Passive Transport

What can move into and out of cells?

Active TransportHow do cells maintain homeostasis?

http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html

Warm-up: Write answers in spaces.

1. Why is it necessary for cells to control what enters and leaves them?____________________________________________________

1. Does passive transport take energy? ______2. Give one of the diffusion examples discussed

last class.____________________________3. Explain what a concentration gradient is.

____________________________________4. Does diffusion involve going up or down a

concentration gradient? _________________

The Cell Membrane – a selectively permeable The Cell Membrane – a selectively permeable phospholipid bilayer with embedded proteinsphospholipid bilayer with embedded proteins

Passive Transport What can move into and out of cells?

1. Diffusion is Caused by the Random Movement of Particles

– random motion and concentration causes…

– movement of substances from an area of higher concentration to an area of lower concentration

How does temperature affect the rate of diffusion? As temperature increases, the rate of diffusion _____________ .

Concentration GradientType of

transport?

Passive Transport = Diffusion (and Osmosis!)• Movement of substances

across a semi-permeable membrane from high to low concentration

** movement is down a concentration gradient

example: clothes falling out of a packed closet

your example:_______________

Does passive transport take energy? _____

Osmosis – the diffusion of water through a selectively permeable membrane

Does this take energy? _____ because we are talking about

________ transport

1. Water Diffuses into and out of Cells by Osmosis

red blood cellsred blood cells (animal)(animal)

onion cells onion cells (plant) (plant)

Osmosis of red onion cellsNormal cells in tap water ______________

salt water is added…salt water is added…

Salt water is Salt water is __________________________________compared to the red compared to the red onion cells. onion cells. ____________________________________

Table 4-1 Hypertonic, Hypotonic, and Isotonic Solutions

If the fluid outside the cell has…

Then the outside fluid is…

Water diffuses…

Effect on the cell

... lower water concentration than the cytoplasm inside

...hypertonicHigher solute

...out of the cell Cell shrinks

…higher water concentration than the cytoplasm inside

…hypotonicLower solute …into cell Cell swells

…same water concentration as the cytoplasm inside

…isotonicEqual solute

…into and out of the cell at equal rates (equilibrium)

Cell stays the same size

Did you know?

H2O

On humid days, wooden drawers in dressers absorb water from the air because of osmosis.

more ways of passive transport…

3. Proteins Help Some Substances Cross the Cell Membrane

– Diffusion though ion channels

Cystic Fibrosis Website: http://Cystic Fibrosis Website: http://www.dwmtech.com/Medical/cysticfibrosis.htmwww.dwmtech.com/Medical/cysticfibrosis.htm

• A doughnut shaped protein with a polar hole

•pulls ions through cell membrane like a magnet

PhospholipidPhospholipidbilayerbilayer

< Ion channel…< Ion channel…inside is polarinside is polar

more ways of passive transport…• Facilitated diffusion

– Uses carrier proteins to transport specific substances into or out of the cell

• Movement of substances across a semi-permeable membrane from low to high concentration

** up a concentration gradientex: stuffing clothes into a closet to

clean up your roomyour example:_______________________

Does this take energy? ________

Active TransportHow do cells maintain homeostasis?

Sodium-Potassium Pumppurpose: enables nerves and muscles cells to send electro-chemical signals

http://http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.htmlwww.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html

the sodium-potassium pump...

• You may noticed every time the sodium-potassium pump operates, it pumps 2 K+ in and 3 Na+ out.  That is not an even exchange, right?

• By pumping more positive charges out than in, this pump helps to keep a more negative (less positive) environment inside the cell. 

• sodium-potassium pump is an electrogenic pump. 

• electrogenic means "electric charge generating." 

Na+K+ pump

•purpose: cells able to send electrical signals to respond (react) to stimuli.

•Is this passive or active transport? _________ (hint: is energy being used?)

•Name 2 body systems that need to be able to respond to the environment. ______________

2. Vesicles Move Large Substances Across Membranes (exocytosis)

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBooktransp.html#The%20Cell%20Membrane

Phagocytosis: a type of endocytosisPhagocytosis of a Reproducing Bacterium by an Phagocytosis of a Reproducing Bacterium by an AmoebaAmoeba

Neat website of Neat website of amoeba eating by amoeba eating by phagocytosisphagocytosis

http://http://www.ivyhall.district96.k12.www.ivyhall.district96.k12.il.us/4th/kkhp/Microbes/il.us/4th/kkhp/Microbes/amoeba1.html#AeatsPamoeba1.html#AeatsP

• Functions of receptor proteins

1. Changes in permeability – may cause the ion channel to open to allow certain ions to cross the membrane

2. Second messengers – causes formation of second messenger inside the cell to activate chemical reaction

3. Enzyme action – may speed up chemical reactions inside the cell

Membrane Receptor Proteins Receive Information

Vesicles move substances across membranes.

Paramecium’s Contractile Vacuole

•http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html