CELL MEMBRANE: FLUID MOSAIC

CELL/ PLASMA MEMBRANE• Separates the inside of the cell from its environment

• Receives messages from outside

• Allows things to move in and out of the cell

• Has markers that identify the type of cell

WHAT ARE CHARACTERISTICS OF THE CELL MEMBRANE?

• Selectively permeable• Only some things can

pass through the membrane

• Polar, charged and large molecules can only get through membrane via transport proteins

• Composed of • phospholipids

• Proteins

BI-LAYER OF PHOSPHOLIPIDSBI-LAYER OF PHOSPHOLIPIDS

Heads are polar• hydrophilic

• Tails are nonpolar• hydrophobic

• Steroid molecules make membrane rigid.

think: What do: “hydro”, “bi”, “philic” & “phobic” mean?

MACROMOLECULES: LIPIDS• Lipids are fats & oils.Lipids are fats & oils.

• Lipids are composed of only C,H,O.

• Lipids are nonpolar.

• Lipids are composed of glycerol and 3 fatty acids.

• Lipids can be saturated (solid at room temperature) or unsaturated (liquid at room temperature) The glycerol forms the “head” and

The 3 fatty acid chains the “tails”

PROTEINS EMBEDDED IN BI-PROTEINS EMBEDDED IN BI-LAYERLAYER

Peripheral proteins• act as recognition

sites on the outside of the cell

• Inside the cell they are enzymes

• Integral proteins• act as channels that

move things through the membrane

Think: What do: “peripheral” & “integral” mean? How does this relate to where the proteins are in the plasma membrane?

FLUID MOSAIC FLUID MOSAIC MODELMODEL

• Phospholipids & proteins move about. (fluid)• Membrane has

many types of molecules in it (mosaic)

SUMMARIZE THE MOST IMPORTANT INFORMATION ABOUT THE CELL MEMBRANE IN A PARAGRAPH