HAPU2: SEC. 3 CELL MEMBRANE + MOVEMENT

the cell membrane follows the ______ ________ model

fluid mosaic

phospholipid bilayer

made of two layers of phospholipids

hydrophilic heads

water loving, face outward toward water

hydrophobic tails

water fearing, face inward away from water

membrane proteins

help substances move across membrane, can also help w/communication

selective permeability

the membrane allows some substances to pass through but blocks others

diffusion

high concentration to low concentration, does NOT require ATP

simple diffusion

high 2 low, goes directly through membrane, no ATP (ex. oxygen crossing the membrane)

facilitated diffusion

high 2 low, uses a membrane protein, no ATP

osmosis

movement of water across a selectively permeable membrane

hypotonic

less solute outside, water moves into cell, cell SWELLS (H2O goes IN)

hypertonic

more solute outside, water moves out of cell, cell SHRINKS (H2O goes OUT)

isotonic

equal solute concentration, cell stays about the same size

passive transport

does NOT require ATP, usually moves high 2 low

active transport

Requires ATP, can move low 2 high

endocytosis

cell brings substances in using a vesicle (IN)

exocytosis

cell moves substances OUT using a vesicle (OUT)

phagocytosis

takes in large particles/solids, “cell eating” (solids)

pinocytosis

takes in liquids, “cell drinking” (liquids)