1. Online Counseling Resource YCMOU ELearning Drive… School of Architecture, Science and Technology Yashwantrao Chavan Maharashtra Open University, Nashik – 422222, India

2. SEP-SBI074-CP02-04 Introduction Programmes and Courses SEP –SBI074-CP02-U02

3. School of Science and Technology, Online Counseling Resource… Credits  Academic Inputs by Sonali Alkari Faculty YCMOU Nagpur Centre, Faculty LAD college P.G. D of Biotechnology Research officer Ankur Seeds Pvt Ltd sonalisa_alkari@yahoo.co.in Sonalisaal@rediffmail.com 3© 2007, YCMOU. All Rights Reserved.

4. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.4 How to Use This Resource  Counselor at each study center should use this presentation to deliver lecture of 40-60 minutes during Face-To-Face counseling.  Discussion about students difficulties or tutorial with assignments should follow the lecture for about 40-60 minutes.  Handouts (with 6 slides on each A4 size page) of this presentation should be provided to each student.  Each student should discuss on the discussion forum all the terms which could not be understood. This will improve his writing skills and enhance knowledge level about topics, which shall be immensely useful for end exam.  Appear several times, for all the Self-Tests, available for this course.  Student can use handouts for last minutes preparation just before end exam.

5. School of Science and Technology, Online Counseling Resource… © 2007, YCMOU. All Rights Reserved.5 Learning Objectives  After studying this module, you should be able to : Describe structure of Ribosomes Discuss function of Ribosomes

6. School of Science and Technology, Online Counseling Resource… Introduction:Ribosomes  Ribosomes are cytoplasmic granules composed of RNA and protein, at which protein synthesis takes place.  They were first observed by Palade in the electron microscope as dense particles or granules.  Upon isolation, they were shown to contain approximately equal amounts of RNA and protein label.  To function actively in protein synthesis, they must be bound into complete ribosomes. 6© 2007, YCMOU. All Rights Reserved.

7. School of Science and Technology, Online Counseling Resource… Introduction:Ribosomes  We know that ribosomes are, one of the required components necessary for the synthesis of protein.  The others are messenger RNA, which carries the genetic message; soluble RNA, which carries amino acids to be synthesized; and guanosine triphosphate, which is the source of energy.  A number of ribosomes may be attached to the same messenger, each manufacturing its own chain of polypeptides, called a polysome.  Ribosomes are also found in the mitochondria and chloroplasts of eukaryotic cells 7© 2007, YCMOU. All Rights Reserved.

8. School of Science and Technology, Online Counseling Resource… Introduction to Ribosomes  Ribosomes are the large, ribonucleoprotein factories in which proteins are synthesized.  In this process, messenger RNA (mRNA) codons are read by the anticodons of adaptor, transfer RNAs (tRNAs) that carry codon-specific amino acids.  These amino acids are added to a growing protein chain by peptide bond formation in the heart of the ribosome.  Ribosomes are the protein-synthesizing machines of the cell.  They translate the information encoded in messenger RNA (mRNA) into a polypeptide. 8© 2007, YCMOU. All Rights Reserved.

9. School of Science and Technology, Online Counseling Resource… Ribosomes 9© 2007, YCMOU. All Rights Reserved.

10. School of Science and Technology, Online Counseling Resource… Where are Ribosomes found?  Ribosomes are found dispersed in the cytoplasm of all prokaryotic cells: bacteria.  They are also found in the cytoplasm of eukaryotic cells: protists, fungi, plants, and animals, where they are either free to float in the cytoplasm or are bound to networks of endoplasmic reticulum which are membrane- enclosed tubules in the cytoplasm.  In eukaryotic cells, two types of cell structures called mitochondria and chloroplasts contain ribosomes. 10© 2007, YCMOU. All Rights Reserved.

11. School of Science and Technology, Online Counseling Resource… Ribosome's: details:1  Ribosomes are tiny particles, about 200 A.  It is composed of both proteins and RNA; in fact it has approximately 37 - 62% RNA, and rest are made up of proteins Label.  The RNA present in ribosomes are obviously called ribosomal RNA, and they are produced in the nucleolus, which is a prominent globular structure in the nucleus. 11© 2007, YCMOU. All Rights Reserved.

12. School of Science and Technology, Online Counseling Resource… Ribosome's details:2  Thus, the proteins are gene products of themselves, and one ribosome is made up of dozens of genes.  The ribosomes fall into two categories: Those that are free to roam in the cytoplasm, and those that are bound to gigantic, cobwebby organelles made up of membranes, called the endoplasmic reticulum ; thus, causing a rough surface.  Although, the two kinds of ribosomes play similar roles in translating mRNA to produce proteins, they are very distinct in where its product is located. 12© 2007, YCMOU. All Rights Reserved.

13. School of Science and Technology, Online Counseling Resource… Prokaryotic and Eukaryotic: Ribosomes  Ribosomes in the cytoplasm of prokaryotic and eukaryotic cells slightly differ.  Prokaryotic ribosomes are smaller and less dense and each contain only three strands of RNA and about fifty proteins.  Eukaryotic ribosomes consist of four strands of RNA and contain seventy to eighty proteins.  The ribosomes in mitochondria and chloroplasts resemble prokaryotic ribosomes. 13© 2007, YCMOU. All Rights Reserved.

14. School of Science and Technology, Online Counseling Resource… Structure:1 Ribosomes are roughly spherical. With a diameter of ~20 nm, they can be seen only with the electron microscope. They can make up 25% of the dry weight of cells (e.g., pancreas cells) that specialize in protein synthesis. (A single pancreas cell can synthesize 5 million molecules of protein per minute.) 14© 2007, YCMOU. All Rights Reserved.

15. School of Science and Technology, Online Counseling Resource… Structure:2  This spherical particle of 23nm, is composed of two subunits; a large and small label.  In Eukaryotes, the co-efficient of ribosomes are 80s, of which is divided into 60s for the large, and 40s for the small subunit.  The 60s contain 28s rRNA, with a small fragment that is attached noncovalently and can be released upon heating; a 5.8s, and a very small - 120 nucleated of 5sRNA.  Whereas, the 40s subunit has only a single 18s rRNA label. 15© 2007, YCMOU. All Rights Reserved.

16. School of Science and Technology, Online Counseling Resource… Structure:3  In prokaryotes, however, the large and small subunits are split into 50s and 30s, making a total of 70s respectively.  The 50s has two types of rRNA - a 23s and 5s Label.  It also has 32 different proteins. On the other hand, the 30s contains a single 16s rRNA image a, image b, image c, plus, 21 different types of proteins Label. 16© 2007, YCMOU. All Rights Reserved.

17. School of Science and Technology, Online Counseling Resource… Structure:3 Structure of the 30S subunit from T. thermophilus Structure of the 50S subunit from D. radiodurans 17© 2007, YCMOU. All Rights Reserved.

18. School of Science and Technology, Online Counseling Resource… Comparison of Ribosome Bacterial (70S)Eukaryotic (80S)Mitochondrial (55S) Large Subunit50S60S39S rRNAs (1 of each) 23S (2904 nts)28S (4700 nts)16S (1560 nts) 5S (120 nts) 5.8S (160 nts) Proteins33~4948 Small Subunit30S40S28S rRN16S (1542 nts)18S (1900 nts)12S (950 nts) Proteins20~3329 18© 2007, YCMOU. All Rights Reserved.

19. School of Science and Technology, Online Counseling Resource… Function of a Ribosome - 1  Ribosomes are the sites of protein synthesis, where RNA is translated into protein.  When cells need large numbers of proteins, they must first build numerous ribosomes.  Because protein synthesis is so important to cells, there are large numbers of ribosomes found throughout cells often numbering in the hundreds or thousands 19© 2007, YCMOU. All Rights Reserved.

20. School of Science and Technology, Online Counseling Resource… Function of a Ribosome - 2  In eukaryotic cells, three of the four ribosomal RNA strands are synthesized in the nucleolus, a structure in the nucleus.  The fourth ribosomal RNA strand is synthesized outside of the nucleolus and then transported into the nucleolus for ribosome assembly.  Ribosomal proteins enter the nucleolus and combine with the four ribosomal RNA strands to create the large and small subunits which are two ribosomal structures. 20© 2007, YCMOU. All Rights Reserved.

21. School of Science and Technology, Online Counseling Resource… Function of a Ribosome - 3  The two subunits unite outside the nucleus just before the ribosome begins to manufacture proteins.  Prokaryotic cells lack a nucleus or nucleolus and therefor ribosomal synthesis takes place in the cytoplasms.  Without the ribosomes the message would not be read and proteins could not be produced. 21© 2007, YCMOU. All Rights Reserved.

22. School of Science and Technology, Online Counseling Resource… What You Learn…  You have learnt : Ribosomes are the large, ribonucleo protein factories in which proteins are synthesized Ribosomes are found dispersed in the cytoplasm of all prokaryotic as well as eukaryotic cells There is structural difference between prokaryotic and eukaryotic ribosomes. Ribsome is composed of small and large subunit which associates and dissciates. Ribosomes are the sites of protein synthesis, where RNA is translated into protein. 22© 2007, YCMOU. All Rights Reserved.

23. School of Science and Technology, Online Counseling Resource… Critical Thinking Questions 1.Describe in details the structure of Ribosomes. 2.Describe the various functions of Ribosomes. 3.Where are ribosomes found? 4.Is there any difference between Eukaryotic and prokaryotic Ribsome © 2007, YCMOU. All Rights Reserved.23

24. School of Science and Technology, Online Counseling Resource… Hints For Critical Thinking Question ospherical, large and small sub units oprotein synthesis, oCytoplasm oEukaryotes:80sprokaryotes: 70s © 2007, YCMOU. All Rights Reserved.24

25. School of Science and Technology, Online Counseling Resource… Study Tips:1  Book1 Title: Molecular Cell Biology Author: Harvey Lodish, David Baltimore Publisher: W. H. Freeman and Company  Book2 Title: Principles of Biochemistry Author: AlbertL Lehninger Publisher:CBS Publishers & Distributors 25© 2007, YCMOU. All Rights Reserved.

26. School of Science and Technology, Online Counseling Resource… Study Tips:2  Book3 Title: Biochemistry Author: Lubert stryer Publishers: Freeman International  Book4 Title: Biochemistry Author: Keshav Trehan Publishers: Wiley Eastern 26© 2007, YCMOU. All Rights Reserved.

27. School of Science and Technology, Online Counseling Resource… Study Tips www.en.wikipedia.org Microsoft Encarta Encyclopedia http://en.wikipedia.org/wiki/ Wikipedia the free encyclopedia 27© 2007, YCMOU. All Rights Reserved.

28. School of Science and Technology, Online Counseling Resource… End of the Presentation Thank You ! 28© 2007, YCMOU. All Rights Reserved.