Ch. 6 A Tour of the Cell BIOL 222

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1 Ch. 6 A Tour of the Cell BIOL 222 Overview: The Fundamental Units of Life All organisms are made of cells The cell is the simplest collec=on of ma>er that can live Cell structure is correlated to cellular func=on All cells are related by their descent from earlier cells Fig m 1 m 0.1 m 1 cm Human height Length of some nerve and muscle cells Chicken egg Unaided eye 1 mm Frog egg 100 µm 10 µm 100 nm 10 nm Most plant and animal cells Most bacteria Mitochondrion Smallest bacteria Viruses Proteins Light microscope Electron microscope 1 nm Lipids Small molecules 0.1 nm Atoms 1

2 Prokaryo=c cells Prokaryo=c and Eukaryo=c Cells Bacteria and Archaebacteria Eukaryo=c cells Pro=sts, fungi, plants, and animals Prokaryo=c and Eukaryo=c Cells Basic features of all cells: Plasma Semifluid substance called cytosol Cytoplasm = space inside cell filled with cytosol Chromosome(s) Gene=c info Protein synthesis Prokaryo=c cells characterized by: No nucleus Prokaryo=c Cells nucleoid region instead Fimbriae DNA in an unbound area No membranous organelles Bacterial chromosome Nucleoid Plasma Cell wall Capsule only Not bound (a) A typical rod-shaped bacterium Flagella (b) 0.5 µm A thin section through the bacterium Bacillus coagulans (TEM) Cytoplasm enclosed by the plasma 2

3 Eukaryo=c cells characterized by having: nucleus encloses DNA bounded by a double membranous Many membranous organelles Eukaryota much larger than prokaryo=c cells 10x - 100x on average Eukaryo=c Cells plasma Cell Membrane Selec=vely permeable allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell Phospholipid bilayer amphipathic fluid mosaic Limits to the size of cells Diffusion can only work so far efficiency declines with distance Cell Membrane Surface area to volume ra=o of a cell is cri=cal As the surface area increases by a factor of n 2, the volume increases by a factor of n 3 Small cells have a greater surface area rela=ve to volume Total surface area [Sum of the surface areas (height width) of all boxes sides number of boxes] Total volume [height width length number of boxes] Surface-to-volume (S-to-V) ratio [surface area volume] 1 5 Surface area increases while total volume remains constant

4 Flagellum Centrosome CYTOSKELETON: Microfilaments Microtubules Microvilli Peroxisome ENDOPLASMIC RETICULUM (ER) Mitochondrion Smooth ER Lysosome Nucleolus NUCLEUS Internal s A Panoramic View of the Eukaryo=c Cell Nuclear ENDOPLASMIC RETICULUM (ER) Nucleolus Smooth ER Flagellum NUCLEUS Par==on the cell into organelles Same material and Centrosome CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Microvilli Peroxisome Plasma Golgi apparatus construc=on as cell Mitochondrion Lysosome Nuclear Rough endoplasmic NUCLEUS Nucleolus reticulum Smooth endoplasmic reticulum Plant and animal cells have most of the same organelles Golgi apparatus Mitochondrion Peroxisome Plasma Cell wall Wall of adjacent cell Central vacuole Microfilaments Intermediate filaments CYTO- SKELETON Microtubules Chloroplast Plasmodesmata contains most of the cell s genes and is usually the most conspicuous (largest) organelle Mitochondria and/or chloroplasts also have their own DNA mtdna, ptdna Intermediate filaments Nuclear Plasma Nuclear encloses the nucleus, separa=ng it from the cytoplasm double ; each consists of a phospholipid bilayer Studded with nuclear pores Golgi apparatus Fig Nuclear : Inner Outer Nucleolus Nuclear pore Pore complex Surface of nuclear 0.25 µm Ribosome Close-up of nuclear Pore complexes (TEM) Nuclear lamina (TEM) 4

5 Nuclear Pores regulate the entry and exit of molecules from the nucleus Nucleolus Nuclear : Inner Outer Nuclear pore Nuclear lamina maintains shape of the nucleus Surface of nuclear 0.25 µm Ribosome Pore complex Close-up of nuclear composed of protein Pore complexes (TEM) Nuclear lamina (TEM) Intermediate filaments Similar to cytoskeleton Chroma=n Diffuse form of Gene=c material made of DNA and proteins Chromosomes Condensed chroma=n Only during cell division Nucleolus site of ribosomal RNA (rrna) synthesis located within the nucleus Seen as large dark spot par=cles made of ribosomal RNA and protein Only organelle without a enclosure carry out protein synthesis in two loca=ons: In the cytosol (free ribosomes) On the outside of the endoplasmic re=culum or the nuclear (bound ribosomes) 5

6 Fig Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit 0.5 µm TEM showing ER and ribosomes Small subunit Diagram of a ribosome Components of the endo system: Nuclear Endoplasmic re=culum Golgi apparatus Lysosomes Vacuoles Plasma These components are either con=nuous or connected via transfer by vesicles Endo System Biosynthesis: Endoplasmic Re=culum Endoplasmic re=culum (ER) accounts for more than half of the total in many eukaryo=c cells con=nuous with the nuclear Two regions of ER: Smooth ER No ribosomes a>ached 6

7 Fig Smooth ER Nuclear ER lumen Cisternae Transport vesicle Smooth ER Transitional ER 200 nm Smooth Endoplasmic Re=culum The smooth ER Synthesizes lipids Phospholipids Steroids Metabolizes carbs Glycogenolysis / gluconeogenesis Detoxifies poisons Stores calcium Sarcoplasmic re=culum Rough Endoplasmic Re=culum a>ached Sites of and secretory protein synthesis Transport vesicles Proteins surrounded by s Bud from RER Is a manufacturing and assembly factory for the cell Along with SER 7

8 Golgi apparatus The Golgi Apparatus Cisternae fla>ened membranous sacs Func=ons: Modifies products of the ER Manufactures some cis face ( receiving side of Golgi apparatus) Cisternae 0.1 µm polysaccharides (pec=n) Sorts and packages materials into transport vesicles trans face ( shipping side of Golgi apparatus) TEM of Golgi apparatus Lysosomes Lysosome membranous sac of hydroly=c enzymes digest macromolecules hydrolyze proteins, fats, polysaccharides, and nucleic acids 8