नमस्कार मित्रांनो इयत्ता अकरावी Biology या Subject च्या Practical मध्ये PART - A: Experiments to be performed हा भाग Practical Exam च्या दृष्टीने फार महत्त्वाचा आहे. या Blog Post मध्ये आपण Practical Number 2: To Observe Mitochondria in Onion Peel Cells ह्या Practical Experiment चे Answer पाहणार आहोत. खाली दिलेल्या उत्तरांमध्ये काही अडचण असल्यास आम्हाला comment करा किंवा तुमच्या संबंधीत विषय शिक्षकांशी चर्चा करा.
A. EXPERIMENTS TO BE PERFORMED
2. To Observe Mitochondria in Onion Peel Cells.
Introduction :-
You are aware that Mitochondria provides energy in the packaged form, i.e., ATP.
Each cell contains a large number of mitochondria and they can be observed under a light microscope if stained with Janus green B. This stain is bluish green in colour when oxidized. It appears colourless when reduced. When a dilute solution of the stain is applied to the cells, it enters the cytoplasm as well as mitochondria. Mitochondrial inner membrane contains cytochrome oxidase enzymes. It can keep the stain in an oxidized state. Thus mitochondria appear stained while the rest of the cytoplasm appears colourless.
Aim :- To observe mitochondria in onion peel cells.
Requirements :- Slide, cover slip, 0.01% Janus green B stain, fresh onion bulbs, etc.
Procedure :-
1. Tear a fleshy leaf of onion and collect a piece of the peel.
2. Spread the peel carefully on a slide.
3. Put a few drops of Janus green B stain on the peel. Allow it to stain for 5-10 min
4. Wash the extra stain with the help of distilled water. Be careful so that the entire stain doesn't get washed off.
5. Mount the cells in a drop of distilled water.
6. Use a coverslip to cover the peel. Observe the slide under high power of a compound microscope.
The cells can alternatively be mounted in the stain itself. A few air bubbles remaining inside the cover glass give a background stain that makes the viewing easy.
Activity : Label the diagram.
Observation :-
1. Mitochondria appear like bluish coloured spherical or rod shaped structures present in the cytoplasm.
2. Mitochondrion can be easily distinguished from a bacterium as Bacterial cells become more prominently stained and appear sharper than mitochondria.
3. Also as bacteria are on the surface of cells, they will be focused at a slightly different level than mitochondria and can be distinguished.
4. Note your own observation of the slide.
1. The cells appear large and rectangular, tightly interlocking with one another.
2. Distinct cell walls clearly define and surround each cell.
3. A darkly stained nucleus is visible within the cells.
4. Large central vacuoles are prominent in the middle of the cells.
5. Small granules, possibly representing cellular components, can be seen dispersed within the cytoplasm.
Questions
1. Describe the ultrastructure of Mitochondria.
Ans :- Mitochondria have a double membrane structure, consisting of an outer and an inner membrane. Both membranes are composed of phospholipid bilayers, similar to the cell's outer membrane.
The outer membrane encloses the entire mitochondrion, while the inner membrane is folded into structures called cristae. These folds significantly increase the surface area, which is crucial because the inner membrane contains the proteins responsible for the electron transport chain.
Additionally, many other chemical reactions essential for mitochondrial function take place here. The expanded surface area allows for more reactions and increases the mitochondrion's overall efficiency. The space between the outer and inner membranes is known as the intermembrane space, while the area enclosed by the inner membrane is called the matrix.
2. Why thin peel of onion placed in a watch glass containing water?
Ans :- The thin onion peel is placed in a watch glass containing water to keep it from folding and to prevent it from drying out.
3. What is the role of Janus green B stain in this slide preparation.
Ans :- Janus Green B is used as a mitochondrial stain in slide preparation. It acts as an indicator, changing color in the presence of oxygen. When oxidized, it turns blue, while in the absence of oxygen, it shifts to pink. This stain specifically highlights the mitochondria in living cells and can also help reveal any changes occurring in them.
Multiple Choice Questions
1. Which of the following cells will show the maximum number of mitochondria?
a. Skeletal muscle fibres
b. Monocyte
c. Hepatocytes
d. Adipocytes
Ans :- c. Hepatocytes
2. In order to prevent formation of lactic acid, pyruvic acid should enter in
a. Mitochondrial matrix
b. Outer chamber of mitochondria
c. Crista
d. Oxysome
Ans :- a. Mitochondrial matrix
3. To observe cells in an onion peel, we use.....
a. Fruit
b. Stem
c. Leaf
d. Flower
Ans :- b. Stem
4. The less stained central part of onion peel cell is
a. Nucleus
b. Cytoplasm
c. Vacuole
d. Cell wall
Ans :- b. Cytoplasm
5. For observation of onion pea cells are first seen under.....magnification.
a. 10X × 10X
b. 10X x 45X
c. 10X x 40X
d. 10X x 100X
Ans :- a. 10X × 10X
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