Ch. 8 Membrane Structure Know: –Structure of plasma membrane –Phospholipids –Integral proteins –Peripheral proteins –Cholesterol –Glycoproteins –Glycolipids –Oligosaccharides –Functions of membrane proteins

Phospholipid Structure

Phospholipid Bilayer – held together by hydrophobic interactions

Membranes are fluid – they are not static

Factors that affect membrane fluidity 1. Unsaturated fatty acid chains – increase fluidity due to the chains not packing well 2. Temperature – low temperatures can decrease fluidity when phospholipids settle into a tightly packed arrangement 3. Cholesterol – packed in between phosholipids High temp. – disrupts movement of phospholipids, decreases fluidityHigh temp. – disrupts movement of phospholipids, decreases fluidity Low temp. – does not allow phospholipids to pack together, increases fluidityLow temp. – does not allow phospholipids to pack together, increases fluidity

Cholesterol

Fluid Mosaic Model

Membrane structure video

Have distinct inside and outside faces (amphipathic) Proteins dispersed and embedded throughout phospholipids bi-layer (membrane) 2 types of proteins present in membrane: -Integral proteins -Peripheral proteins

Membrane Proteins

Integral Proteins Can be: –Transmembrane- has hydrophobic midsections between hydrophilic ends exposed on each side of membrane –Unilateral- reaching only partway across the membrane Definition-inserted into the membrane, hydrophobic regions are surrounded by hydrocarbon portions of phospholipids

Peripheral Proteins Definition: Not embedded but attached to membrane’s surface, can be attached to integral proteins of filaments of cytoskeleton

Inside and Outside faces Synthesis and modification of the plasma membrane by the ER and the golgi apparatus determines the asymmetric distribution of lipids, proteins and carbohydrates Carbs are restricted to the exterior of the membrane

Sidedness of the plasma membrane – look at Fig. 8.8 in book Proteins on the inside of the vesicle become proteins on the outside face of the cell membrane

Transport Serves as a passage way for certain molecules

Enzymatic Activity Active sites on interior surface which catalyze reactions inside cells

Signal Transduction Docking sites for chemical messengers that will cause a change in protein shape and relays a message to the cell

Intercellular joining Proteins on adjacent cells can hook together

Cell-to-Cell Recognition Glycoproteins serve as identification tags which are recognized by other cells

Attachment to Cytoskeleton and ECM ECM- extracellular matrix Helps maintain cell shape and fixes location of membrane proteins

Membrane 2 video

Helpful Video? the-Mosaic-of-the-Cell-Membrane