BCOR 103 1st Edition Exam 2 Study Guide Lectures 8 14 Lecture 8 February 10 The cytoskeleton is the architectural material of the cell The key activities that it is associated with are cell shape positioning organelles macromolecular metabolism a track for the transport of materials within the cell cell movement and transduction between cells Cytoskeletal Structures Filament System Microtubules Intermediate Filaments Microfilaments Thick Filaments Major Protein Subunit Structure Diameter Major Function s Hollow Tube 22nm Cell Polarity Cell Division Intracellular Transport Variable Fibrous Protein Rope like Fiber 10nm Basic Support Cell Shape Resist Stress Actin Globular Protein Chain 6nm Cell Elasticity Cell Motility Myosin Muscle like Rough Bipolar Fiber 15nm Contractility Tubulins Intermediate Filament Proteins assemble in a building block like sequence Starting with one helical region then a coiled dimer of the two then a combined staggered dimer the association of eight tetramers which come together to make up filaments This building block process produces a stress resistant filament There are N and C terminal domains that project to the surface to provide binding sites for other components Without filaments a layer of cells would not stretch and remain intact they would rupture Dynamic Instability refers to the growth and collapse of microtubules A growing microtubule lengthens when GTP binds to tubulin molecules The microtubule can collapse when GTP hydrolysis occurs and the microtubule peels itself away Additionally some microtubules become stable when they meet a capping protein at the cell membrane Others do not get capped and so they grow and shrink over and over Lecture 9 February 12 There are seven different MAPs that should be known The first is tubulin ring complex which initiates the formation of a microtubule The second MAP to know is XMAP215 which polymerizes the end of the microtubule Next is Kinesins 8 and 13 which depolymerize the end of the microtubule CLASP and EB1 controls tracking Katanin controls severing the microtubule Tau MAP1 MAP2 and MAP4 work to stabilize the microtubule lengthwise Lastly CLASP is also involved in rescue functions of the microtubules Kinesin is made up of two heavy chains and light chains connected by an alpha helix The heavy chains are two globular proteins that attach to the microtubule The light chains attach to the vesicle or protein being transported within the cell The kinesin works with ATP to move its proteins along the microtubule in the direction toward the positive end of the microtubule Dynein serve a similar function to kinesin except it moves its materials toward the negative end of the microtubule Dynein also has a different structure from kinesin Dynein has two heavy chains that link with the microtubule but the other side is made up of lots of light chains approximately seven The light chains bond with the material being moved and the other heavy chains move along the microtubule G actin is the molecule that actin fibers are made up of Actin monomers G actin come together to form dimers then trimers and eventually a microfilament with a positive and negative end These microfilaments layer together called monomer polymerizing The dimer formin can regulate the end of the microfilament Actin works with the motor proteins that are microfilament based myosin There are many different types of myosin proteins We will focus on the mechanism The myosin head that is connected to a microfilament works in tandem with ATP to attach and release to a parallel actin filament Myosin uses ATP to move up actin This is primarily seen in muscles it is how they contract Lecture 10 February 17 There are three types of RNA involved in protein synthesis Those three types are transfer RNA abbreviated tRNA messenger RNA abbreviated mRNA and ribosomal RNA abbreviated rRNA Transfer RNA is responsible for decoding sections of the nucleic acid sequence code into the correct order of amino acids that are in a protein tRNA also brings energy that is needed in these synthetic processes Messenger RNA encodes genetic information that details the specific sequence of amino acids for a protein Ribosomal RNA provides the core component of ribosomes This ribosomal RNA codes for Peptidyl Transferase which is the major active part of ribosomes The genetic code is essentially how all of the genetic information of an organism is stored There are four bases used by humans and 20 amino acids that those four bases code for The little bits of information are called codons Codons are made up of three nucleotide bases for example adenine guanine cytosine AGC codes for the amino acid serine Please note that other codons can code for the same amino acid for example the codon UCU also codes for serine The ribosome is by far the most abundant organelle in the cell This is true for both eukaryotes and prokaryotes The structure and function of ribosomes in the cell is similar for both eukaryotes and prokaryotes yet the eukaryotic ribosome is slightly larger on all accounts than a prokaryotic ribosome A ribosome is made up of two parts a large subunit and a small subunit The primary process a ribosome is responsible for is to synthesize proteins Lecture 11 February 19 The production and synthesis of proteins by ribosomes is important but it is not sufficient for efficient cell processing The proteins need to be organized into complexes in order for cell processes to take place This activity is protein targeting There are two classes of eukaryotic ribosomes membrane bound ribosomes and free ribosomes Membrane bound ribosomes are associated with the rough endoplasmic reticulum rough ER and the proteins that they produce have three specific criteria First these proteins remain associated with some type of membrane whether it is the nuclear membrane the ER the Golgi or the plasma membrane Second these proteins are encased in small vesicles Third these proteins are secreted from the cell Free ribosomes like they sound are not bound to any membranes at all The proteins produced by free ribosomes that are found in the cytoplasm mitochondria and chloroplasts and the cytoskeleton The Endoplasmic Reticulum has two subgroups the rough endoplasmic reticulum RER and the smooth endoplasmic reticulum SER The RER is studded with membrane bound ribosomes The RER is responsible for protein translocation protein folding protein modification and protein packaging for transport The SER does