 Now, we are going to talk about the cells organelles, different types of organelles present inside the cell. What are organelles? Organelles are subcellular structures. For example, the mitochondria as we have seen in the previous diagram, the ribosomes which makes proteins, the lysosomes, vacuoles, so on, we look at them one by one. First of all the nucleus, nucleus is very important part of the cell. It has the heredity of the genetic material in the form of chromosomes. Nucleus is present usually for example in animal cells in the center, but in plant cells the nucleus is not present in the center because particularly the mature plant cells have a very large vacuole present in the center. Due to that nucleus is moved towards a side. So in plant cells nucleus is present towards the site, towards the site and in animal cells mostly it is present inside the center. Nucleus, the structure of the nucleus if we talk about it, it have a nuclear membrane, it have nucleoplasm and it have a small structure called nucleolus and in the nucleoplasm it have the chromatin material, the heredity material, the DNA, deoxyne ribonucleic acid. Now look at the diagram of the nucleus. If you look at the diagram you can see an external membrane. This membrane is called the nuclear membrane. After the nuclear membrane a fluid is present that is called the nucleoplasm. Nucleoplasm of the nucleus plasm the fluid. This nucleoplasm have chromatin material inside. You can see a darkly stained body in inside which is called nucleolus. This is a site where ribosomal RNA is produced. If you observe the nuclear membrane you will find out that there are pores present on the nuclear membrane. These are called nuclear pores. As we know that the nucleus have to exchange materials with the cytoplasm of the cell. These pores are for that transport of materials. For example, if the messenger RNA is produced inside the nucleus it have to be transported out. It will go out through the nuclear pores. Now we talk about the next organelle the ribosome. Ribosomes as you can see in the diagram these are the organelles which makes proteins. These consist of two subunits one large one small. These can read the messenger RNA which is made by the DNA the heredity material and they make proteins after reading this particular material. They are present in the cytoplasm free or attached to the endoplasmic reticular. There are large number of ribosomes present inside the cell. Few cells which are metabolically more active they may have more ribosomes. Few cells which are metabolically less active they may have less number of ribosomes. And the eukaryotic ribosomes are slightly larger than the prokaryotic ones. Next comes the mitochondria. Mitochondria are the organelles which are called the power house of the cell. It produces energy required by the cell in the form of ATP. ATP is a molecule adenosine tri phosphate which have high energy bonding in its side. When it breaks it releases lots of energy in the chemical forms that cells can use for performing their different functions. Mitochondria are double membrane organelles they have a double membrane on their surface. The outer membrane is comparatively simple membrane, a straight membrane and the inner membrane is highly folded. Its folds are called Christie. These membranes are filled with a fluid called the matrix. In this matrix they have enzymes, mitochondria have their own DNA and they perform their many of the functions with the help of their matrix and their inner membrane. The outer membrane is less specific, the inner membrane is more specific and highly organized. Here in the diagram you can see a mitochondrion. Mitochondria is plural, mitochondrion is singular. In the diagram you can see the outer membrane less folded, straight, the inner membrane actually not folded, straight. The inner membrane highly folded have Christie in a matrix inside. On the left you can see an image picture taken through the electron microscope. In this picture you can see a mitochondria in a grayish color. The next organelles these are found only in plants, plastids. Plastids are another type of organelles which produces energy and they produces also carbohydrates. They have another property that they produces carbohydrates. These are also double membrane bound. They also have an outer membrane just like mitochondria which is straight or smooth and an inner membrane which consists of highly folded and organized structures called thylakoids. Plastids are present only in plants. They have specific pigments which can absorb sunlight and produce energy for them in form of ATP and they also can convert inorganic carbon into the organic carbon that is they convert carbon dioxide by series of reactions into the carbohydrates and these are the carbohydrates which are source of stored energy for all living organisms on earth. These plastids are of three types chloroplast, chromoplast and leucoplast. Chloroplasts are green in color, they have a green pigment and these are the organelles which are responsible for the energy production and the carbohydrate production in the plants. We call them photosynthesis in the Kelvin cycle. They produce photosynthesis, they do photosynthesis and they produces energy and carbohydrates. The chromoplasts are other types of plastids which are present in the flowers and the fruits. We observe different beautiful colors of flowers and fruits. These colors are due to the presence of the chromoplasts. Chromoplasts may be yellow, may be red, may be say more darker in color or in different shades. There are third types of plastids called leucoplasts. These are present usually in the roots and in the tubers. These plastids store different types of materials for the plants. For example, protein, leucoplasts have their types. For example, there are proteanoplasts that saves protein. There are other plastids which saves starch like amyloplasts and the others. They also have a double membrane and external is a smooth one, internal is a folded one. Then comes the next organelle, the endoplasmic reticulum. I would say endoplasmic, present inside the plasma, reticulum and network. These are a network of interconnected channels. These are present in various parts of cells, particularly surrounding the nucleus. The endoplasmic reticulum is of two types, rough endoplasmic reticulum and the smooth endoplasmic reticulum. The rough endoplasmic reticulum is called rough because on its surface ribosomes are attached and they appear as granules. So it gives a granulated appearance, we call it rough endoplasmic reticulum. Other is called smooth, don't have a ribosomes attached to its surface. You can observe these in a diagram. In this diagram, you can see on one side of the nucleus, there are rough endoplasmic reticula present. On the right, you can see the same thing in an electron microscope image. What is the function of the endoplasmic reticula? Basically ribosomes makes proteins. These proteins enter inside the endoplasmic reticulum. Inside these reticulum, there are lot many types of enzymes and these enzymes modify these proteins and convert them into their final shapes. So endoplasmic reticulum has very important role in the modifications of proteins from their basic structure into their final structure. And this role is very important because if one protein, even one protein is not formed correctly, the result will be loss of its function and loss of function may result towards various diseases. Now we talk about the next Golgi apparatus. Also sometimes called Golgi complex. Golgi apparatus, we call it Golgi apparatus because it was discovered by the Camillo Golgi scientist. This is also called the post office of the cell. When proteins are produced, they are modified by endoplasmic reticular enzymes. Then they go outside towards the Golgi complex, the Golgi apparatus. The purpose of the Golgi apparatus is to pack these proteins and send them to the appropriate place where they are required. Some proteins are secreted outside. Golgi complex pack them into small vesicles. We can say fluid with packs, which are called secretory vesicles. Some other proteins are packed for sending towards inside of the cell. So Golgi apparatus is the post office of the cell. As in the diagram you can see it consists of various flet and disks and these disks as the diagram shows is releasing different types of vesicle towards various parts of cells. As you can see few vesicles are going down, few are going up. It means they are going in different directions as required by the cell. This is associated with endoplasmic reticulum because it have to get the materials, the proteins prepared by endoplasmic reticulum or maybe lipids produced by other type of endoplasmic reticulum, the smooth one and then pack them and send them different parts of the cell or maybe outside. Next is called centrioles. These are the next organelles. These are present inside the cell near to the nucleus, they are hollow and cylindrical bodies. Two are present near to the nucleus collectively called centromere. Their function is during cell division, when cell divides these centrioles move towards the sides of the nucleus and make the spindle fibers. These are present in animal cells, then comes the vacuoles. Vacuoles are also fluid filled single membrane bound organelles. These are present in different forms for example the food vacuoles or the contractile vacuole and their major function is storage of different types of materials. For example, some proteins, sometimes cell is producing some waste material and they have to preserve that waste material for some time and then remove it towards outside. The food vacuoles particularly in the unicellular organisms like amoeba, when they get a food material they invaginate it and convert it into a vacuole. Then this food is digested. So vacuoles are also very important in the cells. In animal cells there are many small vacuoles, in plant cells there is in particularly mature plant cells there is a single large vacuole which is produced by joining of various small vacuoles. Another organelles that are called lysosomes. Lysosomes are membrane fluid filled sacs. They have different types of enzymes inside. They are called the organelles for garbage disposal. Whenever anything is produced in the cell it have to be broken down. When it is broken down it have to be placed in some time in a particular organelle usually vacuoles do so. Lysosomes have enzymes. They fuse with the vacuoles which have those waste materials and pour their enzymes inside those vacuoles and those enzymes break down those waste materials and convert them into less harmful products for the cell and then they are released out. So lysosomes are the disposal system of cell. Their function is to dispose of various materials which are harmful for the cell. These material may include the bacteria or viruses which invaded the cell and need to be digested.