Topic 1.3 Membrane StructureIB Biology

R. Price

v. 1 2015

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#1: Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules

• Hydrophilic = attracted to water• Hydrophobic = not attracted• Amphipathic = part hydrophilic & part

hydrophobicPhospholipids• Phosphate head = hydrophilic• Hydrocarbon tail = hydrophobic

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#1: Phospholipids form bilayers in water due to the amphipathic properties of phospholipid molecules

Phospholipid Bilayers• Mix phospholipid with water• Phosphate head attracted to water• Hydrocarbon tails attracted to each other• Make double layer = basis of cell membranes

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#2: Membrane proteins are diverse in terms of structure, position in the membrane, and function

Functions of Membrane Proteins•Hormone binding site (insulin receptor)•Immobilized enzymes (in small intestine)•Cell adhesion •Cell to cell communication (neurotransmitters)•Passive transport channels•Active transport pumps

#2: Membrane proteins are diverse in terms of structure, position in the membrane, and function

Integral Protein•Hydrophobic on part•May be transmembrane

Peripheral Protein•Hydrophilic•Attached to surface

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#3: Cholesterol is a component of animal cell membranes

• Animal cell membranes contain cholesterol• Lipid, steroid,

amphipathic• Positioned between

the phospholipids in the membrane

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SourcesContent Allott, Andrew, and David Mindorff. Biology: Course Companion. 2014 ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.

Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge: Cambridge UP, 2014. Print.

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