1.7 Transport

What are the 3 types of Passive Transport?

1. Simple Diffusion

2. Facilitated Diffusion

3. Osmosis

Explain Simple Diffusion*

Movement of small substances directly across membrane from HIGH concentration to LOW concentration until equilibrium reached

No energy needed

Small and non-polar molecules (e.g. O2, CO2, glycerol)

Explain Facilitated Diffusion*

Facilitated = with help

Movement of large, charged, or hydrophilic particles through protein channels or by carrier proteins from HIGH to LOW concentration

No energy needed

Explain Osmosis*

Diffusion of water across a semi-permeable membrane from HIGH concentration to LOW concentration

Equal concentration of water and dissolved substances on both sides of membrane - equilibrium

Define Osmolarity, and the -tonics*

Direction of osmosis is determined by comparing total solute concentrations

Hypertonic - high solute (high osmolarity)

Hypotonic - low solute (low osmolarity)

Isotonic - equal solute concentration (no net water flow)

Tell me about Managing Water Balance

Cell survival depends on balancing water uptake & loss

Explain Active Transport*

Movement of molecules against concentration gradient

Protein pump transports solutes “uphill”

“Costs” energy = ATP

Summary of Transport Systems

Tell me about Vesicular Transport

Materials destined for secretion are transported around cell in vesicles

E.R. - membrane bulges/buds to create vesicle sent to Golgi

Golgi - vesicles fuse, materials modified, then secreted via fusing with plasma membrane, or directly into extracellular fluid, or sent in vesicle to lysosome

Tell me about Bulk Transport

movement of very large molecules or large quantities in/out of cell through vesicles and vacuoles

Endocytosis - enter cell without crossing membrane

Phagocytosis = solid substances are ingested

Pinocytosis = liquids/dissolved substances are ingested

Exocytosis - exit cell without crossing membrane