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Topic 2

Topic 2. Cells. 2.1.1 The Cell Theory 2.1.2 Evidence for the Cell Theory. Theories: Theories are developed after the accumulation of much data. Sometimes, theories are completely abandoned because of conflicting evidence.

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Topic 2

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  1. Topic 2 Cells

  2. 2.1.1 The Cell Theory2.1.2 Evidence for the Cell Theory Theories: Theories are developed after the accumulation of much data. Sometimes, theories are completely abandoned because of conflicting evidence. The formulation of the Cell Theory has taken several hundred years of research and has amassed tremendous credibility through use of the microscope…the electron microscope (EM) has allowed us to study the ultrastructures of cells.

  3. Theories and Laws

  4. 2.1.1 The Cell Theory2.1.2 Evidence for the Cell Theory • All organisms are composed of one or more cells. • Cells are the smallest units of life and the basic units of structure and function in living things. • All cells come from pre-existing cells. The discovery of cells was linked to developments in technology, in particular the production of high quality lenses for microscopes.

  5. The Cell Theory

  6. Discoveries Which Led to the Cell Theory • 1590- Dutch optician, Zacharias Jansen, invents compound microscope- 2 lenses for greater magnification • 1665- Englishman, Robert Hooke, studies cork and names the structures “cells” • 1675- Dutchman, Anton van Leeuwenhoek, discovers unicellular organisms • 1838- German, MathaisSchleiden, suggests all plants are made of cells • 1839- German, Theodor Schwann, suggests all animals are also made of cells • 1840- Czech, Jan Evangelista Purkinje, names the cell contents “protoplasm” • 1855- German, Rudolf Virchow, suggests “all cells come from cells” • 1860s- Louis Pasteur sterilized chicken broth to disprove “spontaneous generation”

  7. Protoplasm

  8. 2.1.3 Functions of Life • Metabolism- all the chemical rxs that occur within an organism • Growth- may be limited, but is always evident • Reproduction- heredity molecules passed to offspring • Response- to the environment is imperative to survival • Homeostasis- maintaining a constant internal environment ex. T° or acid-base levels (pH) • Nutrition- source of compounds (food) with many chemical bonds which can be broken to provide energy and nutrients to maintain life

  9. Characteristics of Cells

  10. Viruses: Living or Non-Living????? Viruses are not considered to be living. They cannot carry out the functions of life on their own (they have no metabolism). However, they do utilize cells to perpetuate themselves.

  11. Introduction to Viruses

  12. 2.1.4 Cells and Sizes • Cells are made up of different subunits. • These subunits are all microscopically small. • Microscopes with high magnification and resolution are needed to observe cells and their subunits. • Cells are relatively large (100 µm), and then in decreasing size order are: learn this: • organelles 10 µm • bacteria 1 µm • viruses 100 nm • membranes 10 nm • molecules 1 nm

  13. Types of Microscopes • Compound Light Microscopes- use light which is passed through a specimen to form an image • Can view living or dead specimens • Magnification = 1000X (classroom = 400X) • Eyepiece = 10X • 3 objective lenses 4X, 10X and 40X • Stains are often used to enhance viewing organelles • Electron Microscopes- electrons (e-) pass through a specimen to form an image • Can only view dead specimens SEM • Magnification = > 100,000X • SEM (scanning electron microscope) produces an image of the surface of a cell or specimen TEM • TEM (transmission electron microscope) produces an image of the interior of a cell or specimen

  14. Electron MicroscopesTEM and SEM

  15. Cells and Size(these are typical sizes- there are exceptions)

  16. 2.1.5 Calculating Magnification and Actual Size of Micrograph Images Magnification = size of image divided by size of specimen or Magnification = magnified size(ruler) realsize (scale bar) USING SCALE BAR Magnified size = 30 mm Real size = 200 nm Mag. = ?????? (units need to be the same) Light, TEM or SEM????????

  17. Find the actual size of the specimen!!! Magnification can be indicated next to a diagram or a scale bar can be given. 3000X 1 mm Find the size of this vessicle in a mouse kidney cell. 1 mm Remember magnification = size of image/size of specimen (measure this)(actual size) So, 3000= 12 mm/x now solve for x x= 12 mm/3000 = .004 mm or 4.00 µm

  18. Using the Field of View to Determine the Size of a Specimen

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