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BIOL 266
Vladimir Titorenko

Lecture 1 Cells and Organelles Cells Overview: All have this in similarity Organic Components (Carbon Based)  Carbohydrates (sugars)  Lipids (Fats)  Nucleic Acids (DNA and RNA)  Protein Inorganic Ions  (5) Na , K , Mg , Ca , Cl- Water compromises 70% of total cell mass All also have a plasma membrane Prokaryotic Cells - “Pro” meaning before - “Karyon” meaning nucleus - DNA is not segregated within a defined nucleus (DNA is just floating around) o Reactions take place in cell are not enclosed in internal membranes They have a single membrane-limited compartment  Cell Wall: Outer Membrane  Plasma Membrane: Inner Membrane  Cytoplasm: Has about 30 000 ribosomes (the site of protein synthesis), accounts for their granular appearance  Nucleoid: Circular DNA molecules not surrounded by a membrane separating it from the cytoplasm (which is the region lying outside the nucleoid) Eukaryotic Cells - “Eu” meaning truly/well - “Karyon” meaning nucleus - DNA is segregated within a defined nucleus - Contains extensive internal membranes that enclose specific compartments (the organelles) and separate them from the rest of the cell (the cytosol). The organelles are isolated (these organelles may not be found in a prokaryotic cell) In common between Animal and Plant Cells  Mitochondrion: Produces energy  Plasma Membrane: The semipermeable membrane that encloses the cytoplasm of a cell  Endoplasmic Reticulum: A membrane network within the cytoplasm of cells involved in the synthesis, modification, and transport of cellular materials  Cytosol: The fluid component of cytoplasm, excluding organelles and the insoluble, usually suspended, cytoplasmic components  Golgi Apparatus: A network of stacked membranous vesicles present in most living cells that functions in the formation of secretions within the cell  Filamentous Cytoskeleton: cellular structure within the cytoplasm in every cell that helps it to keep its structure, protect the cell and allows cellular motion, it also plays a role in intracellular transport and cellular division.  Nucleus: A large, membrane-bound, usually spherical protoplasmic structure within a living cell, containing the cell's hereditary material and controlling its metabolism, growth, and reproduction  Lysosomes: A membrane-bound organelle in the cytoplasm of most cells containing various hydrolytic enzymes that function in intracellular digestion.  Peroxisomes: A cell organelle containing enzymes, such as catalase and oxidase, that catalyze the production and breakdown of hydrogen peroxide. Animal Cells  Centriole: either of two rod like bodies in most animal cells that form the poles of the spindle during mitosis  Cell Wall (Only for Yeast and Fungi which are single-celled/unicellular eukaryotes) Plant Cells – are surrounded by 2 membranes  Cell Wall: The rigid outermost cell layer found in plants and certain algae, bacteria, and fungi but characteristically absent from animal cells.  Chloroplast: Site of photosynthesis  Vacuole: Water is filled within this organelle Cells are the smallest units exhibiting the characteristics of life since they can reproduce themselves by their own effects o Organelles cant reproduce by their own effort, outside of their host cells o Viruses not able to reproduce by themselves, they use the reproductive machinery of cells that they invade - Cells it the fundamental unit of life, underlying building blocks from which all organisms are constructed - Cell Biology: investigates how cells grow, divide, operate, communicate, control their activities and die o Death of a cell can save other cells so it is not a bad thing - Cells are small: typically 5 – 20um in diameter o Only found prior to invention of the light microscope in 17 century by Robert Hooke (1665)  Hooke called the pores from a thin slice of cork cells because they reminded him of the cells inhabited by monks living in a monastery Relative Sizes of Cells and Cell Components Hydrogen Atom Water Molecule DNA Molecule Myoglobin Lipid Bilayer Actin Filament Ribosome HIV Cilium Bacterium Mitochondrion Chloroplast Lymphocyte Epithelial Cell Paramecium Frog Egg 6 9 10 Note: 1m = 10 um = 10 nm = 10 A Nucleus – the information store of a cell - Contains D N A: Deoxyribonucleic Acid- extremely long polymers that encode the genetic specification of the organism o Stored as a double helix o Many molecules of DNA in the form of chromosomes, building block of DNA are nucleotides which are synthesized outside of the nucleus - Nucleus is surrounded by a double membrane, called nuclear envelope - Nucleus communicates with the cytosol via nuclear pores that perforate the envelope  Nuclear Envelope: consists of two concentric membranes, the inner and outer nuclear membranes  Perinuclear Space: the space between the inner and outer nuclear membranes as illustrated in electron microscope recordings  Nucleolus: A small, typically round granular body composed of protein and RNA in the nucleus of a cell, usually associated with a specific chromosomal site and involved in ribosomal RNA synthesis and the formation of ribosomes. Sub organelle of the nucleus where the cell’s ribosomes are assembled. There is no membrane surrounding it  Rough Endoplasmic Reticulum: parts of the endoplasmic reticulum to which ribosomes are attached on the cytoplasmic side; involved in the biosynthesis of proteins for export to the outside of the cell and enzymes to be incorporated into cellular organelles  Nuclear Lamina: a fibrous network that provides structural support to the nucleus – they are many proteins around the nucleus that provide an even pressure on all sides giving the circular shape (Each lamin protein is synthesized outside nucleus)  Nuclear Pore Complexes: The only channels through which molecules are able to travel between the nucleus and the cytoplasm. o The inner and outer nuclear membranes are joined at nuclear pore complexes. - The outer nuclear membrane is continuous with the Rough ER, and the space between the inner and outer nuclear membranes is continuous with the lumen of the rough ER Note: Lumen: is the inside space of a tubular structure Molecular Traffic through NPC (Nuclear Pore Complexes) Passive Diffusion  No energy is needed (From a high concentration gradient to a low concentration gradient  Small molecules such as Mg would pass through Energy-Dependent Transport (Requires the use of energy to let molecules pass through) Enter the Nucleus through the Nuclear Pore Complexes o DNA- Binding Proteins: Histones, nonhistone proteins, activators, and repressors of transcription o Messenger RNA binding proteins o Components of the Nucleus (lamins) o Ribosomal Proteins o Shuttling nuclear transport receptors (importins): Deliver other proteins to the nucleus Exit the Nucleus through the Nuclear Pore Complexes o mRNA’s (Together with mRNA binding proteins) o tRNAs (transport RNAs) o 40S and 60S ribosomal subunits (complexes of Ribosomal RNAs [rRNAs and ribosomal proteins] 3 RNA types – DNA makes all three including the repressors and activators that regulate activity  mRNA: transcribed in nucleus, translated in cytoplasm  rRNA: central component of the ribosome, the protein manufacturing machinery of all living cells. The function of the rRNA is to provide a mechanism for decoding mRNA into amino acids and to interact with the tRNAs during translation by providing peptidyl transferase activity.  tRNA: transports a amino acids to the ribosome, so that a protein can be built Nuclear Lamina Diseases  Emery-Dreifuss Muscular Dystrophy: Elbows, Neck and Heels become stiff, and head problems  Hitchinson-Golford Porgeria: Premature Aging Both are caused by mutations in two genes
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