Bio Essay

Yuliya Zhukova

Seat number: wa71

Lab section: GY2


Biology Midterm Part 2: Essay #8


Cells move around all the time because they need to get around different parts of the body. Single animal cells also move because they either need to get nutrients for themselves or get out of danger. Single animal cells can move around in several ways. They can either change shape or use specialized organelles that extend from the surface of the cell itself.

Single animal cells can move by changing their shape and that requires the use of shape changing molecules. Filaments within cells line the length of the cell and also carry vesicles of material to the edge. When there is a burst of activity, the cell blends with these vesicles and that results in an external movement and a shoving forward. The membrane then attaches beneath and it is released from the trailing edge of the surface of the cell. The vesicles then are taken off and that pulls the membrane toward the inside and the cell forward.

Cells can also move using a special organelle called the cilia. The cilia are short projections that line the surface of the cell and are filled with microtubules. When the microtubules slide past one another, the whole cilia changes its shape. That effect works much like the oars in a boat. The cilia propel the cell in the opposite direction since the water is being propelled over the surface of the cell itself. This action also serves as a cleansing action by getting rid of unwanted particles off of the cell surface.

Flagellum is a whip like organelle, which a cell can also use to move itself around. It extends from the cell surface and is very long. The flagellum is powered by 9 + 2 arrays of microtubules arranged in circles. This arrangement refers to the 9 fused pairs of microtubules on the outside of a cylinder, and the 2 unfused microtubules in the center. The enzyme dynein connects across two microtubules causing them to change shape and therefore, for the flagellum to bend. The flagellum then can either spin like a coil or propel itself like a wave.

Single cells in a multicellular organism also move. They are constantly on the move looking for dangerous bacteria or invading organisms in our bodies. Also, single cells like sperm, for example, move quite a lot while they are searching for an egg to fertilize. When an embryo is developing, cells are constantly moving to different locations where they are needed before they actually stop moving and specialize themselves for the tasks that they have to perform.

In conclusion, cells are on the move all the time because if they weren’t, something as complex as a human body, or something as simple as a single animal cell, would not be able to survive since the movement of cells brings the nutrients, oxygen, or any other materials organisms need to live.