Autophagy = of own cellular organelle. Heterophagy

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Cell Biology 1 Membranous organelle
Krishna T
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Lecture plan

• Cytoplasm
• Organelle
• Membranous
• Plasma membrane
• Endosomes
• Lysosomes
• rEndoplasmic reticulum
• sEndoplasmic reticulum
• Golgi apparatus
• Mitochondria
• Peroxiosomes
• Non membranous
• Microtubules
• Actin filaments
• Intermediate filaments
• Centrioles Microtubule organizing centers
  (MTOC)
• Basal bodies
• Inclusions

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Cell Biology

• How do cell/tissues differ from each other
• Specific proteins
• Shape
• Organization

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Lecture plan

• Cytoplasm
• Organelle
• Membranous
• Plasma membrane
• Endosomes
• Lysosomes
• rEndoplasmic reticulum
• sEndoplasmic reticulum
• Golgi apparatus
• Mitochondria
• Peroxiosomes
• Non membranous
• Microtubules
• Actin filaments
• Intermediate filaments
• Centrioles Microtubule organizing centers
  (MTOC)
• Basal bodies
• Inclusions

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Cell Biology
Modified fluid mosaic model
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Membranous organelle plasma membrane

• Lipids of plasma membrane
• Structure lipid bilayer,
• Composition phospholipids, cholesterol,
  proteins,
• Fatty acids of lipids oriented as ? hydrophilic
  surfaces and inner hydrophobic portions
• Lipid rafts ? specific regions of plasma
  membrane, rich in cholesterol and
  glycosphingolipids, contains membrane proteins,
  function as signaling platforms, each raft has
  its required elements, signal transduction is
  rapid and efficient in rafts,
• Glycoproteins or Glycolipids ? carbohydrates
  attach to Proteins or lipids at extracellular
  surface and forms cell coat or Glycocalyx

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Membranous organelle plasma membrane

• Protein of Plasma membrane
• 50 of plasma membrane mass ?proteins
• Localization of proteins ? done by lipid rafts
• How to study integral proteins ? by freeze
  fracture technique
• With their E (extra cellular)-face and P
  (protoplasmic)-face
• Functions of integral proteins ? pumps, channels,
  receptors, enzymes,
• Integral proteins ? move to a different region,
  helps in precise signaling

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Membranous organelle plasma membrane
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Membranous organelle plasma membrane

• Membrane transport

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Membranous organelle plasma membrane

• Membrane transport
• Fat soluble ones? by simple diffusion (along
  concentration gradient, no need of transport
  proteins)
• Other molecules ? need transport proteins,
  against concentration gradient, by two ways
• Carrier molecules transfer small water soluble
  ones, highly selective, may (Na pump) or may not
  (glucose) need energy
• Channel proteins ? transfer similar molecules,
  create hydrophilic channels across the membrane,
  ion selective, can be regulated by membrane
  potentials (voltage gated) or neurotransmitter (
  ligand gated) or by mechanical stress (
  mechanically gated)

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Membranous organelle plasma membrane

• Vesicular transport

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Membranous organelle plasma membrane

• Vesicular transport

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Membranous organelle plasma membrane

• Vesicular transport
• Maintains membrane integrity
• Transport molecules between different cellular
  compartments
• Precise trafficking of molecules to specific
  sites is ensured by SNARE proteins
• Can be
• Endocytosis substances enter the cell
• Exocytosis substances leave the cell
• Endocytosis ? three mechanisms
• Pinocytosis cell drinking
• Phagocytosis (actin dependent) cell eating
• Receptor mediated (clathrin dependent) cargo
  receptors accumulate at coated pits

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Membranous organelle plasma membrane

• Vesicular transport
• Exocytosis substances leave the cell
• Molecules from the site of synthesis ? Golgi
  apparatus ? sorting and packaging of secretary
  molecules into vesicles ? vesicles fuse with
  plasma membrane
• Specific proteins regulate intracellular
  trafficking ? coatomers ( COP -1 COP-2)
• Two pathways of Exocytosis
• Constitutive no storage vesicles, secretions
  released soon they are formed, Igs form plasma
  cells, Tropocollagen form fibroblasts
• Regulated secretary secretary molecules stored
  temporarily in storage vesicles, after a stimulus
  (hormone or neuronal ) ? Ca influx ? release

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Membranous organelle Endosomes
MVB Multivesicular bodies
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Membranous organelle Endosomes

• Associated with endocytotic pathways of cell
• Sequence early Endosomes (peripheral in
  location)? late Endosomes (close to nucleus) ?
  Lysosomes
• Substances (pro hydrolases) targeted for
  Lysosomes are tagged with mannose -6-hosphate
  (M-6-P)
• M-6-P receptors are present on early and late
  Endosomes
• Multivesicular vesicles ? highly selective
  transport vesicles from early to late Endosomes

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Membranous organelle Lysosomes
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Membranous organelle Lysosomes

• Rich in hydrolases which are responsible for
  degradation of large molecules
• Degradation done by
• Autophagy of own cellular organelle
• Heterophagy degradation of endocytosed
  molecules
• Lysosomes membrane contain unique lipid
  (lyso-biphosphatidic acid) and highly
  glycosylated membrane proteins ( LIMP, LAMPS,
  LGPS)
• Pathways of delivery of substances for lysosomal
  digestion

Knowledge is power what happens if there is lack
of hydrolase (s) in Lysosomes?
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Membranous organelle Lysosomes

• Pathways of delivery of substances for lysosomal
  digestion

Knowledge is power what is the name for
undigested material in Lysosomes?
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Membranous organelle rER
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Membranous organelle rER

• Cytoplasm of cells rich in rER ( engaged in
  protein synthesis) ? is basophilic due to ?? RNA
• Polyribosome or polysomes groups of Ribosomes
  attached to ER in spirals
• Site of protein synthesis
• Well developed in secretary cells (endocrine) and
  in cells that produce lots of plasma membrane
  proteins (neurons)
• it also act as check point of exit of newly
  formed proteins
• New proteins usually delivered to Golgi and the
  bidirectional traffic is regulated by coatomers
• COP-1 for retrograde ( to rER) and COP-2 for
  anterograde ( to Golgi)

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Membranous organelle sER
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Membranous organelle sER

• If cells have large sER (active in fatty acids
  and phospholipids synthesis) ? eosinophilia
• Differs from rER (structurally)
• No polysomes
• Look like tubes rather than sheets
• Rich in steroid producing cells (Leydig cells)
• Called as sarcoplasmic reticulum in skeletal
  cardiac muscle
• Principal role in detoxification (cytochrome
  p450) and conjugation
• Has role in lipid, steroid and glycogen
  metabolism membrane formation and recycling

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Membranous organelle Golgi
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Membranous organelle Golgi

• Well developed in secretary cells (like rER)
• Not stained with H or E
• Perinuclear halo or hof of Plasma cells ? due to
  Golgi
• Close to nucleus and polarized
• Role in post-translational modification, sorting,
  packaging of proteins
• Different pathways for protein secretion from the
  Golgi
• Takes place from the trans Golgi network (TGN)

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Membranous organelle Mitochondria
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Membranous organelle Mitochondria

• Can divide even when the cell is in interphase
• Can change shape or location in cytoplasm
• Generate ATP ( energy)
• Present in large s in metabolically active cells
  ( skeletal muscle, Liver, PCT of kidney)
• Have complete system for its own protein
  synthesis and of their Ribosomes (TOM TIM
  protein complexes)
• ATP synthesis hydrogen ions move down the
  electrochemical gradient along proton pump
• ATP goes out and ADP comes into the mitochondria
• Configurational changes in mitochondria
• Orthodox prominent cristae ? oxidative
  phosphorylation
• Condensed cristae lee prominent ? oxidative
  phosphorylation

Knowledge is power Mitochondria present in all
cells except ?
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Membranous organelle Mitochondria

• Structure
• Have double membranes, inner and outer separated
  by intermitchodrial space
• Matrix space inside the inner membrane
• Outer membrane
• Has voltage dependent anion channels (
  mitochondrial porins)
• environment of intermitchodrial space is
  similar to cytoplasm because of porins
• Has receptors for proteins, polypeptides,
• Contains enzymes ( PL A2, MAO, Acetyl CoA
  synthase)
• Intermitchodrial space
• Has enzymes ( CK, Adenylate kinase, CY C )

Knowledge is power organelle store /sequester
Ca? How Cell death or point of no return is
reflected in cytoplasmic organelle?
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Membranous organelle Mitochondria

• Structure
• Inner membrane
• Thinner than outer
• Arranged in folds cristae,
• Rich in PL- cardilipin (contributes to membrane
  impermeability)
• Elementary particles tennis racquet shaped
  enzyme molecules in TEM
• Functions
• Oxidative reactions of respiratory electron chain
• ATP synthesis
• Regulation of metabolite transport
• Matrix
• Has enzymes of citric acid or krebs cycle
• Products Co2, reduced NADH ( source of electron
  transport)
• Dense matrix granule ? Ca stores

Knowledge is power what happens if cytochrome C
leak into cytoplasm
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Membranous organelle Peroxiosomes

• Single membrane bound, contains oxidative enzymes
  (catalase, peroxidase)
• Role in
• detoxification ( in Liver)
• ß oxidation of very long chain FA
• Abundant in Liver, Kidney cells
• If faulty
• Zellweger syndrome
• Refsums disease

Knowledge is power have any idea about the above
two diseases?