I. THE EUKARYOTIC CELL
A. COMPOSITION AND FUNCTIONS OF EUKARYOTIC CELLULAR STRUCTURES
7. Flagella and Cilia
The overall purpose of this Learning Object is to learn the chemical makeup and the functions associated with cilia and flagella in eukaryotic cells.
The cell is the basic unit of life. Based on the organization of their cellular structures, all living cells can be divided into two groups: prokaryotic and eukaryotic (also spelled procaryotic and eucaryotic). Animals, plants, fungi, protozoans, and algae all possess eukaryotic cell types. Only bacteria have prokaryotic cell types.
Eukaryotic cells are generally much larger and more complex than prokaryotic. Because of their larger size, they require a variety of specialized internal membrane-bound organelles to carry out metabolism, provide energy, and transport chemicals throughout the cell.
We will now look at flagella and cilia of eukaryotic cells.
7. Flagella and Cilia
Flagella are long and few in number whereas cilia are short and numerous. Both consist of 9 fused pairs of protein microtubules with side arms of the motor molecule dynein that originate from a centriole. These form a ring around an inner central pair of microtubules that arise from a plate near the cell surface (see Fig. 34). The arrangement of microtubules is known as a 2X9+2 arrangement. This complex of microtubules is surrounded by a sheath continuous with the cytoplasmic membrane. In the presence of ATP, the dynein side arms of the microtubules in the outer ring elongate and attempt to move along the neighboring pair, causing the flagellum or the cilium to bend. Flagella and cilia function in locomotion. Cilia also function to move various material that may surround a cell.
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