Physiology lecture 1

PHYSICAL STRUCTURES OF THE CELL

The cell contains highly organized physical structures, called "intracellular organelles". The physical nature of each organelle is as important as the cell's chemical constituents for cell function.
Following are some physical structures of the cell:

CELL MEMBRANE:
The cell membrane also called the "plasma membrane" envelopes the cell and is a thin ,pliable, elastic structure only 7.5 to 10 nanometers thick. It is composed almost entirely of proteins, 55%; phospholipids, 25%; cholestrol, 13%; other lipids, 4%; and carbohydrates, 3%.

CYTOPLASM AND ITS ORGANELLES

1.ENDOPLASMIC RETICULUM:

A network of tubular and flat vesicular structures in the cytoplasm, which is the endoplasmic reticulum. 

• This organelle helps process molecules made by the cell.
• Transports them to their specific destinations inside and outside the cell.
• They have many enzymes which provide machinery for metabolic functions of cell.

2.GOLGI APPARATUS:

The golgi apparatus is closely related to endoplasmic reticulum, It has membranes similar to those of the agranular endoplasmic reticulum, The golgi apparatus is usually composed of four or more stacked layersof thin, flat, enclosed vesicles lying near one side of the nucleus. 

• The transported substances are processed in golgi apparatus.
• It forms lysosomes.
• It helps in the detoxification of toxins.

3.LYSOSOMES:

Lysosomes are vesicular organelles that form by breaking off from golgi apparatus and then dispersing throughout the cytoplasm. The lysosomes provide an intracellular digestive system that allows the cell to digest:

1. Damaged cellular structures
2. Food particles that have been ingested
3. Unwanted matter such as bacteria

          

4.PEROXISOMES:

Peroxisomes are similar physically to lysosomes, but they are different in two important ways:

1. First, they are believed to be formed by self replication rather than from golgi apparatus.
2. second, they contain oxidases rather than hydrolases.

• Their major function is to catabolize long chains of fatty acids.

5.MITOCHONDRIA:

It is called the power house of cell . It is very important organelle. It provides energy to the cell. 

It is present in eukaryotic cell. They make most of the cell's ATP.