Class notes Biology

HOW DO SUBSTANCES MOVE IN AND OUT OF CELLS?
DEFINE:
Selectively Permeable: Allows some
material across the membrane but not
others.
Passive Transport: Movement of material
across the membrane; energy not needed
Active Transport: Movement of material across
the membrane; energy required.



MECHANISMS FOR TRANSPORT ACROSS CELL MEMBRANES

Process Diagram How It Works Example(s)

Passive Transport

Diffusion Random molecular O2, CO2
motion produces net Small, nonpolar
Simple Diffusion migration of molecules
towards region of
lower concentration

Facilitated Diffusion Diffusion with the Charged particles,
assistance of channel small, like ions
Channel Protein proteins; channel
proteins offer a way
through the
hydrophobic parts

Carrier Protein Diffusion of larger Glucose, large
molecules with molecules
assistance of a carrier
protein which changes
shape to let it through

Osmosis Pores specifically for Water
the movement of
Aquaporins water through the
membrane; allows
water to avoid
hydrophobic parts

Osmosis and Types of Solutions
Hypotonic Isotonic Hypertonic