The microscope

LICEO SCIENTIFICO “J. DA PONTE”- BASSANO DEL GRAPPA

Brainstorming

What do you know about the parts of a microscope and their different functions?

Look up the word “microscope”in the monolingual dictionary.

• Microscope:

• An instrument used in scientific study for making very small things look larger so that you can examine them carefully

A microscopic slide

The bacteria were then examined under a/the microscope

Watch the video, complete the sentence and match the parts of microscope with their own function. https://www.youtube.com/watch?v=HOhF7LauOys

Parts of MICROSCOPE FUNCTION

1. Body tube a……….. Hold slides in place. Used to keep the slides in place

2. Revolving nosepiece- Rotating objects b………….Steady light source. Sends light up through the diaphragm and through the slide for viewing

3. Scanning objective or Low-power objective

lens

c………… Highest magnification and used to view a slide at the microscope high power.

The highest magnification used. Usually 40x. NEVER use the course adjustment when using this lens.

4. Low-objective power or Medium power

objective

d………Supports the tube and connects it to the base

5. High-power objective e……….Lowest magnification and used to view a slide at the microscope lowest power

The first lens you use when doing proper microscope work. Usually 4x

6. Stage clips f……….. Holds up the microscope. Used to safely transport the microscope

7. Diaphragm g………..Move stage closer/farther away from objective. Broader adjustment. Used to make large changes in focus.

NOTE: never use this when viewing on high power

8. Lamp or Light source h………. Holds the objective lenses and can be easily rotated to change viewing power. Allows for quick change of

objective

9. Eyepiece (ocular lens) i….……. Move stage closer/farther from objective. Specific adjustment. Used to small adjustments of focus.

10. Arm l……….Lens you look through to view slide. The part you look at with your eye. Usually 10x magnification

11. Stage m……..Middle magnification and used after scanning power. The second lens you use when doing proper

microscopy work. Usually 10x

12. Course adjustment knob n……….Changes the intensity of the cone of light. Changes the transparency and contrast.

Used to vary the amount of light passing through the slide. Usually is better if the amount of light is low.

13. Fine adjustment knob o……….Platform where you place the slides

14. .Base p……... Connects eyepiece to the objectives and reflects light up to the viewers eye

Complete the sentences: Stereomicroscope is ……………… (2 eyes), and magnifies ……… x to ………. x, while the light microscope is often …………………..

It magnifies between …… x to ………….. x and is used for ………………………………..and …………………………………………………..and ……………………………

Match parts of microscope with their-own function

Work in pairs Find out the names of the parts of a microscope and their different functions.

Useful language What does the / do the ... do? Which part(s) of the microscope ... ?

from © CLIL Maths and Science Materials 2014

from © CLIL Maths and Science Materials 2014

from © CLIL Maths and Science Materials 2014

from © CLIL Maths and Science Materials 2014

Answers

1)

2)

3)

4)

5)

6)

7)

8)

9)

10)

11)

12)

eyepiece lens

eyepiece tube

stage clips

revolving nosepiece

objective lenses

stage

diaphragm adjustment lever

condenser

light source

coarse and fine adjustment knobs

base and arm

on/off switch from © CLIL Maths and Science Materials 2014

Microscope Question 1. How do you calculate the total power of magnification? 2. What is the total magnification for each lens? 3. What happens to the object when you change the lens? Watch the video and answer the questions (https://www.youtube.com/watch?v=j6VzQr7ZqMY)

What’s my power? -To calculate the power of magnification, multiply the power of ocular lens by the power of the objective. Es. 10x x 40x = 400 x What are the powers of magnification for each of the objectives we have on our microscope? (our microscope has 3 objective lenses and 1 ocular lens…..)

BAND COLOR OBJECTIVE POWER EYEPIECE LENS POWER POWER OF MAGNIFICATION

red 10x 40x

yellow 10x 100x

blue 40x 10x

Watch the video and complete the table

Magnification is the number of times to which an object is made to look larger than its real size. magnification = observed size of the image or M= I actual size A Here I =observed size of the image (that is, what you can measure with a ruler) and A= actual size (that is , the real size- for example, the size of a cell before it is magnified)

From Cambridge International AS and A Level Biology Fourth edition

From Cambridge International AS and A Level Biology Fourth edition

From Cambridge International AS and A Level Biology Fourth edition

VOCABULARY LM Light Microscope An optical instrument with lenses that refract (bend) visible light to magnify images and project them into a viewer’s eye or onto photographic film. EM Electron Microscope An instrument that focuses an electron beam through, or onto surface of, a specimen. An electron microscope achieves a hundredfold greater resolution than a light microscope. SEM Scanning Electron Microscope A microscope that uses an electron beam to study the surface architecture of a cell or other specimens. TEM Transmission Electron Microscope A microscope that uses an electron beam to study the internal structure of thinly sectioned specimens.

SCIENCE LABORATORY Liceo J.Da Ponte- Bassano del Grappa (VI)

Microscopy Observation of cells or tissues in fresh Learning goals (Students Will Be Able to): use the light microscope; prepare wet mount slides of cells or tissues; distinguish between plant and animal cells identify nuclei, chloroplasts, plasma membranes, cell walls and other cell structures under the microscope. Materials microscopic glass slides, microscopic cover slips, a needle, blade, scalpel, knife, blotting paper, dropper, Logol’s Iodine Solution, methylene blue solution (1%). Water. light microscope, animal or plant specimens (onion, potato, bread yeast, banana) Notes: Lugol’s iodine is a reagent used in laboratory test, for starch detection. Its colour changes to dark blue in presence of starch. Methylene Blue is a cationic stain (positively charged blue dye); and binds to negatively charged parts of the cells, such as nucleus (DNA) and RNA in the cytoplasm (with lower affinity). It's a common stain for a large number of tasks including identification of bacteria, cellular structure in both plan and animal cells.

Microscope Use

1.Set the microscope at the 4X (red band) objective.

2.Place the slide on the microscope stage.

3.Adjust until the cells are in focus.

4.Use the coarse adjustment knob on the bottom of the microscope to adjust the height until cells are visible. Use

the fine adjustment knob to focus. Moving the knobs backward lowers the stage. Moving them forward raises the

stage.

5.Change the magnification to 10X (yellow band) and use the fine adjustment knob to focus on the cells.

6.Very carefully change the magnification to 40X (blue band) to ensure that the lens does not touch the slide. Use

the fine adjustment knob to focus on the cells.

STUDY OF PLANT CELLS

Prepare a wet mount of onion epidermal tissue, following the procedure: -remove a small piece of epidermis and spread it smoothly in a drop of water on a slide -gently lower a coverslip to prevent trapping air bubbles -add one or two drops of methylene blue stain to the edge of the cover slip -drew the stain under by touching absorbent paper to the opposite site of the coverslip -examine this tissue under scanning (4x), low power (10X) and high power (40x) objective. -prepare now another wet mount onion epidermal tissue and stain with Lugol iodine solution - take a photo or draw a picture of the onion cells you observed. Be sure to include the magnification the cells were studied and any key organelles you may have seen.

Questions:

1.Which plant organ is modified to produce onion bulbs?

2.Were you able to see individual cells? Which parts of the cell were you able to identify? Where are these different parts placed in the cell?

3. Did you see one type of cell or different types of cells? Which shape/shapes? Provide evidence to support your answer.

4.How does methylene blue work to make onion bulb cytoplasm and nucleus visible?

5.How does iodine work to make onion bulb cytoplasm and nucleus visible?

6. Were you able to see starch grains in the onion?

7.Could you identify structures that are likely present in the cells and that be visible at higher magnification?

8.Were the cells you observed the product of mitosis or meiosis? Provide evidence to support your answer.

STUDY OF CHEEK CELLS

Follow the instructions below to examine epithelial cells obtained from the inner lining of your cheek. -Gently scrape the inside of your cheek with the broad of a toothpick -stir the scraping into a drop of water on a slide -lower a coverslip over your specimen, gently, to avoid trapping air bubbles -examine with your microscope -add one or two drops of methylene blue stain to the edge of the cover slip -drew the stain under by touching absorbent paper to the opposite site of the coverslip -examine this tissue under scanning (4x), low power (10X) and high power (40x) objective. -take a photo or draw a picture of the cheek cells you observed. Be sure to include the magnification at which the cells were studied and any key organelles you have seen. Questions:

1. Which cell structures were visible in your specimens?

2. Which organelles were not visible in specimens?

3. Which shape do cheek cells have? Is it the same shape of onion cells? Why?

STUDY OF BREAD YEAST CELLS (Saccharomyces cerevisae)

-Put a pack of yeast in a bowl.

-Add warm water and 2 tablespoons of sugar and mix with a spoon.

-Transfer the mixture into a bottle.

-Place a balloon around the bottle neck and wait approx. 10mins, during which time the balloon should inflate due to

the released carbon dioxide gas.

- To observe the yeast under the microscope, place a drop of the yeast mixture on the microscope slide (it might be

necessary to dilute it a bit more with water). Place a coverslip on top.

- Add one or two drops of methylene blue to the edge of the coverslip and observe under different magnifications.

High magnifications will be needed to see the yeast well.

- Draw a picture of the yeast cells you observed. Be sure to include the magnification the cells were studied. Compare these cells to the plant and animal cells you have previously observed.

IDENTIFICATION OF STARCH GRAINS IN POTATO CELLS

-Peal a raw potato and scratch its surface using a knife or a scalpel.

-Get two clean slides and place on top of each a drop of potato suspension obtained previously.

-Place a drop of distilled water on top of one of the potato specimens, then cover it with a cover slip.

-Place a drop of Lugol’s iodine solution on top of one of the other specimens, then cover it with a cover slip.

-Observe and compare the two specimens under the light microscope and identify the starch grains.

-Draw and note down what you can see.

IDENTIFICATION OF STARCH GRAINS IN BANANA CELLS

- Smear a little (less than the size of a sesame seed) of an unripe green banana on a microscope slide to rub the cells

apart.

- Place a drop of Lugol solution on top of the banana smear.

- Place a coverslip on top and remove the excess of solution with a tissue.

- Place the slide on the microscope, with 4 x or 10x objective in position and find a field of view containing the cells.

Then view at higher magnifications.

Questions:

1.What colour does iodine add to potato cells compared to that observed on the onion epidermis?

2. Do you think there are differences between the reserve products of onion and those of potatoes?

3. Are there any differences in the shape of starch grains between potatoes and bananas?

SCIENCE LABORATORY Liceo J.Da Ponte- Bassano del Grappa (VI)

Microscopy

Observation of leaf epidermal tissue and stomata Learning goals (Students Will Be Able to): use the light microscope; prepare wet mount slides of tissues; identify and compare the stomata from the leaves of some plant species. Materials microscopic glass slides microscopic cover slips blade, scalpel, knife, tweezers blotting paper, dropper, NaCl solution (10%) water light microscope 3 leaves (1 from 3 different species)

Introduction Plants and animals both have a layer of tissue called the epidermal layer. Plants have special pores called stomata to allow passage of material. The stomata pores are surrounded on both sides by jellybean shaped cells called guard cells. Unlike other plant epidermal cells, the guard cells contain chlorophyll to do photosynthesis. Guard cells open when they gain water to become turgid and close when they lose water and become flaccid. This keeps water in the plant from escaping. The opening or closing of guard cells can be viewed in a microscope by adding different water concentration to the leaf tissue. Most stomata are on the lower epidermis of the leaves on plants. The number of stomata can tell you a lot about a plant. Usually, a high concentration of stomata indicates fast growth and wet climate. Lower concentrations of stomata indicate lower rates of photosynthesis and growth or adaptations for dry weather.

Procedure: • Obtain two leaves from two different types of plants (es. Geranium and cyclamen). • Remove a small piece of epidermis (about one square centimeter) on the underside of the leaf surface using tweezers and spread it

smoothly in a drop of water on a slide. • Gently lower a coverslip . • Label the slide with plant name. • Examine the specimen under a light microscope at 40X, 100X and possibly 400X. • Search for areas where there are numerous stomata, and where there are no thumb prints, dirt, damaged areas, or large leaf veins. Take a

photo or draw the leaf surface with stomata. • Count all the stomata in one microscopic field. Record the number on data table. • Repeat counts for at least three other distinct microscopic fields. Record all the counts and determine an average number per microscopic

field. • Follow procedures with the second leave.

Data: Leaf 1 Leaf 2

Name of plant

Stomata in field 1

Stomata in field 2

Stomata in field 3

Average stomata in flied

Photo or drawing (100x)

Questions:

1. What were the green organelles you observed? What gave them a green colour? 2. Which leaf had the most stomata? 3. Explain, in detail, how guard cells open and close stomata. 4. At what time of the day would stomata be closed and why? 5. Why does the lower epidermis have more stomata than the upper epidermis of a leaf? 6. What two gases move in and out of the leaf stomata?

Science laboratory Microscopy

Observation of cells or tissues in fresh

2^BSA students’s reports