Great Ideas of Biology Lecture 2 Alan Mortimer PhD
The Cell as the Basic Unit of Life Lecture 2 HeLa Cells Fentonics
The Basic Unit In all science we have look for the most basic unit We also seem to want to look for similarities In biology that unit is the cell We can subdivide a cell But it doesn t function
Today History of the idea of a cell Elements of a cell A few types of cell Function of individual and groups of cells Some thoughts on evolution of cells The unknowns
History 1662 Robert Hooke first observed cells Built a rudimentary microscope Head of Royal Society and controlled a lot of communication of science Observed and drew cell structure in cork bark Actually it was cell walls of dead cells
Also known for work in: Materials (Hooke s Law for springs) Chemistry Paleontology Survey
The First View of a Live Cell Anton van Leeuwenhoek developed the first microscope able to resolve living cells He drew, and described micro-organisms in water and their motion He observed and described larger bacteria
The Technology The secret was his ability to make spherical glass lenses No one was able to replicate his lenses He reported his observations at the Royal Society in 1676 (five years after Hooke) Ridiculed because Hooke couldn t repeat them
His Work The idea of a single cell organism had never been proposes Eventually convinced the Royal Society to send a delegation to Delft in 1880 His work was accepted By the time of his death, he had written more than 190 letters to the Royal Society including Protists Bacteria (from the human mouth) The vacuole in a cell Spermatozoa and fertilization
The Geographer Johannes Vermeer
Time Passes, New Technology 1830 Charles Lister: compound elements (spherical aberration), various types of glass reduce (chromatic aberration)
1833 Robert Brown (Scotland) describes the cell nucleus 1838 Matthias Jakob Schleiden (Germany): the building blocks of plants Brownian Motion
1839 Theodor Schwann Cell Theory 1845 Rudolf Virchow Cells develop from other cells
Cell Theory 1. A cell is the basic unit of life 2. All living things are made up of cells 3. Cells come from pre-existing cells 4. All cells are the same with regard to chemical composition 5. All energy flow (i.e. metabolism) takes place within the cell
Sub-units of life The cell is the basic unit of life It is, in turn, made up of multiple elements These element can perform functions but cannot reproduce independently Evolution provides a working solution It does not contribute to over-arching principles
Types of Cells Prokaryotes: no true nucleus Mostly bacteria (also archaea) Eukaryotes: true, double membrane nucleus Fungi, plants and animals
Types of Cells Protists. What s left over Eukaryotic cells that aren t fungus, animal or plant Protozoa Flagellated Ciliated Phagocytic Spore-forming Unicellular algae Some molds e.g. slime mold
The Secret bilipid membrane
Components of a Bacterial Cell Principal Elements of a bacteria Cell Wall Capsule (or slime layer) Cell membrane Cytoplasm Chromosome Ribosome Plasmid Inclusions
Common Structures in Eukaryotic and Prokaryotic Cells Cell Membrane Cell Wall (plants) Cilium Motile Respiratory Epithelium Non-motile Sensory Organs Ribosomes
Unique Structures in Eukaryotic Cells Cell Nucleus Mitochondria Endoplasmic Reticulum Rough Smooth Golgi Apparatus Lysosome
Endoplasmic Reticulum Connected to nucleus RER => protein synthesis ribosomes SER => transport vesicles Lipids, phospholipids, steroids Less common Golgi Apparatus Packages proteins into membrane-bound vesicles Glycosylation of proteins
Mitochondria: a clue Energy source within the cell Creates energy from ATP via respiration Surrounded by membrane Contains it s own DNA and ribosomes DNA has similarities to bacterial DNA Mitochondrial DNA is maternal
Cytoskeleton The cytoskeleton maintains the shape of the cell Three main elements: Microfilaments Intermediate filaments Micro tubules
Cytoskeleton Microfilaments maintain the shape of the membrane Involved in cell movement
Cytoskeleton Intermediate filaments bear tension Play no role in cell movement Maintain cell shape Anchor nucleus and other cell elements
Cytoskeleton Microtubules resist compression Provide structure for movement of vesicles throughout the cell Pull replicated chromosomes to opposite ends of dividing cell
Cytoskeleton
Autonomous Function of a Single Cell Individual cells have the capacity to do quite complicated things Sense their environment Change shape in response to the environment Function differently depending upon the environment
Cholera Bacteria External to the body hard outer shell Must pass through the stomach (very low ph) Once in the intestine develops flagella and cilia and swims to the intestine wall When attached to the intestine wall it starts to reproduce very rapidly Excretes chemicals that cause fluid to flow into the intestine (instead of out of) Ensuing diarrhea washes out bacteria (once again with a hard shell)
Autonomous Function of a Single Cell Phagocytosis White Blood Cell Chasing Bacteria
Slime Mold
Slime mold can solve a maze
Groups of Cells: Tissues The cell is the building block of more complex organisms
Tissues and organs Must have ways if staying attached to each other Must have ways to prevent overcrowding Must have ways to work together Must be able to communicate
Cell attachments There are various forms of cell attachments
Contact Inhibition Stops growth when cells touch Absent in cancer cells
Cells Working Together A variety of mechanisms have been developed for various functions Largely evolutionary Some examples Skin Nerves Digestive system Immune System
Cell to Cell Communication Short Distance Contact receptors on cell surface Important in embryonic development and immune response (MHC) Short distance messenger molecules Fibroblast growth factor in would repair Cytokines Long Distance Hormones Released through the blood stream
Stem Cells A multicellular organism starts out as a single cell Clearly that single cell contains sufficient information to produce a complex organism A key factor in development is the stem cell
Stem Cells Stem cells have the capacity to develop into a variety of different cell types depending upon local conditions They have two major functions: Embryonic Development Repair and Maintain Tissue
Embryonic Stem Cells Appear extremely early in development Placental stem cells appear before fetal stem cells Once the become specific cell types they do not revert
Adult Stem Cells Somatic Stem Cells Generally develop into a more limited set of cell types Bone marrow is a key source of stem cells Pluripotent somatic stem cells are rare and small in number Significant research underway
Stem Cell Therapy Based on the concept of tissue repair by adult stem cells Currently most widely used in cancer therapy Major issues: tissue rejection Stem cell activation More multipotent stem cells are desirable Interest in embryonic stem cells
We Know so Little
1662 Robert Hooke Cells first observed 1670 Anton van Leeuwenhoek Living cells observed 1683 Anton van Leeuwenhoek Miniature animals 1833 Robert Brown Nucleus discovered 1838 Matthias Jakob Schleiden Building block of plants 1839 Theodor Schwann Cell Theory 1840 Albrecht von Roelliker Sperm and eggs are cells 1845 Carl Heinrich Braun Basic unit of life 1855 Rudolf Virchow Cells develop from existing cells