Anatomy of Protozoan Cell

Protozoa ? Unicellular organisms / single cell.Many species of Protozoa.Free Living & Parasitic.

Forms of Protozoa

Large & heterogeneous group of organisms. Various Body forms / plan. Organelles of Protozoa conform to those of metazoan

cells. Ability to move Mostly found in aquatic environment. Can’t synthesize structural substances from inorganic

matter. 200,000 Protozoan species (10,000 Parasitic in

invertebrate & vertebrate hosts.

Prokaryotic Cells

Prokaryotic Cells(Prenucleus)

Small unicellular organisms (0.2 – 2.0 µm in diameter and 2 – 8 µm in length.

Posseses indistinct nucleus (lack of nucleus & nucleoli). Chromosome coiled like skein of wool. Single circular chromosome with out histones. Lack other membranous system (organelles) in

cytoplasm. Cell division by binary fission & fewer cell division

structures than eukaryotes.

No meiosis.

Prokaryotic Cell

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 histones. Mitosis (Sexual reproduction) Meiosis

Eukaryotic Cell (Typical)

Eukaryotic Cell (Typical)

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). Endosome is devoid of DNA. Nucleus have different shapes (spherical, oval,

cylindrical, sausage shape etc.

Protozoa (Nucleus)

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.

Trypanosoma

Protozoa (Cytoplasm)

Substance inside the plasma membrane & Outside the nucleus

Extranuclear portion of cell. Ectoplasm (Homogenous). Endoplasm(granular contains various vacuoles

& organelles). Contains cytoskeleton (microfilaments,

intermediate filaments & cylinders (microtubules) & provide support / shape.

Plasma Membrane & Cell wall

Trilaminar (three layered) 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.

Plasma Membrane

Cell Wall

Some parasitic stages may have & is inside or outside the cell membrane. Its composition is varied but consist of primarily proteins & others like CHO, fatty acids, phospholipid etc

Variable structural composition. Protection. Cell reorganization & nuclear division. Single layered (Entamoeba & Giardia). Double layered (coccidia).

Cyst / oocyst wall

Functions through Cell Membrane

Transport (Endocytic vessicles)

A. Pinocytosis

B. Phagocytosis Non mediated (Conc. 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.

Transport of Molecules

Structures for Ingestion / Excretion

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.

Organelles in Protozoa (Golgi Complex)

Situated near the nucleus Consist of many sacs / cistern like structures. Receives proteins from ER & sorts, pack &

deliver by secretory vesicles internally or externally.

Organelles (Mitochondria)

Spherical or rod shaped. Consist of double membrane. Power house of cell due to ATP production. Have their own DNA

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.

Locomotion

Cilia Flagella Pseudopodia Gliding

Locomotion

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

Reproduction in Protozoa

Budding – Plasmotomy

Internal budding or endopolygeny: multiple daughter cells are formed anywhere in cytoplasm.

Endodyogeny: only two daughter cells are formed.

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.

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 (Anisogametes).

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.

Reproduction in Protozoa (Conjugation)