Name BIO183 Fall 23 Microscopes and Cells LEARNING OBJECTIVES 1 Be able to use the light microscope to draw identify and describe cell structures 2 Examine cells from eukaryotic multicellular organisms 3 Demonstrate osmosis in plant cells 4 Describe and interpret the animated short film The Inner Life of the Cell Please highlight all your answers with a yellow background or use a different color font that is easy to read This lab requires that you sketch You can print out this handout to include your sketches on paper during lab and then scan or take pictures of your sketches and insert these jpg images into your lab handout in the appropriate locations INTRODUCTION The cell is the basic functional unit of all living organisms the smallest and simplest biological structure possessing all key characteristics of life All living organisms are composed of one or more cells and every activity raking place in living organisms is ultimately related to the metabolic activities occurring in each cell Thus understanding the processes of life necessitates an understanding of the structure and function of cells The earliest known cells lacked nuclei and membrane bound organelles Present in the fossil record 3 5 billion years ago these earliest cells were prokaryotes Figure I They possessed the basics a plasma membrane a single circular DNA and used RNA and ribosomes to assemble needed proteins Cells with a nucleus and membrane bound organelles called eukaryotes do not appear in the fossil record for another two billion years Figure 2 shows a typical animal and plant cell both eukaryotic cells Eventual evolution of the eukaryote and its internal compartmentalization led to enormous biological diversity in single cells The evolution of loose aggregates of cells ultimately to colonies of cells paved the way for specialization whereby certain groups of cells played differing functional roles Some were involved in locomotion others in reproduction yet all worked together as a functional unit Multicellularity appears to have evolved more than once among Eukarya and adaptive radiations have given rise to multicellular protists fungi plants and animals Today unicellular organisms exist as prokaryotes in the Domains Bacteria and Archaea and unicellular colonial and multicellular organisms make up Eukarya Today s lab activities are designed to familiarize you with cells from the Eukarya teach you techniques that are used to study them in the lab and explain how osmosis affects cell chemistry Figure 1 Generalized features of prokaryote cells ACTIVITY 1 REVIEW OF LIGHT MICROSCOPY Microscopes of one kind or another are used to study cells Cell size and the limitations of the human eye necessitate the assistance of microscopes to allow us to visualize them Light microscopes which use visible light for illumination are useful for viewing most eukaryote cells They are limited by the smallest wavelength of visible light thus when viewing the smaller structural features of cells or even whole prokaryotes their use is limited They are essential however for examining whole cells and their general features Given the importance of the light microscope s role in the biological sciences it is important for you to have a thorough understanding of its proper use Please review key features of a compound microscope Figure 2 before you get started on today s activities Figure 2 Generalized diagram of a compound microscope with mechanical stage adjustment knobs PROCEDURE 1A PRACTICE USE OF THE COMPOUND MICROSCOPE USING A PREPARED SLIDE Please follow the Microscope Cleaning Precautions outlined by your TA and posted on each lab table 1 Obtain one of the prepared slides at your table Each student should work with their own slide and microscope 2 Place the prepared slide on the microscope stage with the lowest objective lens 4x in place over the slide Use the mechanical stage adjustment knobs to center the specimen under the 4x lens Turn on the light switch so that you can see light shining through the specimen on the slide generally the area under the coverslip 3 Always start to focus using the 4x objective lens and use the coarse focus knob to bring the specimen into focus Once your image is focused you can use the small fine focus knob to fine tune the needed focus 4 Most likely you will want to increase the magnification to better see your specimen or to look for finer details not obvious with the 4x lens The lenses on your microscope are parfocal so that you can rotate the objective lens to the next power lens 10x and the image should be somewhat close to focus You may need to move the stage to re center and find the specimen using the stage adjustment knobs but do not raise or lower the stage You should only use the smaller fine focus knob at any magnification higher than the 4x lens or you risk damaging the expensive lens and or breaking the slide 5 Now look at your specimen using the 10x then the 40x objective lenses Again remember to only use the smaller fine focus knob to better focus on the specimen Do not use the 100x objective lens since special immersion oil is necessary for that level of magnification Our specimen in lab will all be too large to examine with the 100x lens 6 In the circle that follows provide a sketch of the cells tissue or organism found on your slide You will need to determine the best level of magnification to make your drawing Please include the total magnification used for your sketch How do you calculate this Be sure to properly label your drawing indicating the Genus and species if possible or description name as it appears on the slide label the Kingdom and at least two major structures or organelles seen at this appropriate level of magnification If you are unsure of what you are looking at and possible structures you can do a quick Google search Be sure to sketch from what you see on your slide and not from the internet image Different staining or microscopy may be used to show structures you cannot see in the preparation here NucleuseEI M A Kendrite remember to name and label at least 2 major structures seen in your slide Motor Neve cell Organism Kingdom Total magnification x 10 40 4 PROCEDURE 1B SIMPLE STAINING OF AN ANIMAL AND PLANT CELL In order to better visualize key features of some cells we will employ simple staining Simple staining is the use of one stain to help visualize a key structure s Simple stains generally adhere to specific types of molecules found in or on the