Biology

Structure of Cell and Functions (With Labeled Diagram)

In this post, you are going to learn about the Human Body Cell step by step with a Labeled Cell Diagram.

This post Also includes:

  • An overview of the cell.
  • Structure & components of Human cell, for example, Cell membrane, Cytoplasm, Mitochondria, etc.
  • Functions of Cell
  • Prokaryotic Cells vs Eukaryotic Cells
  • Lots more

So if you want to get benefits from this post you’ll love this post.

Let’s Dive right in…

Definition of Cell

“The cell can be defined as the structural and functional unit of life. It is the smallest unit that can carry out all activities of life. Cells are building blocks of complex multicellular organisms”.

OR

“The cell is the smallest part of a living organism. It is the small piece of cytoplasm contains a nucleus and covered by an outer protective layer. i.e. cell membrane”.

so, the bottom line is…!

A cell is a component that carries out all activities of life and is divided into two types i.e., prokaryotic cell and eukaryotic cell. The cell was discovered by Robert Hooke. The cell, nucleus was studied by Robert Brown.

Cell Theory

It is a fundamental theory about cells. This theory was proposed by three well-known scientists, Schleiden (1838), Schwann (1839), and Virchow.

The important features of this theory are as follows:

  1. The body of living organisms is composed of one or many cells.
  2. Cells are the structural and functional unit of life. It is a denovo structure. it is raised from a non-cellular structure.
  3. Virchow Point: A new cell is always produced from a pre-existing alive cell. It indicates that the cell is not a denovo structure.

Structure and Components of Generalized Human Cell:

when a group of cells is combined it forms different tissues while different tissues make organs which finally make up our whole body. The structure of a cell can be studied under a light or electron microscope. Different parts of cells can be isolated by a technique called the Cell Fraction Technique.

Therefore, the structures and functions of these isolated parts can be studied in detail.structure of cell

There are three major components of a cell i.e., Nucleus, Cytoplasm, and Cell Membrane. Each is defined below in detail with their sub-components:

Nucleus

the Nucleus is a spherical body that consists of many organelles such as nucleolus. the majority of the cell’s genetic material present in the nucleus in the shape of linear DNA molecules. these molecules have an organized structure which is known as chromosomes. the major function of the Nucleus is to control many of the functions of the cell.

it is surrounded by a nuclear membrane and also a locus of DNA/RNA synthesis. there is a chromatin present in the nucleus for DNA-protein complexes. the chromatin of the nucleus condenses state during the process of cell division.

Cytoplasm

Rather than a nucleus, the cytoplasm is a jelly-like material that is present outside of the nucleus in the cell. The cell organelles are located in the cytoplasm. Along with many enzymes for general metabolism, there are different types of metabolic events and protein synthesis is also present in the cytoplasm. Some of the fiber of the cytoskeletal system to organize cytoplasmic structure also lies in it.

 Cell Membrane

the cell membrane or plasma membrane is a thin layer of protein and fat that is surrounded into every living cell. it is a semipermeable membrane that allows some kind of substances to enter and others to block from entering the cell. the major constituents of the plasma membrane are highly charged molecules of carbohydrates, proteins, and nucleic acids. moreover, it separates the cell from interior to exterior or outside environment.

 

The technique to Isolate Different Components of Cells

“Isolation of cellular components to determine their chemical composition is known as cell Fraction”.

OR

“The technique to isolate different components of a cell is called Fraction Technique”.

The different parts of cells are isolated separately step by step, and then these parts are studied in a well-accurate manner in detail. In this process, an apparatus is used. The working of this apparatus is called centrifugation.

Steps of Fraction:

  1. Many similar cells are kept in a cold environment in a homogenizer present in a test tube.
  2. Spinning action is applied i.e. shaking of material rapidly, the process is called centrifugation.
  3. Larger particles like nuclei are separated and settled down in the test tube. These are separated to study. Smaller particles remain in the fluid, which is transferred to another test tube.
  4. The fluid with particles is centrifuged at high speed. Different fractions are obtained in different steps. These are separated and used to study.

Parts of a Cell

A cell consists of the following three parts:

  1. The plasma membrane, also a cell wall in plant cells.
  2. Cytoplasm, containing cell organelles.
  3. Nucleus, with nuclear and chromatin material.

Types of Cells

There are two types of cells:

A). Prokaryotic Cells:

It is a primitive type of cell in which cell lake definite nucleus. The nuclear membrane is absent. The nuclear material directly submerged in the cytoplasm and it is not separated from the cytoplasm by a membrane. The organisms which contain prokaryotic cells are called Prokaryotes. Examples are bacteria and blue-green algae.

OR

These cells are found in simple living organisms like blue-green algae and bacteria. These cells do not contain a complete and true nucleus. Nuclear membrane and nucleolus are absent so instead of a true nucleus, the genetic material is found in those organelles, which are covered by membranes such as Mitochondria, Golgi bodies, Lysosomes, and Chloroplasts. These cells contain mesosomes. Their nuclear material does not produce true chromosomes.

B). Eukaryotic Cells:

These cells contain a definite nucleus. A nuclear membrane is present and chromatin material is bounded by a membrane. The organisms which contain eukaryotic cells are called Eukaryotes. Examples are all plants and animals.

OR

These cells are present in algae, fungi, protozoa, plants, and animals. These cells have a true nucleus. They also contain other organelles like Mitochondria, Golgi bodies, Lysosomes, and Chloroplasts. Their nucleus produces true chromosomes. These cells do not contain mesosomes.

Try Also: Difference between Prokaryotic and Eukaryotic Replication

Structure of Eukaryotic Cells:

A typical eukaryotic cell consists of the following parts:

  1. Plasma membrane (cell membrane) is present.
  2. Cell Wall is found in plant cells, bacterial cells, fungal cells, but absent in animal cells.
  3. The nucleus is present.
  4. Cytoplasm and Cytoplasmic Organelles are present.

Size of Cells

The eukaryotic cells vary in size. The biggest cell is the egg of Ostrich. Most of the cells are microscopic and cannot be seen with the naked eye. Their size is measured in micrometer (μm). One μm is 0.000,001 meter (1×10-6 of a meter).

Difference between Plant and Animal Cells

plant cell

animal cell

Plant Cells

Animal Cells

They contain a cell wall. They do not contain a cell wall.
Centrioles are absent in them. They contain centrioles.
They contain a large central vacuole. They do not contain this vacuole.
Plastids are present in plant cells. Plastids are absent in them.

 

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