 So, cellular biology without light is better without voice. So, we are getting to the grand finale of the preparatory school and the final act is introduction. Not so good, not so good. Very good. Introduction to cellular biology by Prof. Indrana Ashram. Thank you. If you have presented me eventually. So, we will do a brief introduction of cellular biology and I will look for the help with those people who have done degree in engineering, genetic engineering and so. A brief introduction what is a living organisms? Two kinds of living cells which is prokaryotes and eukaryotes. The basis of cell, basic components of cell, its nucleus, these structures, specified structures are called organelles and then cell nucleus. Then I will give a brief introduction of DNA structure and its function. Then we will do the final bit of what is a protein because I thought that we might need this for a green fluorescence protein because protein is a part of cell. So, millions of different types of organism on earth has at least one thing in common. What is that? That they are made of cell. Cell is the smallest and the basic unit of life that is classified as the living. Cell is an independent entity capable of creating copies of itself by growing and dividing into two daughter cells. So, it provides structure for the body taking to nutrients from food, converted into energy and can do or can perform specialized function. If a cell is a part of your nerve system or brain or heart, so they are specified to do things related to that part of the body. So, each cell store its own set of instruction for carry out each of these activities. Cell are very small. For example, a bacterium which is consist of a single cell has a diameter of one micron. But there are cell which are very heavy like an ostrich egg is the largest cell which is whose weight is almost 2 pound or at some places they say that it is 3 pound and longest cell is the human nerve cell which is around 2 meter. So, we human are made of trillions of cells and there are smaller pieces of cell that include organelles. So, like we know that in a molecule or in an atom, atom is consist of nucleus and electrons are beating around that molecule is consist of different kinds of atoms and group of atoms. Similarly, the cell is not is the basic unit, but it consist of small structures, specified structures which are called organelles. There are two main types of cell we encounter with in life. One is called animal like cell, the other is called the plant like cell. So, animal cell can be a skin cell, it can be a muscle cell, it can be a fat cell and this is a nerve cell. So, they are a tiny microorganism to a nerve cell in a human brain. Humans may have hundreds of different types of cells like I mentioned before and some some cells are used to carry out oxygen through the bloods and these are called red blood cells and the others might be specific to heart or your brain or these things. So, animal cell can be a small organism that we will see in a minute. So, the plant like cells are they you easily identify them because they have a protective layer outside which is called cell wall or it is made of cellulose. And then they contain organelles like the chloroplast and very large water filled vacuoles, we will see that plant has big vacuoles and the animal cell have very tiny vacuoles. So, living they can say that life started almost 4 billion years ago. The first living things is the bacteria around 3.5 billion years ago and we divide living organism in two classes. One is prokaryotes the other one is eukaryotes. So, prokaryotes are usually independent and unicellular and the what is the main difference between prokaryotes and eukaryotes is that prokaryotes does not have this nucleus and eukaryotes are complex multicellular organisms. We animals plants and fungi are part of eukaryotes. They also include unicellular organisms such as yeast and amoeba. Sorry prokaryotes does not have a nucleus, but eukaryotes have nucleus. So, these are the simplest and the first type of organism to evolve on earth about 4 billion years ago contains organisms whose cell do not contain a nucleus it does not have a nucleus lack most of the intracellular organelles and structures, but an important exception is ribosome. We will see what ribosome does in a minute. So, most function of organelles such as mitochondria, chloroplast and Golgi operators are taken over by prokaryotes plasma membrane. Plasma membrane is the outer shelling of that prokaryotes cell. So, then I will give you I will show you this instead of reading that this is a bacteria which is a unicellular organism without any nucleus. It is an example of prokaryotes it is consist of this is a cell wall it is a capsule like then it has some the inner part of this cell is called cytoplasm then it has a big phlegm by with the help of that it moves around and it has a DNA, but not inside the nucleus it is just in the cytoplasm this DNA is present there then they it has a plasma membrane which carry out most of the things of this such as are taken over by the prokaryotes plasma membrane. So, it instead of those organelles it use its plasma membrane to perform many functions. So, this was the example of a prokaryotes cell. Then we have there are different kinds of eukaryotes organism there are animals plants fungi and protests. So, animal and plants are the most familiar eukaryotes cells and fungi and protests have many substantial differences. The cell of eukaryotes organisms are complex and contain a nucleus and other membrane bounded structures. Different cell cells in a eukaryote organism like human look and function differently like I showed you this cartoon. So, where is that animal like. So, these all look and function differently cells from the red blood cell epithelial cell they all work and look differently. So, fungi is a decomposer of dead animals and plant matter it breaks dead organic matters simple into simple compounds that can be absorbed by a plant around it. During this fungi returns carbon dioxide into the atmosphere. So, green plants use the carbon dioxide during photosynthesis to produce food. So, oxygen is released into the atmosphere during the process of photosynthesis. So, animal and human life depends on fungi for survival because it decomposes it produce carbon dioxide which is used by the plants to and they convert or they produce oxygen. So, we human needs oxygen. So, some fungi like mushrooms are used as ingredient and recipes. So, this is another example of unicellular eukaryote protester the ancestor of plants animal and fungi they may have been around as long as 2 billion years ago. It is an organism made of a single cell yet it can let it reproduce like other living things. So, one of the most fascinating protest is the amoeba I think when we start reading this biology this was the first example my teacher give me ok amoeba and the bacteria. So, these are the eukaryotes plant cells the plant cells have membrane I think I should go to the photo. So, this is a typical plant cell you can find many photos on the net I used of course it is not my field I took advantage of web and took some photos from there. So, it has a plasma membrane then it has Golgi operators we will see what is the Golgi operators then it has a mitochondria the chloroplast I already mentioned and then it has a vacuum which is quite heavy and if you water the plant it gets bigger and bigger and it gives the shape and structure to that plant cell. So, then it has some endoplasmic reticulum ribosomes and I will give the definition of these things. So, if you want to see the details that plants have membrane includes nuclei and organelles. Its chloroplast contains chlorophyll gives plants their green color enables them to use sunlight to convert water and carbon dioxide into sugars and carbohydrates during a process which is called photosynthesis. Vocule is a membrane bound sac plays role in intracellular digestion to release the cellular waste products and vocules tend to be large in plant cells typical is a 50 percent of cell yet it can take up to 95 percent of a cell. It is responsible for maintaining the shape and structure of the cell. You can see that this is quite big as it contains the whole almost 50 percent of this plant cell or if you are watering the plant it can take up to 95 percent of that plant cell. So, human cell each of the 100 trillion cell in human being is a living structure. So, they can survive for months or years provided the surrounding fluid contain appropriate nutrients. So, to understand the function of organs and other structure of the body. So, we need to understand the basic organization of the cell and its other different compounds the components and these kind of thing. So, typical cell has two major parts the nucleus and the cytoplasm. So, nucleus is separated from the cytoplasm by a nuclear membrane and cytoplasm is separated from the surrounding molecules and the fluid by a cell membrane which is called plasma membrane. So, the different substances that make up the cell are collectively called a protoplasm. So, it is composed of it has different kinds of nutrients like water, ions, proteins, lipid and carbohydrates. So, basically you can divide an animal cell into two parts. One is nucleus the other outer jelly like structure is called cytoplasm and all the organelles are in that cytoplasm. So, this is a kind of fluid which nutrient which is present in the protoplasm or in the cytoplasm. So, water is the principle fluid of the cell present in most cells except fat cell. Concentration of water is 75 to 85 percent many cellular chemicals are dissolved in water other are suspended in it has a solid particle. For example, fat has not been dissolved in water. So, it is suspended in that. So, then there are some ions that most important ion in cell is potassium, magnesium, phosphate, sulfate and bicarbonate. That helps to indigestion in respiratory systems and other kind of processes. So, smaller entities of sodium chloride and calcium are also present. These ions provide inorganic chemicals for cellular reactions. Then we have proteins and it is very important and after water the most abundant substance in most cells are proteins. They normally constitute 10 to 20 percent of a cell. We divide proteins into two types. One is the structural protein and the other one is the functional protein. The structural protein is the form of large filament make micro tubers that provide cytoskeleton. I will explain what is a cytoskeleton to the cellular organelles and functional proteins. Many the enzymes that cell use for different purposes and they can mobile in cell fluid catalyzed specific chemical reactions. So, then we have lipids. Lipids is usually grouped together because of their common property of being soluble in fat solvents. Only they are not soluble in water. So, important lipids is phospholipids and cholestrols constitute only 2 percent of total cell mass. Some cells contain lipid neutral fat that is almost 95 percent of fat cell. Then we have carbohydrates and this is the same ratio. So, carbohydrate is a form of glucose that is present in extracellular fluids and glycogen is another form of carbohydrates present in that. So, this is a kind of an example of an animal cell. It is this is the plasma membrane. Then we have endoplasmic recticulum. It is this kind of tubes. Then we have a nucleus ribosomes, lysosomes, mitochondria, Golgi operators. So, there are the basic is cell membrane, cytoplasm and cytoskeleton. Then we have different organelles which I will show you in the coming slides that the basic is the cell membrane. The first thing it is the outer lining of eukaryotic cells and it is called the plasma membrane. It separates and protects a cell from its surrounding environment. It is made of a double layer of proteins and lipids. You can see these are membrane protein and this is a cholesterol which is a lipid. So, then there are variety of molecules are embedded within it that act as a channel and pumps moving different molecules into and out of the cell. Like during the cell devion or during other processes they help cell to get into this different nutrients move into and out of this cell membrane. Then we have cytoplasm. It is the second part of this cell. This is this jelly like structure in which all other organelles are present. So, it holds the organelles in place within the cell. It contains dissolved nutrients, mainly protein, electrolytes and glucose. It helps to break down waste products. The nucleus flows with the cytoplasm changing its shape as it moves. So, the function of cytoplasm the organelles which reside in it are critical for a cell structure. So, this is the cytoskeleton because you can see that it helps to retain the shape of the cell to organize and maintain the cell. Shelf anchors organelles in place move parts of the cell in process of growth and mobility. The eukaryotic cytoskeleton is composed of micro filaments, intermediate filaments and microtubes. So, these are this is the plasma membrane. These are the filaments you can see. This is a micro tubulate. So, they give shape and to this eukaryotic cell. There is a great number of protein associated with them each controlling a cell structure by directing, bundling and aligning filaments. So, my God my student put this slide and they make it. So, the human body contains many different organs such as heart, lungs and which each organ perform a different function. Similarly, the cell has organelles which are the small specified structures like we saw this mitochondria, Golgi operators and different we will see in a minute. So, membrane bound organelles are found only in eukaryotic cells because prokaryotic does not have any membrane bounded structure. They even do not have this nucleus. So, this is the centriole or the cylindrical structure found in animal cell. They help during the cell devion in both mitosis and meiosis. We will see what is cell devion by using mitosis and meiosis. They are found near the nucleus. They cannot be seen when cell is not dividing. It is only visible when the cell is dividing. So, then we have endoplasmic reticulum. We have two types. One is the rough. Rough has ribosome all over its outer surface. The endoplasmic reticulum is where protein and lipids are produced. They produce protein and lipids and it is also concerned with the transport of these material within the cell. So, smooth endoplasmic reticulum is responsible for generating new layers for the Golgi bodies. Golgi bodies are also called Golgi operators in different books. So, this is the Golgi operators. I will show you the picture of this. It looks like this. Each cell contains a number of Golgi operators or bodies. Golgi operators are light little stacks of hollow membrane pancakes. Function is to produce materials arrived from the smooth endoplasmic reticulum, packed product into small structures that are called Golgi vehicles. So, they process material that come from this endoplasmic reticulum and then packed that material and in small vehicles which is called Golgi vehicles. Two types of Golgi vehicles which is micro bodies and secretory vesicles. So, micro bodies remain in the cell, contain usually enzymes needed by the cell for different kind of reactions, but remain packaged away from the cells other kind. The best known micro body is the lysosome. This is the structure of this Golgi operators or the Golgi body. So, these are the vesicles. They are the small interest cellular membrane enclosed sac that store or transport substances. Things which are produced by the endoplasmic reticulum or which are produced in the Golgi, the body is separated from cytosol by at least one lipid bilayer. These are the basic tool organizing metabolism and the transport and the storage of enzyme. So, vesicles made in the Golgi operators are in the endoplasmic reticulum or from the parts of the plasma membrane. These transport vehicles can move protein from rough endoplasmic reticulum to the Golgi. So, they act as a transporter between endoplasmic reticulum and the Golgi bodies. So, then we have this lysosome. It is synthesized by the endoplasmic reticulum again and the Golgi complex. So, lysosomes are tiny sacs almost of 500 nanometer in size filled with digestive enzymes that enables the cell to utilize it nutrients. So, lysosomes also destroy the cell after it is dead. So, due to the disease or condition if the cell is not working properly, these lysosomes help to kill that cell properly. So, these are kind of hair like finger like projections on the outer surface of the cell. Not all cell has microbiolite. So, function is the diffusion of material both into and out of the cells. They are particularly apparent on the surface of absorptive and secretive cells. So, now the mitochondria it is called the cell powerhouse. It produce often referred to as the power plant of the cell. The reaction that produce energy take place in mitochondria. The quantity of mitochondria each cell can have different numbers of mitochondria. And if more energy is needed, the more mitochondria are present in that cell. So, then again the cell workcule. Vehicles are membrane bound sacs within the cytoplasm of the cell that function in several different space. Workcules in animal cell tend to be much smaller than the plant like cell, because in plant we saw that vehicle almost occupies 50 percent of a plant cell. More commonly used to temporarily store materials or transport substances. This is the nucleus. The cell nucleus is found in eukaryotic cells, because prokaryote cell do not have this nucleus or in fact any membrane bounded structure. So, it is spherical in shape separated from the cytoplasm by a double nuclear membrane. So, this is the membrane contain a nuclear pole that permits nutrient waste and cellular information to pass both into and out of the nucleus. So, this is a nucleus. The nucleus is the control center that contains DNA or genetic information for the formation of proteins. So, in prokaryotes DNA processing take place in the cytoplasm, because they do not have any nucleus, they do not have any membrane bounded organelles. So, it is processing take place in the cytoplasm of the prokaryotic cells. So, the nucleus dense spherical structure within the nucleus of the cell, it contain ribonucleic acid which is RNA for the synthesis of ribosomes. It has an important role in the production of protein and RNA. The nucleus is a part of nucleus of the cell that disappears during cell devion. So, it again disappears during the cell devion. So, the ribosomes the protein producing machine, each cell contains thousands of ribosomes. These are the miniatures protein factories, it composes 25 percent of cell mass. There are the stationary type which are embedded in rough endoplasmic recticulum. Mobile type injects proteins directly into cytoplasm. So, if it is produced in ribosome, so they carried and inject them into the cytoplasm so that the protein is needed for the well-being of that cell. The formation of a new protein molecule from amino acid based on information encoded in DNA and RNA. So, one thing that all human cells have in common from brain, eye, muscle, skin, cell is that they contain DNA and DNA is called the blueprint of life. So, DNA stands for deoxy. This is deoxy. So, it is the oxyribonucleic acid. So, deoxy means that it lacks one of the oxygen or hydro. So, DNA found within the nucleus of eukaryotic organisms. In 1940s, DNA identified as the carrier of genetic information. So, any question? I heard some, okay. Contains the instruction for a cell determines how animal, human characteristics are passed from one generation to another, whether a person has blue eye or brown, whether he or she has dark or blonde is determined by DNA. So, this is the building block of the DNA molecule are called nucleotides. So, these are four nucleotides which make a structure of DNA. Nucleotides link together into a chain by covalent bonding. So, of the DNA strand, this bonding between these four, this is adenine, thiamine, galvanine and cytosine. So, these are the main nucleotides of DNA. So, this double helix structure of molecule was discovered in 1953. The two strands of DNA molecule held together by hydrogen bonding. Hydrogen bonding is the bonding between hydrogen and an electronegative atom. So, that can be this one. So, each nucleotide is composed of three parts. It is a deoxyribose sugar, then a phosphate group and then a nitrogen base. Deoxyribose molecule occupies the center position in the nucleotide. A phosphate group on one side and the base is on the other side. So, I think we can see this is a deoxyribose sugar. It is pentahose 5 carbon sugar and you can see one carbon is here, the second is here, third, fourth and fifth carbon is here. You can see this is called deoxyribose because there is no oxygen connecting this carbon which is at position 2. Third has this O, one has this oxygen, four has this oxygen, five has this oxygen. So, one of the oxygen at position 2 is missing. So, four carbons and an oxygen make up the five membered ring. The DNA sugar is called a deoxy because it is lacking a hydroxyl group at this two position. So, the phosphate group is the second part of the backbone of DNA molecule. So, a phosphate group act as a bridge between adjacent deoxyribose sugar which carries in turns the nitrogen bases. The end of the chain on which the phosphate is explored is called the 5 prime and because the phosphate binds to the carbon on the fifth position. As you can see from this that at fifth position it is combined with the phosphate group. So, if it ends the chain which phosphate is exposed is called 5 prime and because phosphate binds to the carbon DNA is always read from 5 prime to 3 prime. So, this is I think I have a photo of ok. So, this is a 5 end here you can see this is the phosphate at phosphate group and this is end three where it there is no phosphate group. So, let us go back and there are two classes of nitrogen bases one is purine and the other one is pyrimidines the purines are characterized by their double ring structure. So, these are adenine and guanine are purines and pyrimidines are have a single ring cytosine and thiamine are these pyrimidines. So, the number of purine bases equal the number of pyrimidines bases in a this nitrogen base. So, the base do not pair at random is complementary to T and two hydrogen bonds between A and T. So, this is A is complementary it always binds with T and C is complementary to G. So, three hydrogen bonds are present between C and G guanine and cytosine. So, the hydrogen bond is 20 times weaker than the covalent bond. So, the two ends of DNA stands are chemically different as I explained earlier because this is called the 5 prime end and this is called the 3 prime end. The one end is a 5 prime terminates with the phosphate group attached to the fifth carbon on the 2. The second end is the 3 prime 3 terminates with hydroxide group on the third carbon on the sugar ring. So, this is the 3 prime end the other one is 5 prime end. The human DNA is almost 1.5 to 2 meters long the nucleus diameter is 6 micrometer. So, DNA must be compact to fit in nucleus. So, DNA must be organized enough to become the uncoiled to be replicated and transcribed. So, the DNA packed along with protein histones complex form of chromatin. The continuous folding of chromatin is called it is the this portion is called the chromosomes and some organisms have only one chromosome and we human have 23 pair of chromosomes. So, humans are deployed each cell has two copies of each chromosome one from each parent. So, the entire genetic material is called genome. So, how the replication of DNA take place? DNA replication is the production of two complete identical double helix for from one original DNA molecule. So, it splits and you can see the one arrow is going down the other arrow is going up. So, in eukaryotic DNA replication must happen before the cell doing. So, that they have their own set of DNA. So, prokaryotes replicate their DNA throughout the interval between cell to be in. So, enzymes like protein catalyzed biochemical reactions which are essential for DNA replication. So, DNA stand is separated forming a Y shape join this is a kind of Y shape junction called replication for for enzymes. So, a short DNA segment called the premier base pair the template by premise enzymes there are different kinds of enzymes which are involved in the replication of this. So, basically what these enzymes do is that they attach with this separated for the nucleotides according to same that adenine is complementary to thiamine and the other one is complementary to guionine. So, finally, DNA from a enzyme synthesize a new DNA strand by adding three nucleotides nucleotides were those A, T, C, G and error in DNA molecule is called mutation. So, DNA polymerized has ability to do the proof reading. So, the rate of error is very low 1 per 10 10 raise to power 9 basis. So, it is very rare to have a mutation the replication fork is is metrical one new DNA stand is formed on template running from 3 prime to 5 prime that is called the leading strand the other is formed on template running from 5 prime to 3 prime the Langing strand. So, a gene is a sanction or a sanction of DNA strand that carries the instruction for a specific function. So, how was section of DNA gives instruction in any language we know that words seldom convey complete or understandable information for that we need a set of words that convey a complete thought in the form of a sentence. So, DNA language consists of four words each word is the single unit of DNA molecule that is the nucleotide and those are those A, T, C and G. So, each sentence is a large string of nucleotides called a gene. So, in order the gene is basically a combination of A, T, C, G in a particular order the that codes for a defined biochemical function usually through the production of particular protein. So, the transformation of gene into a protein is called an expression. So, genes have specific jobs at specific time not all genes are turned on all the time for example, something a gene has instruction to reproduce it will be active only when there is a time for reproduction or cell division or they are not on all the time. So, cells are I will be I am very quick I deleted many slides. So, cells are capable of synthesizing new protein based on the information encoded in DNA and RNA. So, proteins are the biological molecules give living cells forms and functions. So, protein synthesizes generally protein synthesis generally consists of two major step transcription and translation. So, transcription is DNA information copied into RNA and then RNA moves and the proteins are synthesized using the information in RNA as a template. So, from DNA RNA copies some information and then it take to the ribosomes and they produce the protein and the message has been transferred from the DNA to protein. So, both nucleic acid that is the DNA are sugar phosphate polymers nitrogen bases attack to the sugar of the backbone. They differ in composition the sugar in RNA is ribose not the deoxyribose because it has oxygen at even position 2 and they have base uracels present in RNA instead of thiamine they do not have thiamine they have uracels. So, they also different size and structure RNA molecules are smaller or shorter than the DNA molecules RNA is single strand not double strand like DNA. So, the different function to DNA has only one function storing genetic information in its sequence of nucleotide bases, but there are three main kinds of function for RNA each of which has a specific job to do. So, RNA has three types and it has a specific job all three types have different jobs to do while DNA has only one job to store the genetic information. So, there are three kinds of RNA ribosomal RNAs exist outside the nucleus and in the structures called ribosome which produce proteins a complex consisting of about 60 percent ribosomal RNA and 40 percent of protein. Then there is a messenger RNA the nucleic acid records information from DNA this part of RNA records information from DNA in the cell nucleus carried to the ribosomes known as the messenger RNA. Then there is a transfer RNA the function of transfer RNA is to deliver a amino acid one by one to proteins chains growing at ribosomes are machines that make protein and this transfer RNA actually carries of different amino acid to ribosome to make to carry out the protein synthesis. Now, we will move to salduvian there are two kinds of salduvian one is called neosis and the other one is called itosis. So, anybody knows genetic engineer part. So, for unicellular organism reproduction is a cell duplication because amoeba bacteria they do the duplication and that is a cell reproduction by replicating all their parts and then split it into two cells by binary fusion. This is a method in which they duplicate and then divide into two daughter cells. This process not just give two new cell, but also two new organisms for multicellular organism cell replication and reproduction are two separate process. This is mytosis it is the replication just the cell is replicated and then it divides into two and meiosis is the reproduction. So, it is it reproduce and divides the chromosome and every kind of this thing. So, multicellular organisms replace damaged cell through replication process and this is called mitosis. Mitosis is process by which they are deployed nucleus like we human have are deployed because we have two sets of chromosome one from each parent homologous chromosomes that is the same gene of the cell divided to produce two genetically identical daughter nuclear both still deployed. So, this is the replication. So, in which this is DNA set of this is a deployed structure because it has one chromosome from one parent and the other from the other parent and then they did the replication and you have two daughter cells with the same two kinds of chromosome or DNS. So, in meiosis is the multicellular reproduce new organisms through a process that is called meiosis a deployed somatic cell undergo meiosis to produce haploid cells. Now, these terminologies are really very different from for me. So, this is a same kind of reproduction processes we human do that there is a egg cell, there is a sperm cell and then it is deviant take place and eventually you have daughter nuclei. Somiosis reduces the chromosome number by half. So, now the question is what is protein? Protein is the principal constituent of cells that drives most of its function. Proteins are composed of linear chains which is called polypeptides of amino acids linked with peptide base bonds. So, these are 20 different kinds of amino acids and they are joined together with the help of ribosomes which produce these under the instruction of DNA carried out by RNA to ribosome and then order of amino acid in protein molecules determine its structure and function because if the order and arrangement is different that protein will perform some different kind of function. So, protein may serve as enzymes that make new molecule and catalyze nearly all chemical reactions then hormones they transmit signals throughout the body. So, then they have protein all protein also make structural component that gives cell their shape and help them to move. So, they also produce antibodies that attack or defend cell against any kind of antigens. So, they also transport molecules or they carry oxygen and take oxygen where it is needed. So, proteins have a different function and all it is always made up of a amino acid and there are only 20 amino acid just the arrangement is different and then their function is different. So, these are the amino acids are the subunits of protein the chain of amino acid takes on different shape to form different proteins. So, if the chain is different of course, it will be a different protein, but there are only 20 amino acid. So, various shapes allow protein to take different characteristic in cell all amino acid found in proteins have same basic structure different only in the structure of the R group. So, this is a kind of R group in this amino acid chain. So, if this is different the protein will be different the simplest and the smallest amino acid is glycine the R group is an hydrogen. So, a chain like molecule of a amino acid is called polypeptide. So, these all terminologies are also new for me ok not new, but it is hard to remember. So, protein synthesis generally consists of two major step what are the two major steps it is transcription and translation. Transcription is the transferring the code from DNA to RNA. So, one strand of DNA double helix is used as a template by the RNA polymerized to synthesize messenger RNA. As I told you before this is a bit complicated slide, but this is a double helix this red is a DNA. So, it splits from here and this blue one is messenger RNA it get them all the transcription from this DNA and then they move to ribosome this is a kind of ribosome which is a protein making machine kind of thing. So, it carried the instruction from DNA and move bring it to this ribosome and with different kind of amino acids present this ribosome is making this chain long chain of polypeptide. So, the messenger RNA migrates from the nucleus to the cytoplasm decoding the messenger RNA sequence can be described as a unit of three nucleotide and it is called codon. So, this is a kind of it carries all the information here and then the protein synthesis take place. Then the second part is the translation because it got the message from there and now this polypeptide chain is ready. So, translations involve three processes is initiation and elongation and terminations. So, this is a messenger RNA binds to protein which is called complexes called ribosome which is a protein producing machine and then the unique initiation code even if it is A, U, G it is what was A was it was Uracil and Gavanine and A was adenine. Determines the beginning point of translation there are 64 different set of codons and only 20 amino acids. So, if you want to see these, so these are the codes and they make different basically it is a combination of three. So, U, U, U, U is Uracil, C, A because in RNA there is no thiamine. So, instead of thiamine you have Uracil. So, this is kind of codes which RNA carried from DNA and take it to the ribosome and then according to the available nucleotides they make a polypeptide chain. Then the transfer RNA match each triplet on a messenger RNA to its corresponding amino acid and elongate the new polypeptide chain synthesized on the ribosome. The ribosome moves from codon to codon along the messenger RNA. So, then you have need to terminate that polypeptide chain. So, a release factor binds to the top codon terminating translation and releasing the complete polypeptide form to the ribosome. So, there are three different termination codes this is U, A, A, U, A, G and U, G, A. So, in this manner you can instruction is RNA take instructions from DNA move to the ribosome, ribosome collect those nucleotide and make proteins and these there are 20 different kinds of amino acid, but there are many possibilities to have. So, they copied those instruction they make a polypeptide chain then they terminate it and then that protein is ready for different kinds of functions for this and that is it. Thank you. Thank you. Thank you. Thank you. So, by the way the slides I gave to Federica they have few more slides which I deleted the last minute. So, any question which I am not so good I can ask.