active and passive Flashcards
characteristics of cell membrane
- it covers the cell
- thickness 7.5 - 10 cm
- selectively permeable
- it is fluid, not solid
- composed of:
55% proteins
42% lipids
3% other (can be carbohydrates)
is composed of lipid bilayer
cell membrane
cell membrane is also known as
plasma membrane
the two categories of membrane protein
integral
peripheral
span the thickness of the membrane
integral
what are the functions of integral
channels
carrier proteins
receptors
only attach to the surface of the membrane (or attached to integral proteins)
peripheral
what are the functions of peripheral
hormone receptors
enzymes
the membrane allows some substances to cross it but not others
selective permeability
selective permeability through proteins:
water-soluble substances - glucose
selective permeability directly through the bilayer:
fat soluble substances - O2, CO2, OH
this controls the type and amount of substances entering and leaving the cell
selective permeability
it arises from the membrane structure
selective permeability
form a open pores that allow molecules of the appropriate size (e.g. ions) to pass the membrane
like a door
channel proteins
selectively bind the small molecule to be transported and then undergo a conformational change to release the molecule on the other side of the membrane
like a electronic door
carrier proteins
also called carrier mediated diffusion
facilitated diffusion
diffusion of a substance is facilitated using a specific carrier protein
facilitated diffusion
diffusion continues until ——– is reached or terminated
equilibrium
example of facilitated diffusion:
glucose, amino
occurs when a cell membrane moves molecules or ions “up-hill” against a concentration gradient
active transport
requires energy and a carrier protein
active transport
examples of active transport
sodium
potassium
calcium
iron
iodine
amino acids
glucose
carrier proteins
indirectly by using the concentration or electrochemical gradient generated by a primary active transport
secondary active transport
when both substances are transported together in the same direction
counter transport
when one substance is transported in the opposite direction to the other substances.
counter
transport
examples of secondary active transport:
NA+H+ -kidney
direct source of energy
primary active transport
indirect source of energy
secondary active transport
breakdown ATP and ADP
primary active
examples of primary active:
sodium-potassium pump
calcium pimp
hydrogen pump
functions of active transport
maintain NA plus and K plus concentration
establish potential inside the cell
maintains a normal cell volume
the basis of nerve signal transmission
membranes are on the surface bounded to lipids or proteins to the membrane
carbohydrates
if attached to proteins
glycoproteins
if attached to lipids
glycolipids
type of membrane movement
passive transport
active transport
simple diffusion
facilitated diffusion
osmosis
passive transport
primary active transport
secondary active transport
active transport
movement of water from an area of low solute concentration (hypotonic) to an area of high solute concentration (hypertonic)
osmosis
type of diffusion
simple diffusion
facilitated diffusion
the movement of molecules through the intermolecular spaces or membrane openings ( channels ) without the necessity of binding to a carrier protein on the membrane
simple diffusion
the transported molecules binds to a carrier protein which then undergoes a conformational change allowing the molecule to pass through to the other side of the cell membrane
facilitated diffusion
function of passive
- receptors
- attach cells to each other
- immune reaction
- give most of cells overall negative surface
molecules move down or along their energy gradient
does not require energy
passive transport
molecules move against their energy gradient
require energy
active transport
random movement of substances either through the membrane directly or in combination with carrier protein down concentration gradient
concentration pressure
passive transport (diffusion)
mediated transport down an electrochemical gradient
non carrier
from high concentration to low concentration (uncharged)
diffusion of non-electrolytes
depends on both chemical as well as electrical potential difference (charged)
diffusion of electrolytes
