1. Topic 2
Cells

2. 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.

3. Theories and Laws

4. 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.

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, 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”

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 µm
bacteria µm
viruses nm
membranes nm
molecules nm
meter m 1
# in 1 m
millimeter mm
10-3
1000
micrometer µm
10-6
nanometer nm
10-9
Resolution refers to clarity

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 Microscopes TEM and SEM

15. 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) µm
Prokaryotic Cell (bacteria)
1 - 5 µm
Nucleus µm
Chloroplast µm
Mitochrondion 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

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)
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????????

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 = mm or µm

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