Thursday, March 01, 2012

The Protoplasm

The function of protoplasm are reproduction, irritability, chemical, excretion, movement, and growth. The protoplasm of a cell is made up of three parts: the cell surface membrane, cytoplasm, and nucleus.

Cell Surface Membrane
The cell surface membrane or plasma membrane surrounds the cytoplasm of the cell. The cell surface membrane is a partially permeable membrane. This means that it allows only some substances to cross it. Hence, the cell surface membrane controls substances entering or leaving the cell.

The cytoplasm is the part of the protoplasm between cell surface membrane and the nucleus. It is where most cell activities occur. The cytoplasm contains enzymes and specialised structures called organelles. Organelles carry out various functions in the cell.
Many organelles, such as centrioles, are not visible under the light microscope. They can only be studied under the electron microscope. Cytoplasm can exist in either sol or liquid state or in gel or semi-solid state, so called because of its jelly-like consistency. Outer regions of the cell are usually in the gel state, while the inner regions are usually in the sol state.

The nucleus consists of a small round mass of denser protoplasm called nucleoplasm, surrounded by a membrane called the nuclear envelope. Functions of the nucleus:
- It controls cell activities such as cell growth and the repair of worn-out parts.
- It is essential for cell division. Cell without a nucleus, for example, the red blood cell of a mammal, have a short lifespan and are unable to divide.

Biology Matters

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