August 27, 2015
Benjamin Wajsberg
Lab Report 1: Microscopes & Cells Purpose To learn how images are created and distorted by a microscope and how to use its different functions in order to gain a better understanding un derstanding of different complex cell types and their respective parts.
Introduction Microscopes are one of the most important tools used in a lab to observe minuscule minu scule forms of life in greater detail. Microscopes work by magnifying objects and creating an image that is visible to the naked eye. The quality of the microscope is not determined by its ability to magnify objects, but by its ability to resolve objects, to distinguish detail. Light microscopes use visible light and an arrangement of lenses to magnify and resolve objects. Additionally, microscop y allows scientists to see transparent and translucent objects through the use of various staining techniques to enhance contrast in the image. Cells are the basic units of life. All organisms are made up of one or o r more cells. All cells emerge from pre-existing cells. This is known as “cell theory” theory”. There are two types of cells: prokaryotic and eukaryotic cells. Prokaryotic cells are the simpler cells with simple circular DNA and some basic organelles, and no nuclear envelope and no chromosomal proteins. For example, bacteria and blue green algae. Eukaryotic cells (eu (eu = = true, karyote = nucleus) have a nuclear envelope, contain chromosomal proteins and various complex organelles. For example, single-celled protists, plant cells and animal cells.
Materials and methods As described in the lab manual on pages 29 to 44.
Data: -
No magnification
4x objective
Slide 1: Letter “e”
e
e
wa s mirrored around Findings : It was observed with the 4X objective lens that the letter “e” was the x-axis and the y-axis.
-1-
-
Slide 2: Field of view
4.6 mm
2.0 mm
Findings :
Objective lens 4X
10X 40X
-
Field of view 3
4.6 mm or 4.6 x 10 m Remeasured: 5.0 mm or 5.0 x 103 m * refer to conclusions for errors 2.0 mm or 2.0 x 103 m Not able to measure because the lines were too thick. Based on calculation: 0.5 mm or 0.5 x 103 m (* refer to conclusions)
Slide 3: Tricolor layered thread
Findings 1: From upper to bottom layer: red, blue, and yellow
1
Not able to measure
Data adapted from Josh Birnbaum and Avi Gordon -2-
-
Slide 4: Protist – amoeba amoeba without staining 10X objective
10X objective
Findings : Amoeba’s slow movement and shift of internal structures was observed as well as the formation of pseudopodia (“fake legs” legs”). Surrounding food was also observed.
-
Slide 5: Plant cell – onion onion cell with staining 10X objective
4X objective lens
Findings: Findings : The cells seemed well-organized and ordered. Th e rigid cell wall was clearly visible. The internal structures were not clearly visible, except for the nu cleus.
-3-
-
Slide 6: Animal cell – cheek cheek epithelial cells with staining 10X objective
Findings: The cells were stuck together and overlapped. The nuclei were clearly visible, but the internal structures were unnoticeable.
Conclusions: Microscopes are very useful tools to study different cell types and cell structures. When using a microscope, it is very important to know how to manipulate its it s different parts in order to get a clear and detailed image. The microscope has four levels of magnification ability: Scanning – Scanning – 4X 4X Lower power – power – 10X 10X High power – power – 40X 40X Oil immersion – immersion – 100X 100X (not used during experimentation) ex perimentation) The above multiplication powers are multiplied by 10 (the magnification ability of ocular lens) in order to get the total magnification. Slide 1 shows that when viewing a specimen under the microscope, it is mirrored around the xaxis and the y-axis. This has to be taken into account when moving the specimen with the stage motion knobs and when placing the specimen on the stage. The field of view of a microscope is the diameter of the microscopic image. Slide 2 showed that the magnification and the field of view are a re inversely proportional. In other words, if the magnification increases by factor k, the diameter o f the field of view decreases by factor k. In mathematical terms – terms – objective objective lens magnification x field of view = factor k Based upon this, one can calculate the field of view for the 40X objective lens, which was unable to be measured: 40 (objective lens magnification) x f (field of view) = 20 (factor k) <=> f = 0.5 mm Thus the field of view for the 40X objective lens is 0.5 mm.
-4-
It is also important to note that initially the field of view of the 4X lens was 4.6 mm, which was then remeasured to be 5.0 mm. This initial error was ascribed to human error. In slide 3, by using the fine adjustments, one can focus on d ifferent layers of the specimen and determine their vertical position. This is important in order to get a better understanding of the specimen’s three-dimensional three-dimensional structure. The amoeba from slide 4 moved slowly and changed shapes while altering its path. It exhibited long, blunt feet-like structures called pseudopodia (“fake legs”). legs”). These structures enabled movement through shifting internal structures to one side. When viewing the onion cells from slide 5, 5 , the nucleus was clearly visible as well as the surrounding cell wall. Unlike animal cells that have exoskeletons and endoskeletons, plant cells have a rigid cell wall composed of cellulose, which provides structural support and protection. The onion cells have a fixed shape resembling a rectangle. The onion cells that were observed did not have chloroplasts because they th ey do not carry out ph otosynthesis as they grow underground. Cheek cells from slide 6 can visibly be distinguished from plant cells by their round shape and the lack of a cell wall. The cheek cells were stuck together because they do not have a cell wall for protection so it was difficult to discern the difference cells. Both methylene blue and bromocresol green were used in slides 5 and 6 to enhance contrast between the parts of the specimen.
-5-
