Page 18 - 84 human physiolofy part-1

Chapter 2

Parts of the Cell

Cytoplasm

The gel-like material within the cell membrane is referred to as the cytoplasm. It is a fluid matrix,
the cytosol, which consists of 80% to 90% water, salts, organic molecules and many enzymes that
catalyze reactions, along with dissolved substances such as proteins and nutrients. The cytoplasm plays
an important role in a cell, serving as a "molecular soup" in which organelles are suspended and held
together by a fatty membrane.

Within the plasma membrane of a cell, the cytoplasm surrounds the nuclear envelope and the
cytoplasmic organelles. It plays a mechanical role by moving around inside the membrane and pushing
against the cell membrane helping to maintain the shape and consistency of the cell and again, to
provide suspension to the organelles. It is also a storage space for chemical substances indispensable to
life, which are involved in vital metabolic reactions, such as anaerobic glycolysis and protein synthesis.

The cell membrane keeps the cytoplasm from leaking out. It contains many different organelles
which are considered the insoluble constituents of the cytoplasm, such as the mitochondria, lysosomes,
peroxysomes, ribosomes, several vacuoles and cytoskeletons, as well as complex cell membrane
structures such as the endoplasmic reticulum and the Golgi apparatus that each have specific functions
within the cell.

• Cytoskeleton

Threadlike proteins that make up the cytoskeleton continually reconstruct to adapt to the cells
constantly changing needs. It helps cells maintain their shape and allows cells and their contents to

18 | Human Physiology