Cellular Transport Notes PDF

Cell membrane Regulates movement of substances Concentration gradient - difference in concentration of a solutes across a region High and low concentration sides Passive transport Diffusion of different solutes is only dependent on its own concentration Typically move from HIGH →...

Cell membrane Regulates movement of substances Concentration gradient - difference in concentration of a solutes across a region High and low concentration sides Passive transport Diffusion of different solutes is only dependent on its own concentration Typically move from HIGH → LOW concentration of solute Down the concentration gradient No energy required for movement of solute across the membrane/barrier ○ Exergonic Diffusion ○ Simple Diffusion → can move on its own ONLY small nonpolar molecules can diffuse access the lipid bilayer (ex.O2) ○ Facilitated Diffusion → needs help moving Polar and charged molecules can still diffuse across the lipid bilayer with help → integral membrane proteins Move down the concentration gradient Channel proteins Acts as small pores in the membrane  Allow small charged/polar molecules to diffuse across the cell membrane Can open and close → gated ○ Ligand gates Small ions/compounds and cause protein to change shape Ligand is a signal either inside or outside of the cell (stimulus molecule) When ligand binds, it become the key to open the channel ○ Voltage gated Electrical (chemical) gradient → inside of cell is slightly more negative open/close in response to change voltage (difference in charges) across the membrane Action potential proteins are voltage gated ion channels Very specific with what goes through for one type of ion/molecule ○ Size and interactions dictates Channel is lined with proteins that can interact Controls regulation ○ Ex. K channels, Cl channels, etc. Aquaporins are channel proteins that allow water to diffuse across the cell membrane Carrier proteins Bind polar molecules on one side of the membrane and change conformation to allow passage of the polar molecules Typically move sugars and amino acids (bigger items than ions) Ex. glucose transporter  ○ Movement/transport by carrier proteins is slower than channel proteins Osmosis ○ Diffusion of water ○ Consider the ratio of water to solute in the solution Which side has more or less water than solute More water than solute = low concentration of solute Less water than solute = high concentration of solute ○ Selectively permeable membrane ○ Only allows for movement of water across the membrane Moves from low solute to high solute AKA more water to less water ○ Aquaporins are channel proteins that allow water to diffuse across the cell membrane Regulates and gated Open and close in response to environmental signals Find in kidney cells ○ Aquaporins play an important role in water balance in cells Isotonic solution: solute concentration is the same inside and outside the cell; no net water movement across the plasma membrane Hypotonic solution: solute concentration outside the cell is lower than that inside the cell; more water outside the cell and cell will gain water Ex. animal cells can lyse (burst) when placed in a hypotonic solution Hypertonic solution: solute concentration outside the cell is higher than that inside the cell; more water inside the cell and cell will lose water Ex. animal cells will shrivel when placed in a hypertonic solution Cytoplasm shrinks inwards Not good for any cell Active transport LOW → HIGH ○ Movement AGAINST the concentration gradient with ATP Requires energy input for movement of solute across the membrane/barrier ○ Endergonic Pumps: Transport proteins involved in active transport with ATP 2 types: ○ ATP Hydrolysis (Primary active transport) K is found inside the cell NA+ K+ pump uses energy released from ATP hydrolysis to move NA+ and K+ions against their concentration gradient Something becomes phosphorylated Conformation change occurs and NA moves against the concentration gradient Another change Something becomes dephosphorylated K moved against gradient Allows for change of shape to move across the gradient Setting up the gradient is important for electrochemical gradient and maintaining voltage and signal transduction and muscle contraction Other proteins that allow these ions to diffuse back the gradient and dissipate Moving against gradient using ATP hydrolysis ○ Concentration gradient of an ion (Secondary active transport) Co-transport of 2 substances - one down its concentration gradient (energy releasing) and one against its concentration gradient (energy requiring) Ex. move sucrose against gradient  Anitporters: move 2 different things in different directions Diffusion of H+ used to power the movement of sucrose against the concentration gradient