Biomembranes and Cell Organelles By Melisha Kenedy Phospholipid

Biomembranes and Cell Organelles By: Melisha Kenedy

Phospholipid Bilayer è Amphipathic è è è Hydrophilic head group Hydrophobic core Hydrophobic and van der Waals interactions Cytosolic face and exoplasmic face Fluid structure

Biomembrane Lipids u Phosphoglycerides u u u two fatty acyl chains phosphate Sphingolipids u u long fatty acid chain sphingosine amino group u Steroids u u 4 -ring hydrocarbon cholesterol

Proteins Interacting with Membranes • Integral Membrane Proteins – Span the phospholipid bilayer • Lipid Anchored Proteins – Covalent bonds with one or more lipid molecules • Peripheral Membrane Proteins – No interaction with the membrane’s hydrophobic core – interact with integral proteins or head group of lipids

Biomembrane Functions • • • Prevents unwanted materials from entering Prevents metabolites from exiting Allows nutrients to enter Allows wastes to exist Isolates cells and organelles

Nucleus • Functions – regulates the cell – contains genetic information • Surrounded by two membranes • Structures – nuclear pores – nucleolus • synthesis of r. RNA • not bound by a phospholipid membrane

Cytomembrane System v Endoplasmic Reticulum v Smooth ER v v synthesis of fatty acids and phospholipids Rough ER v contain ribosomes: synthesis of proteins v Golgi Complex v v v Modifies ER products Cis, medial, and trans regions Regions with different enzymes

Mitochondria • ATP production • Two membranes – Outer membrane • more permeable • half lipid and half protein – Inner membrane • less permeable • cristae increase surface area • Contain DNA

Chloroplasts â â â Photosynthesis Two membranes Thylakoids- capture light Grana- stacks of thylakoids Stroma Contain DNA

Summary • The phospholipid bilayer is an amphipathic and fluid structure. • The three lipids associated with biomembranes include phosphoglycerides, sphingolipids, and steroids. • The three classes of proteins associated with biomembranes include integral membrane proteins, lipid anchored proteins, and peripheral membrane proteins. • Biomembranes control materials that enter and exist cells and organelles. • The nucleus regulates the cell and stores genetic information. • The cytomembrane system includes the endoplasmic reticulum and the golgi complex. • The mitochondria is the site of ATP production. • The chloroplasts are important in photosynthesis.

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