AP Biology o TODAY: Is bigger better? Does size matter? o Plasma Membrane Homework due NOW. o Cells Quiz on Friday. o Quick KAHOOTS on tomorrow.

AP Biology

CYTOPLASMIC STREAMING the directed flow of cytosol and organelles around cells mediated by “motor” proteins and use ATP aids in the delivery of organelles, nutrients, metabolites, genetic information, and other materials to all parts of the cell. protoplasmic streaming also called protoplasmic streaming

AP Biology The PLASMA Membrane

AP Biology The membrane is a collage of proteins & other molecules embedded in the fluid matrix of the lipid bilayer. Extracellular fluid Cholesterol Cytoplasm Glycolipid Transmembrane proteins Filaments of cytoskeleton Peripheral protein Glycoprotein Phospholipids

AP Biology More than lipids… In 1972, S.J. Singer & G. Nicolson proposed that membrane proteins are inserted into the phospholipid bilayer

AP Biology Cell membrane separates living cell from nonliving surroundings o thin barrier = 8 nanometers thick Controls traffic in & out of the cell o selectively permeable: allows some substances to cross more easily than others hydrophobic vs hydrophilic Made of phospholipids, proteins, & other macromolecules

AP Biology Fatty acid tails o hydrophobic Phosphate group head o hydrophilic Arranged as a bilayer Fatty acid Phosphate Phospholipids

AP Biology Phospholipid bilayer polar hydrophilic heads nonpolar hydrophobic tails polar hydrophilic heads

AP Biology Membrane Carbohydrates Play a key role in cell-cell recognition o ability of a cell to distinguish one cell from another antigens o important in organ & tissue development o basis for rejection of foreign cells by immune system

AP Biology

Cholesterolreduces membrane fluidity at moderate temperatures but hinders solidification of phospholipids at low temperatures maintains membrane integrity. Cholesterol = reduces membrane fluidity at moderate temperatures but hinders solidification of phospholipids at low temperatures; animal cells do not need cell walls; maintains membrane integrity. Integral proteins transport, enzymes, cell identification Integral proteins = penetrate the hydrophobic core of the lipid bilayer; transport, enzymes, cell identification Peripheral proteins signal transduction or intercellular joining (gap junctions/tight junctions) Peripheral proteins = appendages bound to the membrane surface; signal transduction or intercellular joining (gap junctions/tight junctions) Glycolipid cellular recognition Glycolipid = molecules that are formed by a covalent bond between carbohydrates and lipids; cellular recognition Glycoprotein cellular recognition Glycoprotein = molecules formed by a covalent bond between carbohydrates and proteins; cellular recognition

AP Biology Proteins domains anchor molecule Within membrane o nonpolar amino acids hydrophobic anchors protein into membrane On outer surfaces of membrane o polar amino acids hydrophilic extend into extracellular fluid & into cytosol Polar areas of protein Nonpolar areas of protein

AP Biology Fibers of extracellular matrix (ECM) provides structure and support Fibers of extracellular matrix (ECM) = attached to certain membrane proteins on the exterior of the cell; provides structure and support Microfilaments of cytoskeleton Microfilaments of cytoskeleton = may be bonded to membrane proteins; maintains cell shape; stabilizes the location of certain membrane proteins; aids in cell movement (cytoplasmic streaming, cell division, etc.)

AP Biology membrane fat composition varies Fat composition affects flexibility o membrane must be fluid & flexible about as fluid as thick salad oil o % unsaturated fatty acids in phospholipids keep membrane less viscous cold-adapted organisms, like winter wheat o increase % in autumn o Fish? o cholesterol in membrane

AP Biology Membrane Proteins Proteins determine membrane’s specific functions Membrane proteins: o peripheral proteins loosely bound to surface of membrane cell surface identity marker (antigens) o integral proteins penetrate lipid bilayer, usually across whole membrane aka: transmembrane protein transport proteins o channels, permeases (pumps )

AP Biology Classes of amino acids What do these amino acids have in common? nonpolar & hydrophobic

AP Biology Classes of amino acids What do these amino acids have in common? polar & hydrophilic I like the polar ones the best!

AP Biology Many Functions of Membrane Proteins Outside Plasma membrane Inside Transporter Cell surface receptor Enzyme activity Cell surface identity marker Attachment to the cytoskeleton Cell adhesion