MODULE-5-Membrane-Structure-Properties-and-Functions.pdf

MEMBRANE STRUCTURE, PROPERTIES AND FUNCTIONS The Fluid Mosaic Model In 1972, S. Jonathan Singer and Garth Nicolson of the University of California, San Diego (USA), proposed a model of the cell membrane called the fluid mosaic model. A new model that better explains both the microscopic observa...

MEMBRANE STRUCTURE, PROPERTIES AND FUNCTIONS The Fluid Mosaic Model In 1972, S. Jonathan Singer and Garth Nicolson of the University of California, San Diego (USA), proposed a model of the cell membrane called the fluid mosaic model. A new model that better explains both the microscopic observations and the function of that plasma membrane was proposed by S.J. Singer and Garth L. Nicolson in 1972. What is Fluid Mosaic Model? The arrangement and movement of lipids and proteins within the lipid bilayer. Lipids are hydrophobic because they consist mostly of hydrocarbons. The head contains a molecule called phosphate, a polar molecule, making this region able to interact with water (hydrophilic). We can also see that the two layers of phospholipids are arranged with their phosphate containing-heads on the outer surfaces while their lipid tails are found on the inside facing each other. Tails are molecules called fatty acids – hydrocarbons that can contain either single or double bonds. Unsaturated Fatty Saturated Fatty Acids Acids bent fatty acid linear fatty acid double bond has single bonds  Cholesterol can occupy the spaces left by the kinks of unsaturated fatty acid tails. It can therefore increase membrane fluidity even if temperatures decrease as it is wedged between the fatty acids. Once temperatures increase beyond the optimum, cholesterol tends to hold the phospholipids together to prevent the membrane from being destroyed. MEMBRANE PROTEINS INTEGRAL MEMBRANE PROTEIN PERIPHERAL MEMBRANE PROTEIN Directly interact with the Do not length of the bilayer passing interact directly with the through its hydrophilic exterior membrane and hydrophobic interior. MEMBRANE PROTEINS FUNCTIONS 1. Signal transmission 2. Enzymatic activity 3. Cell-to-cell recognition 4. Attachment to cells and other molecules 5. For transport CARBOHYDRATES Sources of energy. Examples: sugars, starch, and glycogen, can also be found in the cell membrane. CARBOHYDRATES Glycoproteins - Carbohydrates are attached to the membrane proteins. Glycolipids - Carbohydrates are directly attached to the phospholipid heads. God bless you all! See you next meeting!