Download Lab in a Box 1 MICROSCOPE AND CELL

LAB IN A BOX – BOX 1
Lab in a Box
1
MICROSCOPE
AND
CELL
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LAB IN A BOX – BOX 1
Inventory
S.No
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
Materials
Glassware
Beakers – glass, 500 ml
Cover slips
Microscopic slides
Petridish - plastic
Watch glass
Equipment/Material
Microscope
Forceps
Painting brush (small)
Chemicals and Reagents
Iodine solution
Methylene blue
Saffranine
Charts
Onion cell chart
Buccal cells chart
Internal structure of feather chart
Internal structure of hydrilla leaf
Starch granules in potato chart
Internal structure of Dicot stem
Internal structure of Monocot stem
Models
Animal cell model
Plant cell model
Consumables
Onion
Blades
Ice cream sticks/spoons
Needles
Cutters
Tissue papers
Quantity
2
1 box
1 box
2
5
1
5
5
1
1
1
1
1
1
1
1
1
1
1
1
1
1 pack
1 pack
2
2
1 pack
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LAB IN A BOX – BOX 1
CONTENTS
Sl. No.
Topic
Page
Parts of Microscope
4
1.1
Working of Microscope
7
1.2
Using and handling of Microscope
8
Observing Onion cell
10
2.2
Observing cheek cells
12
2.3
Plant cell and Animal cell
15
2.4
Observing Hydrilla leaf
19
2.5
Observing starch granules in potato
21
2.6
Observing the internal structure of
feather
24
Meristamatic tissues
27
Permanent tissues
30
1
2.1
3.1
3.2
`Microscope
Experiment/ Activity
Cell
Plant tissues
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LAB IN A BOX – BOX 1
1. MICROSCOPE
Microscope is the first powerful tool in the history of biology. It is an instrument
used to magnify (enlarge) objects. Structures that are too small to be seen by the
unaided (naked) eye can be observed using a microscope.
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1.2 PARTS OF COMPOUND MICROSCOPE
Parts of microscope can be categorized as mechanical and optical parts, which are
as follows
Mechanical Parts – The parts which deals in handling of microscope.
1. Base and pillar: The base is generally horse shoe shaped, usually base
attached pillar are made heavy in order to minimize vibrations.
2. Inclination joint: It joins the arm of microscope to the pillar. This joint
permits the tilting of the microscope
3. Arm: The arm is slightly curved and is a solid piece of metal. It is attached
at one end to the pillar by the inclination joint and at the other end holds the
body tube.
4. Stage: This is called the table of the microscope, where the slide or
specimen is placed for observation
5. Body tube: It is a cylindrical tube, to which the principle optical systems are
attached.
6. Nose piece: It is a circular rotating disc attached to the body-tube.
7. Coarse adjustment knob: A pair of large knob positioned one on each side
of the body. Rotations of these knobs move the body tube with lenses. It is
used to focus the specimens or objects.
8. Fine adjustment knob: This is a smaller round knob on the side of the
microscope. It is used for slight and fine adjustment of the body tube.
Optical Parts – The parts which deals with the magnification and image formation
1. Condenser: Condenser consists of several lenses that concentrate light on
the slide.
2. Iris diaphragm: it is a mechanical device mounted underneath the
condenser and controls the amount of light entering the condenser.
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3. Mirror: Mirror is placed below the condenser and iris. It collects the light
from the natural (sun) or artificial (bulb) and reflects rays into the condenser.
4. Objective lenses: These are attached to the nose piece. They magnify and
form the primary image of the specimen. There are three i.e., 10X, 45X and
100X. Our microscope has 10X and 45X objective lenses.
5. Eye piece: Eye piece is the upper optical component that further magnifies
the primary image and brings the light rays to a focus at the eye point.
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1.3 WORKING OF MICROSCOPE
Microscope magnifies and resolves the specimens/objects seen though it.
Microscope increases the size of retinal image (the image formed on the retina of
eye) of the specimen. The ratio of increased image to that formed on retina of an
unaided eye is termed as magnification of the microscope.
How many times does our microscope enlarge an image?
The magnification power of microscope depends on the lenses which are used.
The microscope has 10X and 45X objective lenses and a 10X/15X eye piece. The
product of objective lens and eye piece gives the magnification.
Magnification = Magnification of objective lens x Magnification of eye piece
When you are observing with an eye piece of 10X and objective lens of 10X, then
the magnification would be 100 times. If you switch to 45 X objective lens, then
the magnification would be 450 (10 x 45) times.
Resolution
The term resolution (or resolving power) refers to the ability to distinguish two
close points as two separate points.
Note:
Human eyes have a limited resolving power and cannot distinguish the object
smaller than 0.1 mm (100 micron), hence to study the structures which are smaller
than 0.1 mm, microscopes are used.
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1.3 USING AND HANDLING OF MICROSCOPE
Aim
To study, how the microscope should be handled and care of microscope
Materials Required
Microscope
Procedure
Step 1
Carry the microscope by holding the arm with one hand and supporting the base
with the other hand. Place the microscope at the centre of the desk or table.
Step 2
Rotate the nose piece and select the objective lens with low magnification (10X).
Step 3
Adjust the light by turning the mirror towards the source of light and also by
moving the condenser.
Step 4
Place the prepared slide on the stage and adjust the object just over the stage
aperture.
Step 6
By looking though eye piece, slowly rotate the coarse adjustment knob till you get
a clear image.
Step 7
For more detailed structure, switch to 40 X objective lens. Use only fine
adjustment at this stage.
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Precautions
 Handle the microscope carefully.
 Place the microscope in maximum diffuse light. Direct sunlight is harmful
for the eyes.
 Before and after the use, all the lenses and metal parts including the stage
should be cleaned.
 The lenses should be cleaned with soft tissue paper or muslin cloth.
 Microscope should be kept covered when not in use.
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2.1 OBSERVING ONION CELLS
Aim
To observe onion peel under the microscope
Materials Required
Fresh or preserved material of onion peel, forceps, iodine solution, saffranine,
dropper, slides, cover slip, microscope, tissue paper and onion cells chart.
Procedure
Step 1
Divide the students into 5 groups and distribute the materials.
Step 2
Cut a small piece of onion and using forceps peel off the inner layer from the cut
piece.
Step 3
Transfer the removed peel on the slide, (spread the peel flat) and add 1 or 2 drops
of iodine/saffranine
Step 4
Place the coverslip using the needle, make sure that there are no air bubbles.
Remove the excess stain using tissue paper.
This makes the temporary slide (or temporary mount) of onion peel.
Step 5
Place the slide on the stage of microscope and observe first under low power
objective lens and then switch to high power objective lens.
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Step 6
Draw your observations, also refer to the onion cells chart.
Observation
Inference
Onion peel has closely packed rectangular structures. These structures look similar
to each other. These structures are called cells, which are the basic building units
of the onion bulb. Together they form a big structure like an onion bulb. Not only
onions, but all organisms that we see are made up of cells.
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2.2 OBSERVING THE CHEEK CELLS
Aim
To observe the cheek cells under microscope.
Materials Required
Ice cream spoon, methylene blue, dropper, slides, cover slip, microscope, tissue
paper
Procedure
Step 1
Divide the students into 5 groups and ask one person from each group to
wash/rinse his/her mouth before the activity. He/she will be the donor of cheek
cells
Step 2
Gently scrap the inner surface of the cheek with one end of the ice cream stick or
ice cream spoon.
Do not use tooth pick.
Step 3
Transfer the scraping collected on to a clean slide and add a drop of methylene
blue stain over it.
Step 4
Place the coverslip using the needle.
Make sure that there are no air bubbles. (Remove the excess stain using tissue
paper)
Step 5
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Place the slide on the stage of microscope and observe first under low power
objective lens and then switch to high power objective lens.
Step 6
Draw the figure of your observations.
Is the outer covering of onion peel cells and these cells are similar?
Observation
Inference
The cheek cells are roughly polygonal. These are called as buccal mucosa cells.
The boundary of a cheek cells is the cell membrane. This gives a shape to the cell
and selectively allows substances to pass through it. In the case of onion peel, the
outer covering is clearer than in the cheek cells because there is another layer
present over the cell membrane, called cell wall. This gives rigidity to the cell.
Both the cells have dense round body called nucleus. In cheek cells, nucleus is
present more or less at the center of the cell. Whereas in the onion cells it is
scattered. The jelly like substance between the nucleus and the cell membrane is
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called the cytoplasm, which contains several structures called cell organelles,
which carry out major functions within the cell.
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2.3 PLANT CELL AND ANIMAL CELL
Aim
To study the similarities and differences between plant and animal cells
Materials Required
Plant cell model, animal cell model, onion cells chart, buccal cells chart.
Procedure
Step 1
Ask the students to compare the slides/observation of animal and plant cells and
list out the similarities and differences.
Step 2
With help of animal cell model and plant cell model, explain the various cell
organelles present in the plant and animal cell.
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Inference
Animal cell and plant cell are different yet share some common features.
Similarities

A basic similarity is the cell organelles, many organelles are found in both
types of cells.

They are both Eukaryotic cells.

Many of the organelles serve for the same purpose.

Both divide to create new cells
Differences

Even though most of the parts are the same, not all are.

The shape of the cell is different, a plant cell is rectangular, and an animal
cell is roughly spherical.

Only the plant cell performs the process of photosynthesis.

Only a plant cell has a cell wall.

Even though both have a vacuole, the vacuole in a plant cell is much larger,
it can take up to 90% of the space in the cell. Still, the vacuole serves for the
same purpose.
Cell organelles
Cell wall
 Most commonly found in plant cells
 Keeps cell turgid
 Extracellular structure surrounding plasma membrane
Plasma membrane
 Outer membrane of cell that controls cellular traffic
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 Contains proteins that move through the membrane and allows the passage
of materials
Nucleus
 One or more per cell
 Spherical shape
 Denser than surrounding cytoplasm
Nuclear membrane
 Surrounds nucleus
 Composed of two layers
 Numerous openings for nuclear traffic
Nucleolus
 Spherical shape
 Visible when cell is not dividing
Chromosomes
 Usually in the form of chromatin
 Composed of DNA and contains genetic information
 Number specific (species - i.e. 23 pairs for human)
Cytoplasm
 Collective term for Cytosol and contains organelles
 Colloidal suspension
 Cytosol mainly composed of water with free-floating molecules
Endoplasmic reticulum
 Tubular network attached to the nuclear membrane
 Runs through cytoplasm onto cell membrane
 Stores, separates, and serves as cell's transport system
 Rough type: ribosomes embedded in surface
 Smooth type: lacks ribosomes
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Golgi apparatus
 Protein 'packaging plant'
 A membrane structure found near nucleus
 Composed of numerous layers forming a sac
Lysosome
 Digestive 'plant' for proteins, lipids, and carbohydrates
 Transports undigested material to cell membrane for removal
 Vary in shape depending on process being carried out
 Generally referred as suicidal bag of cell.
Mitochondria
 Second largest organelle
 Double-layered outer membrane with inner folds called cristae
 Energy-producing reactions take place on cristae
 Controls level of water and other materials in cell
 Recycles and decomposes proteins, fats, and carbohydrates, and forms urea
Ribosomes
 Each cell contains hundreds of ribosomes
 Miniature 'protein factories'
 Composes 25% of cell's mass
Vacuoles
 Membrane-bound sacs for storage
 Contains water solution
 Contractile vacuoles for water removal (in unicellular organisms)
Chloroplasts
 A plastid usually found in plant cells
 Contain green chlorophyll where photosynthesis takes place
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2.4 OBSERVING HYDRILLA LEAF
Aim
To observe Hydrilla leaf under microscope
Materials Required
Fresh and healthy Hydrilla twigs, forceps, slides, cover slip and microscope
Procedure
Step 1
Take a fresh and healthy hydrilla leaf and place it on the slide.
Step 2
Place the coverslip using the needle, make sure that there are no air bubbles.
(Remove the excess stain using tissue/blotting paper)
Step 3
Place the slide on the stage of microscope and observe first under low power
objective lens and then switch to high power objective lens.
Step 6
Draw the figures of your observation.
Observation
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Inference
Hydrilla leaf shows closely packed rectangular cells. The cells show green colour
dots, which are chloroplasts, containing chlorophyll. These are the chief centers for
photosynthesis.
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2.5 OBSERVING STARCH GRANULES IN POTATO
Aim
To observe the starch granules in potato
Materials Required
Potato, cutter/spoon, slide, needle, iodine solution, dropper, cover slip, tissue
paper, microscope
Procedure
Step 1
Take a piece of potato and scrape it with the help of spoon/cutter and transfer the
scrapping on to a clean slide
Step 2
Place the coverslip with the help of needle and observe under microscope.
What do you observe?
Step 3
Scrape the potato again and transfer to a fresh slide, now add a drop of dilute
iodine solution.
Step 4
Observe the slide under microscope. Do not put the coverslip,
Step 5
After observing the blue spots, add 2 drops of saliva on to the scrapings.
Step 6
Now place a coverslip and observe under microscope.
Can you make out any difference?
Observation
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Inference
The scrapping shows starch granules (bead like structures). On adding iodine, these
starch granules turns into blue spots/dots forming starch-iodine complex.
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On adding saliva the blue spots/dots disappear because our saliva contains an
enzyme called salivary amylase (or ptyalin) which breaks the starch molecules into
simpler molecules like (dextrins and maltoses).
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2.6 OBSERVING THE INTERNAL STRUCTURE OF FEATHER
Aim
To observe the internal structure of feather
Materials Required
Feather of birds, slide, needle, cover slip, microscope
Procedure
Step 1
Collect the feathers of birds (hen, pigeon, crow)
Step 2
Place the feather as such on the slide and observe under the microscope.
What do you observe?
Move the slide and observe the complete feather.
Step 3
Draw your observations.
Step 4
Similarly collect the wings of some insects and observe
Observation
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Inference
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Typical wing feather consists of a central, stiff shaft with the softer vanes on each
side. The central shaft of a feather is divided into two regions. The calamus is the
part of the shaft closest to the bird's body. It is hollow and does not contain any
vanes. The distal end of the central shaft is referred to as the rachis. The rachis is
solid and is defined as the area to which vanes are attached.
Vanes:
The vanes extend from each side of the feather. A series of parallel branches called
barbs make up the vane. Extending from the barbs are a series of short branchlets
called barbules.
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3.1 MERISTAMATIC TISSUES
Aim
To observe and study the meristamatic tissue in onion
(This activity requires about 5 to 6 days for the results, plan accordingly and make
it ready during your session)
Materials Required
Conical flasks/gas jars, onions, cutter
Procedure
Step 1
Take two conical flasks or transparent jars and label them 1 and 2. Fill the conical
flasks (or jars) with water up to the brim.
Step 2
Take two similar sized onions, (the onions should be slightly bigger than the mouth
of conical flasks/jars) cut the base as shown in the figure.
Step 3
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Place one onion in each conical flask (or jar) in such a way that the onion base
touches the water in the conical flask(jar).
Step 4
Keep the set up undisturbed for 2 days and observe on 3 rd day. You will white
roots in both the onions.
Step 5
After prominent roots are observed, take out the onion in
conical flask 2, cut the root tips by about 1 cm and place the
onion with left out roots back in to the conical flask (jar).
Step 6
Observe the growth in the two conical flasks day by day.
Take care that enough water is present in the conical flasks
and roots are submerged well in water.
What so you observe?
Observation
White coloured roots developed in the both the onions, the roots continued growth
day by day.
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The growth stopped in conical flask 2 after cutting the root tips.
Inference
The growth in the plants occurs only in certain specific regions. This is because the
dividing tissue called as meristamatic tissue is located in these regions. Cells of the
meristamatic tissue divide continuously and help in increasing the length and girth
of the plant.
The tips of the roots (and stems) contain these meristamatic cells (cells of
meristamatic tissue) which actively divide and grow (can be seen by increase in
length). When the root tips are removed, the growth is stopped as these cells are
lost.
Depending on the region where they are present, meristamatic tissue are classified
as
1. Apical meristems: these are present at the growing tips of stems and roots and
increase the length of stem and root.
2. Intercalary meristems: these are located at the base of the leaves or internodes
(on either side of nodes) on twigs.
3. Lateral meristems: these are found beneath the bark and cause increase in
thickness (or diameter of organs like stem, root) 2
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3.2 PERMANENT TISSUES
Aim
To study the permanent tissues of a plant through a transverse section of stem
Materials Required
Fresh material of monocot (maize) stem, dicot (sunflower stem, potato, watch
glass, new blade, slides, coverslips, petridish, saffranine, brush, needle and blotting
paper
Procedure
Step 1
Take a 2-3 cm long piece of sunflower stem and place it between potato pieces and
hold it horizontally between thumb and first finger of your left hand.
Any stem can be used, but the stem should be soft, tender and thin.
Step 2
Hold the blade in your right hand, dip it in the water
Step 3
Cut the sections of the material quickly and transfer the sections in watch glass
containing water.
Step 4
Select a thin uniform and complete section and place it in a drop of water on a
glass slide.
Step 6
Cover the section with coverslip and observe it under microscope.
Step 7
Draw your observations.
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Step 8
Repeat the activity for the monocot stems like grass stems
Observation
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Inference
In the transverse section of stem, we can see all the 7 (epidermal, collenchymas,
parenchyma, parenchyma, sclerenchyma, xylem, phloem, and cambium) types of
cells. All these cells perform different functions.
Simple permanent tissues
1. Parenchyma
Parenchyma is the widely distributed tissue in the plant body. It is made up of
unspecialized cells which are similar in structure and function. Parenchyma
tissue is found in the cortex, pith, and ground tissue, mesophyll tissue of leaves
and also in vascular bundles.
2. Collenchyma
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Collenchymas being a strong and flexible tissue, it is a mechanical tissue of the
growing organs. It is found in the peripheral regions of stems and leaves.
3. Sclerenchyma
Like collenchyma, sclerenchyma is also a strengthen and mechanical tissue. It is
simple tissue, composed of dead cells.
Complex permanent tissues
1. Xylem
Xylem is a complex tissue consisting of both parenchymatous and
sclerenchymatous cells. Hence it consists of living and non living cells. In roots,
stems, leaves of higher plants, xylem and phloem usually occur together
forming vascular bundles. Main function of xylem is conduction of water.
2. Phloem
Like xylem, phloem also consists of parenchymatous and sclerenchymatous
cells. Main function is to conduct food materials from the leaves to the other
regions of plants and also to storage organs.
Protective tissues
1. Epidermis
It is present as the outermost layer of the plant body, in the roots, stem, leaves,
flowers and fruits. It is usually one cell thick and covered with a waterproof
coating or layer called cuticle.
2. Cork
In old roots and stems the epidermal tissue at the periphery is replaced by cork.
The cork cells are dead and lack intercellular spaces. The walls of cork cells are
heavily thick and impermeable to water and gases.
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