Cell Membrane Structure

1. Cell Membrane
Structure and Function

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Membrane Design
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 fluid-mosaic model
a. Fluid = pliable/easily moved
b. Mosaic = made of many different
molecules (lipids, proteins, carbohydrates)
Cell Membrane Animation

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Predict the two reasons things can’t directly go through
the membrane:
Selectively Permeable
1) Size (duh)
2) Polarity (from last unit)

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The cell membrane only lets certain substances in and
out of the cell
Selectively Permeable

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Phosopholipid Bi-Layer
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-polar heads are hydrophilic “water loving”
-tails (fatty acids) are hydrophobic “water fearing” and face inward

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Cholesterol
 Type of steroid (lipid)
 Changes fluidity of cell membrane
 Higher temps – stiffens membrane
 Lower temps – prevents membrane from freezing

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Proteins
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 Recognition Proteins
 Proteins that have carbohydrate
chains attached
 Carbohydrate chains aid in cell
identification
 “Name Tags”
 Example: Red Blood Cells (A, B),
Identify Viruses as foreign
 Receptor Proteins
 Proteins that receive chemical
signals from other cells
 Such as nervous system cells

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 Channel Proteins
 Proteins that involved in letting certain substances in and out
of cells
 Aquaporins- let water in and out of cells
Proteins

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 Integral
 Proteins that cross both layers of the phosphoplipid
bilayer
 Peripheral
 proteins that are only on the top half or bottom half
of the phospholipid bilayer
Proteins