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Lecture 7


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Natural Science
NATS 1670
Motti Anafi

NATS 1670 LECTURE 7 CELLS May 29, 2012  The Cell Theory  Developed during 1600’s o Discovery and development of microscopy  Experimentation with glass lenses vs. magnifying glass  Van Leeuwenhoek (1632-1732) o All living organisms are made of cells o New cells are created by old cells dividing into two o Cells are the basic building units of life  Every living organism is made up of cells  The Eukaryotic Cellwhat we’ll discuss o Eukaryotic cells are highly organized with many functional units-organelles o Distinguished from prokaryotic cells by the presence of membrane enclosed organelles within their cytoplasm  Provide discrete compartments in which specific and simultaneous cellular activities take place  Plasma membrane o Integral membrane proteins  Organelles in cytoplasm  Translation o Mitochondria o Endoplasmic Reticulum  Ribosomes o Nucleus  DNA replication  Transcription  Nucleolus  RNA o Vesicles (i.e. lysosomes, vacuoles) Plasma membrane  Function: separation of the inside of the cell from the outer environment, allowing different molecules to be found on the inner or outer cell area o Bilayers of the naturally occurring phospholipids are flexible jelly-like fluids, not solidsstable chemical barrier o Separates cells from one another o Regulate the passage of materials into/out of cellscontrolled channels  Concentration gradientdiffusion  Active transport against a concentration gradient o Provide a surface on which chemical reactions catalyzed by different enzymes occur NATS 1670 LECTURE 7 CELLS May 29, 2012  Structure of phospholipids is responsible for the basic function of membranes as barriers between two polar (water) compartments o Mixing water and oil (doesn’t happen)  Lipids assemble in phospholipid bilayer o The phospholipid polymer is made up of o Phospholipids are polymers because they are composed of 2 fatty acid molecules attached to a glycerol molecule. Fatty acids are the monomers of lipids. Phospholipid also creates the bilayerpolymer a string of monomers  Glycerol monomer  Fatty acid monomer o Hydrophilic headsphosphate and glycerol form a hydrophilic head (polar) o hydrophobic tailsfatty acid tail form a hydrophobic tail (non-polar) o Water-soluble molecules are impermeable to the plasma membrane  Vesicles allow for molecules to pass through the membrane that otherwise would not be permissible to  Vesicles just like the plasma membrane of the cell, are formed from the same phospholipid layer.  1 phospholipid= unilamellar  More than 1= multilamellar  Vesicles can fuse with the plasma membrane to release their contents outside of the cell  macrophages  Types of vesicles  Vacuoles  Lysosomes  Transport vesicles  Secretory vesiclesexocytosis  Lipid-protein mosaicdifferent cell types have different set of membrane proteins  Transmembrane proteins o Proteins embedded within bilayer to carry out the specific functions of the plasma membrane o Control the passage of most biological molecules across the plasma membrane o Channel proteinstransport proteins facilitated diffusion o Recognition proteins o Contact inhibition o Mediate interaction between cells (without this ability, cancer exists with the abundance of cells o Membrane proteins are able to diffuse laterally through the membrane NATS 1670 LECTURE 7 CELLS May 29, 2012  Glycoproteinsproteins that contain oligosaccharide chains attached to polypeptide side chains  Play role in cell-cell interactions  Most Transmembrane proteins off the plasma membrane are glycoproteins with their oligosaccharides exposed on the surface of the cell  Consequently the surface of the cell is covered by a carbohydrate coat formed by the oligosaccharides of glycolipids and Transmembrane glycoproteins (glococalyx)  Role: protect the cell surface and serve as markers for a variety of cell-cell interactions o Signal transduction  Extracellular signaling molecule activates a cell surface receptor, in turn altering intracellular molecules creating a response  Signaling molecule activates a specific receptor protein on the cell membrane  Second messenger transmits the signal into the cell, eliciting a physiological response o Receptor proteins o Oligosacch
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