Topic 4: Cell Membranes and Walls Flashcards
____ ____ are asymmetric.
plasma membranes
Integral proteins act as ____ or ____ that work in one direction
channels or pumps
____ and ____ molecules can pass through easier than the ____ or ___ molecules
Small and uncharged; large or charged
Why can ions not pass through the membrane easily?
the charge
Why can simple sugars and amino acids not pass through the membrane easily?
their large size
Define concentration gradient
difference in concentration of a single substance
What does it mean to go down a concentration gradient?
going from high to low concentration
Define passive transport
naturally occurring phenomenon and does not require the cell the expend energy to accomplish the movement
What does it mean to go up a concentration gradient?
going from low to high concentration
Define diffusion
passive process of transport used by living organisms
Define solvent
fluid within which other molecules are dissolved
Define solutes
the molecules dissolved
Define solution
combined form of solutes and solvent
Diffusion requires no additional energy other than _____ energy already present in the molecule
thermodynamic
How does the extent of the concentration gradient effect the rate of diffusion?
the greater the difference in concentration, the more rapid the rate of diffusion
How does the mass of molecules effect the rate of diffusion?
the more massive the molecules the slower the rate of diffusion
How does temperature effect the rate of diffusion?
the higher the temperature the faster the rate of diffusion
How does solute density effect the rate of diffusion?
the more dense a solute, the slower the rate of diffusion
What are the required conditions for passive transport to take place?
- concentration gradient
- permeability of the molecule to the membrane
What kind of molecules can pass through via simple diffusion?
Nonpolar neutral molecules like oxygen and carbon dioxide
Define facilitated diffusion
material moves across the plasma membrane with the assistance of transmembrane proteins
What kind of molecules pass through via facilitated diffusion?
Polar molecules and ions
What are the two steps of facilitated transport?
- material is attached to protein/glycoprotein receptors on exterior
- passed to specific integral/transport proteins that facilitate passage
Define uniporter
allows transport down a concentration gradient of a single molecule
What are the two cotransporters?
symporter and antiporter
Define symporter
uses concentration gradient of one molecule to move another at the same time in the same direction
Define antiporter
uses concentration gradient of one molecule to move another at the same time in the opposite direction
What is active transport?
Form of facilitated transport that uses a pump, protein transporter, and cellular energy
Define osmosis
the net diffusion of water through a semipermeable membrane according to the availability of water on either side of the membrane
Since the concentration of water is not usually known, how is it known where water will move?
difference in solute concentration
Water moves from ____ solute to ____ solute.
less; more
What is homeostasis and how is it maintained?
State of stability that provides optimal conditions needed to sustain life; to maintain water will continue to move back and forth but there is not net movement
Define osmolarity
total amount of solutes dissolved within a specific volume of solution
Define tonicity
describes how the solutes in a solution influence the movement of water into or out of the cell
How does water move in a hypotonic solution?
water will enter the cell
How does water move in
How does water move in a hypertonic cell?
Water moves out of the cell
Define endocytosis
type of active transport that moves particles, such as large molecules, part of cells, and even whole cells, into a cell
Define exocytosis
purpose to expel material from the cell into the extracellular fluid
