Tour of the Cell

Robert Hooke ( )

Robert Hooke : examined thinly sliced cork and coined term “cell”

van Leeuwenhoek : first to observe living cells

van Leeuwenhoek

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 The cell theory

Light microscopy

Cilia Electron microscopy

Cilia Light microscopy Electron microscopy

Chromosomes Light microscopy

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:  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 nm. cell membranes: ~10nm cytoskeletal structures such as microtubules, microfilaments are generallly measured in nm. DNA helix ~2nm

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 10 m 1 m Human height Length of some nerve and muscle cells Chicken egg 0.1 m 1 cm Frog egg 1 mm 100 µm Most plant and animal cells 10 µm Nucleus 1 µm Most bacteria Mitochondrion Smallest bacteria Viruses 100 nm 10 nm Ribosomes Proteins Lipids 1 nm Small molecules Atoms 0.1 nm Unaided eye Light microscope Electron microscope Sizes

Why are cells so small?

1 1 5 Surface area increases while Total volume remains constant Surface to volume ratio

A typical rod-shaped bacterium A thin section through the bacterium Bacillus coagulans (TEM) 0.5 µm Pili Nucleoid Ribosomes Plasma membrane Cell wall Capsule Flagella Bacterial chromosome Prokaryotic Cells

There are two types of cells…..

Prokaryotic Cell Example: bacteria cell

Eukaryotic Cells Animal Plant

Cell parts and functions….

Plasma Membrane (cell membrane)

Close-up of nuclear envelope Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Ribosome Pore complexes (TEM)Nuclear lamina (TEM) 1 µm Rough ER Nucleus 1 µm 0.25 µm Surface of nuclear envelope Nucleus

Ribosomes 0.5 µm ER Cytosol Endoplasmic reticulum (ER) Free ribosomes Bound ribosomes Large subunit Small subunit Diagram of a ribosome TEM showing ER and ribosomes Ribosomes

Smooth ER Rough ER ER lumen Cisternae Transport vesicle Smooth ER Rough ER Transitional ER 200 nm Nuclear envelope Endoplasmic reticulum

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 Lysosome Nucleus Phagocytosis: lysosome digesting food Plasma membrane Food vacuole Digestive enzymes Digestion Lysosome Vesicles

5 µm Central vacuole Cytosol Tonoplast Central vacuole Nucleus Cell wall Chloroplast Vacuoles

Contractile Vacuole

Nuclear envelope Nucleus Rough ER Smooth ER

Nuclear envelope Nucleus Rough ER Smooth ER Transport vesicle cis Golgi trans Golgi

Nuclear envelope Nucleus Rough ER Smooth ER Transport vesicle cis Golgi trans Golgi Plasma membrane

Organelles

Mitochondrion Chloroplasts

Mitochondrion Intermembrane space Outer membrane Inner membrane Cristae Matrix 100 nm Mitochondrial DNA Free ribosomes in the mitochondrial matrix Mitochondria

Chloroplast DNA Ribosomes Stroma Inner and outer membranes Granum Thylakoid 1 µm Chloroplast

Cytoskeleton microfilament

8-10 nm 25 nm 7 nm Cytoskeleton

Microtubules

Microfilaments

Microfilaments (actin filaments) Microvillus Plasma membrane Intermediate filaments 0.25 µm Lining of intestine Microfilaments

Intermediate filaments

Extracellular components

Central vacuole of cell Plasma membrane Secondary cell wall Primary cell wall Middle lamella 1 µm Central vacuole of cell Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata Plant Cell Walls

Plant Cells cellulose

Animal Cell exterior Extra cellular matrix

Extracellular components: intercellular junctions

Interior of cell Interior of cell 0.5 µm PlasmodesmataPlasma membranes Cell walls Plasmodesmata: found in plants

Tight junctions prevent fluid from moving across a layer of cells Tight junction 0.5 µm 1 µm 0.1 µm Gap junction Extracellular matrix Space between cells Plasma membranes of adjacent cells Intermediate filaments Tight junction Desmosome Gap junctions Animals tight junctions, desmosomes and gap junctions

Tight junctions

Desmosome

Gap junctions