolar molecules
are hydrophobic and can dissolve in the phospholipid bilayer and cross the membrane easily EX: hydrocarbons, carbon dioxide, and oxygen
transport proteins
span the membbrane and allows hydrophilic substances to avoid the lipid bilayer and pass through the membrane
aquaporins
special transport proteins that allow water molecules to move across the membrane and accelerates the speed
passive diffusion
when a substance travels from where it is more concentrated to where it is less concentrated. No energy is required
osmosis
the diffusion of water across a selectively permeable membrane
isotonic solution
there will be no net movement of water across the plasma membrane. Water crosses the membrane, but at the same rate in both directions
hypertonic solutions
the cell will lose water to its surroundings. The hyper- prefix refers to more solutes in the water around the cell causing a movement of water to the higher concentration of solutes meaning the cell loses water to the environment, shrivels, and might die.
hyoptonic solutions
water will enter the cell faster than it leaves causing the cell to swell and possibly burst. The hypo= prefix refers to fewer solutes in the water around the cell which is why the movement of water is into the cell because more solutes are present in the cell
flaccid
limp plant cell
plasmolyzed
a plant cell that has lost water and is shrivelled
turgid
plant cells that have full vacuoles and are very firm
facilitated diffusion
process by which ions and hydrophilic substances diffuse across the cell membrane with the help of transport proteins that are specific for the substances they transport and works by:
- providing a hydrophilic channel through which the molecules such as ions and polar molecules can pass
- they bind loosely to the ions and polar molecules and carry them trhough the membrane
active transport
when substances are moved against their concentration gradient (from less concentrated to more concentrated). requires energy
sodium-potassium pump
a type of active transport. this transmembrane protein pumps sodium out of the cell and potassium into the cell. the sodium-potassium pump is necessary for proper nerve transmission and is a major energy consumer in your body
membrane potential
the difference in electric charge across a membrane that is expressed in voltage. the inside of the cell is negatively charged compared with outside the cell
two forces that drive the diffusion of ions across a membrane are:
chemical force (which is the ions concentration gradient) and voltage gradient (which attracts positively charged ions and repels negatively charged ions)
electrochemical gradient
the combination of chemical force and voltage gradient action on ions
electrogenic pump
a transport protein that generates voltage across the membrane
cotransport
an ATP pump that transports a specific solute indirectly drives the active transport of oter substances. In this process, the substance that was initially pumped across the membrane can do work as it moves back across the membrane by diffusion and brings with it a second compound against its gradient
exocytosis
vesicles from the cell’s interior fuse with the cell membrane, expelling their contents
endocytosis
the cell forms new vesicles from the plasma membrane; this allows the cell to take in macromolecules.
phagocytosis
“cellular eating” occurs when the cell wraps pseudopodia around a solid particle and brings it into the cell
pinocytosis
“cellular drinking” is when the cell takes in small droplets of extracellular fluid within small vesicles. It is not specific, beacause any and all included solutes are taken into the cell
receptor-mediated endocytosis
certain substances (generally referred to as ligands) bind to specific receptors on the cell’s surface and this causes a vesicle to form around the substance and then to pinch off into the cytoplasm
