Anatomy of Protozoa

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Anatomy of Protozoan Cell

• Shifa Ul Haq
• PhD Scholar, UVAS, Pakistan.

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Protozoa

• Heterogeneous group of organisms.
• Organelles of Protozoa are related to those of
  metazoan cells.
• Some have ability to move
• Protozoa found everywhere, but mostly present in
  aquatic environment.
• Cant synthesize structural substances from
  inorganic matter.
• More than 200,000 Protozoan species (10,000
  Parasitic in invertebrate vertebrate hosts.

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Prokaryotic Cells
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Prokaryotic Cells(Prenucleus)

• Small unicellular organisms (0.2 2.0 µm in
  diameter and 2 8 µm in length.
• Possess indistinct nucleus (lack of nucleus
  nucleoli).
• Chromosome coiled like skein of wool.
• Single circular chromosome with out histons.
• Lack other membranous system (organelles) in
  cytoplasm.
• Cell division by binary fission fewer cell
  division structures than eukaryotes.
• No meiosis.

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Eukaryotic Cell (Protozoa)

• Eukaryotic cells are large structurally more
  complex (10 100 µm in diameter).
• Have membrane bound organelles.
• Genetic material (DNA) is membrane bound i.e.
  enclosed in nucleus on chromosomes.
• Nucleoli present.
• Cell wall absent when present it is simple.
• Multiple linear chromosomes with histone.
• Mitosis
• (Sexual reproduction) Meiosis

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Eukaryotic Cell (Typical)
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Organelles in Protozoa (Nucleus)

• Organelles Specialized structure for various
  functions.
• Bounded by double membrane nuclear envelope.
• Membrane is perforated connected with ER
• Contains nucleolus or nucleoli (rRNA synthesized)
  or endosome (Karyosome). Somatic function.
• Endosome is devoid of DNA.
• Nucleus have different shapes (spherical, oval,
  cylindrical, sausage shape etc.

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Nucleus (Types)

• Macronucleus in ciliates (Cytoplasmic functions).
• Micronucleus in Ciliates (dormant but active at
  sexual reproduction).
• Two similar nuclei (Giardia).
• Trophonucleus in trypanosome (control general
  life of cell).
• Kinetoplast (kinetonucleus) regulate locomotion.

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Protozoa (Cytoplasm)

• Substance inside the plasma membrane Outside
  the nucleus
• Extra-nuclear portion of cell.
• Ectoplasm (Homogenous).
• Endoplasm (granular contains various vacuoles
  organelles).
• Contains cytoskeleton (microfilaments,
  intermediate filaments cylinders (microtubules)
  provide support / shape.

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Plasma Membrane Cell wall

• 4 10 nm thick
• Double layer of lipid and single layer of
  protein.
• Semi-permeable
• Cell recognition
• Secretion excretion process
• Membrane bound structures for binding
• Junctions help in binding with host cells.

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Plasma Membrane
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Cell Wall

• Some protozoan in their life stages may have is
  inside or outside the cell membrane. Variable
  structural composition.
• Protection.
• Cell reorganization nuclear division.
• Single layered (Entamoeba Giardia).
• Double layered (Coccidia).

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Functions through Cell Membrane

• Transport (Endocytic vesicles)
• A. Pinocytosis
• B. Phagocytosis
• Non mediated (Concentration Gradient)
• Mediated transport (Active Transport)
• Specialized structures for ingestion e.g.
  Cytostome
• Specialized structures for excretion e.g.
  Cytopyge
• Many protozoa have inner membrane known as
  Pellicle.
• Outer surface coat known as glycocalyx.

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Organelles in Protozoa

• Endoplasmic Reticulum (ER)
• Rough ER ((Ribosome bounded), Smooth ER.
• Membranous sacs or cisterns.
• Synthesize lipid store lipids proteins.
• Transport molecules to other parts of cells.

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Organelles in Protozoa (Golgi Complex)

• Situated near the nucleus
• Consist of many sacs / cistern like structures.
• Receives proteins from ER sorts, pack deliver
  by secretary vesicles internally or externally.

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Organelles (Mitochondria)

• Spherical or rod shaped.
• Single large elongate or sausauge shaped
  structures.
• Consist of double membrane.
• Have enzymes of oxidative phosphorylation
  tricarboxylic acid cycle.
• Power house of cell due to ATP production.
• Have their own DNA

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Organelles

• Lysosome formed from Golgi complex, membrane
  bound spheres, contain enzymes.
• Vacuoles Derived from Golgi bodies, storage
  place for sugar, proteins etc.
• Centriole Near nucleus, important in cell
  division.
• Kinetosome (Basal Body) Axoneme originate from
  kinetosome.

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Locomotion

• Cilia
• Flagella
• Pseudopodia
• Gliding

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Reproduction in Protozoa

• Asexual Reproduction
• A. Binary Fission e.g. Giardia duodenalis, B.
  coli.
• Division is random in Amoeba, longitudinal in
  flagellates, transverse in ciliates.
• Sequence of division is Kinetosome, kinetoplast,
  nucleus cytokinesis.
• B. Multiple Fission (Merogony, shizogony)
• Repeated division of nucleus other organelles
  before cytokinesis e.g. Apicomplexa
• Schizont, meronts segmenters

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Reproduction in Protozoa

• Budding Plasmotomy
• Internal budding or endopolygeny multiple
  daughter cells are formed anywhere in cytoplasm.
• Endodyogeny only two daughter cells are formed.

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Reproduction in Protozoa(Sexual Reproduction)

• Gamonts cells producing gametes
• Gametogony process of gamete production.
• Amphimictic Reproduction union of gametes from
  two parents.
• Automictic Reproduction One parent produces both
  gametes.

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Reproduction in Protozoa(Sexual Reproduction)

• Syngamy
• Union of gametes when they are whole cells is
  called syngamy.
• This union can be
• similar gametes (Isogametes) or
• different gametes (Anisogametes).

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Reproduction in Protozoa(Sexual Reproduction

• Conjugation
• Union of nuclei. Found in ciliates only.
  Macronuclei in each disintegrate and micronuclei
  undergo meiotic divisions into four haploid
  pronuclei. Two disintegrate and one migratory
  pronuclei will go to other cell fuse with
  stationary pronuclei to form haploid cells.

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Reproduction in Protozoa(Conjugation)