Microscopy
Microscopy
Cell are very Small
Metabolic requirements set upper limits on the size of cells
The surface area to volume ratio of a cell is critical
As the surface area increases by a factor of n2, the volume increases by a factor of n3
Small cells have a greater surface area relative to volume Figure 6.7
Surface area increases while total volume remains constant
5
1
1
Total surface area
[sum of the surface areas
(height width) of all box sides number of boxes]
6
150
750
Total volume
[height width length
number of boxes]
1
125
125
Surface-to-volume
(S-to-V) ratio
[surface area volume]
6
1.2
6
Microscopy
Scientists use microscopes to visualize cells – too small to see with the naked eye
Two types of microscope:
Light Microscope (LM)
Electron Microscope
Scanning Electron
Microscope (SEM)
Transmission Electron
Microscope (TEM)
Microscopy
In light microscope, visible light is passed through a specimen and then through glass lenses
Lenses refract (bend) the light so that the image is magnified
Three important parameters of microscopy:
Magnification – the ratio of an object’s image size to its real size
Resolution – the measure of the clarity of the image, or the minimum distance of two distinguishable points
Contrast – visible differences in parts of the sample
Microscopy
LMs can magnify effectively to about 1,000 times the size of the actual specimen Most subcellular structures, including organelles are too small to be resolved by an LM
Microscopy
Various techniques has been used to enhance contrast and enable cell components to be stained or labeled
Recent advances in light microscopy:
Confocal microscopy and deconvolution microscopy provide sharper images of three-dimensional tissues and cells
New techniques for labeling cells improve resolution
Figure 6.3a
50 m
Brightfield
(unstained specimen)
Figure 6.3b
Brightfield
(stained specimen)
Figure 6.3c
Cell are very Small
Metabolic requirements set upper limits on the size of cells
The surface area to volume ratio of a cell is critical
As the surface area increases by a factor of n2, the volume increases by a factor of n3
Small cells have a greater surface area relative to volume Figure 6.7
Surface area increases while total volume remains constant
5
1
1
Total surface area
[sum of the surface areas
(height width) of all box sides number of boxes]
6
150
750
Total volume
[height width length
number of boxes]
1
125
125
Surface-to-volume
(S-to-V) ratio
[surface area volume]
6
1.2
6
Microscopy
Scientists use microscopes to visualize cells – too small to see with the naked eye
Two types of microscope:
Light Microscope (LM)
Electron Microscope
Scanning Electron
Microscope (SEM)
Transmission Electron
Microscope (TEM)
Microscopy
In light microscope, visible light is passed through a specimen and then through glass lenses
Lenses refract (bend) the light so that the image is magnified
Three important parameters of microscopy:
Magnification – the ratio of an object’s image size to its real size
Resolution – the measure of the clarity of the image, or the minimum distance of two distinguishable points
Contrast – visible differences in parts of the sample
Microscopy
LMs can magnify effectively to about 1,000 times the size of the actual specimen Most subcellular structures, including organelles are too small to be resolved by an LM
Microscopy
Various techniques has been used to enhance contrast and enable cell components to be stained or labeled
Recent advances in light microscopy:
Confocal microscopy and deconvolution microscopy provide sharper images of three-dimensional tissues and cells
New techniques for labeling cells improve resolution
Figure 6.3a
50 m
Brightfield
(unstained specimen)
Figure 6.3b
Brightfield
(stained specimen)
Figure 6.3c