2 The Discovery of the Cell Without a tool to make them visible cells were until the invention of the microscopeRobert Hooke used an early microscope to look at cork cells.About the same time Anton van Leeuwenhoek observed tiny organisms in pond water.
3 Early DiscoveriesMatthias Schleiden a German botanist concluded that all plants are made of cells.Theodor Schwann a German biologist stated that all animals are made of cells.Rudolf Virchow a German physician concluded that new cells can only be produced by division of existing cells
4 Cell Theory All living things are made up of cells. Cells are the basic units of structure and function in all living things.New cells are produced from existing cells through cell division.
5 How do microscopes work? Most use lenses to magnify the image of an object by focusing light or electrons.Types of microscopes:Light microscopes – images 1 millionth of mElectron microscopes – images 1billionth of mTEM – transmission – thin samples, can see cell structures & moleculesSEM – scanning – 3-D surface images
9 Examples of Cells Amoeba Proteus Plant Stem Bacteria Red Blood Cell Nerve Cell
10 As you can see cells come in many sizes and shapes
11 All cells have some similarities: At some point they contain DNAAll cells are surrounded by a thin flexible barrier called a cell membrane or plasma membrane.But they also have differences and so are seperated into 2 broad groups:Eukaryotes and Prokaryotes
12 Prokaryotic Do not have structures surrounded by membranes Do not separate DNA within a nucleusOne-celled organisms, Bacteria
14 Eukaryotic Plant Animal Contain organelles, specialized structures that perform specific functions; surrounded by membranesNucleus separates DNA from the rest of the cellMost living organisms, great varietyPlantAnimal
20 Cytoplasm Gel-like mixture also called cytosol Portion outside the nucleusSurrounded by cell membraneContains organelles of eukaryotes – specialized structures that perform specific tasks
21 Nucleus Directs cell activities Separated from cytoplasm by nuclear membraneContains genetic material – DNA – which contains coded information to make proteinsProkaryote cells lack a nucleus but they do contain DNA
22 Nuclear Membrane Surrounds nucleus Made of two layers Openings called nuclear pores allow material to enter and leave nucleusAlso called the nuclear envelope
23 Chromosomes In nucleus Made of DNA Contain instructions for traits & characteristicsUsually in the form of long thin threads called chromatin
24 Nucleolus Small dense region inside nucleus Involved in the assembly of organelles called ribosomes
25 VacuolesMembrane-bound sacs for storage of water, salts, proteins, and carbohydratesPlants usually have a large vacuole that helps maintain shapeParamecium – contractile vacuole
26 Lysosome Small organelles filled with enzymes to digest waste Transports digested material to cell membrane for removalAlso breaks down old organelles no longer needed
27 Cytoskeleton Helps maintain cell shape and also in movement. Internal network of protein fibers:MicrofilamentsMicrotubules
28 Ribosomes Each cell contains thousands Make proteins using instructions from DNA
29 Endoplasmic Reticulum Internal membrane system where compounds are assembled and transportedSmooth ER: lacks ribosomes; makes lipidsRough ER(pictured): ribosomes embedded in surface; modify proteins made by ribosomes
30 Golgi ApparatusModifies, sorts, and packages proteins and other materials from the ER for storage in the cell or released outside the cell.Bundles proteins in tiny vesicles.
31 MitochondriaConvert chemical energy stored in food (glucose) into compounds that are able to be used by cells –ATPIn humans most all of our mitochondria come from the cytoplasm of the egg cell – so you got yours from your mother.They also contain their own DNA!
32 ChloroplastCapture energy from sunlight and convert it into food – sugars – that contain chemical energy in a process called photosynthesis.Surrounded by two membranesContain pigment called chlorophyll