TP:SWBAT understand how nutrients and wastes are exchanged between

cells?Do Now: Define Homeostasis.

Explain how the cell membrane helps a cell maintain homeostasis.

There are two types of transport…

• Passive transport

• Active transport

Passive Passive Transport:Transport:

• Does NOT require any ENERGY to move materials through the cell membrane.

• Materials will pass through on their own if they are small enough to fit through.

• And if the molecules move with the concentration gradient (going from a higher to a lower concentration).

Passive Transport

Concentration Concentration Gradient:Gradient:

•Materials will continue to move into the cell until there is a balance both inside and outside.

• This balance is called Dynamic Equilibrium

There are 2 types There are 2 types of Passive of Passive Transport:Transport:

•Diffusion•Osmosis

Diffusion is the net movement of a substance (liquid or gas) from an area of higher concentration to an area of lower

concentration.• Scenario: You enter the

girls or boys bathroom. • An obnoxious fellow

student lights a stink bomb after entering one of the stalls.

• Disliking the smell you go to the farthest stall you can.

• But the smell creeps up on you!

• This is an example of diffusion in action.

DiffusionDiffusion• Does NOT require

any energy• Particles move from

a higher concentration to a lower concentration

• Diffusion spreads the particles evenly until Dynamic Equilibrium is reached

Diffusion

HighLowLow

The overall (or net) movement is from high to low concentration. Eventually, if no energy is input into the system the

molecules will reach a state of equilibrium where they will be

distributed equally throughout the system.

Diffusion of a dye in a beaker of water

OsmosisOsmosis• Does NOT require

energy• Specific to WATER

only• Water will flow from

a high concentration to a low concentration

• In this case, water moves through root cells to give life to the plant

OsmosisOsmosis

TP: SWBAT understand how the

solutions impact diffusion.

Do Now: A common remedy used to relieve a sore throat (swollen throat tissue) is to gargle with salt water.

Explain why this is helpful.

SolutesSolutes• Most liquids

have dissolved particles floating in them called solutes.

• These solutes take up space with water molecules

SolutesSolutes• A solution that contains very few

dissolved non-water molecules is considered to have a very high concentration of water, because water makes up a high proportion of the molecules present.

• Conversely, a solution that contains a high concentration of solutes is considered to have a relatively low concentration of water molecules.

Which solution has more solutes?

Salt Water Tap Water= salt

Slug OsmosisSlug Osmosis• Living cells are

surrounded by a membrane that many substances cannot penetrate.

• An example of such a substance is salt.

• If salt is sprinkled on a slug, the salt increases the solute concentration in the water that lies on the outside of the animal's skin.

Poor SlugsPoor Slugs• The salt (represented

by the orange particles in the illustration) cannot penetrate the skin in significant amounts.

• However, the difference in the concentration of water between the inside and outside of the cells results in osmosis.

• Water (represented by the blue particles and arrows) rapidly leaves the animal's tissues, leading to death.

Osmosis in Osmosis in HumansHumans• Humans are much better protected

against water loss, because our skin cells are covered with a protein called keratin.

• However, osmosis is still a life-and-death matter for us in other ways.

• For example, the functioning of our kidneys relies heavily on osmosis.

• Excessive salt in the diet is thought to be one factor promoting high blood pressure, because the salt goes into the fluids surrounding your cells and draws water out by osmosis.

There are 3 different There are 3 different types of Solutionstypes of Solutions::

•Hypertonic (“viper”)•Hypotonic (“hippo”)•Isotonic (same)

HyperHypertonic tonic SolutionSolution

• The solution contains MORE SOLUTES (hyper) than water

• Water moves out of the cell

• The cell shrinks and dies

• Hyper Viper

80% water

90% water

Solution Solution AnimationsAnimations

HypoHypotonic tonic SolutionSolution

• Solution contains LESS SOLUTES (hypo) and MORE WATER

• Water moves into the cell

• Cell will swell and burst

• Hypo hippo

90% Water

80% water

Solution Solution AnimationsAnimations

IsoIsotonic tonic SolutionSolution

• Solution contains the SAME amount of solutes and water

• Under these conditions, water diffuses into and out of the cell at EQUAL RATES, so there is NO Net Movement of Water.

Solution Solution AnimationsAnimations

Image showing what happens when a blood cell is in a

hypotonic environment & a hypertonic environment

Image showing what happens when a plant cell is in a hypotonic

environment & a hypertonic environment

Which side has more Which side has more water?water?

A B = salt

membrane

Which side is Which side is Hypertonic?Hypertonic?

A B = salt

membrane

Which way will the water Which way will the water move?move?

A B = salt

membrane

Task:•Create a table comparing Hypertonic, Hypotonic and Isotonic. •Make sure to include what leads to each situation, how water will diffuse and the effect on the cell.

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• You are stranded on a desert island, with nothing but a cell phone. You know that help will arrive within a couple days, but you are dehydrated and need to quench your thirst. You are surrounded by the ocean on all sides; should you drink the salt water? Why or why not?

• In the days before refrigeration, a common practice to preserve meat was to add a lot of salt to the meat. Why was this a relatively effective technique?

• Design a procedure using osmosis and/or diffusion that will produce a shriveled cell.

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If I put a Red blood cell in a

hypotonic solution, what will happen to it?

Before After

If I put a liver cell in a hypertonic solution, what

will happen to it?

Before After

TP: SWBAT understand when cell’s require energy

for transport

Do Now: What kinds of solutions may lead to a cell’s death? Why

would this happen?

Active Active TransportTransport

• Cells MUST use their own energy (ATP) to move molecules AGAINST the concentration gradient

• Here, molecules are moving from areas of LOW to areas of HIGH concentration

HighLow

Active TransportThere are 2 types of active

transport

1. Endocytosis (in)

2. Exocytosis (out)

ENdocytosis

• During endocytosis, the cell membrane folds IN and forms a small pouch.

• The pouch then pinches off from the cell membrane to become a vesicle.

There are actually 2 types of

endocytosis:1.Phagocytosis – when an

entire cell is gobbled up.

(Phago = BIG)2.Pinocytosis – when

external fluid is engulfed. (pino = small)

PinoPinocytosicytosiss• The cell “gulps”

droplets of extracellular fluid (nutrients) and then forms a vacuole inside the cell in which the nutrients are distributed

Pinocytosis

PhagoPhagocytocytosissis

• When portions of the cell engulf prey or large chunks of matter flowing around them

• Ex: white blood cells engulf bacteria

PhagocytosisPhagocytosis

Of course this type of transport doesn’t go just one

way…• We just talked about

endocytosis, which is a process where cells take in material from the outside.

• Do you think cells also send material outside?

• YES!• This is process is called

EXOcytosis

Exocytosis• Material from within

the cell is transported to the cell membrane inside a vesicle

• The vesicle attaches itself to the cell membrane

• The cell membrane opens up to allow the materials to escape from the vesicle

• The vesicle’s membrane becomes part of the outer cell membrane

Task

• Move to your learning style groups.• Each group must create a way of

showing and explaining their assigned transport.

• Some groups may choose to make a skit, sign, song, etc.

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Task

• 1) As waste chemicals build up in a cell, homeostasis is threatened.  State how diffusion helps a cell maintain homeostasis.

• 2) Compare and contrast:  Diffusion and active transport are processes that are important to the cell maintenance of homeostasis in organisms.  Compare and contrast the two processes 53