Class 22: Cell Components PDF

MCDB 1150 Class 22: Cell Components Compare key elements of bacterial versus eukaryotic cell structure. Predict what would happen to a cell if a particular organelle or structure were altered in a specific manner. Compare the structure and function of microtubules, actin filaments and intermed...

MCDB 1150 Class 22: Cell Components Compare key elements of bacterial versus eukaryotic cell structure. Predict what would happen to a cell if a particular organelle or structure were altered in a specific manner. Compare the structure and function of microtubules, actin filaments and intermediate filaments  Domains of Life Based on comparisons of 16s ribosomal RNA gene sequences in living organisms  The Cell = the smallest functional unit of life 2 kinds of cells: 1-Prokaryotic (bacteria and archaea) 2-Eukaryotic (mammalian and plant) Things in common-Prokaryotic and eukaryotic cells: a plasma membrane one or more chromosomes ribosomes Only Eukaryotic cells: membrane-bound nucleus organelles Only Prokaryotes: have a nucleoid and no true organelles.  Bacteria and Archaea Is enclosed by a plasma membrane and is usually encased in a rigid cell wall – The cell wall may be covered by a sticky capsule - Lack membrane bound organelles (NO nucleus) but do have some cellular structures – Small (1-10m) ~1/10 size of a eukaryotic cell. – Usually unicellular, although there are exceptions…..  Eukaryotic (animal/mammalian) cell structures Larger than bacteria or archaea DNA is encased in the nucleus Multicellular (although not always), more complex Membrane bound organelles-this increases surface area and allows eukaryotic cells to be BIGGER!  Ribosomes Ribosomes are involved in the cell’s protein synthesis.~~And not an organelle (not membrane bound)! – Free ribosomes suspended in the cytoplasm typically involved in making proteins that function within the cytoplasm. – Bound ribosomes attached to the endoplasmic reticulum (ER) associated with the nuclear envelope associated with proteins packed in certain organelles or exported from the cell. Eukaryotic (animal/mammalian) cell structures comprise four functional categories Manufacture Nucleus, ER, Golgi, Nucleolus, Ribosome Breakdown Lysosome Energy Production Mitochondria Support and Movement Microfilament, Intermediate filament, Microtubule Nucleus has a double membrane and nuclear pores Function: House and protect genetic material (DNA) Gene regulation (transcription) mRNA processing Nucleolus – ribosome production  Endoplasmic Reticulum (ER) Function: Protein production and modification Distribution of molecules (proteins, lipids, and fats) Cisternae are the flattened stacks of the ER Rough ER has ribosomes, smooth ER doesn’t. Golgi Apparatus is a distribution center Function: Transport, sorting and modification of proteins and lipids Secretory vesicles transport molecules outside the cell Proteins are transported in vesicles Mitochondria produce ATP – energy used by the cell Lysosomes break down biological molecules The cytoskeleton is composed of networks of 3 different filaments The Cytoskeleton is important for cell structure, movement and transport of molecules within cells Actin Actin filaments are made of actin monomers Function: Provide rigidity to cell shape Important for muscle contraction and cell motility Actin is dynamic – it polymerizes and depolymerizes The Cytoskeleton is important for cell structure, movement and transport of molecules within cells Several different proteins are intermediate filaments Keritan, desmins, laminin Intermediate filaments Characterized by size between actin and microtubule Function: Maintain cell shape, anchor organelles Form nuclear lamina – lines inner nuclear membrane helps nucleus keep its shape Intermediate filaments are dynamic The Cytoskeleton is important for cell structure, movement and transport of molecules within cells Microtubules Made of a tubulin heterodimer Function: Motility – cilia and flagella Cell division – mitosis and meiosis Intercellular transport – vesicles travel on microtubules Microtubules are dynamic  Microtubules An , -tubulin heterodimer is the basic structural unit of microtubules. The heterodimer does not come apart, once formed. Dynamic system of assembly and disassembly – Straight hollow tubes – Give the cell rigidity – Provide anchors for organelles – Act as tracks for organelle movement  Microtubule Toxins & Drugs Some toxins and drugs (all of which inhibit mitosis) affect polymerization or depolymerization of tubulin:  Taxol, an anti-cancer drug, stabilizes microtubules.  Colchicine binds tubulin & blocks polymerization. Microtubules depolymerize at high [colchicine].  Vinblastine causes depolymerization and formation of vinblastine-tubulin para crystals.  Nocodazole causes depolymerization of microtubules.  Crystal structures of cytoskeletal proteins Which cytoskeletal element is https://www.rcsb.org/3d-view/jsmol/6bno shown in the crystal structure? A. Actin B. Intermediate filament https://www.rcsb.org/3d-view/jsmol/7sj8 C. Microtubule