STRUKTUR DAN FUNGSI SEL MIKROBA

Pokok Bahasan Mata Kuliah Mikrobiologi Dasar Program Studi Biologi (S1) Fak. Biologi UNSOED

Matriks Sitoplasma

The cytoplasmic matrix is the substance between the membrane and the nucleoid; it is featureless in electron micrographs but is often packed with ribosomes and inclusion bodies; although lacking a true cytoskeleton, the cytoplasmic matrix of bacteria does have a cytoskeleton-like system of proteins
Inclusion Bodies
1 Many inclusion bodies are granules of organic or inorganic material that are stockpiled by the cell for future use; some are not bounded by a membrane, but others are enclosed by a single-layered membrane
2 Gas vacuoles are a type of inclusion body found in cyanobacteria and some other aquatic forms; they provide buoyancy for these organisms and keep them at or near the surface of their aqueous habitat
3 Magnetosomes are inclusion bodies that contain iron in the form of magnetite; they are used by some bacteria to orient in the Earthís magnetic field
Ribosomes
1 Ribosomes are complex structures consisting of protein and RNA
2 They are responsible for the synthesis of cellular proteins
3 Procaryotic ribosomes are similar in structure to, but smaller than, eucaryotic ribosomes
The Nucleoid
1 The nucleoid is an irregularly shaped region in which the chromosome of the procaryote is found
2 In most procaryotes, the nucleoid contains a single circular chromosome, though some have more than one chromosome or have one or more linear chromosomes
3 The nucleoid is not bounded by a membrane, but it is sometimes found to be associated with the plasma membrane or with mesosomes
4 The bacterial chromosome is an efficiently packed DNA molecule that is looped and coiled extensively
5 In addition to the chromosome, many bacteria contain plasmids; plasmids are usually small, closed circular DNA molecules
6 - They can exist and replicate independently of the bacterial chromosome
- They are not required for bacterial growth and reproduction, but they may carry genes that give the bacterium a selective advantage (e.g., drug resistance, enhanced metabolic activities, etc.)

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