AP Biology 2007-2008

Movement across the Cell Membrane

AP Biology

Diffusion ______________________________

governs biological systems universe tends towards disorder (entropy)

Diffusion movement from ___________concentration

Diffusion movement from ___________concentration

AP Biology

Diffusion Move from ______to _____concentration

“passive transport” no energy needed

diffusion osmosis

movement of water

AP Biology

Diffusion across cell membrane Cell membrane is the boundary between

inside & outside… separates cell from its environment

IN_________carbohydratessugars, proteinsamino acidslipidssalts, O2, H2O

OUT________ammoniasaltsCO2

H2O products

______________________________________________

IN

OUT

Can it be an impenetrable boundary? NO!

AP Biology

Diffusion through phospholipid bilayer What molecules can get through directly?

fats & other lipids Small polar molecules (H20)

inside cell

outside cell

lipid

salt

aa H2Osugar

NH3

What molecules can ________get through directly?

ions salts, ammonia

large molecules starches, proteins

AP Biology

Channels through cell membrane Membrane becomes ________________

with protein channels specific channels allow specific material

across cell membrane

inside cell

outside cell

sugaraaH2O

saltNH3

AP Biology

Facilitated Diffusion Diffusion through protein channels

channels move specific molecules across cell membrane

no energy neededopen channel = fast transport

facilitated = with help

_____

______

AP Biology

Active Transport Cells may need to move molecules ___________

concentration gradient shape change transports solute from

one side of membrane to other _________________ “costs” energy = _____ low

high

AP Biology

Getting through cell membrane ____________________

_______________________ diffusion of nonpolar, hydrophobic molecules

lipids high low concentration gradient

_____________________ diffusion of polar, hydrophilic molecules through a ____________________

high low concentration gradient

_______________________ diffusion __________________________

low high uses a _________________ requires _____

ATP

AP Biology

Transport summary

simplediffusion

facilitateddiffusion

activetransport

ATP

AP Biology

How about large molecules? Moving large molecules into & out of cell

through vesicles & vacuoles ______________

_____________________ = “cellular eating” _____________________ = “cellular drinking”

________________

exocytosis

AP Biology

Endocytosis

_________________

_________________

________________________________

fuse with lysosome for digestion

non-specificprocess

triggered bymolecular signal

AP Biology

Phagocytosis

AP Biology

Osmosis is diffusion of water Water is very important to life,

so we talk about water separately Diffusion of water from

__________________of water to __________________of water across a

semi-permeable membrane

AP Biology

Concentration of water Direction of osmosis is determined by

comparing total solute concentrations ___________ - more solute, less water

___________ - less solute, more water

___________ - equal solute, equal water

hypotonic hypertonic

water

_____ movement of water

AP Biology ___________ ___________ __________

Managing water balance Cell survival depends on balancing

water uptake & loss

AP Biology

Managing water balance Isotonic

animal cell immersed in ___________solution example:

________________________ problem: none

_________________of water flows across membrane

equally, in both directions

volume of cell is stable

balanced

AP Biology

Managing water balance Hypotonic

a cell in ____________ example: __________________ problem: __________________

swells & can burst water continually enters

Paramecium cell

solution: __________________ pumps water out of cell ATP

plant cells turgid

freshwater

ATP

AP Biology

Water regulation Contractile vacuole in Paramecium

ATP

AP Biology

Managing water balance Hypertonic

a cell in ________________ example: ________________ problem: _________________ solution: take up water or

pump out salt plant cells

________________ = wilt

saltwater

AP Biology

Cell (compared to beaker) hypertonic or hypotonic

Beaker (compared to cell) hypertonic or hypotonic

Which way does the water flow? in or out of cell

.05 M .03 M

Osmosis…

AP Biology

Any Questions??