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The Cell Cell Biology A discipline of biology: 1. Cell structure 2. Cellular processes 3. Cell division Tight connection with 1. Molecular biology 2. Biochemistry 1 2 Cell theory 1838, 1839 Theodor Schwann Matthias J. Schleiden 1. All living things are composed of one or more cells 2. Cells are the basic units of structure and function in living things Cell theory 3. Omnis cellula e cellula All cells are derived from cells (by means of multiplication) Rudolph Virchow 2 Germ theory 3 Louis Pasteur 1860’s Microorganisms are not generated from inanimate material but rather as a result of biogenesis (from other microbes) - The discovery that a prokaryotic cell stems from another prokaryotic cell 5 Prokaryotes Eukaryotes Classification of living beings Plants III. Eubacteria I. Animals Fungi Protista Archaebacteria II. What about the viruses? They are not living beings, since they are not capable for independent life (cell parasites) Origin: I. Simplified cells II. Derived from the DNA of host cell 6 The origin of cells 7 DNA RNA DNA nucleus cytoplasmic DNA RNA cells prokaryotic cell eukaryotic cell The origin of DNA „DNA world” RNA world The virus hypothesis: - viruses discovered the DNA 8 9 The origin of proteins RNA world „protein world” Origin of nucleus The arhaezoa hypothesis Thomas Cavalier-Smith Origin of ER andGolgi 10 11 Origin of mitochondrion - Endosymbiotic theory Lynn Margulis Origin of chloroplast - Endosymbiotic theory Lynn Margulis Elysia chlorotica A plant-animal 12 Prokaryotic cell plasmid Prokaryotic cell Spherical cells e.g. Streptococcus Rod-shaped cells e.g. Escerichia coli Spiral cells e.g. Treponema pallidum Multicellular prokaryotes Nitrogen fixation spore photosynthesis Anabaena cylindrica Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Compartmentalization Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Nucleus Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Mitochondrion Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Cytoskeleton Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Ribosomes Rough ER Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Golgi apparatus Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Smooth ER Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Extracellular space Intracellular space Cell membrane Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Ribosomes bound to rough ER Figure 4.7 Eukaryotic Cells (Part 1) Animal cell Centrioles Plant cell Plant cell Free ribosomes Plant cell Nucleus Nucleolus Plant cell Golgi apparatus Plant cell Plasmodesm Plant cell Chloroplast Plant cell Mitochondrion Plant cell Cell wall Plant cell Peroxisome Plant cell Cell membrane Plant cell Smooth ER Plant cell Rough ER Plant cell Inclusion body Animal cell – Plant cell Inclusion body chloroplast cell wall Prokaryotic cells vs. eukaryotic cells Differences Only in eukaryotes: 1. Cell nucleus 2. Membrane-bound organelles Only in prokaryotes 1. Proteoglycan cell wall 2. Capsule Eukaryotic (animal) cell Prokaryotic cell Cell membrane 1. Separation – selective transport 2. Communication Cell membrane - fluid mosaic model 1. lipid double layer 1. Phospholipid molecules Protein molecules 2. Phospholipid molecule 1. 3. Protein Phospholipids Cholesterol: decreases fluidity phosphatidyl choline Glycocalyx glycocalyx cytoplasm nucleus cell membrane 22 Membrane microdomains - lipid rafts phospholipids and membrane proteins are not randomly distributed in cell membranes Nucleus Outer membrane Nucleoplasm Inner membrane Nucleolus Chromatin Nuclear lamina Nuclear membrane Pore Nuclear membrane importin exportin Nuclear membrane inner outer ER membrane ER lumen protein protein protein Nuklear lamina RNA perinuclear space Nuclear pore NLS: nuclear localization signal NES: nuclear export signal Signal peptides Chromosomes Human: haploid chromosome set Giemsa staining Chromatin Metaphase chromosome 8 histone core Histone H1 DNA Solid form Relaxed form DNA DNA and nucleosomes H1 H2A H3 H4 NUCLEOSOME H2B DNA and nucleosomes DNA 8 histone core Ribosomes Ribosomes are complexes of proteins and RNA molecules. They carry out the synthesis of proteins. Soluble proteins are synthesized by cytoplasmic ribosomes, while membrane and exported proteins are produced by ribosomes of the rough endoplasmic reticulum. 30S subunit Proteins: blue RNAs: orange Endoplasmic reticulum Rough ER Rough ER Smooth ER Smooth ER ribosomes FUNCTION 1. 2. 3. 4. Lysosomal enzymes Secreted proteins Trans-membrane proteins Glycosylation 1. 2. 3. 4. Lipid and steroid synthesis Carbohydrate metabolism Calcium storage etc. Protein maturation in the rough ER Golgi apparatus FUNCTION: 1. Proteins and lipids (a) chemical modification (glycosylation and phosphorylation) (b) packaging and (c) sorting 2. Carbohydrate synthesis 3. Proteoglycan synthesis cisterns incoming (from ER) Transport vesicles outgoing Golgi apparatus Inside of cell Nucleus Rough endoplasmic reticulum cis region medial region trans region Golgi apparatus Proteins for use within the cell Plasma membrane Proteins for use outside the cell Outside of cell Peroxysomes, lysosomes peroxysome lysososome - Small membrane vesicles, containing enzymes that degrade peroxides and free radicals - Metabolism of fatty acids - Enzymes of the peroxisomes are found in crystalline form Acidic vesicles full of enzymes (they digest: proteins, nucleic acids, lipids, polysaccharides) Lysosomes Inside of cell Primary lysosome Phagosome Secondary lysosome Food particles taken in by phagocytosis Outside of cell Plasma membrane Proteasomes Proteasomes are enzyme complexes degrading proteins Proteins are degraded for several reasons: - misfolded (abnormal) proteins are destroyed - some proteins are made only for short periods of time - enzymes, regulatory proteins are degraded, when not needed - when cells are starving for amino acids There are labels (ubiquitin peptide), which identify protein molecules to be degraded. lysosome Mitochondrion outer membrane matrix Inter-membrane space inner membrane Chloroplast Chloroplast Granum - stacks of thylakoids Cytoskeleton Cytoskeleton Microtubule Intermediate filament Microfilaments rough ER Cytoskeleton 1. Maintains cell shape 2. Provides for various types of cell movement 3. Helps move things within the cell Microtubules Intermediate filament rough ER cell membrane Microfilament Microfilaments • Made up of strands of the protein actin and often interact with strands of other proteins • They change cell shape and drive cellular motion, including contraction, cytoplasmic streaming, and the “pinched” shape changes that occur during cell division • Microfilaments and myosin strands together drive muscle action Actin monomer Intermediate filaments • Made up of fibrous proteins organized into tough, ropelike assemblages that stabilize a cell’s structure and help maintain its shape • Some intermediate filaments help to hold neighboring cells together • Others make up the nuclear lamina Fibrous subunit • Long, hollow cylinders made up of many molecules of the protein tubulin. Tubulin consists of two subunits, -tubulin and -tubulin • Microtubules lengthen or shorten by adding or subtracting tubulin dimers • Microtubule shortening moves chromosomes • Interactions between microtubules drive the movement of cells • Microtubules serve as “tracks” for the movement of vesicles Microtubules -Tubulin monomer Tubulin dimer -Tubulin monomer Cytoskeleton - Cell division
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