Regents Biology

BW #3

Watch the video…Write

down 3 things you

learned.

video

Regents Biology

What is homeostasis?

Let’s ask an expert!

Regents Biology

Cell Membrane

Substances move in and out of the cell in

order for the cell to function properly and

maintain homeostasis.

Homeostasis

Homeostasis -- the ability of an organism to

maintain a constant internal balance even

when the conditions around it change.

Which organelle in the cell is responsible for

maintaining homeostasis?

Regents Biology

Cell (plasma) membrane

Cells need an inside & an outside…

separate cell from its environment

cell membrane is the boundary

Regents Biology

Semi-permeable membrane

Cell membrane controls what gets in or out

Need to allow some materials — but not all — to pass through the membrane

semi-permeable only some material can get in or out

aa H2Osugar lipids salt waste

So what needs to get across the membrane?

O2

Regents Biology

Building a membrane

How do you build a barrier that keeps

the watery contents of the cell separate

from the watery environment?

What substance

do you know

that doesn’t mix

with water?

FATS

LIPIDS

Remember: oil & water don’t mix!!

Regents Biology

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Lipids of cell membrane Membrane is made of special kind of lipid

phospholipids

“split personality”

Membrane is a double layer

phospholipid bilayer

lipid

“repelled by water”

“attracted to water”

phosphate

Regents Biology

Crossing the cell membrane

What molecules can get through the cell

membrane directly?

fats and oils can pass directly through

inside cell

outside cell

lipid

salt

aa H2Osugar

waste

but…

what about

other stuff?

Regents Biology

Cell membrane channels

Need to make “doors” through membrane

protein channels allow substances in & out

specific channels allow specific material in & out

H2O channel, salt channel, sugar channel, etc.

inside cell

outside cell

sugaraaH2O

saltwaste

Regents Biology

How do you build a semi-permeable

cell membrane?

Channels are made of proteins

proteins both “like” water & “like” lipids

bi-lipidmembrane

protein channelsin bi-lipid membrane

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Protein channels

Proteins act as doors in the membrane

channels to move specific molecules

through cell membrane

HIGH

LOW

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Molecules move from high to low

Diffusion

Molecules move from HIGH to LOW

concentration

EXAMPLE

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Concentration???

Think of it as how crowded something

is…

Which is more concentrated? WHY?

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Simple vs. facilitated diffusion

inside cell

outside cell

lipidinside cell

outside cell

glucose

simple diffusion facilitated diffusion

glucose

protein channel

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Diffusion

Move from HIGH to LOW concentration

directly through membrane

simple diffusion

no energy needed

help through a protein channel

facilitated diffusion (with help)

no energy needed HIGH

LOW

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Facilitated Diffusion

Move from HIGH to LOW through a channel

inside cell

outside cell

sugar

sugar

sugar

sugar

sugarsugar

sugarsugar

sugarsugar

sugar

Which way will

sugar move?

sugar

sugar

LOW

HIGH

Regents Biology

BW #4

Name 2 things about simple

diffusion, facilitated diffusion,

and osmosis that are the

same. (you may use your

notes from last class)

Regents Biology

Active transport

Cells may need molecules to move

against concentration “hill”

need to pump “uphill”

from LOW to HIGH using energy

requires energy (ATP)

Moves Through Proteins

ATP

Regents Biology

Food is moved into the cell by Endocytosis

Wastes are moved out of the cell by Exocytosis

animation

Movement through Vesicles

• Endocytosis and Exocytosis is the mechanism by which very large molecules (such as food and wastes) get into and out of the cell

• ENERGY is needed for this process to occur.

Regents Biology

NO ENERGY NEEDED: (passive transport)DiffusionOsmosisFacilitated Diffusion

ENERGY NEEDED:Active TransportEndocytosis, exocytosis

ANALOGY:

Regents Biology 2006-2007

OsmosisMovement of Water Across

Cell Membrane

Regents Biology

Osmosis

Water is very important, so we talk about

water separately

Osmosis

diffusion of water from HIGH concentration

of water to LOW concentration of water

across a semi-permeable membrane

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Keeping water balance

Cell survival depends on balancing

water uptake & water loss

freshwater balanced saltwater

Regents Biology

Keeping right amount of water in cell

Hypotonic

high concentration of water outside cell

Which means water moves intothe cell and the cell swells

Example

a cell in fresh water

freshwater

No problem,here

KABOOM!

1

Regents Biology

Keeping right amount of water in cell

Hypertonic Solution

lower concentration of water outside cell

Which means water moves out of the cell and the Cell Shrinks

Example Cells in salt water

saltwater

I willsurvive!

I’m shrinking,I’m shrinking!

2

Regents Biology

Keeping right amount of water in cell

Isotonic Solutions

no difference in concentration of water between cell & environment

No change in the size of cell

How different cells handle too much or too little water

balanced

I couldbe better…

That’sbetter!

3

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HYPERTONIC ISOTONIC HYPOTONIC

HYPOTONIC ISOTONIC HYPERTONIC HYPOTONIC ISOTONIC HYPERTONIC

Regents Biology

Regents Biology

Type of Transport

Definition

Energy Needed

Y/NProtein Helpers

Type of Molecule

Transported

Diffusion

(p. 72)

Molecules moving

from high to low

concentrations

NO None ANY molecule

Osmosis

(p. 73)

WATER moving

from high to low

concentrations

across a

membrane

NO*None

*AquaporinsWater

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Type of Transport

Definition

Energy

Needed Y/NProtein Helpers

Type of Molecule

Transported

Facilitated

Diffusion

(pg. 73-74)

Diffusion

through a

protein in the

cell membrane

No YES

Some

charged or

Large

molecules

Regents Biology

Type of Transport

Definition

Energy

Needed Y/NProtein Helpers

Type of Molecule

Transported

Active

Transport

(p. 74)

Molecules

move from

LOW to HIGH

concentrations

YES YES

*Large

Molecules

*Charged

Molecules

Regents Biology

Type of Transport

Definition

Energy

Needed Y/NProtein Helpers

Type of Molecule

Transported

Vesicles

(p. 74-75)

Large

molecules are

packaged in a

vesicle for

movement in or

out of the cell

YES NoneLARGE

molecules