EUKARYOTIC CELL- FEATURES,STRUCTURE,ORGANELLES AND FUNCTIONS

EUKARYOTIC CELL

  • FEATURES,
  • STRUCTURE,
  • ORGANELLES AND FUNCTIONS


FEATURES OF EUKARYOTIC CELL

  • Cell- structural and functional unit of organism
  • Nucleus is present .
  • DNA complex with histone present
  • More than one chromosomes
  • Mitosis and meiosis occurs
  • Ribosomes are 80S(cytosol) & 70S (organelles)
  • Membrane bound organelles are present
  • Sterol present in plasma membrane
  • Cell wall made of cellulose(plant), chitin(fungi), and absent in animal cell

STUCTURAL OF EUKARYOTIC CELL

PLASMA MEMBRANE

  • Dynamic ,fluid structure & selectively permeable membrane.
  • Fluid mosaic model made of lipid bilayer , protein(integral and peripheral protein) and carbohydrates.
  • Plasma membrane in human(43% lipid & 49% protein by weight) 
  • Plasma membrane in mouse liver cell(54% lipid & 46% )protein by weight.
  • Carbohydrates (5-10%).
  • Lipid bilayer composed of amphipathic molecules(one hydrophilic head and two hydrophobic tail) consist of sphingomyelin & phosphatidylcholine (more amount in extracellular non- cytosolic leaflet), phosphatidylethanolamine & phosphatidylserine (more amount in cytosolic leaflet).       
Hydropathy plot – movement of amino side chain from hydrophobic solvent into
water
Freeze fracture structure –frozen by liquid nitrogen at -196°C





Transport across P.M
Ions < large uncharged molecules < small polar molecules < Hydrophobic molecules

  1. Passive transport – along the concentration gradient without use of energy
  2. Active transport –against concentration gradient with use of energy diffusion
  3. facilated diffusion – movement of solute along concentration gradient
Transport of macromolecules through P.M
Endocytosis(insisde the cell)
    1. Phagocytosis(cellular eating)
    2. Pinocytosis(cellular drinking)
Exocytosis(outside the cell)


ORGANELLES OF CELLS

RIBOSOMES( made up of RNA and Proteins)




Bacterial-70S(5S,23S/16S) , Chloroplast-70S(5S,23S/16S),
Mitochondria – 55S(16S/12S), Archaebacteria- 70S(5S, 23S/16S) ,
Eukaryotes(cytosol)- 80S(5S,5.8S, 28s/18S)

Function – Protein targeting and transclocation

ENDOPLASMIC RETICULUM(network of closed and flattened membrane bound structure)

  • Differentiated into rough(ribosomes present) and smooth region(ribosomes absent)
  • Microsomes- ER break into fragment and reseals into small fragment)

  • Function of RER- Addition and processing of caarbohydrates
  1. Formation of disulfide bond
  2. Protein folding
  3. Specific preteolytic cleavage
  4. Assembly in multimeric protein
  • Function of SER- 
  1. Lipid Biosynthesis
  2. Detoxification of xenobiotics compounds
  3. Calcium regulation

GOLGI APPARATUS(single membrane bound organelle part of ER)

Cisternae -five to eight flattened membrane bound sacs
Cis face- entry face
Trans face – maturing face

Function of compartmentalization of golgi apparatus 




Function - glycosylation of protein and lipid & polysaccharides metabolism

VACUOLES(fluid filled vesicles)

tonoplast – single membrane

LYSOSOME(single membrane bound organellenin animal cell)

Have acidic pH and filled with hydrolytic enzyme

Two types of lysosomes
  1. Primary lysosomes(do not contain material for intracellular digestion)
  2. Secondary lysosomes(contain material that are understanding digestion ot that is digested.
Heterophagy – process by which substances are taken into the cell from external environment and
broken down by lysosomes.
Autophapy – The degradation of cytoplasmic component within lysosomes
Phagolysosomes – phagosomes fuses with a lysosomes
Endolysosomes - fusion with pre existing lysososme and progressive acidification

PLASTIDS( self autonomous organelle present in plant cell and photosynthetic protists

Propastids- immature stage
Etioplast- yellow chlorophyll precursor pigment
Chromoplast- pigment synthesis and storage
Amyloplast(starch storage), Elaioplast(fat storage), Aleuroplast(storing and modififying protein)

CHOLOROPLAST(green colour pigment)

Structure of choloroplast
Fluid filled region- Stroma
Group of stack- Grana single stack- Granum
Flattened sac which makes up the granum- Thylakoid
consist of 80% lipid made of uncharged Diacylglycerols & 10% by phospholipids

PEROXISOMES (Produce and consume Hydrogen peroxide)

  • Discovered by Christian de durve
  • Lack DNA and Ribosomes
  • Conversion of peroxide into water and oxygen by enzyme catalase

NUCLEUS (Center of cell)

Nuclear envelope-covering of nucleus
Nuclear matrix- structure framework to chromatin
Nucleolus – diappear in late prophase and reappear in telophase
Nucleoporin- copies of protein
Nuclear lamina- network of intermediate filament
Chromatin- organized structure of DNA
Chromosome – chromatin condensation




MITOCHONDRIA( power house of cell)
  • Produce cellular energy in the form of ATP
  • Double membrane bound structure
  • Outer membrane is smooth protect organelle and contain transport protein called porins
  • Inner membrane is highly convoluted form fold called cristae, made of cardiolipin contain ATP synthase complex
Maternal inheritance take place
Hydrogenosome – mitochondria present in protists involved in synthesis of ATP and
hydrogen
Mitosome – cryptic mitochondria

CYTOSKELETON( intracellular network of protein)

ex. Microtubules , kinins, dyneins

Cell junction
  • Occluding junctions – seal cell in epithelium
  • Anchoring junction – attach cell to extracellular matrix
  • Communicating junction – passage of chemical or electrical signal
  • plasmodesmata-communication in plant cell
Cell signaling
  • Endocrine- signal at far distance through blood stream
  • Paracrine – signal to close proximty
  • Autocrine – signal on same cell
  •  Juxtacrine – doesnot diffuses in a cell.




Apoptosis-cell death

Necrosis- degradation process after cell death
Pyknosis- condensation of chromatin after cell death
Karyorrhexis- nuclear fragmentation
Karyolysis- dissolution of the chromatin

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