Microbiology and Immunology

Cytoplasm, prokaryotic WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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The microtubules are tubes that are formed by a spiral

arrangement of the constituent protein. They function in the

movement of the chromosomesto either pole of the cell dur-

ing the cell division process. The microtubules are also known

as the spindle apparatus. Microfilaments are a composed of

two strands of protein that are twisted around one another.

They function in the contraction of muscle in higher eukary-

otic cells and in the change in cell shape that occurs in organ-

isms such as the amoeba. Finally, the intermediate filaments

act as more rigid scaffolding to maintain the cell shape.

The organelles of the cell are dispersed throughout the

cytoplasm. The nucleusis bound by its own membrane to pro-

tect the genetic material from potentially damaging reactions

that occur in the cytoplasm. Thus, the cytoplasm is not a part

of the interior of the organelles.

The cytoplasm also contains ribosomes, which float

around and allow protein to be synthesized all through the cell.

Ribosomes are also associated with a structure called the

endoplasmic reticulum. The golgi apparatus is also present, in

association with the endoplasmic reticulum. Enzymes that

degrade compounds are in the cytoplasm, in organelles called

lysosomes. Also present throughout the cytoplasm are the

mitochondria, which are the principal energy generating struc-

tures of the cell. If the eukaryotic cell is capable of photosyn-

thetic activity, then chlorophyllcontaining organelles known

as chloroplasts are also present.

The cytoplasm of eukaryotic cells also functions to

transport dissolved nutrients around the cell and move waste

material out of the cell. These functions are possible because

of a process dubbed cytoplasmic streaming.

See alsoEukaryotes

CCytoplasm, prokaryoticYTOPLASM, PROKARYOTIC

The cytoplasm of a prokaryotic cell is everything that is pres-

ent inside the bacterium. In contrast to a eukaryotic cell, there

is not a functional segregation inside bacteria. The cytoplasm

houses all the chemicals and components that are used to sus-

Scanning electron micrograph of an eukaryotic cell, showing the nucleus in the center surrounded by the cytoplasm. The oval objects to the lower

left are ribosomes.

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