1.4 Membrane Transport Flashcards
What materials do cells need to import and export to survive ?
import for metabolism - glucose, hormones and ions
export - enzymes and hormones
Two types of transport and define them
Active transport (requiring energy in the form of ATP and against a concentration gradient)
- occurs via a protein pump
- may involve bulk transport, endo and exocytosis
Passive transport (does not require any energy)
- simple diffusion
- facilitated diffusion
- osmosis
Definition of diffusion
net movement of particles from a region of a high concentration to a region of low concentration, result in the random motion of particles
What are the factors that affect diffusion
temperature - molecules diffuse faster at high temp
SA of membrane - increase in SA allows more molecules to diffuse
size of particles - smaller molecules diffuse faster than larger ones
concentration gradient - the bigger the gradient the faster the diffusion
explain simple diffusion across membrane
small molecules are able to diffuse across the membrane down a concentration gradient without the aid of a protein pump or channel
explain facilitated diffusion
requires channel proteins or carrier proteins (molecules transported across the plasma membrane)
the size and shape of protein carrier rand channels determine what substance can cross the membrane
key qualities of the cell membrane
They are semi-permeable (only certain materials may freely cross – large and charged substances are typically blocked)
They are selective (membrane proteins may regulate the passage of material that cannot freely cross)
Explain osmosis
passive movement of water molecules from a region of high water potential to a low water potential, waters move through a partially permeable membrane
or
move from a low solute concentration to the side with higher solute concentration
what protein speeds the movement of water molecules ?
aquaporin an integral protein
Define hypertonic, isotonic and hypotonic
hypertonic (plasmolyzed) higher solute concentration to a lower area of solute concentration- osmotic loss of water
hypotonic (turgid) - low solute concentration move to high solute concentration, osmotic uptake of water
isotonic (flaccid) - equal water potential outside and inside, no net movement of water
Why is osmotic control important
preventing damage to cells and tissues
the sodium and potassium pump cycle
- the pump is open to the inside of the axon, three sodium ions enter the pump and attach to their binding site
- ATP donates a phosphate group to the pump
- the previous stage causes the protein to change shape expelling the sodium to the outside
- two potassium ions then enters and attach to their binding site
- the binding of the potassium releases a phosphate, making the pump change shape again, so it only open to the inside of the axon
- potassium released inside
- sodium enters and binds to the pump again
define endocytosis and exocytosis
endocytosis - cells take in substances from outside of the cell by engulfing them in a vesicle.
exocytosis - active process that requires ATP. The release of substances from a cell (secretion) when a vesicle joins with the cell plasma membrane.
What are the two types of endocytosis and explain the differences ?
phagocytosis - the absorption of solids
pinocytosis -taking in liquid substances
What is the role of vesicle in the transportation of materials in the cell
Vesicles are small spheroidal packages that bud off of the RER and the Golgi apparatus
They carry proteins produced by ribosomes on the RER to the Golgi apparatus, where they are prepared for export from the cell via another vesicle
