Cell membrane: Fluid mosaic

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Cell membrane Fluid mosaic
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What Are Characteristics Of The Cell Membrane?

• Selectively permeable
• Composed of
• Lipids
• Proteins

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bi-layer of phospholipids

• Heads are polar
• hydrophilic
• Tails are nonpolar
• hydrophobic
• Steroid molecules make membrane rigid.

think What do hydro philic phobic mean?
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Macromolecules Lipids

• Lipids are fats oils.
• Lipids are composed of only C,H,O.
• Lipids are nonpolar.
• Lipids are composed of glycerol and 3 fatty acids.

The glycerol forms the head and The 3 fatty
acid chains the tails
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Lipids saturated fat

• Has all single bonds in the fatty acid segment.
• Fatty acids are straight.
• Are solids at room temp.
• animal fats.

Fatty acids
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Lipids Unsaturated fats

• Have at least one double bond.
• have bend.
• Are liquid at room temp
• come from plants
• Ex olive oil.

Think Which fatty acid would you expect to have
a bent shape and where would the bend be?
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Proteins embedded in bi-layer

• Peripheral proteins
• act as recognition sites
• Integral proteins
• act as channels

Think What do peripheral integral mean?
How does this relate to where the proteins are in
the plasma membrane?
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Fluid Mosaic Model

• Phospholipids move about.
• Proteins move about.
• Water keeps the membrane in position.

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Review

1. Why do the lipids in the membrane have a polar
   and nonpolar end?
2. What do peripheral proteins do?
3. Why is the membrane selectively permeable?