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

2. Cell Organelles – specialized cellular parts 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
Always present and membrane bound
Often able to divide (self replicate)

3. Cell Organelles - the list 8
Nucleus, Endoplasmic Reticulum and Golgi complex
Lysosomes and Mitochondria
Ribosome
Peroxisome/ Micro bodies
Secretary Vesicles

4. Cell organelle – Nucleus to secretary vesicles

5. Lysosomes – the definition Membranous boxes
Are membranous bags which contain hydrolytic enzymes to digest macromolecules :
Cell debris and microorganisms

6. Lysosomes- the background
Lysosomes are synthesized in ER and pinched off from Golgi apparatus and :
Can undergo self replication
Are dispersed through out the cytoplasm
Are more abundant in secretary cells like Pancreas and Thyroid glands – 100s to thousands

7. Lysosomes – Structure and self replication

9. Lysosomes – the waste boxes
Constitute an Intracellular Digestive System for the :
Damaged cellular structures / debris
The materials taken by Endocytosis and Phagocytosis
Food particles ingested by the cell
Unwanted Matter like Bacteria
Macromolecules like proteins (Proteolysis)

10. Lysosomal action

11. Enzymes of Lysosomes – the nature 1
Contain a Group of enzymes, Hydrolases that degrade polymers into their monomer units (hydrolysis)
Over 40 in number and include :
Nucleases- degrade DNA and RNA into mononucleotides
Proteases- degrade proteins and peptides to Amino acids

12. Enzymes of Lysosomes - the nature 2
Phosphatases – Remove phosphate groups from mononucleotides and phospholipids
Lipases degrade lipids into fatty acids and glycerol
Deficiency of Hydrolases result in building of toxic products that are digested by Lysosomes

13. Damage to Lysosomal Membranes The consequences
Bilayered membranes of the Lysosomes prevents the leakage of the hydrolytic enzymes into cytoplasm
Damage to Lysosomal membrane causes release of hydrolytic enzymes which work at acid medium 5
Released Lysosomal enzymes, split intra cellular organic compounds that cause cell death

14. Peroxisome – Produce 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
Are present in all animal cells except RBC

15. 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

17. Biogenesis of Peroxisome- ER

18. Peroxisome – Detoxication uric acid and amino acid

19. Mitochondria – the background the power house
Mitochondria, are the power house of cells and are the principal site for ATP production in aerobic cells
Extract energy from the nutrients to carry out cell function.
Number of mitochondria is variable and depends upon activity of cell-100 to several thousands like :
Thyroid gland, ,Pancreas and epithelium

20. Mitochondria - structure in general are mobile
Mitochondria are variable in size and shape
May be Globular or elongated
Mitochondria migrate from one place to another with in the cells
Mitochondria are doubled layered with Inner and Outer membranes.
An inter membranous space exists B/w the 2 layers

21. Mitochondria – power house of the body

22. Mitochondria – membrane composition outer and inner Mit.Membranes
The 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

23. Mitochondria – Inner membrane and matrix Ultra structure
Inner membrane has folding shelves and Cristie to increase 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

24. Enzymes of Mitochondria membranes and matrix

25. Enzymes of Mitochondria membranes and matrix
Outer Mitt. membrane has Fatty Acyl Co A Synthetase for the activation of LCFAs (outer surface) and
Carnitine Acyl Transferase(CAT 1) for Carnitine shuttle(inner surf.
Inner Mitt. membrane has ATP Synthase and enzymes for Oxidative Phosphorylation (ETC)
Ribosomes and DNA are also part of the inner Mitt. Membrane
Matrix has the enzymes for Citric acid cycle and FA oxidation

26. Carnitine shuttle

27. Mitochondria – the synthetic role Mitt.DNA and Ribosomes
Mitochondria have their own DNA with 37 no of genes that encode for all the Mitochondrial proteins
Have their Ribosomes and DNA on inner Mitt. Membrane
Expression of these genes leads to the translation, and synthesis of proteins via mRNA in the matrix
These proteins are then shifted to have their place in Mitt. Membranes to carry out various functions
Ketogenesis by hepatic mitochondria

28. 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

29. Major role of Mitochondria – ATP synthesis