Download Enzymatic constitution of cell organells -1.Lecture

Enzymatic Constituents of Cell Organelles - 1
Lecture NO: 1st MBBS
Dr. Muhammad Ramzan
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)
Cell Organelles - the list 8
•
Nucleus, Endoplasmic Reticulum and Golgi complex
• Lysosomes and Mitochondria
• Ribosome
• Peroxisome/ Micro bodies
• Secretary Vesicles
Cell organelle – Nucleus to secretary vesicles
Lysosomes – the definition
Membranous boxes
• Are membranous bags which contain hydrolytic enzymes
to digest macromolecules :
• Cell debris and microorganisms
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
Lysosomes – Structure and self replication
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)
Lysosomal action
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
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
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
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
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
Biogenesis of Peroxisome- ER
Peroxisome – Detoxication
uric acid and amino acid
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
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
Mitochondria – power house of the body
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
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
Enzymes of Mitochondria
membranes and matrix
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
Carnitine shuttle
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
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
Major role of Mitochondria – ATP synthesis