Passive and Active transport

Diffusion (passive, no energy/ cell to use ATP)

Osmosis

net movement of substances from area of ↑ concentration to area of
↓ concentration.
-small, non polar molecules e.g, O2, CO2 cross membrane via simple diffusion

Passive transport of water down its concentration gradient across semi-permeable membrane
-water moves from ↑ H2O concen (lower solute concen) to ↓ H20 concen (higher solute concen).

Concentration Gradients

Down & with gradient: movement from ↑ concentration to
↓ concentration (Passive)

Up or against gradient: movement
↓ concentration to ↑ concentration. requires energy input (active)

Osmosis solution descriptions
-based on solute concentrations

Isotonic: solu w/ equal concentrations of solute - no net movement of H20

Hypertonic: high concentration of solute, low amount of water - H20 = move out cell → shrink (plasmolysis)

Hypotonic: low concentration of solute, high amount of water. H20 = move in cell → swell or burst. (turgor pressure)

Facilitated Diffusion (passive)
+ different transport proteins

Allows specific substances to diffuse across membrane down concentration gradient via transport proteins
-faster than diffusion
-ions, larger hydrophilic molecules e.g glucose, polar molecules

Channel proteins: form hydrophilic pores, allow small, hydrophilic substances e.g ions, to pass through

Carrier proteins: bind w/specific particles e.g., gluc + undergo a conformational change to shuttle particle across membrane

Active Transport
-require energy ATP

Moves substances up, against concentration gradient
-use carrier proteins only
-↓ concentration to area ↑ concentration
-maintain internal concen chem in cell
-ions, glucose, amino acids only

Exocytosis
-bulk transport, require ATP
-intake

Movement of secretory proteins, cellular products/cellular wastes release out cell

-membrane proteins facilitate fusion of secretory vesicles (from golgi) w/ plasma mem. During membrane fusion → contents = released

Endocytosis
-bulk transport, require ATP
-uptake

Process where substances from extracell enviro = engulfed inside cell

-Sections of plasma membrane sink inwards bring substance in cell in transport vesicle

Different types of endocytosis

Phagocytosis: cell engulf solid substance in pseudopodia which extend around particle
-common in phagocytes + protist

Pinocytosis: plasma membrane forms vesicle inwards around dissolved substances/fluids

Receptor-mediated : Protein receptors on plasma membrane bind w/specific molecule, initiate endocytosis + vesicles form