Structure and Function of the Eucaryotic Cells

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Structure and Function of the Eucaryotic Cells

• Hanna Kubiak,M.D.,Ph.D.

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What are Eucaryotic cells?

• All cellular organism we divide into
• Procaryota and Eucaryota
• Procaryotic (Gr. pro before karyon nucleus)
  cell has a nucleoid (without nuclear
  envelope).BACTERIA
• ALGAE
• Eucaryotic (Gr. eu good, karyon nucleus) cell
  has a nucleus separated from cytoplasm by nuclear
  envelope.
• PLANT CELLS
• ANIMAL CELLS
• HUMAN CELLS

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Definition of cytology and histology

• Gr. kytos cell logos studyCytology the
  study of the cell (its structure and function)
• Gr. histo web or tissueHistology the study
  of the tissues of the body

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Chemical elements present in living cells

• 59 Hydrogen (H)
• 24 Oxygen (O)
• 11 Carbon (C)
• 4 Nitrogen (N)
• 2 Others - Phosphorus (P), Sulphur (S), etc.

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Molecules that make up the cell

• 50 protein
• 15 nucleic acids
• 15 carbohydrates
• 10 lipids
• 10 other

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Sizes

• 1 mm 10-3 m
• 1 mm 10-6 m
• 1 nm 10-9 m
• 1 nm 10A

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Examples of sizes

• 0.1 nm (nanometer) diameter of a hydrogen atom
  
• 0.8 nm amino acid
• 2 nm diameter of a DNA alpha helix
• 4 nm globular protein
• 6 nm microfilaments
• 7.5 -10 nm thickness of the cell membranes
  (unit membrane)

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Examples of sizes (continued)

• (1 - 10 mm ) the general sizes for Prokaryotes
• 2 mm E.coli - a bacterium
• (10 - 30 mm ) Most Eukaryotic animal cells
• 7.5 mm Human red blood cell
• Striated muscle cells up to 100 mm in diameter
  and even several cm in length

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Examples of sizes (continued)

• 25 nm Microtubule
• 50 nm Nuclear pore
• 100 nm Large Virus
• 200 nm Centriole
• 200 nm (200 to 500 nm) Lysosomes
• 200 nm (200 to 500 nm) Peroxisomes
• 1 mm (micrometer)
• 0.5 - 3 mm Mitochondrion
• 6 mm (3 - 10 micrometers) the Nucleus

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Optical resolutionOptical capacity to reveal
detail

• Electron microscope
• 1 - 2 nm

• Light microscope
• 0.2 mm 200 nm

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Histological specimens main techniques

• Light microscope
• Paraffin technique preparing sections 4 10 mm
  thickness
• Cell smears (blood, scrapigs from the cervix of
  uterus)
• Freezing and cryostat sections for
  histochemistry and immunocytochemistry

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Histological techniques types of light
microscopes

• phase contrast microscopy
• difference interference microscopy
• polarizing microscopy
• confocal microscopy
• fluorescence microscopy

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Electron microscopes

• Transmission electron microscopy
• Scanning electron microscopy
• Freeze-fracture technique.

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Shape of animal cells

• Mainly streamline
• Frequently round or oval
• Sometimes long and narrow
• With cytoplasm projections
• Shape of cell may change

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The main components of cell

• Cytoplasm
• 1. Plasmalemma - (cell membrane)
• 2. Cytosol - a lot of water - all except the
  organelles
• 3. Organelles (which also have membranes) in
  'higher' Eukaryote organisms
• 4. Cytoskeleton microtubules, microfilaments
  (actin filaments), intermediate filaments
• and
• Nucleus

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Histological staining of cells and tissues

• Haematoxylin and eosin staining (standard) HE
• haematoxylin is basic, blue and stains nucleus
• eosin is acidic, pink and stains cytoplasm

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Cell fractionation by differential centrifugation
(using different forces). Fraction s of the cells
can be analyzed in electron microscope or with
biochemical methods in vitro
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Cell membrane (unit membrane) 7.5 10 nm

• Components
  Phospholipids, Cholesterol, Glycolipids, Proteins
• Main structure
• phospholipid bilayer
  
  
  
  
  

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Types of lipids present in cell membranes

• - Cholesterol
• - Glycolipids
• - Phosphatidylcholine
• - Sphingomyelin
• - Phosphatidylethnolamine
• - Phosphatydilinositol
• - Phosphatidylserine
• - Phosphatidylglycerol
• - Diphosphatidylglycerol (Cardiolipin)
• - Phosphatidic acid

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Assymetry of cell membrane

• Phosphatidylcholine and sphingomyelin in external
  lipid layer
• Phosphatidylserine and phosphatidylethonolamine
  in inner layer
• Glycolipids (with oligosaccharide compound) only
  in external layer

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Proteins present in plasmalemma

• Enzymes
• Receptors
• Transport channels
• Integral proteins
• Connection to cytoskeleton and to extracellular
  matrix

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Transport across plasma membranes

• Passive diffusion small molecules water, urea,
  gases
• Facilitated diffusion larger hydrophilic
  molecules glucose, transmembrane protein is
  needed as carrier
• Active transport ions Na and K sodium pump
  mechanism, energy from ATP is requied
• Bulk transport large and small particles
  transported by endocytosis. If excretion at
  another place transcytosis.

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Alkaline phosphatase histochemical reaction
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Nucleus

• The most obvious organelle in any eukaryotic cell
• Surrounded by a double unit membrane
• Communication with the surrounding cytosol via
  numerous nuclear pores
• Within the nucleus - the DNA responsible for
  providing the cell with its unique
  characteristics
• DNA is similar in every cell of the body, but
  depending on the specific cell type, some genes
  may be turned on or off - that's why a liver cell
  is different from a muscle cell, and a muscle
  cell is different from a fat cell
• During cell division, the DNA and surrounding
  protein condense into chromosomes that are
  visible by microscopy
• The nucleolus - prominent structure in the
  nucleus is. The nucleolus produces ribosomes,
  which move out of the nucleus to positions on the
  rough endoplasmic reticulum where they are
  critical in protein synthesis

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Nucleolus

• Deeply stained structure without membrane
• rRNA forming

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Smooth endoplasmic reticulum
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Rough endoplasmc reticulum
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Endoplasmic reticulum

• Rough (contains ribosomes). Protein
  biosynthesis.
• Smooth (without ribosomes).
• Lipid biosynthesis, mainly steroids.
• Calcium ions storage.

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Lysosomes

• contain around 40 enzymes for intercellular
  digestion
• The lysosome membrane helps to protect the
  enzymes as much as it helps protect the cell.
• Optimal pH for these enzymes is around a pH of 5.
  The membrane of the lysosome is again a lipid
  bilayer and is thought to have a ATP hydrolysis
  to pump H into the lysosome to maintain the pH.
  This also has another affect, that is free
  protons
• necessary for endocytosis process

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Lysosomes hydrolytic enzymes acid
phosphatase, beta-glucuronodase, cathepsins,
DNA-se, RNA-se
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Endocytosis

• Endosomes and lysosomes are involved in the
  ingestion, sequestering and degradation of the
  substances ingested from intercellular space
• Phagocytosis endocytosed vesicle is gt 250 nm
  (phagosome)
• Pinocytosis (cell drinking) vesicle is lt 150 nm
  (pinocytotic vesicle)
• Early endosome and late endosome (multivesicular
  body)
• Fusion of endosome with lysosome (phagolysosome)
  and digestion

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Endocytosis
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Enzymes present in peroxisomes

• oxidation enzymes associated with peroxisomes
• D-amino acid oxidase
• Urate Oxidase
• Catalase

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Mitochondria
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Outer membrane transport of substances Inner
membrane cytochromes, electron transport
chain, production of ATP Matrix Krebs
cycle, enzymes dehydrogenases (succinic
dehydrogenase)
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The chemiosmotic theory of mitochondrial energy
transduction. Middle The flux of protons is
directed from the matrix to the intermembranous
space promoted at the expense of energy derived
from the electron transport system in the inner
membrane. Left Half the energy derived from
proton reflux produces ATP the remaining energy
produces heat. Right The protein thermogenin,
present in multilocular adipose tissue, forms a
shunt for reflux of protons. This reflux, which
dissipates energy as heat, does not produce ATP.
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Lysosomes and mitochondria
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Golgi apparatus

• The enzymatic or hormonal contents of lysosomes,
  peroxisomes and secretory vesicles are packaged
  in membrane-bound vesicles at the periphery of
  the Golgi apparatus.
• membrane-bound vesicles that are important in
  packaging macromolecules for transport elsewhere
  in the cell and secretion

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Golgi apparatus
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Centrioles and Basal Bodies

• Centrioles are associated with the cytoskeleton
• A centriole is made up of nine (9) sets of
  triplet microtubules, is commonly found in the
  centrosome, which is where the asters originate
  during metaphase of cell division
• Plant cells commonly do not have centrioles and
  they are not required for division.
• The centriole is a short cylinder-like structure.
  A triplet contains one complete microtubule fused
  to two incomplete microtubules. The centriole is
  important in the formation of cilia or flagella,
  then it is called a basal body are typically
  thought in relation to cilium or flagellum, where
  as

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Intermediate filaments

• 10 15 nm in diameter
• Characteristic for different tissues
• Epithelia cytokeratins
• Connective tissue - vimentin
• Muscles desmin
• Nervous tissue neurofilament proteins and glial
  fibrillary acidic protein