BIOLOGY 111 1st Edition Lecture 8 Outline of Last Lecture I Cell size II Prokaryotic Cell III Plasma membrane IV Eukaryotic cell A Animal B Plant V Endosymbiont Theory Outline of Current Lecture I Microtubules II Microfilaments III Intermediate Filaments IV Membrane Structure and Function Current Lecture Microtubules tubulin polymers Made up of tubulin 13 columns of hollow tubes Functions Maintain cell shape Cell motility cilia and flagella Chromosome movements in cell division Organelle movements Microfilaments actin filaments Made up of actin two intertwined strands Found mostly in muscle Functions Maintain and changes cell shape anchored cellular extensions These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Muscle contraction Myosin motors in muscle cells contraction is a result of actin and myosin sliding past each other shortening the cell Cytoplasmic streaming circular flow of cytoplasm within plant cells speeds up the distribution of materials within the cell o Nonmoving cortical cytoplasm gel o Moving streaming cytoplasm sol Cell motility and division Intermediate Filaments Made up of Keratin and is supercoiled keratin found in hair and skin Functions Maintain cell shape Anchorage of nucleus and certain other organelles Formation of nuclear lamina Chapter 7 Membrane Structure and Function Acts as a selective gate allowing some things to enter and leave Plasma membrane is a boundary that separates living cell from its surroundings and is selectively permeable and dynamic constantly changing to adapt to changing environments made up of phospholipids amphipathetic most abundant lipids spontaneously form bilayers in aqueous environments o polar need help non polar enter with not problems o amphipathetic loving and fearing water lipids are o laterally mobile everything moves sideways most common o rotational movements rotate on own axis o flip flop flippase catalyzes the two layers to switch place why do they move o fluidity is affected by degree of saturation saturated vs unsaturated bonds more unsaturated bonds more fluid more saturated bonds more viscous solid state These changes also depend on environment ex unsaturated in hot environment would make more liquid state saturated in cold would be more solid plasma membrane of cells in extreme cold would probably be made more of unsaturated to maintain fluidity cells in very extreme high temps expect more saturated to maintain fluidity humans have equal ration of saturated and unsaturated bc not living in an extreme environment Cholesterol main component of plasma membrane o acts as a buffer in resisting temperature changes at high temperatures restrains phospholipid movement and holds them together at low temperatures does not allow packing of phospholipids Proteins determine most of the membranes specific function Integral membrane located embedded in the lipid bilayer Intrinsic and Extrinsic function Transport enzymatic activity signal transduction cell cell recognition intercellular joining attaches cytoskeleton and ExtraCellular Membrane ECM transmembrane span the membrane in alpha helices almost 30 of genes encoded for all organisms Peripheral membrane located on outside of membrane not embedded in lipid bilayer Glycoprotein protein with one or more covalently attached carbohydrates Glycolipids lipid with one or more covalently attached carbohydrates Carbohydrates mono di or polysaccharides Extracellular leaflet Cytosolic leaflet cholesterol found only in animals Permeability High permeability gases nonpolar very small uncharged polar molecules needs no help Moderate water and urea needs some help Low polar organic molecules needs lots of help Very low ions and charged polar molecules and macromolecules will not go through not matter what Passive transport is diffusion across a membrane with no energy investment Diffusion tendency for molecules to spread out evenly into available space Facilitated diffusion transport proteins speed the passive movement of molecules across the plasma membrane channel proteins allow passage of hydrophilic substances across the membrane carrier proteins bind molecule and change shape to shuttle them across the membrane