1. Enzymatic Constituents of Cell Organelles-3 Lecture NO: 1st MBBS
Dr. Muhammad Ramzan

2. Ribosome – the definition non membranous organelle
Are small rounded particles in a cell, made up of proteins and rRNA that are primarily involved in the :
Assembly of proteins by translating the mRNA
Also called as Translation complex
Are non membranous organelle
online.gov

3. Ribosome – the background has 80 different proteins
Ribosome has rRNA 60% and proteins 40% (Riboproteins)
Each ribosome has 3- 4 moles of rRNA, can bind to one (1 ) mole of mRNA and up to 3 tRNA
Ribosome decode genetic information stored in mRNA for translation Polysome is a single mRNA with many Ribosome

4. Ribosome – background cont.
Single Ribosome can add 200AA/mint to product protein
Ribosome is short lived and dies after completion of product protein
Like Titin is a muscle protein(30,000 AAs)
It takes 2 to 3 hrs for completion
Ribosome are synthesized in Nucleolus. short

5. Ribosome

6. Ribosome- Types and location synthesize proteins
2 types: free and fixed
Free Ribosome are floating in the Cytosole- are mobile
Free Ribosome, synthesize proteins which are released and used in the Cytosole
Fixed ribosome are located on the surface of ER membrane, giving beaded appearance to ER
Produce proteins for intra/extra cellular use

7. Ribosome – A protein assembly plant

8. Protein distribution after synthesis

9. Parts of a Ribosome – 2 Large and small subunits
A Ribosome has 2 portions :
Small 40S (Svedberg's)
Large 60S
Synthesize proteins/enzymes together

10. Ribosomal enzymes of the subunits
Functional ribosome is the major share holder in protein synthesis and gives attachment to the :
mRNA and product protein at the smaller and larger subunit respectively
Ribosome have the enzymes to carry out this function
Smaller subunit is for decoding and larger one for the catalytic activity

11. enzymes of larger subunit Major enzymes - 2
Large ribosomal subunit has Peptidyl Transferase which establishes the peptide bond B/W the:
Amino acids at P site 1
This enzyme is rRNA and is also known as Ribozyme

12. Enzymes of Large Subunit cont.
A 2nd enzyme is also available at E site which sets free the empty tRNA for reuse in the cytoplasm
Reaction is carried out by the hydrolysis of Peptidyl Transferase
Hydrolysis of enzyme changes its activity and sets free the peptide chain by the appearance of :
Stop Codon at A site and Releasing factor (A protein)

13. Termination of translation

14. Nucleus – structure A prominent organelle
Nucleus is the prominent cell organelle that contains the genetic material -1o% of cell
It is Bilayered which separate it from the cytoplasm
Nuclear envelope has the nuclear pores that allow the entry and exit of small moles B/W nucleus and cytoplasm
Is well connected with the Endoplasmic reticulum
– on line.gov

15. Nucleus, nucleoplasm and nucleoli
Nucleus is surrounded by jell like fluid called Nucleoplasm
It contains condensed form of DNA – the chromatin
Chromatin is organized into chromosome during cell division
Nucleoplasm also contain one or more nucleoli that produces Ribosome and tRNA
Ribosome is a protein producing factory

16. The nucleus

17. Chromatin and Chromosomes Chromatin is DNA and protein
6 feet DNA is divided into 46 molecules of DNA
Each DNA mole give rise to a chromosome inches long
DNA binds with the proteins and arranges into a dense string like fiber called chromatin
It condenses further into chromosome in cell division
It makes the DNA to function properly

18. Chromatin and Chromosome

19. Nucleolus Nucleolus is a membrane less organelle? within the Nucleus
It appears like a dark spot in the nucleus by microscope
A nucleus may contain up to 4 nucleoli
It disappears during cell division and reappears again
Nucleoli produce Ribosome and tRNA
(Florida state university)

20. Enzymes of the Nuclear membrane
Peripheral proteins are attached to integral proteins / lipid layer and act as enzymes, also participate in the:
metabolism of different membrane compounds.
These include: Phospholipases; Phosphatases
Cholesterol Oxidases, Sphingomyelinases

21. Nuclear enzymes – NO: 3 the major ones
Nucleus is the hub for the production of enzymes as it contains Genes
It produces 3 major enzymes
DNA Polymerase
DNA Ligase and
RNA Polymerase

22. Major Nuclear Enzymes cont.
DNA polymerase is an enzyme that catalyzes the replication of DNA molecule
DNA Ligase is yet another enzyme that binds the useful parts (Exones) of the:
newly synthesized DNA molecule
Also repairs the damaged DNA Duplex
RNA Polymerase catalyses the Transcription of RNA
www,wikepedia.com

23. Nuclear Enzymes – DNA polymerase

24. Nuclear - RNA polymerase