Membrane Structure and Homesostasis 2007

8/10/2019 Membrane Structure and Homesostasis 2007

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Chapter 3.4

Homeostasis and thePlasma Membrane


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What is the Plasma

Membrane?

Forms inner and outer boundary

of the cell

Made of a phospholipid bilayer

Protein and cholesterol

molecules inside the FLEXIBLE

membrane


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Hydrophilic

Hydrophobic

Draw a phosopholipid


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hydrophilic

hydrophilic

hydrophobic

Protein


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Hydrophilic

head

Hydrophobictail

Molecular model of the

Phospholipid


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Water

Water

Hates water

Membrane association with water


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FLUID MOSAIC MODEL
http://www.phschool.com/science/biology_place/biocoach/biomembrane1/structure.html


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Fluid Mosaic Model


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Hydrophilic Heads

Hydrophobic interior

Cholesterol (sterol)

Peripheral Protein

Integral Protein

Carbohydrate marker

Add labels to your diagram


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Video - fluid mosaic

model


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Channel Proteintransport of molecules

across a membrane
http://personal.tmlp.com/Jimr57/textbook/chapter3/cmf1A1.htmhttp://personal.tmlp.com/Jimr57/textbook/chapter3/cmf1A1.htm


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ReceptorsReceives and

Transmits info into the cell
http://personal.tmlp.com/Jimr57/textbook/chapter3/cmf1A1.htm


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Glycoproteinson the cell

surface

identify types of cells (like a flag)tells if the cell is a part of self

or invader.

Carbohydrate

Protein


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How White Blood Cells

recognize an invader and

ATTACK!!!

White

Blood

Cell

Glycoprotein

Marker

Virus

Nucleus
http://personal.tmlp.com/Jimr57/textbook/chapter3/cmf1a.htm


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Carrier proteinsThey move specific molecules

through the membrane one at a

time.
http://personal.tmlp.com/Jimr57/textbook/chapter3/cmf1a.htm


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VideoMembrane

Transport


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Integral Proteins

Are proteins that spanthe membrane

(go all the way through)


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Peripheral Proteins

Are proteins that

are on the

PERIMETER(outside edges)

of the membrane


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All components are free to drift

sideways


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Draw a Phospholipid Bilayer

Include all the proteins andmolecules in the textbook p 82.

Drawing can be exact from

book or your one rendition- aslong as all the labels included

in the book are in the drawing.

You MUST add color.


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Semi-Permeable =

- only certain

kindsof

molecules are

able to pass

through the

membrane
http://www.phschool.com/science/biology_place/biocoach/biomembrane1/permeability.html


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How do substances

pass in and out of cells?

Diffusiona movement of particles from an

area of HIGH concentration TO an area of

LOW concentration .

CONTINUES until equilibrium is reached


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Solutes (such as sodium) will

pass down the concentration

gradient

Meaning they will flow across

the membrane from high soluteto the side with low solute.


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Water will diffuse through a cell

membrane.

Diffusion of WATER across acell membrane is called

osmosis.

(A special kind of diffusion.)


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How are these different?

Diffusion:

The movement of

any substancefrom an area of

high

concentration to

an area of lowconcentration.

Osmosis:

The movement of

water across acell membrane

from an area of

high water

concentration toan area of low

water

concentration.


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Osmosis is

WATER

passingthrough a cell

membrane!

-- Nothing Else!


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h // bi l /l i /bi b 1/i d h l
http://www.biology.com/learning/biomembrane1/induce.htmlhttp://www.biology.com/learning/biomembrane1/induce.html


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http://www.biology.com/learning/biomembrane1/induce.html

Make sure everyone understands why water is moving--

before moving to the next slide.

Which one is hypotonic? Which one is hypertonic?

Check page 86 of your textbook. (pictures)

Isotonic Animation

Hypotonic

AnimationHypertoninc

Animation
http://www.biology.com/learning/biomembrane1/induce.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/isotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/hypotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/isotonic.htmlhttp://www.phschool.com/science/biology_place/biocoach/biomembrane1/osmosis.htmlhttp://www.biology.com/learning/biomembrane1/induce.html


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IsotonicEnvironment

Hypertonic

Environment

Cell Shrinks

SAME

Hypotonic

Environment

Cell Swells

may burst

Arrows are the direction of water movement.


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SIMPLE DIFFUSION ACROSS

A MEMBRANE


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Facilitated Diffusion

Transport proteins

help or facilitate

diffusion Specific

PASSIVE (down

gradient)High Conc. Low Conc.
http://www.phschool.com/science/biology_place/biocoach/biomembrane1/diffusion.html


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Active Transport

Cells move substances AGAINSTthe concentration gradient.

LOW HIGH Require ENERGY (ATP)

Very importantmoves

moleculesagainst

aconcentration gradient

U hill t t (


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Uphill transport (uses

ATP)

Active transport helps
http://www.phschool.com/science/biology_place/biocoach/biomembrane1/diffusion.html


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Active transport helps

to maintain

Homeostasis

High K+

Low Na+

Low K+

High Na+
http://personal.tmlp.com/Jimr57/textbook/chapter3/cmf1c.htm


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High

Yellow

High

Orange
http://personal.tmlp.com/Jimr57/textbook/chapter3/cmf1c.htm


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ATP powers active

transport bytransferring its third

P group directly to

protein.

Changes proteins

structure allowingprotein to move the

substance across a

membrane.

http://www.biology.com/learning/biomembrane1/operation.html


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How areLARGEmolecules passed

through the membrane?

?


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Exocytosisoutfolding of the

membrane by the fusion of

vesicles to the plasmamembrane.

(secretion)


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EndocytosisInfolding of

membrane pushes largemolecules into cell forming

vesicles.

Pinocytosis=cell drinking

liquid solutions

Phagocytosis=

cell eatingsolid/large particles


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http://www.phschool.com/science/biology_place/biocoach/biomembrane2/cytosis.html


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http://www.biology.com/learning/biomembrane2/guiding.html

http://www.biology.com/learning/biomembrane2/process.html


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Endosymbiotic Theory

Possible origin of organelles?

Prokaryote may have eaten another prokaryote

(remember how small they are.)

Evidencemitochondria and chloroplast havetheir own DNA and ribosomes and are about the

same size as a bacteria.

Mitochondria and chloroplasts may have first

started as individual cells.

They copy through binary fission (splitting in two)when the bigger cell divides.

They have been in eukaryotic cells ever since.

Practice show which


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Practiceshow which

direction WATER will

move

2%

NaCl(salt)2% NaCl (salt)


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Practice

2%

NaCl2% NaCl

Isotonic Environment

Situation = isoosmotic


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Practice

0%

NaCl2% NaCl


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Practice

0%

NaCl

100%

water

2% NaCl

Hypotonic

Environment

Situation = Hypoosmoticcell swells (may burst)


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Practice

10%

NaCl2% NaCl


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Practice

10%

NaCl2% NaCl

Hypertonic Environment

Situation = Hyperosmotic - Cell shrinks

Membrane Structure and Homesostasis 2007

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