lab in a box 1 microscope and cell -...

L A B I N A B O X – B O X 1

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Lab in a Box 1

MICROSCOPE

AND

CELL


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Inventory

S.No Materials Quantity

Glassware 1. Beakers – glass, 500 ml 2

2. Cover slips 1 box

3. Microscopic slides 1 box

4. Petridish - plastic 2

5. Watch glass 5

Equipment/Material

6. Microscope 1

7. Forceps 5

8. Painting brush (small) 5

Chemicals and Reagents

9. Iodine solution 1

10. Methylene blue 1

11. Saffranine 1

Charts

12. Onion cell chart 1

13. Buccal cells chart 1

14. Internal structure of feather chart 1

15. Internal structure of hydrilla leaf 1

16. Starch granules in potato chart 1

17. Internal structure of Dicot stem 1

18. Internal structure of Monocot stem 1

Models

19. Animal cell model 1

20. Plant cell model 1

Consumables

21. Onion 1

22. Blades 1 pack

23. Ice cream sticks/spoons 1 pack

24. Needles 2

25. Cutters 2

26. Tissue papers 1 pack


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CONTENTS

Sl. No.

Topic

Experiment/ Activity

Page

1 `Microscope Parts of Microscope 4

1.1 Working of Microscope 7

1.2 Using and handling of Microscope 8

2.1 Cell 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

3.1 Plant tissues Meristamatic tissues 27

3.2 Permanent tissues 30


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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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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



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 3rd

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.

lab in a box 1 microscope and cell -...

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