Membranes

Cell membrane = Plasmalemma = Plasma membrane

Surrounds cells and most organelles

Forms a network of passages

Mitochondria, chloroplasts, and the nucleus all have a double membrane

Functions of plasmalemma

1. Keep cell contents together and separate from other cells

2. Controls movement of substances into and out of cells

3. Allow communication between cells

4. Attachment for intracellular cytoskeleton, cell walls and intercellular adhesions

Membranes are made of Phospholipids

Hydrophilic Polar head

Hydrophobic Non-polar tails

Hydrophobic tails

Hydrophilic heads

Watery cytosol

Water outside cell

Hydrophobic tails

Watery Cytoplasm

Fluid mosaic theory

• Phospholipids are not bound to each other

• Like oil on water

• Water inside and outside the cell

http://www.youtube.com/watch?v=ULR79TiUj80&feature=related

(fluid mosaic model, 1.5 min)

Permeability

Membranes are selectively permeable

Allow some molecules through but not all

Permeability of membrane

Some membranes impermeable (eg surfaces designed to retain water such as skin, scales, exoskeletons)

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Key Words

Exercises

Quick Quiz

Videos

Extra slides

Key wordsPhospholipidsBilayerFatty tailsPhosphate headImpermeablePermeableLarge moleculesIonsFluid Mosaic

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(VERY) Quick quiz1. ____ are the main component of membranes 2. They consist of hydrophobic ____3. And a hydrophilic ____4. They also have integral and peripheral ____

Answers

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(VERY) Quick quiz1. Phospholipids are the main component of

membranes

2. They consist of hydrophobic tails3. And a hydrophilic head4. They also have integral and peripheral proteins

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Exercise

Workbook pp50-52, qq18-20 and 22-23Booklet p3

READING• Pathfinder p48 (or p42) Enzymes & reaction

rate• Excellence in Biology pp114-6

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Videos

http://www.youtube.com/watch?v=E90D4BmaVJM&feature=related

(10 min, includes biotechnology)http://www.teachersdomain.org/asset/tdc02_int_membraneweb/

(interactive - membrane)

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Glycoproteins & glycolipids for cell recognitionhttp://www.5min.com/Video/Proteins-as-the-Mosaic-of-the-Cell-Membrane-150624158 Back to

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Peripheral proteins

Partially embedded intrinsic – inside cell extrinsic – outside cell

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OIL AND WATER

I told you this would be important!

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Trans-membrane (integral) proteins

• involved in facilitated and active transport

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