• Gatekeeper• Regulates what comes in and out

of the cell• Main components: proteins and

phospholipids• The cell membrane is selectively

permeable• Allows some things through without energy,

but not everything

1.All cells have a cell membrane

2.Functions: a.Controls what enters and exits the cell to maintain an internal balance called homeostasis

b.Provides protection and support for the cell

TEM picture of a real cell

membrane.

• Found only in plant cells and bacteria cells

• Main function is support

• phosopholipids• made of two sides: head and tail• the head is hydrophillic (able to

interact with water)• the tail is hydrophobic (not able to

interact with water)

3.Structure of cell membrane

Lipid Bilayer -2 layers of phospholipidsa.Phosphate head is polar (water loving)

b.Fatty acid tails non-polar (water fearing)

c.Proteins embedded in membrane

Phospholipid

Lipid Bilayer

• carrier proteins• allow larger or difficult molecules to get

through the membrane• sometimes they require energy to

open/close like a door• other times they simply act as a tunnel

Proteins

Membrane movement animation

Polar heads love water & dissolve.

Non-polar tails hide from water.

Carbohydrate cell markers

Fluid Mosaic Model of the cell

membrane

4. Cell membranes have pores (holes) in ita.Selectively permeable: Allows some molecules in and keeps other molecules out

b.The structure helps it be selective!

Pores

Outside of cell

Inside of cell (cytoplasm)

Lipid Bilayer

Proteins

Transport Protein Phospholipids

Carbohydratechains

Structure of the Cell Membrane

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Animations of membrane

structure