3.3 Cell Membrane

• In the top margin of pg 28 or 29:

Explain why animal cells cannot undergo photosynthesis.

Hint: Look at the difference in organelles.

3.3 Cell Membrane

• Animal cells lack chloroplasts which is the organelle needed to convert solar energy into energy that the cell can use.

Animals cannot make their own food…plants can because they havechloroplasts!

3.3 Cell Membrane

Standard

1.a Students know cells are enclosed within a semipermeable membranes that regulate their interaction with their surroundings.

3.3 Cell MembraneSponge: Set up Cornell Notes on pg. 31

Topic: 3.3 Cell Membrane

Essential Question:

Explain how membrane receptors transmit messages across the cell membrane

Don’t forget to add it to your T.O.Contents!

2.1 Atoms, Ions, and Molecules

Explain how membrane receptors transmit messages across the cell membrane

3.3 Cell Membrane

Key Concept: The cell membrane is a barrier that separates a cell from the external environment

3.3 Cell MembraneSet up your paper on pg. 30

Divide your paper in to 3 even rows

2.1 Atoms, Ions, and Molecules

3.3 Cell Membrane

KEY CONCEPT The cell membrane is a barrier that separates a cell from the external environment.

What can we compare

this to in our bodies?

3.3 Cell Membrane

• The cell membrane has two major functions.

cell membrane

3.3 Cell Membrane

• The cell membrane has two major functions.

1. forms a boundary between inside and outside of the cell

cell membrane outside cell

inside cell

3.3 Cell Membrane

• The cell membrane has two major functions.

1. forms a boundary between inside and outside of the cell

2. controls passage of materials

cell membrane outside cell

inside cell

3.3 Cell Membrane

Cell membranes are composed of two phospholipid layers.

3.3 Cell Membrane

• A phospholipid is a molecule composed of three basic parts:

– A charged phosphate groupA charged phosphate group– GlycerolGlycerol

– two fatty acid chainstwo fatty acid chains

*Draw and label this phospholipid on the top of pg 30

3.3 Cell Membrane

Head

Tail

• The head is polar

• interacts with water

• Hydrophilic

• Attracted to water

• The tail is non-polar

• repelled by water

• hydrophobic

• Attracted to other tails

3.3 Cell Membrane

cell membrane

*Phospholipids arrange themselves like a sandwich into two layers.

protein

cholesterol

proteincarbohydratechain

protein channel

Contain:•Proteins•Cholesterol•Carbohydrates

3.3 Cell Membrane

protein

cholesterol

proteincarbohydratechain

protein channel

Pg. 30-middle: draw and label the cell membrane and its parts

3.3 Cell Membrane

Fluid mosaic model: • Flexible• Phospholipids can move from side to side and slide past

one another• Behaves like a fluid

3.3 Cell Membrane

• The cell membrane is selectively permeable.

Some molecules can cross the membrane while others cannot.

*Draw a picture on the bottom of pg. 30

3.3 Cell Membrane

• The cell membrane is selectively permeable.

Some molecules can cross the membrane while others cannot.

*Draw a picture on the bottom of pg. 30

3.3 Cell Membrane

Receptors are proteins that detect a signal molecule and performs an action in response

– It binds with It binds with ligandsligands on the outside of the cell on the outside of the cell– Once they bind, the receptor changes shape and sends Once they bind, the receptor changes shape and sends

a message to the inside of the cella message to the inside of the cell