Cell Theory. Chapter 6. cell. fundamental unit of structure and function for all living organisms. arise only from previously existing cell

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1 Chapter 6 cell Cell Theory fundamental unit of structure and function for all living organisms arise only from previously existing cell Figure 5.4 The size range of cells WHY are your brain cells the same size as hamster brain cells? diffusion plasma membrane 1

2 light um (most organelles smaller) compound (one plane at a time) magnify in stages using multiple lenses DIFFERENTIAL INTERFERENCE confocal (eliminates blurring, 3D image) FLUORESCENCE Resolution - minimum distance two points can be apart and still be distinguished as two separate points electron um transmission (electrons absorbed differently, thin sections) scanning ATOMIC LEVEL!(electrons bounced off 3D image) scanning tunneling (scans with electrons or ions) 2

3 prokaryotic cells NO true nucleus Bacteria and Archaea nucleoid (no membrane); ribosomes? gram-positive or gram-negative Susceptibility of bacteria to antibiotics depends on cell wall structure. peptidoglycan Cells walls of bacteria complicated peptidoglycan - sugars Gram negative (do not pick up stain - Ecoli) Gram positive (DO pick up stain - Staph) Penicillin inactivates enzyme in cell wall No new cells can form (gram negative bacteria resist penicillin ) Killing bacteria Penicillin - replication cell wall can t form (bedpans, parachute silk and cantaloupe) H2O2 replication DNA (bacteria have no repair mechanism) Tetracycline - ribosomes 3

4 eukaryotic control center DNA, chromatin, chromosomes nuclear envelope: double membrane double lipid bilayer DNA copied to mrna, which travels to cytoplasm, where ribosomes make proteins nucleolus ribosomal RNA (rrna) and proteins form ribosomal subunits 0.25 µ m 1 µ m The Nucleus Surface of nuclear envelope Pore complexes (TEM) Ribosome Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex 1 µ m Nucleolus Chromatin Close-up of nuclear envelope Chromatin Nuclear lamina (TEM) Nucleus Rough ER Figure 6.9 Nucleolus Chromatin Nucleus Nuclear envelope: Inner membrane Outer membrane Nuclear pore Surface of nuclear envelope Ribosome Pore complex Rough ER 0.25 µm Close-up of nuclear envelope Chromatin Pore complexes (TEM) Nuclear lamina (TEM) single DNA + proteins = chromatin, chromosome chromatin chromosome before cell division nucleolus within nucleus site of ribosomal RNA (rrna) synthesis RNA, proteins enter/exit via pores nuclear lamina maintains shape Ribosome Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Nucleolus Chromatin Nucleus Rough ER Close-up of nuclear Chromatin envelope Figure 6.9a 4

5 ribosomes: protein factories Ribosomes - made of ribosomal RNA and protein proteins synthesis in cytosol (free ribosomes) on outside of endoplasmic reticulum (ER) or of nuclear envelope (bound ribosomes) Figure 6.10 Figure µm Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER Large subunit TEM showing ER and ribosomes Small subunit Diagram of a ribosome endomembrane system Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane Either continuous or connected via transfer by vesicles 5

6 The Endoplasmic Reticulum: Biosynthetic Factory more than half of total membrane in many eukaryotic cells Continuous with nuclear envelope Smooth ER, few ribosomes Rough ER, studded with ribosomes Figure 6.11 Rough ER Smooth ER Nuclear envelope ER lumen Cisternae Ribosomes Transport vesicle Smooth ER Rough ER Transitional ER 200 nm Functions of Smooth ER enzymes of smooth ER in liver cells: detoxify drugs and poisons Synthesizes lipids Metabolizes carbohydrates Stores calcium ions Smooth ER 6

7 Functions of Rough ER secretory proteins, proteins bound for membrane via transport vesicles membrane factory Rough ER Golgi apparatus: shipping and receiving center flattened membranous sacs - cisternae Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles cis face ( receiving side of Golgi apparatus) Cisternae 0. trans face ( shipping side of Golgi apparatus) TEM of Golgi apparatus cis - faces ER trans - exit, towards plasma membrane Figure 6.12 cis face ( receiving side of Golgi apparatus) Cisternae 0. trans face ( shipping side of Golgi apparatus) TEM of Golgi apparatus 7

8 Figure Nucleus Rough ER Smooth ER cis Golgi trans Golgi Plasma membrane Lysosomes: Digestive Compartments membranous sac of hydrolytic enzymes - digests macromolecules hydrolyze proteins, fats, polysaccharides, and nucleic acids recycle defective organelles work best at ph 5 phagocytosis enzymes recycle cell s own organelles and macromolecules, autophagy Nucleus Vesicle containing two damaged organelles Mitochondrion fragment Lysosome Peroxisome fragment Digestive enzymes Lysosome Lysosome Plasma membrane Peroxisome Figure 6.13 Food vacuole Digestion Vesicle Mitochondrion Digestion (a) Phagocytosis (b) Autophagy 8

9 Figure 6.13 Nucleus Vesicle containing two damaged organelles Mitochondrion fragment Lysosome Peroxisome fragment Digestive enzymes Lysosome Lysosome Plasma membrane Digestion Peroxisome Food vacuole Vesicle Mitochondrion Digestion (a) Phagocytosis (b) Autophagy Vacuoles: Diverse Maintenance Compartments one or several vacuoles, derived from ER and Golgi food, contractile, central vacuoles variety of functions Central vacuole Cytosol Nucleus Central vacuole Cell wall Chloroplast Figure µm central vacuole - stockpiling proteins inorganic ions depositing metabolic byproducts storing pigments storing defensive compounds ALSO increases surface to volume ratio for whole cell tonoplast selective in transport into central vacuole 9

10 organelles with DNA mitochondria cellular respiration chloroplasts photosynthesis peroxisomes oxidation, H 2 O 2 The Evolutionary Origins of Mitochondria and Chloroplasts Mitochondria and chloroplasts similar to bacteria double membrane free ribosomes, circular DNA autonomous growth and reproduction Engulfing of oxygenusing nonphotosynthetic prokaryote, which becomes a mitochondrion Mitochondrion Nonphotosynthetic eukaryote Endoplasmic reticulum Nuclear envelope At least one cell Mitochondrion Nucleus Ancestor of eukaryotic cells (host cell) Engulfing of photosynthetic prokaryote Chloroplast Photosynthetic eukaryote Figure 6.16 Engulfing of oxygenusing nonphotosynthetic prokaryote, which becomes a mitochondrion Mitochondrion Endoplasmic reticulum Nuclear envelope Nucleus Ancestor of eukaryotic cells (host cell) Nonphotosynthetic eukaryote At least one cell Engulfing of photosynthetic prokaryote Chloroplast Mitochondrion Photosynthetic eukaryote 10

11 Mitochondria: Chemical Energy Conversion present in nearly all eukaryotic cells smooth outer membrane; inner membrane folded into cristae enzymes in intermembrane space and mitochondrial matrix - cellular respiration, ATP 10 µm Intermembrane space Outer membrane Mitochondria DNA Free Inner ribosomes membrane in the mitochondrial Cristae matrix Matrix (a) Diagram and TEM of mitochondrion Mitochondrial DNA Nuclear DNA 0. (b) Network of mitochondria in a protist cell (LM) Figure µm Intermembrane space Outer membrane Mitochondria DNA Inner Free membrane ribosomes in the Cristae mitochondrial Matrix matrix (a) Diagram and TEM of mitochondrion Mitochondrial DNA Nuclear DNA 0. (b) Network of mitochondria in a protist cell (LM) Chloroplasts: Capture of Light Energy found in leaves of plants and in algae chlorophyll, thylakoids, stroma Figure 6.18 Ribosomes Stroma 50 µm Inner and outer membranes Granum DNA Thylakoid Intermembrane space (a) Diagram and TEM of chloroplast Chloroplasts (red) (b) Chloroplasts in an algal cell 11

12 Peroxisomes: Oxidation specialized metabolic compartments bounded by a single membrane produce hydrogen peroxide and convert it to water Figure 6.19 Chloroplast Peroxisome Mitochondrion Cytoskeleton network of fibers throughout cytoplasm internal scaffolding for organelles, organellar activity Microtubules Microfilaments Intermediate filaments Figure µm support cell, maintain shape motor proteins monorails (a) ATP Microtubule Vesicle Motor protein Microtubule (ATP powered) of cytoskeleton Vesicles Receptor for motor protein 0.25 µm may help regulate biochemical activities (b) Figure

13 Three main types of fibers Microtubules are the thickest components Microfilaments, actin filaments, thinnest components Intermediate filaments are fibers in a middle range Table 6.1a 10 µm Column of tubulin dimers 25 nm α β Tubulin dimer Centrosomes and Centrioles microtubules grow out from a centrosome near nucleus The centrosome is a microtubule-organizing center animal centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring 13

14 cilia and flagella locomotor appendages Direction of swimming differ in their beating patterns (a) Motion of flagella 5 µm Direction of organism s movement Power stroke Recovery stroke (b) Motion of cilia 15 µm cell extensions Cilia Hair-like growths move back and forth to propel cell common in single-celled organisms, cells of simple animals (jellyfish, sponges), and our cells (lining of lungs) Flagella tail-like growths used for propulsion (sperm) Figure 6.23 Direction of swimming (a) Motion of flagella 5 µm Direction of organism s movement Power stroke Recovery stroke (b) Motion of cilia 15 µm 14

15 common structure core of microtubules, plasma membrane sheath basal body anchor motor protein, dynein, drives the bending movements Figure Outer microtubule doublet Dynein proteins Plasma membrane Central microtubule Radial spoke Microtubules Plasma membrane (b) Cross section of motile cilium Cross-linking proteins between outer doublets Basal body 0.5 µm 0. (a) Longitudinal section Triplet of motile cilium (c) Cross section of basal body Figure 6.24 Microtubules Plasma membrane Basal body 0. (b) Cross section of motile cilium Outer microtubule doublet Dynein proteins Central microtubule Radial spoke Cross-linking proteins between outer doublets Plasma membrane 0.5 µm 0. (a) Longitudinal section of motile cilium Triplet (c) Cross section of basal body flagellum - undulatory movement. Force generated parallel to the flagellum s axis. Cilia oars, alternating power and recovery strokes. force perpendicular to the cilia s axis. 15

16 bending of both driven by arms of a motor protein dynein Addition and removal of phosphate group (from ATP) causes conformation changes dynein Table 6.1b 10 µm Actin subunit 7 nm Table 6.1c 5 µm Keratin proteins Fibrous subunit (keratins coiled together) 8 12 nm 16

17 Figure 6.26 Microvillus Plasma membrane Microfilaments (actin filaments) Intermediate filaments 0.25 µm Extracellular components and connections plant cell walls extracellular matrix (ECM) of animal cells Plant Cell Walls protects cell, maintains shape, limits water absorption cellulose fibers embedded in other polysaccharides and protein Secondary cell wall Primary cell wall Middle lamella Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata 17

18 multiple layers Primary: relatively thin and flexible Middle lamella: thin layer between primary walls of adjacent cells Secondary (in some cells): added between the plasma membrane and the primary cell wall Plasmodesmata channels between adjacent plant cells Figure 6.28 Secondary cell wall Primary cell wall Middle lamella Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata Plant cell walls continuous w/ neighbors wood lots of secondary walls Note not like walls of prokaryotes Also other eukaryotes: fungi protists (paramecium, slime molds, algae) 18

19 Plasmodesmata channels that perforate plant cell walls water and small solutes can pass from cell to cell Interior of cell Cell walls Interior of cell 0.5 µm Plasmodesmata Plasma membranes Figure 6.31 Animal Cells Animal cells lack cell walls extracellular matrix ECM provides support, strength, and resilience Also problems AD - tangles Extracellular matrix (ECM) of an animal cell glycoprotein (aka proteoglycan) collagen 30-50% proteins in humans 19

20 Figure 6.30 Collagen EXTRACELLULAR FLUID Polysaccharide molecule Proteoglycan complex Fibronectin Core protein Integrins Plasma membrane Proteoglycan molecule Proteoglycan complex CYTOPLASM Functions of the ECM Support Adhesion Movement Regulation Collagen EXTRACELLULAR FLUID Polysaccharide molecule Proteoglycan complex Microfilaments Carbohydrates Fibronectin Core protein Integrins Plasma membrane Proteoglycan molecule Proteoglycan complex Microfilaments Carbohydrates CYTOPLASM Figure 6.32 Tight junctions prevent fluid from moving across a layer of cells Tight junction TEM 0.5 µm Tight junction Intermediate filaments Desmosome Gap junction TEM Ions or small molecules Space between cells Plasma membranes of adjacent cells Extracellular matrix TEM 0. 20

21 The Cell: A Living Unit Greater Than the Sum of Its Parts Cell functions rely on integration of structures and organelles example: coordination among cytoskeleton, lysosomes, and plasma membrane enables macrophage defense 5 µm Figure µm Figure 6.UN01 Nucleus (ER) (Nuclear envelope) 21