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. 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.

Theories and Laws

2.1.1 The Cell Theory 2.1.2 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.

The Cell Theory

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, Mathais Schleiden, 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”

Protoplasm

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

Characteristics of Cells

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.

Introduction to Viruses

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 meter m 1 # in 1 m millimeter mm 10-3 1000 micrometer µm 10-6 1000000 nanometer nm 10-9 1000000000 Resolution refers to clarity

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

Electron Microscopes TEM and SEM

Cells and Size (these are typical sizes- there are exceptions) STRUCTURE SIZE Eukaryotic Cell (animal and plant) (plant cells and egg cells are generally larger) 10 - 100 µm Prokaryotic Cell (bacteria) 1 - 5 µm Nucleus 10 - 20 µm Chloroplast 2 - 10 µm Mitochrondion 0.5 - 5 µm Bacteria (largest known = 1 mm) Large Virus (HIV) 100 nm Ribosome 25 nm Cell Membrane 7.5 nm thick DNA Double Helix 2 nm diameter Hydrogen Atom 0.1 nm

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) real size (scale bar) USING SCALE BAR Magnified size = 30 mm Real size = 200 nm Mag. = ?????? (units need to be the same) Magnification = 150,000 Light, TEM or SEM????????

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

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