Topic 3 Flashcards
phospholipid bilayer
in cell membranes
head: hydrophilic (water loving)
tail: hydrophobic (water fearing)
Fluid Mosaic Model
- made by Singer & Nicolson in 1972
- used fluorescence tagging to disprove Trilaminar model
- proteins embedded in lipid bylayer
- proteins transport substances across & carry out chemical reactions
- fluidity of membrane lets proteins change shape in response to signals
Trilaminar Model
- Davson & Danielli in 1935 based on electron micrograph images
- protein layers sandwich lipids
integral proteins
in lipid bylayer, permanently embedded
peripheral proteins
surface of membrane, temporary
cholesterol
- maintains fluidity of cell membrane while it changes shape
- makes membrane less permeable (leaky) for small water-soluble solutes
selective transport
only some substances are allowed to cross cell membrane
passive transport
movement of molecules from high to low concentration w/out energy
passive transport #1
diffusion: movement of solute from high to low concentration
passive transport #2
osmosis: movement of water from high to low concentration
hypotonic solution
solute concentration is lower on outside of cell, water moves in via osmosis
hypertonic solution
solute higher on outside, water moves out via osmosis
passive transport #3
facilitated diffusion: transport of substances that cant cross membrane w/out proteins, moves from high to low concentration
active transport
movement of molecules from low to high concentration w energy
endocytosis
- used when molecules cant dissolve in water/too large to cross
- takes molecules into cell
