Cell organelles
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Cell organelles






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  • Depending on developmental stage and environment, #, size, enzymes, metabolic function, varies. Grow on sugar: small peroxisomes Grow on methanol: large peroxisomes that oxidize methanol Grow on FA: large and break down FA to AcetylCoA by  -oxidation

Cell organelles Cell organelles Presentation Transcript

  • The organelles of animal and plant cells are similar to each other except that __________ are present only in animal cells, and ___________ are present only in plant cells. ORGANELLES Animal and plant cells have organelles . Organelles compartmentalize functions within the cell.
    • Electron micrographs of cells show mitochondria as rod like structures.
    • 0.5 μ ,m-1 μ m in diametre
    • 7 μ m in length
    • Component of electron transport system.
    • Impermeable to most ions and large molecules e.g; H,Na,ATP,GTP ,Pyruvate,Citrate etc.
    • For transport special carriers are present e.g Adenine nucleotide carrier system(ATP-ADP Transport)
    • Complex II,Succinate dehydrogenase
    • Complex V,ATP Synthetase complex.
    • Permeable to all ions
    • Matrix
    • Inclosed by inner mitochondrial membrane.
    • Contain enzymes of:
    • Citric acid cycle
    • β oxidation of fatty acids
    • Amino acid oxidation
    • Urea and heme synthesis
    • NAD
    • FAD
    • ADP,Pi
    • Mitochondrial DNA
    • Circular DNA,has information for 13 mitochondrial proteins and some RNAs
    • Mitochondrial cytochrome P450 system
    • P450 system is involved in the hydroxylation of cholesterol to steroid hormones(placenta,adrenal cortex,ovaries and testes)
    • Bile acid Synthesis (liver)
    • Vitamin D formation(kidney)
    • Mitochondria plays a key role in aging.Cytochrome C component of ETC plays a main role in cell death and Apoptosis.
    • Fatal infantile mitochondrial myopathy and renal dysfunction.
    • MELAS(Mitochondrial encaphalopathy lactic acidosis and stroke)
    • Myoclonic epilepsy etc.
    • ROUGH ER
    • Biosynthesis of proteins.
    • Special proteins called CHAPERONS are present ,involved in proper folding of proteins.
    • Protein glycosylation
    • SMOTH ER
    • Synthesis of lipids,cholesterol and steroid hormones.
    • Detoxification of endogeneous and exogeneous substances
    • Microsomal cytochrome P450 monoxygenase system(Xenobiotic metabolism)
    • Elongation of fatty acids
    • Desaturation of fatty acids
    • Omega oxidation of fatty acids
    • Synthesis of other organelles ,peroxisomes and lysosomes in association with Golgi Apparatus.
  • _________ ___________ GOLGI APPARATUS
      • Function: Packages, modifies, and transports materials to different location inside/outside of the cell.
      • Appearance: Stack of pancakes
    • Consists of a stack of curved saccules.
    • Receives protein and also lipid-filled vesicles from the ER, packages, processes, and distributes them within the cell or for export out of the cell (secretion) .
    • Also encloses digestive enzymes into membranes to form lysosomes.
    • Golgi complex is the site for the formation of carbohydrate side chains of glycoproteins and mucopolysacchrides(GAGs)
    • It gives rise to acroblast of spermatozoa that is converted to acrosome.It contains lysosomal enzymes and proteinases invoved in the fertilization of ovum.
    • Extracellular digestion of both intracellular and extracellular substances.
    • Single limiting membrane.
    • Acidic pH 5.
    • They have group of enzymes called HYDROLASES.The enzymes destined to inter lysosomes has mannose at their ends,which change to manose 6 phosphate and enter into the lysosomes.
    • An osteoclast breaks the bone matrix down into fragments by means of secreated acid and lysosomal hydrolases .It completes the breakdown by endocytosis and lysosomal digestion of the fragment.
    • Age pigment wear and tear pigment.
    • Release of lysosomal enzymes in response to ionizing rediations,some carcinogens,silca particles,dust,hypoxia,heat and certain drugs leading to cell death, mutaions in genome and malignancies.
    • Lysosomal storage diseases
    • First observed by electron microscopy in animal cells (1950s), then in plant cells (1960s)
    • Christian deDuve (1965)
      • Isolated from liver cells by centrifugation
      • Called them peroxisomes because they generate and destroy H 2 O 2
    • Single membrane
    • Roughly spherical
      • 0.2 - 1.7  m
    • Composition varies
    • Rich in enzymes.
    • 50 Enzymes have been demonstrated in them.
    • Proteins called PEROXINS are involved in the various stages of their production.
    • These are involved in the metabolism of lipids i.e.plasmalogens,cholesterol.
    • Involved in the β oxidation of very long and branched chain fatty acids.
    • Shortens the chain of cholesterol in the formation of bile acids.
    • Peroxisomes are involved in the production and detoxification of H ₂O₂
    • PPARs α :expresses genes hepatic enzymes for β oxidation and formation of ketone bodies.
    • PPARs γ :express genes encoding for protein synthesis involved in lipid synthesis and storage in the fat cells.
    • PPARs δ :express genes encoding proteins of liver and muscles involved in the β oxidation of fatty acids and dissipation of free energy as heat.
  • Adrenoleukodystrophy: Deficiency in  -oxidation of very long- chain fatty acids Zellweger syndrome: Defect in protein import, giving rise to “ghost peroxisomes”
      • An apparent amorphous mass enclosed by a nuclear envelope,Literally mean central core of the body or object.
      • Within:
        • Chromosomes
          • Chromatin
        • Nuclear matrix
          • Fibrillar network
        • Nucleoli
          • r-RNA and ribosomes
        • Nucleoplasm
          • Fluid of the nucleus
    • The nuclear envelope
      • Components:
        • Two cellular membranes
          • Barrier to ions, solutes, macromolecules
        • Membranes fused to form pores
          • Complex assemblies of proteins
        • Outer membrane
          • Ribosomes
          • Continuous with RER
        • Inner membrane
          • Bound to nuclear lamina
            • Filamentous network
          • Nuclear lamina
            • Supports envelope
            • Attachment of chromatin
          • Nuclear lamina fibers
            • Proteins – lamins
            • superfamily – Intermediate filaments of cytoplasm.
    • The nuclear pore complex (NPC)
      • Large numbers of proteins – synthesized in cytoplasm and transported into the nucleus
      • RNAs manufactured in nucleus – transported to cytoplasm
    • NPC is made up of about 50 proteins called nucleoporins.
    • Show both selective and non selective movements of ions and substances.
    • Larger proteins(RNA polymerases)need special mechanisms to move from cytoplasm into the nucleus.Signal system….
    • Expenditure of energy by GTP hydrolysis.
    • RNA move from nucleus to cytoplasm through these pores.
    • The nuclear envelope
      • Components:
    • The nuclear pore complex (NPC)
    Eukaryotic Nucleus - Structure
  • Chromatin
    • Represents substance of chromosomes.
    • Each chromatid in a chromosome represents one DNA molecule that occurs in a highly condensed form.
    • The nucleic acids present in the chromatin is mostly DNA but small ammount of RNA is also present.
    • Chromatin is a combination of DNA and protein.
    • The most abundant proteins are histones(5 types),NUCLEOSOMES.
    • Other proteins include enzymes like DNA and RNA polymerases,Protins involved in the regulation of DNA transcription and replication.
    • Chromatin occurs in two forms,
    • Euchromatin
    • Stains lightly,partially or completely
    • uncoiled,active transcription.
    • Hetrochromatin
    • Stains deeply,highly coiled,generally
    • inactive include noncoding
    • regions,telomere and centromere.
    • Constitutive heterochromatin
    • Facultative
    • X chromosome inactivation, bar b0ody.
    • Also called micronucleus.
    • Nucleolonema,network of
    • Strands containing RNA.
    • Size varies depending
    • upon the activity.
    • Nucleoli are formed around specific genetic loci called nucleolar organizing regions (NORs).
    • Consists of two parts.
    • Fibrillar part.(site for rRNA transcription).Genes for 28s,18s and 5.8s are located there.
    • Granular part.(assembly of ribosomal subunits takes place there).