cell theory
� All living organisms are made of one or more cells � Cell is the basic unit of life � Cells are produced only from pre-existing cells
all cells ____ their genetic instructions from a common ____ cell
inherited, ancestral
Basic chemistry of a cell:
�DNA encodes genetic information
�Enclosed by membrane composed of a lipid-bilayer
�Essential biochemical processes
Three major divisions of the living world:
bacteria, archaea, and eukaryotes
Diversity is generated by ____ processes (gene mutation and natural selection) through billions of years
evolutionary
Prokaryotic Cell Structure
� Small and simple (0.2-2 �m)
� Does not have a nucleus and other organelles
� Has a single circular DNA in the cytoplasm
� unicellular
Eukaryotic cell structure
� Has a nucleus and other organelles (Mitochondrion Golgi apparatus ER)
� Has a single circular DNA in the cytoplasm
� Has multiple linear DNA's in the nucleus
� Large and complex (10 - 100 �m)
� unicellular or multicellular
Cell -> _____ -> organ -> _____ -> organism
tissue, organ system
Cells in different ____ have different ___ and _____
tissues, sizes, shapes
light microscopy
use light as a source of illumination
Living cells growing in a dish can be observed by light microscopy with various optics such as:
Bright field and phase contrast
Cells in a tissue biopsy can be observed under a light microscopy by ____ and ____ the specimen
fixing, staining
fixation
a procedure to terminate all ongoing biochemical reactions
staining
color or fluorescence
hematoxylin
stains nuclei purple
eosin
stains cytoplasm pink
Fluorescence microscopy
imaging cells with fluorescently labeled molecules
Yellow: actin filaments within microvilli Blue: microtubules Pink: DNA within the nuclei
Immunofluorescence
proteins are fluorescently labeled with antibodies
direct labeling
primary antibody carries the die
indirect labeling
primary antibody needs secondary antibody that has the dye
Live cell imaging by tagging a protein with _____
green fluorescent protein (GFP)
Confocal microscopy
eliminates unfocused background fluorescence
a 3D image can be constructed from optical sections
Resolving power (resolution)
ability to discriminate between two separate points
Magnification power
the extent of enlargement by the lenses of the microscope
Limitation of light microscope
low resolving power (ability to discriminate between two separate points)
Transmission electron microscopy (TEM)
� samples are fixed and sectioned into very thin slices
� stained with heavy metal salts that block transmission of electrons
� significantly higher magnification and resolution (resolution limit: 0.2 nm)
� visualize fine structures inside an organelle or
Scanning electron microscopy (SEM)
� Samples are fixed and the surfaces are coated with heavy metal
� Electrons excite emission of secondary electrons from the surface of the specimen
� Produce 3D image of a surface
� Allow detailed study of surfaces
� Resolution limit: 1 nm
� 3D image of
Atomic force microscopy (AFM)
� scanning mode: 3D imaging of a surface (3D topology) by scanning the surface with the tip of a cantilever
� force mode: measuring the mechanical properties of cells and tissues (will be discussed in L4)
� Resolution limit: 0.2 nm