IMPORTANT CONCEPTS The modern cell theory By schwann in 1839, cell theory had two basic principles: 1. All organisms consist of one or more cells. 2. The cell is the basic unit of structure for all organisms. : The third principle of the modern cell theory by Rudolf Virchow in 1855 : 3. All cells arise only from preexisting cells.

Units of measurement in cell biology The micrometer (μm) sometimes also called a micron) is one millionth of a meter is the most useful unit for expressing the size of cells. The nanometer (nm) for molecules and subcellular structures that are too small to be seen with the light microscope. nanometer is one-billionth of a meter Angstrom (Å), is used in cell biology when measuring dimensions within proteins and DNA molecules. An angstrom equals 0.1 nm, which is about the size of a hydrogen atom.

Date First lecture The Emergence of Modern Cell Biology Modern cell biology results from introducing together of three different strands : 1- Cytology 2- B iochemistry 3- Genetics Look to the FIGURE 1-2 The Cell Biology Time Line that I submit it to you Modern cell biology results from introducing together of three different strands : 1- Cytology 2- B iochemistry 3- Genetics Look to the FIGURE 1-2 The Cell Biology Time Line that I submit it to you

The Cytological Strand The light microscope has allowed us to visualize individual cells, which are approximately 1-50 µ m in size. Historically, its limited resolving power did not allow us to see details of structure smaller than about 0.2 µ m (200 nm), but modern light microscopes are surpassing that limit..

The Cytological Strand Several types of light microscopes allow us to view preserved or living specimens at magnifications of about 1000X These include brightfield, phase- contrast, differential interference contrast, fluorescence, confocal, and digital video microscopes, each of which offers particular advantages in studying and understanding cells.

The Biochemical Strand -Discoveries in biochemistry have revealed how many of the chemical processes in cells are carried out, greatly expanding our knowledge of how cells function. -Major discoveries in biochemistry were the identification of enzymes as biological catalysts, and the discovery of adenosine triphosphate (ATP)

The Biochemical Strand Several important biochemical techniques that have allowed us to understand cell structure and function are - subcellular fractionation, - ultracentrifugation, - chromatography, - electrophoresis, - mass spectrometry

The Genetic Strand - The chromosome theory of heredity states that the characteristics of organisms passed down from generation to generation result from the inheritance of chromosomes carrying discrete physical units known as genes. -Each gene is a specific sequence of DNA that contains the information to direct the synthesis of one cellular protein. -DNA itself is a double helix of complementary strands held together by precise base pairing. This structure allows the DNA to be accurately duplicated as it is passed down to successive generations.