FLUID MOSAIC MODEL

FLUID MOSAIC MODEL Model describing structure of the cell membrane Model says cell membrane is not solid, fluid. Has the consistency of olive oil

FUNCTIONS OF PLASMA MEMBRANE

FUNCTIONS OF PLASMA MEMBRANE Protective barrier - contains cytoplasm (contents of the cell)

FUNCTIONS OF PLASMA MEMBRANE Transport Regulates movement of substances in / out of cell (selectively permeable)

FUNCTIONS OF PLASMA MEMBRANE Cell recognition Allows cells to identify surrounding cells http://www.dailymail.co.uk/sciencetech/article-491062/Multicoloured-brainbow-shows-nerve-activity.html

FUNCTIONS OF PLASMA MEMBRANE Cellular Attachment Cell membranes have junctions – surfaces which interlock keeps cells together – and surfaces which attach them to the extra cellular matrix.

FUNCTIONS OF PLASMA MEMBRANE Signal Transduction converts a mechanical/chemical stimulus to a cell into a specific cellular response.

FUNCTIONS OF PLASMA MEMBRANE Enzyme Activity Cells rely on thousands of different enzymes to catalyze metabolic reactions, many of these occur at the cell membrane. http://www.nature.com/scitable/topicpage/protein-function-14123348

STRUCTURE OF PLASMA MEMBRANE

MEMBRANE COMPONENTS Phospholipids Cholesterol Proteins (intergral & peripheral) Carbohydrates (glucose)

PHOSPHOLIPIDS Make up 30-70% of the cell membrane Phospholipids are like triglycerides with a phosphate Come together to make a fluid membrane

PHOSPHOLIPID ORIENTATION In water, phospholipids form a bilayer A cell membrane is a bilayer

PHOSPHOLIPID ORIENTATION Liposome is a small vesicle, with an aqueous compartment surrounded by a bilayer

PHOSPHOLIPID ORIENTATION PHOSPHATE HEADS – are water loving and point toward water FATTY ACID TAILS – are water fearing and orient themselves to each other

PHOSPHATE HEAD – HYDROPHYLIC FATTY ACID TAILS – HYDROPHOBIC

CLOSER LOOK OF THE PLASMA MEMBRANE

PROTEINS

INTEGRAL PROTEINS Proteins surrounded by phospholipids which go through the membrane Functions: serve as ion channels, membrane pumps, or receptors

FLUID MOSAIC MODEL

INTEGRAL PROTEINS

PERIPHERAL PROTEINS Proteins which attach to the membrane Predominately interact with integral proteins Can attach by weak hydrogen bonds 1. interaction by an amphipathic α-helix parallel to the membrane plane (in-plane membrane helix) 2. interaction by a hydrophobic loop 3. interaction by a covalently bound membrane lipid (lipidation) 4. electrostatic or ionic interactions with membrane lipids (e.g.through a calcium ion)

PERIPHERAL PROTEINS

GLYCOPROTEINS GLYCOPROTEINS found on the surface of the membrane Serve as recognition sites for chemicals Involved in cell to cell interactions

GLYCOLIPIDS Between phospholipids Face extracellular fluid and serve as “cell identifiers”

CHOLESTEROL Involved in keeping membrane “fluid”

GLYCOLIPIDS

REVIEW

http://bio-animations. blogspot http://bio-animations.blogspot.ca/2008/04/plasma-membrance-fluid-mosaic-model.html

References Original presentation by M.Bregar (Dante C.S.S.) http://www.authorstream.com/Presentation/aSGuest77986-711145-fluid-mosaic-model/ Modified by D. Machacek