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Tour of the Cell Robert Hooke (1635-1703) Robert Hooke -- 1665: examined thinly sliced cork and coined term “cell” van Leeuwenhoek --1674: first to observe living cells van Leeuwenhoek The cell theory Schleiden and Schwann + others • 1. all organisms consist of one or more cells • 2. the cell is the basic unit of structure for all organisms • 3. all cells arise only from preexisting cells Light microscopy Electron microscopy Cilia Electron microscopy Cilia Light microscopy Light microscopy Chromosomes Electron microscopy Fluorescence microscopy Fluorescent micrograph of dividing cells Green: DNA Red: Microtubules Units of measurement in cell biology micrometer (micron, )- 1/1,000,000 of a meter, or 1/1000 of a millimeter. • useful for measuring the sizes of cells and organelles. • “typical” animal cell: 20-40 m • “typical” nucleus: 5-10 m • bacteria, mitochondria, chloroplasts - few m in diameter nanometer - 1/1000 of a m or 1/1,000,000 of a mm. • used for molecules and subcellular structures too small to be seen with light microscopy. • ribosomes - diameter of 25-30 nm. • cell membranes: ~10nm • cytoskeletal structures such as microtubules, microfilaments are generallly measured in nm. • DNA helix ~2nm 10 m Human height Length of some nerve and muscle cells Sizes 0.1 m Chicken egg Unaided eye 1m 1 cm Frog egg 100 µm Most plant and animal cells 10 µm Nucleus Most bacteria 1 µm 100 nm Mitochondrion Smallest bacteria Viruses Ribosomes 10 nm Proteins Lipids 1 nm Small molecules 0.1 nm Atoms Electron microscope Measurements 1 centimeter (cm) = 10–2 meter (m) = 0.4 inch 1 millimeter (mm) = 10–3 m 1 micrometer (µm) = 10–3 mm = 10–6 m 1 nanometer (nm) = 10–3 µm = 10–9 m Light microscope 1 mm Why are cells so small? Surface to volume ratio Surface area increases while Total volume remains constant 5 1 1 Prokaryotic Cells Pili Nucleoid Ribosomes Plasma membrane Bacterial chromosome Cell wall Capsule 0.5 µm Flagella A typical rod-shaped bacterium A thin section through the bacterium Bacillus coagulans (TEM) There are two types of cells….. Prokaryotic Cell Example: bacteria cell Eukaryotic Cells Animal Plant Cell parts and functions…. Plasma Membrane (cell membrane) Nucleus Nucleus Nucleus 1 µm Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Rough ER Surface of nuclear envelope Ribosome 1 µm 0.25 µm Close-up of nuclear envelope Pore complexes (TEM) Nuclear lamina (TEM) Nucleus Ribosomes Ribosomes ER Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit 0.5 µm TEM showing ER and ribosomes Diagram of a ribosome Smooth ER Endoplasmic reticulum Rough ER Nuclear envelope ER lumen Cisternae Ribosomes Transport vesicle Smooth ER Transitional ER Rough ER 200 nm Endoplasmic reticulum smooth ER and rough ER Golgi apparatus Glycosylation, sorting and distribution of proteins and lipids Golgi apparatus Camillo Golgi (1843 – 1926) 1 µm Nucleus Vesicles Lysosome Plasma membrane Digestive enzymes Lysosome Digestion Food vacuole Phagocytosis: lysosome digesting food Vacuoles Central vacuole Cytosol Tonoplast Nucleus Central vacuole Cell wall Chloroplast 5 µm Contractile Vacuole Nucleus Rough ER Smooth ER Nuclear envelope Nucleus Rough ER Smooth ER Nuclear envelope cis Golgi Transport vesicle trans Golgi Nucleus Rough ER Smooth ER Nuclear envelope cis Golgi Transport vesicle Plasma membrane trans Golgi Organelles Mitochondrion Chloroplasts Mitochondria Mitochondrion Intermembrane space Outer membrane Free ribosomes in the mitochondrial matrix Inner membrane Cristae Matrix Mitochondrial DNA 100 nm Chloroplast Chloroplast Ribosomes Stroma Chloroplast DNA Inner and outer membranes Granum 1 µm Thylakoid Chloroplast Cytoskeleton microfilament Cytoskeleton 8-10 nm 25 nm 7 nm Microtubules Microfilaments Microvillus Microfilaments Plasma membrane Lining of intestine Microfilaments (actin filaments) Intermediate filaments 0.25 µm Intermediate filaments Extracellular components Central vacuole of cell Plasma membrane Secondary cell wall Plant Cell Walls Primary cell wall Central vacuole of cell Middle lamella 1 µm Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata Plant Cells cellulose Animal Cell exterior Extra cellular matrix Extracellular components: intercellular junctions Plasmodesmata: found in plants Cell walls Interior of cell Interior of cell 0.5 µm Plasmodesmata Plasma membranes Animals Tight junctions prevent fluid from moving across a layer of cells tight junctions, desmosomes and gap junctions Tight junction 0.5 µm Tight junction Intermediate filaments Desmosome 1 µm Space between cells Gap junctions Plasma membranes of adjacent cells Gap junction Extracellular matrix 0.1 µm Tight junctions Desmosome Gap junctions
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