| How does membrane transport occur? (2) | Passive: along a conc G and doesn't use ATP (high = low)
Active: against a conc G, uses ATP (low = high) |
| What are 3 types of passive transport? | simple = small / lipophilic molecule can freely cross the membrane
facilitated = large / charged molecules need transport with membrane proteins
osmosis = water movement that depends on solute concs |
| What does simple diffusion mean? | net movement of particles from high conc to low conc (along a conc g) until equilibrium is reached |
| What does facilitated diffusion mean? (4) | uses membrane proteins for certain substances that can't easily cross the membrane (ions, polar macromolecules)
uses:
protein channels = hydrophilic pores for ions
carrier proteins = allows changing of shape to allow translocation |
| How do carrier proteins work? (3) | integral glycoproteins binds to a solute to undergo conformational change = translocate solute across membrane
only binds to a specific molecule
move molecules against conc gradient with ATP |
| How do channel proteins work? | integral lipoproteins have a pore in which ions can ceoss from one side of the membrane to another
ion selective
only move molecules across a conc g
faster than carrier proteins |
| How do potassium channel proteins work for facilitated diffusion? (4) | they have a hydrophilic inner pore to transport K+ ions
a filter restricts the passage of other ions
the channels open / close depending on membrane polarity = voltage-gated
or NT binding = ligand gated |
| How does the nerve cells transmit electrical impulses with sodium and potassium channels? | by translocating ions to create a voltage difference across membrane
at rest: Na-K pumps remove Na ions from the nerve cells while K ions build up within
when the neuron fires these ions swap places by facilitated diffusion |
| What is osmosis? | net movement of water molecules across a semi permeable membrane from low solute conc to high solute conc |
| What is osmolarity? | measure of solute concentration |
| What does it mean if a solution is hypertonic? | higher relative solute concentration = gain water by osmosis
too much solute = hyper
causes shriveling (crenation) |
| What does it mean if a solution is hypotonic? | lower relative solute concentration = lose water by osmosis
hypo= hypnotic = calm = less solute
causes lysis= rupturing of the cell |
| What does it mean if a solution is isotonic? | same relative solute concentration
no net water movement |
| Why do plant cells have a fixed shape compared to animal cells? | because they have a rigid cell wall
hypertonic: cytoplasm shrinks (plasmolysis but cell wall maintains the shape
hypotonic: cytoplasm expands but doesn't rupture because of the cell wall (turgor) |
| What is active transport? | uses energy to pump molecules against a conc gradient (low to high) |
| What are the 2 types of active transport? | direct (primary): ATP hydrolysis
indirect (secondary): joined with another molecule to move across an electrochemical gradient = contransport |
| How does a sodium-potassium protein pump work for active transport? (4) | 3 Na+ ions attach to the binding sites on the pump
ATP hydrolysis changes shape of pump (conformation) = expose extracellular binding sites
2 K+ ions attach to these sites = ions are exchanged once the phosphate group is released to make the pump return to its original conformation
translocate potassium across membrane |
| What is vesicular transport? (3) | Ribosomes make secretory proteins into the lumen of rough ER
ER membrane create a vesicle to transport the protein into the golgi body = membrane bulges and buds to create a vesicle around the material
the protein is transported from the golgi body to the membrane via a vesicle |
| How does bulk transport happen with the cell membrane? | bilayer is held with hydrophobic interactions bw fatty acid tails = can be easily broken and reformed with ATP hydrolysis
= allows materials to be transported in bulk |
| What is endocytosis? | when substances enter the cell without passing across the membrane = is kept inside a vesicle
endo = enter |
| What are the 2 types of endocytosis? | phagocytosis: ingestion of solid substances (food particles)
Pinocytosis: ingestion of liquid (dissolved solutes) |
| What is exocytosis? | when materials exit a cell without crossing the membrane by being packaged and stored in the golgi complex before secretion |
| What are the 2 types of exocytosis? | constitutive secretion: immediately released after synthesis
regulatory secretion: delayed until a signal is received |
| What can the rate of diffusion be affected by? | temp: affects kinetic energy of particles
molecule size: larger particles have greater resistance in a fluid
gradient: higher diffusion with a higher conc gradient |
