Flashcards in chp 7 cells and membranes' Deck (27):
the directional movement of any substance so tht they can spread out into available space.
the diffusion of water
Hypotonic: (meaning less solutes)(More H2O) lesser concentration of solutes
Hypertonic:(meaning more solutes)(Less H2O) greater concentration of solutes
define concentration gradient
the region along which the density of a chemical substance increases or decreases .
A substance will diffuse from higher concentration to lower concentration to achieve equilibrium
the control of solute concentrations and water balance
As the plant cell shrivels, its plasma membrane pulls away from the cell wall at multiple places.
define facilitated diffusion
Many polar molecules and ions impeded by the lipid bilayer of the membrane diffuse passively with help of transport proteins tht span the membrane.
define active transport
the transport protein tht move solutes against the concentration gradient are all carrier proteins rather than channel proteins.
define membrane potential
The voltage across the membrane
define proton pump
which actively transports protons out of the cell
the cell secretes certain molecules by the fusion of vesicles with the plasma membrane
the cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane
define sodium-potassium pump
One way ATP can power active transport is by transferring its terminal phosphate grp directly to the transport protein. Thus changing the shape of the protein. exchanging Na+ for K+ across the plasma membrane.
define electrochemical gradient
2 forces drive the diffusion of ions across a membrane.
Chemical force - the ions concentration gradient
Electrical force - the effect of the membrane potential on the ions movement.'
the combinations of forces acting on an ion is the electrochemical gradient
define transport proteins
specific ions and a variety of polar molecules cant move through cell membranes on their own.
These hydrophilic substances can avoid contact w/ the lipid bilayer by passing through transport proteins
define selective permeability
it allows some substances to cross it more eaily than others
a type of endocytosis in which a lg or small organism is taken up by a cell
a type of endocytosis in which the cell ingests extracellular fluid and its dissolved solutes
define receptor-mediated endocytosis
the movement of specific molecules into a cell by the infolding of vesicles containing proteins w/ receptor sites specific to the molecules being taken in; enables a cell to acquire bulk quantities of specific substances.
in the fluid mosaic model which part is the fluid and which part is the mosaic?
the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids
explain the movement of different molecules across the plasma membrane.
Through what part of the membrane does each type of molecule pass?
small molecules tht are nonpolar are hydrophobic. they can dissolve in the lipid bilayer of the membrane and cross it.
ions move across the membrane in both directions crossing the transport proteins.
polar molecule can cross the membrane through transport proteins.
Sugars, Amino Acids, and other nutrients enter the cell and metabolic waste products leave it.
disaccharides have to b broken down by lysosomes to be able to cross the membrane through the transport protein.
list the 6 functions of membrane associated proteins
1) Transport proteins (gates) -
2) Enzymes -
3) Receptors - cell-cell recognition
4) Cell-cell recognition
5) intercellular joining (unit 2 cells together)
6) attachment to cytockeleton / ECM
compare and contrast Facilitated diffusion, active transport and co-transport
Facilitated diffusion - helps pass polar molecules and ions through the membrane by a transport protein.
Active transport - exerts energy to pump a solute across a membrane against its gradient.
Co-transport- a transport prortein can couple the "down hill" diffusion of a solute to the "uphill" transport of a second substance against its own concentration gradient.
how can the cell wall of plants deal w/ hypo and hypertonic environments?
in a hypotonic solution (bathed in rain) the cell wall helps maintain the cells water balance. cells hav a relatively inelastic wall so when the wall cannot take in any more water the cell is turgid(very firm) this is a healthy state for a plant.
hypertonic the cell wall of a plant has no advantage it will lose its water to its surroundings and shrink.