Exam (elaborations) Biology Notes(The Fundamental Unit980

to destroy almost all the structures in the cell but didn’t damage it. This puzzle was solved when lysosomes were discovered as tiny particles visible in the cytoplasm. It was found that they contained the destructive enzymes. These enzymes normally do not come in contact with the rest of the cell. The materials that need to be destroyed are transported to the lysosomes. Then the lysosomes get them digested at times, the lysosomes burst and the enzymes are released to digest the cell. Hence, lysosomes are also known as the suicidal bags of the cell. Mitochondria Activity -2 Observing Mitochondria Let us do this activity with onion peel. i) Make a fresh solution of Janus Green-B in a Beaker ii) Mix 200mg Janus Green-B in 100ml of water iii) Take a watch glass pour some solution. Put the onion peel in this solution and keep it for about half an hour. iv) Keep a piece of onion peel on the slide and wash thoroughly with water. v) Cover the slide with a cover slip and observe it under micro-scope at high magnification. Observe and make a sketch of the same in your note book. Compare it with the given diagram. You can do this activity by taking other available material like leaves of Cassia tora or Cheek cells. You may have observed green oval (or) cylindrical grains scattered in the cytoplasm. These are the mitochondria. Fig-8(a) Mitochondria in onion peel cell Mitochondria are small, spherical or cylindrical organelles. Generally a mitochondrion is 2-8 micron long and about 0.5 micron wide. It is about 150 times smaller than the nucleus. There are about 100-150 mitochondria in each cell. When seen under the compound microscope, the mitochondria appear as oval or cylindrical dots in the cell. The diagram of mitocondria shown in typical cell is hypothetical. Electron microscope reveals their unique internal structure in great detail. Information derived from the electron microscope tells us that the mitochondria are made up of a double-membrane wall. The inner membrane of the wall protrudes into the interior in folds and forms structures called cristae; the space between cristae is known as the matrix. Mitochondria are responsible for cellular respiration, a process through which the cell derives its energy to do work. Because of this, mitochondria are also known as the powerhouses of the cell. Matrix SCERT ii) Mix 200mg Janus Green-B in 100ml ake a watch glass pour some solution. Put the onion peel in this solution and keep it for about half an hour. iv) Keep a piece of onion peel on the slide and wash thoroughly with water. v) Cover the slide with a cover slip and observe it under micro-scope at high magnification. Observe and make a sketch of the same in your note book. TELANGANA Cristae Fig-8(b) L.S. of Mitochondria Let us do this activity with onion peel. i) Make a fresh solution of Janus ii) Mix 200mg Janus Green-B in 100ml You can do this activity by taking other Cassia tora You may have observed green oval (or) cylindrical grains scattered in the cytoplasm. These are the mitochondria. Mitochondria are small, spherical or cylindrical organelles. Generally a mitochondrion is 2-8 micron long and about 0.5 micron wide. It is about 150 times Matrix 8 Cell its structure and functions Ribosomes There are small granule like structures in the cytoplasm of the cell. They are called ribosomes. They are formed of RNA protiens. They are two types. Free ribosomes are scattered in cytoplasm. Attached ribosomes are on the surface of rough endoplasmic reticulum. Ribosomes are the sites for protein synthesis. Plastids Activity - 3 Observation of chloroplast in Rheo leaf 1. Take the peel of Rheo leaf and mount it in the water drop on a slide. 2. Observe it under compound microscope. Let us make a drawing of the observations. You will observe small green granules called chloroplast. They mainly contain green substance called chlorophyll. Activity-4 Observing chloroplast in algae Collect some algae from pond and separate out thin filaments of them. Place a few filaments on a slide. Observe it under the microscope. Take the help of given figure and draw the picture of chloroplast that you have observed under the microscope. Chloroplast is a type of plastids in green colour. Plastids are present only in plant cells. Plastids are mainly of three types: (i) chromoplasts (coloured) (ii) leucoplasts (colourless) and (iii) chloroplasts (green coloured). Fig-9(a) Fig-9(b) Chloroplasts in Algae Chloroplasts are of different shapes i.e. disc, oval etc. In algae, these can be found as ladders or star or spirally coiled or reticulate structures. The diameter of chloroplasts in higher plants can vary between 4 to 10 micron. The primary function of chloroplasts is to trap the energy from sunlight and transform it to chemical energy, thus helping to carry out photosynthesis. Vacuole Activity-5 Observing vacuoles 1. Take the leaf or stem of any succulent plant (like the torch cactus). 2. Take thin cross section of stem of cactus in a watch glass containing water. Fig-9(c) : Structure of chloroplast Lumen Granum Thylakoids Stroma Inner Membrane Outer Membrane Do you know? Certain organelles are present in large number in the cell for example cells involved in photosynthesis may contain around 50 to 200 chloroplasts. SCERT green substance called chlorophyll. Activity-4 Observing chloroplast in algae Collect some algae from pond and separate out thin filaments of them. Place a few filaments on a slide. Observe it under the microscope. Take the help of given figure and draw the picture of chloroplast Fig-9(a) TELANGANA Let us make a drawing of the that you have observed under the Chloroplast is a type of plastids in green colour. Plastids are present only in plant cells. Plastids are mainly of three types: (i) chromoplasts (coloured) (ii) leucoplasts (colourless) and (iii) chloroplasts (green coloured). Chloroplasts are of different shapes i.e. disc, oval etc. In algae, these can be found as ladders or star or spirally coiled or reticulate structures. The diameter of chloroplasts in higher plants can vary between 4 to 10 micron. The primary Fig-9(c) : Structure of chloroplast Granum Stroma Inner Membrane Free distribution by T.S. Government 2019-20 9 3. Stain it with dilute safranine solution. 4. Observe the section under low and high power microscope. What do you observe? The large empty spaces present in the cell are vacuoles. These are fluid-filled saclike structures. In animal cells vacuoles are small in size while in plant cells they are large. In mature plant cells they might occupy almost the entire cell space. Vacuoles maintain turgur pressure within the cell. They export unwanted substances from the cell. Are cells flat? Usually when cells are seen under the microscope, the image appears as flat and two-dimensional. It seems that all the organelles in the cell are situated in one plane. In reality, cells have length, breadth and thickness. We can easily see the length and breadth. Since we cannot see the thickness of the cells under the microscope, we tend to think that these are flat objects. However, there are a few easy ways to observe the thickness of the cells. The easiest method is to slightly change the focus while viewing plant cells on the slide and look at the cell wall. You’ll find that you are able to see the thickness of the wall. This threedimensional image becomes clear if you reduce the intensity of light as well. Each cell thus acquires its structure and ability to function because of the organization of its membrane and organelles in a specific way. Where do cells come from? The observations so far made it clear that all living beings are made up of cells and that each cell has a nucleus. Around 1838-39, two scientists expressed this in the form of a theory. The scientists were Matthias Jakob Schleiden () and Theodor Schwann (). Schleiden was a Botanist while Schwann was a Zoologist. For the record, it should be mentioned that quite a few scientists had recognized by that time that cells were present in all living organisms and were expressing it in their own ways. However, Schleiden and Schwann were the first to claim that this fact was true for the entire plant and animal kingdom. In other words, they took the first bold step of generalizing from observations and coming up with a theory which was applicable to all living organisms. And because of this, the credit for propounding the cell theory goes to them. What is noteworthy is that there was a gap of about 200 years between Robert Hooke first observing cells and the formulation of the cell theory. Schleiden and Schwann together formulated the cell theory. This theory however did not explain as to how the new cells were formed. Rudolf Carl Virchow