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

2. Cell Organelles – the definition
Organelle - Little organ- analogous to an organ
Are the specialized components of the living cell
Carry out various functions that are essential for cell life and metabolism
online.org

3. Cell organelle – the background Are insulated by membrane
All the organelle are Bilayered. Peroxisome is single layered
Ribosome has no membrane
Are always present and able to self replicate
Ribosome is produced by the Nucleolus
Their numbers , size and shape is variable
Are abundant in metabolically active cells like thyroid/ Pancreas
– academy.com

4. Cell Organelles - the list of 8
Nucleus, Endoplasmic Reticulum and Golgi complex
Lysosome, Mitochondria and :
Ribosome
Peroxisome/ Micro bodies and
Secretary Vesicles
com

5. Cell organelle – Nucleus to secretary vesicles

6. Lysosomes – the definition Present in all cells except RBC
Are spherical vesicles which contain acid Hydrolases (50) to degrade all types of biological polymers
(Proteins; nucleic acids, CHO and lipids)
Lysosomes are referred to as Suicide bags because of their role in Autolysis
online org.

7. Lysosomes- the background
Lysosomal enzymes are synthesized in ER and pinched off from Golgi as Transport vesicles
Acid Hydrolases work best at acidic pH(5) VS pH 7.2
Lysosome actively concentrate proton(H+) via Proton pump in its membranes via ATP hydrolysis
Degrade extra cellar material and damage organelle
– online.org – book shelf.org

8. Lysosome

9. Proton pump - Conc. H+

10. Role of Lysosomal Membranes Prevention of Damage
Lysosomal membranes prevent the leakage of the acid hydrolytic enzymes into Cytosole
Their damage causes release of acid hydrolases which are inactive at neutral Cytosolic pH
This provides double protection against the digestion of Cytoplasmic contents in membrane rupture

11. Synthesis of Lysosome 2 pathways Secretary pathway
Secretary endocytic pathway
Secretary pathway: Lysosome and their enzymes are produced separately and pinched off from Golgi
Enzymes in Transport vesicles and Lysosome bind together cytoplasm to have mature Lysosome

12. Synthesis of Lysosome Endocytic/secretary Pathway ````
Extra cellular moles are taken up in the cell as endocytic vesicles which fuse with the early endosome
Early endosome matures into late endosome
Transport vesicles from Golgi fuse with late endosome that also contain certain moles taken up by the Endocytosis
Enzymes in Transport vesicles are delivered to endosome via receptors of Mannose – 6 Phosphate
Transport vesicles and endosome are transformed into Lysosome

13. Endocytosis and Lysosome formation

14. Lysosome – the waste boxes
Constitute an Intracellular Digestive System for the :
Damaged cellular structures / debris
The materials taken by Endocytosis and Phagocytosis EXT
Food particles ingested by the cell
Unwanted Matter like Bacteria
Macromolecules like Proteins; nucleic acids, CHO and lipids

16. Lysosomal enzymes- Disposal of products
Lysosomes are now known to contain ˃ 50 acid Hydrolases that can digest all macro moles in the cells
The breakdown products are transported back to the Cytosole by specific transport proteins in the Lysosomal membrane
Functional deficiencies of these enzymes result in the Lysosomal storage disease like Gauchors" disease

17. Lysosomal enzymes – the list
Proteases : that degrade Proteins/peptides into AAs
Nucleases: Degrade DNA/RNA into mononucleotides
Phosphatases: Remove PO4 group from mononucleotides/Phospholipids
Lipases degrade lipids into fatty acids and glycerol

18. Lysosomal Storage diseases Gauchors" disease
The mutations of the genes for Lysosomal enzymes give rise to 30 different genetic diseases
Lysosomal storage diseases
There is accumulation of un degraded materials due to the deficiency of Lysosomal enzymes
Guachars" Disease: is due to the deficiency of the enzyme for the degradation of Glycolipids

19. Peroxisome – Produces H2O2 is single layered
Peroxisome are so called as they all produce H2O2 through the process of per oxidation
Peroxisome are produced through self replication or from endoplasmic reticulum (ER)
Is a single layered organelle and is self replicated
Are present in all animal cells except RBC

20. Peroxisome – Oxidases and Catalases the major enzymes
Contain about 50 enzymes – Oxidases and Catalases
Oxidases split organic moles (FA) to produce H2O2 by the process of oxidation – A free radical
Catalases then split H2O2 to water and O2 to make it safe
Peroxisome also break down uric acid and amino acids

22. Mitochondria – the cellular power house
Mitochondria, are power house of cells and the principal site for ATP production in aerobic cells
Extract energy from the nutrients to carry out cell function.
No. of mitochondria are variable and depend upon activity of the cell - from100 to several thousands like :
Thyroid gland, Pancreas and renal tubules

23. Mitochondria - structure in general are mobile
Mitochondria are variable in size and shape
May be Globular or elongated
Mitochondria move freely with in the cells
Mitochondria are bilayered with Inner and Outer membranes.1
An inter membranous space exists B/w the 2 layers

24. Mitochondria – structure

25. Composition of the Mito.membranes
Outer membrane of mitochondria is composed of about half lipids and half protein
Low Protein in the outer membrane render it permeable to molecules having molecular weight < 10,000KD
The inner one has 80% proteins and 2o% lipids and is less permeable to large molecules like LCFAs
This is significant for entry of FAs into matrix for oxidation

26. Mitochondria – Enzymes of membranes and matrix
Inner membrane has folding shelves and Cristie to ↑ the surface area for enzyme action
Cavity under inner membrane has fluid – the Matrix
Matrix contains abundantly dissolved Oxidative enzymes to extract energy from nutrients
Liberated energy is utilized to synthesize ATP

27. Enzymes of outer Mitochondria membrane NO:2
External surface of Outer mitochondrial membrane has
Fatty Acyl Co A Synthetase for the:
Activation of Long chain saturated fatty acid (LCSFA)
Inner surface of outer mitochondrial membrane has :
Carnitine Acyltransferase(CAT 1) to transfer LCSFA to the mitochondrial matrix

28. Enzymes of inner Mitochondrial membrane No:2+5
Inner surface of external Mitochondrial membrane has :
Carnitine Acyltransferase 11
It separates Carnitine from Acyl Carnitine so that LCSFA remains in the matrix for oxidation
Carnitine is translocated to the inter membranous space for reuse by the Carnitine Translocase

29. Enzymes of inner Mitochondrial membrane cont. and Matrix
Inner surface of the Inner Mitochondrial membrane has 5 enzymes including ATP Synthase and:
enzymes for Oxidative Phospho rylation (ETC)
Ribosome and Ribosomal DNA for protein synthesis
Matrix has the enzymes for :
Citric acid cycle and Fatty acid oxidation

30. Carnitine shuttle

31. Mitochondria – the synthetic role
Mitochondria have their own DNA with 37 no of genes that encode for the required Mitochondrial proteins
Have their Ribosomes and DNA on the :
inner Mitochondrial Membrane
Expression of these genes leads to the translation and synthesis of proteins via mRNA in the matrix
The product proteins are used with in the mitochondria

32. Mitochondria – the Metabolic role
Mitochondria carry out oxidation of the nutrients in matrix like FAs to yield energy for ATP synthesis
The process is called oxidation of FAs that releases 129 no of ATP for a single mole of Palmatic acid(16C)
This energy is used to carry out cell function and survival

33. Electron transport chain Oxidative Phosphorylation