Biological Membranes and Transportation

all life forms have membranes made of

lipid bilayers

Phospholipid bilayer

selectively permeable barrier, hydrophobic interior prevents polar/charged molecules from passing9

Unsaturated fatty acids have kinks which

increases fluidity

Cholesterol helps maintain

fluidity (prevents leaking or rigidity)

Transmembrane proteins

uses helixes to pass bilayer

Channel proteins allow

passage of specific ions/molecules

Passive transport

no energy requires, move substances down concentration gradient

Simple diffusion

small, no polar molecules move directly through membrane

Osmosis

water moves across membrane down concentration gradient

Hypotonic animals

swells, burst, water gors in cell

Isotonic animals

ideal, water goes in and out

Hypertonic animals

shrivels up, water goes outside cell

Hypotonic plants

ideal, plant grows strait, cell walls prevent bursting

isotonic plants

dosen’t grow straight

Hypertonic plants

very wilted and almost dead

Facilitated diffusion

movement throught membrane proteins

carrier proteins

bind solute, change shape, transport across membrane

active transport

moves solute against concentration gradient, requires ATP, highly specific

Bulk transport

Move large materials using vesicles

Exocytosis

Vesicles fuses w plasma membrane and then releases contents

Endocytosis

Vesicle brings material into cell

Phagocytosis

Engulfs solid particles

Pinocytosis

Engulfs liquids

Receptor-medicated

Highly specific and fast