Source: Inkcape illustrator

This Chapter of General Physiology will comprise of Subchapters that will together explain the chapter.

I will be discussing
THE CELL
THE STRUCTURE OF THE CELL
CELL MEMBRANE
CYTOPLASM
ORGANELLES IN THE CYTOPLASM
ORGANELLES WITH LIMITING MEMBRANES
ORGANELLES WITHOUT LIMITING MEMBRANE
NUCLEUS
DEOXYRIBONUCLEIC ACID
GENE
RIBONUCLEIC ACID
GENE EXPRESSION
GROWTH FACTORS
CELL DEATH
CELL ADAPTATION
CELL DEGENERATION
CELL AGING
STEM CELLS

I will be taking 2 sub-chapters per day so that in 7 days I will be done with this chapter.

So without further ado!! I present to you THE CELL and THE STRUCTURE OF THE CELL

THE CELL

Source: Inkcape illustrator

The cell is the smallest form of life that exhibits the basic functions of life. Humans being part of life have cells that act in the same manner.

• Every cell in the body utilizes nutrients from its environment.
• These nutrients are used for all the cell's activities.
• Every cell produces water after its activities.
• Every cell is involved in maintaining balance in its environment.
• They all respond to the entry of invaders such as bacteria, viruses, or toxic substances.
• Every cell except for some cells like neurons reproduce by division.

TISSUE
When cells organize themselves to perform a particular function they do so to form tissues. There are 4 main tissue types:

1. Muscle tissue- forming all types of muscles.
2. Nervous tissue- the main tissue of the nervous system
3. Epithelial tissue- making the covering of every tissue
4. Connective tissue- forming a supporting role in every tissue.

ORGANS
When cells organize themselves at a higher level they form organs. Organs are made up of primary tissues, like the heart...it has muscle tissue (Cardiac muscle) but it also has connective tissue (pericardium) and nervous tissue, and epithelial tissue (those lining the cavity of the heart.

SYSTEM
Cells organize themselves at an even higher level to form systems. There are groups of organs in a system and they come together to perform a particular function.

The digestive system is involved with the digestion of food and the nervous system conducts electrical impulses throughout the body.

The importance of a system can not be over-emphasized as if a few cells die the body may be able to compensate but without a system, the body would struggle to survive and usually, the failure of one system would lead to failure of other systems.

STRUCTURE OF THE CELL

We will look at the outside of the cell down into its insides.

CELL MEMBRANE

Source: Inkcape illustrator

The cell membrane or plasma membrane or the plasmalemma forms the outer covering of the cell. The cell is bathed in fluid on the exterior known as the extracellular fluid and has fluid on the inside known as intracellular fluid.

The membrane is semipermeable and allows for the exchange of certain substances.

Electron microscopy has revealed that the cell membrane is like a sandwich with the bread being layers of protein and the center is a lipid layer.

• Lipid layer
  This is the fluid portion of the cell membrane and it encourages substances to move from one point to the other over the membrane. The lipids that form the layer are mainly Phospholipids and cholesterol.

The lipid layer helps to select the type of substances going through the cell. Substances like alcohol, carbon dioxide, and oxygen that are lipid-soluble can cross the membrane. Other substances like glucose or urea cannot pass through this layer.

• The protein layer
  This layer protects the central lipid layer and is made up of the integral and the peripheral proteins.

The proteins in the cell membrane:
Maintain the structural integrity of the cell membrane.

Help substances that are insoluble in lipid can be channeled
through protein

Actively move substances across the cell membrane.

Act as receptors for communication

REFERENCES

• Essentials of Medical Physiology
• Lumen Learning
• Science Direct