3B passive transport Flashcards
types of transport across the membrane
passive- cell does not require energy to transport molecule- with the gradient
active- cell requires energy to transport molecule-against the gradient
what is diffusion?
random movement of molecules /solutes from an area of high solute concentration to an area of low solute concentration.
Diffusion continues until all molecules are evenly spaced (equilibrium is reached).
what are the 2 types of diffusion and what are they? whats similar?
Simple Diffusion- diffusion through the phospholipid bilayer
Facilitated Diffusion – diffusion with the help of transport proteins
eg. A protein channel
same as they both involve movement of substances across a membrane
does diffusion require a cell membrane
no
passive transport- molecules move from an area of…
high solute concentration to an area of low solute concentration (if permeable), molecules move randomly down a concentration gradient.
simple diffusion
Some molecules such as: oxygen, carbon dioxide, fat-soluble molecules and water can move down the concentration gradient directly through the phospholipid bilayer as they are small &
hydrophobic (non-polar)
facilitated diffusion
Other small polar, hydrophilic (water-soluble) substances such as :
Amino acids or glucose and
charged molecules or ions
move into a cell down ( high to low) the
concentration gradient but must be
assisted by a PROTEIN CHANNEL
or CARRIER PROTEIN in the
membrane.
transport proteins
are specific – they “select” only certain molecules to cross the membrane
osmosis
movement of water through a selectively permeable membrane.
Water moves from a low solute to a high solute concentration.
Water moves as the solute cannot move ( it is impermeable)
tonicity
the concentration of solutes on either side of a membrane.
hypertonic, hypotonic, isotonic
hypotonic
The solution has a LOWER concentration of solutes and a higher concentration of water than inside the cell.
(Low solute; High water = Dilute solution)
Water moves from the hypotonic solution to inside the cell: Cell Swells and bursts open (lysis)!
hypertonic
The solution has a HIGHER concentration of solutes and a lower concentration of water than inside the cell. (High solute; Low water = concentrated solution))
Water moves from inside the cell into the solution: Cell shrinks.
isotonic
The concentration of solutes in the solution is EQUAL to the concentration of solutes inside the cell.
Water moves equally in both directions and the cell remains the same size!
bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called
turgor pressure ( plant cell is TURGID)
plasmolysis plant cell
is the process in which cells lose water in hypertonic solution. the cell membrane pinches in while the cell wall maintains structure
turgid plant cell
water movies into cell, pushes the membrane against the cell wall
flaccid plant cell
membrane a little droopy, lacks water, loss of turger pressure
animals cells in hypertonic solutions
water will leave the cell and the cell will shrink and collapse
animals cells in hypotonic solutions
water will move in the cell and the cell will swell
Salt water fish
lose water by osmosis. They pump salt out of specialized glands so they do not dehydrate.
Freshwater fish
gain water by osmosis. They get rid of excess water by their special kidneys.
how would the structure of the cell membrane of an artic fish differ from that of tropical fish species
artic fish would have more unstaturated fatty acids to help maintain membrane fluidity in the low temperatures while tropical fish would have less
