Typical structure of Fungi cell.pptx

fungal stracture

1. Typical structure of Fungi cell

2. Fungi Eucaryotic lower plants devoid of chlorophyll . usually multicellular but are not differentiated into roots, stems and leaves. They range in size and shape from single celled microscopic yeast to giant multicellular mushrooms and puff balls . are either saprophytes or parasites. They have eukaryotic cell structures which, like algae, have rigid cell walls . Size range of molds is 2.0-10 μm and yeast has size varying in the range of 5-10 μm.

3. They reproduce by: fission budding or spores – e.g. molds, mildews, yeasts and rusts belong to this group. They form fruiting structures called conidia or exospores and endospores . Spores of fungi are always present in air, dust and soil. Fungal Nutrition Heterotrophs that acquire nutrients by absorption Digests food outside their body by secreting enzymes into the food Fungi then absorb decomposed molecules

4. Structure of Fungi Fungi can be unicellular (e.g., yeasts). Most fungi are multicellular in structure. The thallus (body) of most fungi is a mycelium. True fungi are composed of filaments and masses of cells, which make up the body of the organism called mycelium . Mycelium: - the vegetative part (body) of a fungus made of a collection of thread like structure . Hyphae is the individual branches or filaments of the mycelium . They form characteristic hyphae called mycelium which may be septate, non septate or coenocytic. It could be Aseptate :- mycelium which do not have cross wall. Eg. Oomycetes, P. infestans Septate: - mycelium which do not have cross wall -Eg. Fusarium

5. Hyphae are filaments that provide a large surface area and aid absorption of nutrients . When a fungus reproduces, a portion of the mycelium becomes reproductive structures. Fungal cells lack chloroplasts and have a cell wall made of chitin, not cellulose. The energy reserve of fungi is glycogen as in animals, and not starch. are nonmotile ; their cells lack basal bodies and do not have flagella at any stage in their life. Fungi move to a food source by growing toward it; hyphae can grow up to a kilometer a day ! Nonseptate hyphae lack septa or cross walls; hyphae are multinucleated. Septate fungi have cross walls in their hyphae; pores allow cytoplasm and organelles to pass freely.

6. Taxonomy of Fungi The classification is based on the following:-  The morphology of hyphea Absence or presence of sexual cycle The type of spores Class Zygomycetes  Have aseptated hyphea The hyphea is coenocytic (contain more than one nuclei) Produce no motile cell Produce sporangia Sexually reproduced by conjugating of mating hyphea Eg. Rhizopus stolonifa ( black bread mold)

7. Class Ascomycetes Possess asci (a sac like structure) – fruiting body consists of 8 ascospores Hyphea produce partially Septated (Yeasts are unicellular, but most ascomycetes are composed of septate hyphea ) Sexual reproduction involves production of eight ascospores within ascus contained within sac like ascocarp Asexual reproduction, which is the norm, involves the production of conidiospores . There are no sporangia in ascomycetes Conidiospores (conidia) develop directly on tips of conidiophores, modified aerial hyphae, and are windblown when released Eg. yeast - Saccharomyces cerevisiae

8. Class Basidomycetes Have completely Septated hyphea Sexual reproduction involves production of basidiospores within clublike basidia contained within a basidiocarp; Asexual reproduction is rare and involves the production of conidiospores. Eg. Smuts and Rusts

9. Class Deutromycetes They reproduce asexually by forming conidiospores ; They are “ imperfect ” because no sexual stage is known and may not exist; thus it cannot be easily classified. Cell morphology and biochemistry indicate some are sac fungi that lost ability to reproduce sexually. Several species of imperfect fungi are of great economic importance Some species of Penicillium mold provide antibiotic penicillin ; others give a characteristic aroma and flavor to certain cheeses (e.g., Roquefort and Camembert). Aspergillus is used in the production of citric acid and gallic acids Some imperfect fungi cause human diseases. Aspergillosis is a respiratory infection caused by inhaling spores . An aspergillus that grows on moist seeds secretes aflatoxin , a potent natural carcinogen.

10. Protozoa are unicellular eukaryotic organisms (animals), are motile having cilia, flagella Pseudopodia , they are either saprophytic or parasitic. They are generally present in soil, water and marshy ( muddy ) place s their size varies from 5-200 μm . They are differentiated on the basis of morphological, nutritional and physiological characteristics. The best known protozoa are the few that cause disease in human beings and animals. Some protozoa are beneficial, such as those found in stomach of cattle, sheep and termites help digest food.

11. Other features include: Eukaryotes are hypothesized to be more complex than prokaryotes. Prokaryotes have evolved a multitude of metabolic strategies and are found in a wide range of habitats, including conditions where most other organisms (Eukaryotes) fail to survive. The plasma membrane resembles that of prokaryotes in function, with minor differences in the set up. Cell walls may or may not be present. The eukaryotic DNA is organized in one or more linear molecules, called chromosomes , which are associated with histone proteins. All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles also contain some DNA. Eukaryotes can move using cilia or flagella.

12. Part 2 3.2 . Prokaryotic microbes (Bacteria, archae and virus) Prokaryotes Are organisms that lack membrane-bound organelles, have no true necuelus Are unicellular, Their cells are usually single. Prokaryotes are one-celled and often live in clusters or colonies. lack most of the intracellular organelles and structures that are characteristic of eukaryotic cells (an important exception is the ribosomes, which are present in both prokaryotic and eukaryotic cells). Most of the functions performed by the plasma membrane . Prokaryotes consist of two domains – Bacteria and Archaea and viruses. .

13. In contrast to most eukaryotes, prokaryotes reproduce asexually and reproduce their clones. While sexual reproduction in eukaryotes results in offspring with genetic material . During reproduction, eukaryotes generate genetic variation by sexual reproduction whereas genetic variation mechanisms of prokaryotes are not tied to reproduction. are generally smaller than eukaryotes. have higher growth rates and shorter generation times. Because of the asexual reproduction and short generation time relative to larger organisms, prokaryotes pass the genome rapidly on to subsequent generations.

14. Other features include:

15. The plasma membrane (a phospholipid bilayer) separates the interior of the cell from its environment. Most prokaryotes have a cell wall (some exceptions are Mycoplasma , a bacterium , and Thermoplasma , an archaea ). It consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from "exploding" (cytolysis) from osmotic pressure against a hypotonic environment. A cell wall is also present in some eukaryotes like fungi, but has a different chemical composition. A prokaryotic chromosome is usually a circular molecule (an exception is that of the bacterium Borrelia burgdorferi, which causes Lyme disease). Even without a real nucleus, the DNA is condensed in a nucleoid. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular.