Cells

• Catabolism


  Reaction resulting in the degradation of cellular components with the release of energy
• Contractility is the ability of the cell to shorten along their long axes (special property of muscle)
• The Nucleus may vary in number, shape, and position, and has components like Nuclear membrane, Karyolymph, Chromatin, Nucleolus
• Metabolism


  Sum of all chemical reactions occurring within the cell
• Excretion

  Ability of the cell to get rid of waste products of metabolism. Example - urine by the kidney, feces by the GIT
• Cell shape may vary and is influenced by factors such as cellular contact and pressure
• Cellular structure includes shape diversity of cell organelles but they are spatially organized within the cell
• Endocytosis


  Process by which materials gain access to the cell either by diffusion or pinocytosis in case of fluids; or phagocytosis in case of particulate matter. Exocytosis is the exit of materials from the cell
• Secretion

  Ability of the cell to elaborate useful new substances. Example - secretion of bile by hepatocytes, pancreatic juice by the pancreas
• Anabolism


  Reaction resulting from the synthesis of new molecular components essential for growth, maintenance, and repair
• Irritability is the ability of the cell to respond to stimuli in their environment
• Conductivity

  Ability of the cell to transmit impulses along their cell membrane (special property of nerve cells)
• Universal properties of protoplasm

  • Growth
  • Maintenance
  • Reproduction
• Cell is divided into Cytoplasm and Nucleus, and is a semi-open system requiring a diffusion barrier
• Heterochromatin is the condensed form of chromatin which stains deeply with basic dyes and is metabolically inert. Euchromatin is the dispersed form that stains
• Cell size varies per cell type: Sperm 3-5 µm, RBC 5-7 µm, Hepatocyte 30-50 µm, Egg cell 100 µm
• Euchromatin


  • The dispersed form that stains lightly and metabolically active
• Chromatin


  Term used to describe any area in the nucleus suspected to contain DNA and its bound proteins
• Ground substance is an admixture of H2O, CHON, CHO, organic and inorganic salts
• Nucleolus

  • Non-membrane-bound component of the nucleus which may occur freely or attached to the inner nuclear membrane
  • Composed of granular and filamentous materials both of which contain RNA
  • Is the center for the synthesis of RNA (ribosomes)
  • May occur singly or more in the cell and this determines the malignancy of a cell
• Non-membrane-bound cell organelles

  • Ribosomes
• Endoplasmic Reticulum


  • A system of hollow structures either tubules or flattened vesicles (cisterna) extending throughout the cytoplasm
  • There are 2 types: RER & SER
  • RER continuous with the nuclear membrane studded with ribosomes (appears basophilic due to ribonucleoproteins)
  • Functions: Protein synthesis destined for secretion (e.g. digestive enzyme), Glycogen biosynthesis, Production of degradative enzymes e.g. glucose-6-PO4
  • SER not studded with ribosomes, thus has no distinct staining characteristics, less extensive than RER except in certain cells like hepatocytes
  • Functions: Participates in glycogen metabolism, synthesis, Participates in ion concentration, distribution, and C, Believed to contribute to the formation of Golgi apparatus
• Membranous organelles

  • Cell membrane/plasma membrane/plasmalemma and cell coat
  • Endoplasmic reticulum (smooth & rough)
  • Golgi apparatus
  • Mitochondria
  • Lysosomes
• Components of the cytoplasm

  • Ground substance/hyaloplasm/cytoplasm matrix
  • Organelles
  • Inclusion bodies
• Heterochromatin


  • The condensed form of chromatin which stains deeply with basic dyes and is metabolically inert
• Membrane-bound cell organelles

  • Cell membrane/plasma membrane/plasmalemma and cell coat
  • Endoplasmic reticulum (smooth & rough)
  • Golgi apparatus
  • Mitochondria
  • Lysosomes
• Barr body


  A distinguishable heterochromatin believed to contain the X chromosome, a distinct feature in females
• Plasma membrane

  • Structure: Phospholipid bilayer
  • Membrane Protein: 25-75% of the weight of cell membrane, distinguished according to function
  • Membrane Carbohydrates: 2-10% of the weight of cell membrane; covalently bound to membrane proteins (glycoproteins) or membrane lipids (glycolipids)
• Golgi apparatus/complex

  Has a lamellated profile (4 or more) usually dilated sacks or cisternae; has 2 faces: convex face or immature/formative/cis face closely associated with transfer vesicle from RER, concave or mature/open/trans face intimately associated with secretory vesicles
• Ribosomes

  • The only non-membranous cell organelle
  • Are RNA-containing bodies in the nucleus and cytoplasm of the cell
  • In the nucleus, they are found in the nuclear matrix of the nucleolus
  • In the cytoplasm, they occur as free ribosomes individually or in groups called polyribosomes or polysomes or attached to the RER
  • Synthesize proteins for intracellular use
• Centrioles are two small bodies contained within an area of the cytoplasm known as centrosphere
• Mitochondria


  • Appears as thread or granules, can be stained specifically with janus green B
  • Number varies in the cell depending on energy requirements
  • Ultrastructurally appears as a double membrane structure with inner and outer walls
  • Inner wall forms plate-like or tubular folds called mitochondrial cristae
• Inclusion bodies can be either absorbed or generated and may contain pigments or reserved materials
• Lysosomes

  • Membrane-bound particles containing hydrolytic enzymes collectively called acid hydrolases
  • Specific granules of basophils, eosinophils, and neutrophils are representative of lysosomes believed to come from Golgi apparatus
  • Fates include intracellular digestion, autolysis, and post mortem degeneration
• Microtubules are composed of proteins, tubulin, found in cilia, flagella, and spermatids
• Golgi apparatus/complex

  • Has a lamellated profile with dilated sacks or cisternae
  • Has two faces: convex face (immature/cis face) closely associated with transfer vesicles from RER, concave face (mature/trans face) associated with secretory vesicles
  • Chromophobic and cannot be stained routinely
  • Membranous cisterns are in constant flux with new membrane added at the convex face and old membrane lost at the concave face
• Plasma membrane appendages include microvilli, stereocilia/villi, microplicae, and cilia
• Apical border of columnar cells

  Found in epididymal epithelium and hair cells in the inner ear
• Anchoring Junction


  Mechanically attaching cells to other cells or to ECM
• Cilia

  • motile; lash-shaped; can occur singly (spermatozoa) or in complexes (epithelium of fallopian tube and trachea)