The Cell Membrane

Selectively Permeable??

CATALYSTAmount of Money Spent On Road Repairs per Year

0

10

20

30

40

50

60

2002 2003 2004 2005 2006 2007

Year

Am

ou

nt

of

Mo

ney S

pen

t o

n R

oad

Rep

air

s (

millio

ns)

Amount of Snowfall per Year in Inches

0

10

20

30

40

50

60

2002 2003 2004 2005 2006 2007

Year

Am

ou

nt

of

Sn

ow

fall (

inch

es)

Bell Ringer1. What is the title of

each of these graphs?

2. How much snow fell in 2003 and how much money was spent on road repairs?

3. Is there a relationship between the amount of snowfall per year and the amount of money spent on road repairs each year?

Objective/Agenda

Objective:

• SWBAT: Describe how a cells’ plasma membrane functions.

Agenda:

• Bell Ringer• Announcements• Lecture• Analysis Questions• Homework

Plasma Membrane

How is a window screen similar to a plasma membrane?

What are some things that can pass through a window screen?

What are some things that cannot?Why is it important to keep these things

from moving through the screen?The cell is surrounded by a plasma

membrane, which regulates what enters and leaves the cell. Why is it important to regulate what moves into and out of a cell?

The job of the plasma membrane is to:

1. Allow glucose, amino acids, and lipids into and out of the cell

2. Allow waste to leave the cell

Ex. Carbon Dioxide

Take Notes!

How is the membrane selectively permeable?

How does the membrane maintain homeostasis?

• It allows some molecules in while keeping others out

• It keeps the cell in balance with the outside environment

Take Notes!

Homeostasis requires the inside of the cell to be similar to the outside.

INSIDE CELL

OUTSIDE

CELL

Which means…

Sometimes things need to move back and forth!

Demo

• In what way does this sandwich bag represent a cell?

• How was the coffee filter analogous to a cell membrane?

Think, Pair, Share

• Think: Write down your own analogy for the cell membrane.

• Pair: turn to your partner and critique their analogy.

• Share: Pick the best analogy at your table to share aloud with the class.

Describe the structure of the plasma membrane:

1. Made up of a lipid bilayer

2. Transport proteins are tunnels that allow certain substances in and out of the cell

Take Notes!

Fluid Mosaic Model The bilayer creates a “sea” where other molecules float along the surface creating patterns or “mosaics”.

Take Notes!

Label Your Diagram!

1. Phospholipid (polar head)

2. Cholesterol

3. Carbohydrate chains

4. Transport Proteins

5. Fatty acid tail (nonpolar tail)

Check For Understanding

a. A c. C

b. B d. D

What structure is analogous to a sewage system?

Analysis Questions:

• 1. Describe why the structure of the plasma membrane is referred to as a fluid mosaic.

• 2. What are the specialized parts of the lipid bilayer, and how do their structures relate to the structure of the plasma membrane.