Cell: Prokaryotes Flashcards
what are prokaryotes ?
The prokaryotic cells are represented by bacteria, blue-green algae,
mycoplasma and PPLO (Pleuro Pneumonia Like Organisms). They are
generally smaller and multiply more rapidly than the eukaryotic cells
(Figure 8.2). They may vary greatly in shape and size. The four basic
shapes of bacteria are bacillus (rod like), coccus (spherical), vibrio (comma
shaped) and spirillum (spiral).
which bacteria does not have cell wall?
all bacteria have cell wall except mycoplasma
what are the tyoes of genetic material?
the genetic material is naked, and not covered by a nuclear envelope. Asides from the genomic DNA(single chromosome/ circular) , most bacteria have a small circular double stranded DNA in the cytoplasm called PLASMIDS.
What are plasmids?
These are small circular double stranded DNA in the cytoplasm which confer certain specific phenotypic traits ot the bacterium.One such charac is resistance to antibacteria They can replicate themselves. They facilitate bacterial transformation which is when passing the plasmid from one bacterium to the other via conjugation tube.
what is the cell envelope
Most prokaryotic cells, particularly the bacterial cells, have a chemically
complex cell envelope. The cell envelope consists of a tightly bound three
layered structure i.e., the outermost glycocalyx followed by the cell wall and
then the plasma membrane. Although each layer of the envelope performs
distinct function, they act together as a single protective unit.
What is glycocalyx what are its types:
Glycocalyx literally means sugar coat. It is a polysaccharide layer outer most layer of cell envelope.
Glycocalyx differs in composition and thickness among different
bacteria.
It could be a loose and diffuse sheath called the slime layer in some,
it may be thick and tough, called the capsule.in general pathogenic bacteria have cell capsules
What is cell wall?
The cell wall
determines the shape of the cell and provides a strong structural support
to prevent the bacterium from bursting or collapsing.
Bacteria can be classified into 2 on the basis of cell wall structure he manner in which they respond to the staining procedure developed
by Gram viz., those that take up the gram stain are Gram positive and the
others that do not are called Gram negative bacteria.
how does cell wall structure vary in gram +ve and gram -ve bacteria
Gram +ve bacteria have a thick peptidoglycan layer. While gam -ve bacteria have a thin layer of peptidoglycan and a surrounding of lipids.
plasma membrane?
it is selectively permeable and it interacts with outside environment. Structural configuration is same for eukaryotes and prokaryote
What are mesosomes
Mesosomes are special membranous strcutures extensions of cell membrane into the cell to form infoldings. These occur in 3 formd: tubules, vesicles,lamellae.
What are the functions of mesosomes
- key role in formation of cell wall
- dna replication and distrubutuion to duaghter cells
- responsible for respiration
- responsible for secretion
- increases the overall surface area of plasma membrane
- increase enzymatic content( more space for biochemical reacns)
what are chromatophores
In some prokaryotes like
cyanobacteria, there are other membranous extensions into the cytoplasm
called chromatophores which contain pigments. These are photosynthetic pigments embedded in the lamellae
what is nuceloids?
It is the nuclear region of the cell which contains genomic DNA( single chromosomal circular dna)
what is flagella
If motile, they have thin
filamentous extensions from their cell wall called flagella. Bacteria show a
range in the number and arrangement of flagella. Bacterial flagellum is
composed of three parts – filament, hook and basal body. The filament
is the longest portion and extends from the cell surface to the outside.
m/o flagellin protein
what is pili
The pili are elongated tubular
structures made of a special protein arising from glycocalyx. They act as a conjugation channel.
