Question

What are the three basic components of Human cells?

Answer 1

Hint: The cell is the basic structural, functional, and biological unit of all known living organisms. Cells are the smallest units of life, and hence are often referred to as the "building blocks of life". It has been estimated that humans contain somewhere around 40 trillion (4×$10^13$) cells. Cells were discovered by Robert Hooke in 1665. Cells are of two types: eukaryotic, which contain a nucleus, and prokaryotic, which do not.

Complete answer:
Human cells are eukaryotic i.e. they have a well defined nucleus and other membrane bound organelles, in addition, eukaryotic cells have a variety of complex locomotory and cytoskeletal structures,their genetic material is organized into chromosomes.

The human cells have many components (or organelles)-
Nucleus,cell membrane, mitochondria, endoplasmic reticulum(ER), golgi apparatus, lysosomes,ribosomes etc.

Three basic components of Human cells are-

1. Cell Membrane:
It is universal i.e. it is present in all the cells. It is majorly composed of lipids and proteins. The major lipids are phospholipids that are arranged in the bilayer.
The lipids are arranged within the membrane in such a way with the polar head towards the outer sides and the hydrophobic tails towards the inner side. It ensures that the nonvolatile tail of saturated hydrocarbons is protected from the aqueous environment.
Other than phospholipids, the membrane also contains cholesterol, protein and carbohydrates.
The ratio of protein and lipid varies considerably from cell to cell. For example, in human beings, the membrane of the erythrocyte has approximately 52 percent protein and 40 percent lipids.
One of the major functions of a plasma membrane is the transport of the molecules across it.

2. Nucleus:
Robert Brown in 1831 first described the nucleus as a cell organelle.
Nucleus is a membrane bound organelle, it has two parallel membranes outer and inner with a space between them called the perinuclear space.
The outer membrane of the nucleus remains continuous with the endoplasmic reticulum and has ribosomes present on it.
At a number of places the nuclear envelope is interrupted by minute pores,which are formed by fusion of its two membranes;these nuclear pores are the passages through which movement of RNA and protein molecules takes place in both directions between the nucleus and the cytoplasm.

Normally there is only one nucleus per cell ,but there are some cells in the human body which are multinucleated e.g. osteoclast cells whereas some cells lack nucleus e.g. mature RBCs.

The nuclear matrix or nucleoplasm contains nucleolus and chromatin; the content of nucleolus is continuous with the rest of the nucleoplasm as it is not a membrane bound structure,it is a site for active ribosomal RNA synthesis.

3. Mitochondria:
It is a sausage-shaped organelle having a diameter of about 0.2-1.0 micro meter and length 1.0-4.1 micrometer.
Mitochondrion is a double membrane bound structure with the outer membrane and the inner membrane dividing its lumen distinctly into two aqueous compartments, i.e. the outer compartment and the inner compartment.
The inner compartment of mitochondria is filled with a dense homogeneous substance called the matrix. The inner membrane forms a number of foldings called the cristae towards the matrix. The cristae helps in increasing the surface area.
The matrix also possesses a single circular DNA molecule, a few RNA molecules,ribosomes (70S) and the components required for the synthesis of proteins.
Mitochondria divide by fission.
Mitochondria is the site of aerobic respiration; it produces cellular energy in the form of ATP, hence they are called the powerhouse of cells.

Note:
All eukaryotic cells are not identical,plant and animal cells are different as plant cells possess cell walls, plastids, and a large central vacuole which are absent in animal cells, on the other hand animal cells have control which are absent in almost all plant cells.