Cell : Structure, components and its types

 

Cell is a fundamental building block of all living organisms. It is the smallest unit of life, and it consists of a membrane, genetic material (DNA), proteins, lipids, and carbohydrates. Cells are the basic units of structure and function of all living things and carry out processes such as energy production, metabolism, growth, and reproduction. An example of a cell is the human egg cell, which is the largest cell in the human body and contains all of the genetic information necessary to create a new human being. Other examples include bacteria, which are single-celled organisms, and plant cells, which have a cell wall and contain chloroplasts that allow them to photosynthesize. Cells vary in size and shape, and can range anywhere from 1 micrometer to 100 micrometers in diameter. They are able to divide and replicate, which allows for growth and repair of any damage that may occur. Cells are also able to adapt to their environment in order to survive.

 Fun Fact: The human body is composed of over 37 trillion cells!

Components of the cell

A cell is the basic unit of life, and is made up of several components that all work together to keep the cell functioning. The components of a cell can be divided into two main parts; the organelles, which are specialized structures within the cell that perform specific functions, and the cytoplasm, which is the substance that surrounds the organelles. Organelles are the “organs” of the cell and include structures such as the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes.

1.  Nucleus

The nucleus is like the brain of the cell, and it contains the genetic information that determines the characteristics of the organism. The nucleus is the most important part of the cell, as it contains the majority of the cell's genetic material. It is a spherical or ellipsoidal organelle that is usually located near the center of the cell and is surrounded by a double membrane called the nuclear envelope. The nucleus is responsible for controlling the cell's growth and metabolism, and it contains the genetic information necessary for the cell to function and reproduce. An analogy to help you understand the nucleus would be to think of it as the "brain" of the cell. Just like the brain is responsible for controlling the body, the nucleus is responsible for controlling the cell. The nucleus is like the brain in the sense that it contains all the genetic information necessary for the cell to function and reproduce.

 Fun fact: The nucleus is the largest organelle in most cells, and can reach sizes up to 10,000 times larger than any other organelle!

2.  Mitochondria

Mitochondria are essential components of the cells in all living organisms. They are often referred to as the "powerhouses of the cell" because they are the structures responsible for generating the energy that cells need to do their work. Mitochondria are found in the cytoplasm of all eukaryotic cells, and are made up of a double membrane, inner and outer, and an intermembrane space. The inner membrane is folded into structures called cristae, which increase the surface area of the inner membrane and allow it to contain many enzymes and proteins. These enzymes and proteins are responsible for generating the energy that cells need for their normal functions. This energy is generated in a process known as cellular respiration, which involves the breakdown of glucose molecules to produce ATP (Adenosine Triphosphate). ATP is used by cells as a source of energy to carry out their metabolic activities. An analogy to help understand mitochondria is to think of them as tiny factories within the cell. Just like factories, mitochondria take in raw materials (in this case, glucose molecules) and turn them into something useful (in this case, ATP).

 Fun fact: Mitochondria are believed to have evolved from bacteria that were taken up by an ancient ancestor of all eukaryotic cells.

3.  Endoplasmic Reticulum

The endoplasmic reticulum helps create proteins, while the Golgi apparatus helps to package and transport the proteins. The endoplasmic reticulum (ER) is an organelle that is present in all eukaryotic cells, and it is responsible for a variety of functions such as protein synthesis, lipid metabolism, and calcium storage. The ER is composed of a network of membranous tubules and flattened sacs, and looks like a mesh or spider web inside the cell. The ER is divided into two main types: smooth and rough. The smooth ER lacks ribosomes and is mainly involved in lipid metabolism, steroid synthesis, and detoxification. The rough ER, on the other hand, is studded with ribosomes and is involved in the synthesis of proteins, which are then packaged into vesicles and transported to the Golgi apparatus for further processing. The ER plays an important role in the cell's ability to transport materials and substances, as well as in the regulation of the cell's calcium levels. For example, when a signal from the cell's surface triggers a change in the cell's calcium levels, the ER is able to quickly release or absorb calcium to maintain the cell's calcium balance.

 Fun Fact: The ER is so large and extensive that it makes up about 10% of a cell's total volume!

4.  Chloroplast

 Chloroplasts are organelles found in plant cells and are responsible for photosynthesis. Photosynthesis is the process of converting sunlight into energy. Chloroplasts have an outer membrane, an inner membrane, and a gel-like substance called the stroma. Inside the stroma are structures called thylakoids, which are arranged in stacks called grana. The thylakoids contain a green pigment called chlorophyll, which absorbs light energy from the sun and helps convert it into chemical energy. An analogy for chloroplasts is a solar panel. Just like a solar panel, chloroplasts absorb energy from the sun and convert it into energy that can be used by the cell. 

Fun Fact: Chloroplasts are believed to have originated from cyanobacteria, which are some of the oldest forms of life on Earth!

5.  Cell Membrane

The cell membrane, also known as the plasma membrane, is a thin, protective barrier found in the outer layer of all cells. It is made of two layers of phospholipids and proteins that are arranged in a bilayer, with the hydrophobic (water-hating) tails of the phospholipids facing inward and the hydrophilic (water-loving) heads facing outward. This arrangement prevents water-soluble molecules, such as ions and sugars, from entering the cell. The proteins embedded in the cell membrane act as gates that control the passage of molecules in and out of the cell. An analogy that can help explain the cell membrane is a house. The walls of the house act like a cell membrane, keeping unwanted guests out and allowing only certain people to enter. The door of the house functions like the proteins in the cell membrane, allowing certain molecules to pass through while blocking others from entering.

 Fun Fact: The cell membrane is constantly in motion and is constantly undergoing changes in shape and size as it interacts with its environment.

6.  Cell Wall

 

The cell wall is a structure found in most bacteria and plant cells. It is composed of carbohydrate polymers and proteins, which provide the cell with protection, strength, and shape. This wall is found outside the cell membrane and is usually about 10 nanometers thick. The cell wall is like a brick wall around a house, providing protection from the outside environment and keeping the cell from bursting under normal pressure. The cell wall also serves as a filter, allowing certain molecules to enter the cell while keeping out others. For example, some molecules can enter the cell through special channels in the cell wall, while others are blocked. In addition to providing protection and structure, the cell wall also helps bacteria move around in their environment. It has tiny pores that allow bacteria to secrete chemicals, such as toxins, into the environment. 

Fun fact: the cell wall of some bacteria can actually be used to make antibiotics! Researchers have discovered that certain compounds in the cell wall of certain bacteria can kill other harmful bacteria.

7.  Golgi Apparatus / Golgi Complex / Golgi Body

A Golgi body, also known as the Golgi apparatus or Golgi complex, is an organelle that is found in most eukaryotic cells. It is named after the Italian physician Camillo Golgi, who first discovered it in the late 19th century. The Golgi body is responsible for processing, sorting, and packaging proteins and lipids that are made in the cell, as well as packaging them into vesicles for transport to other parts of the cell. The Golgi body is composed of stacks of flattened, membrane-bound sacs called cisternae. The cisternae are connected to one another, forming a continuous network of membranes. The cisternae contain enzymes that modify the proteins and lipids, as well as enzymes that package them into vesicles. The vesicles then travel to other parts of the cell, where they release their contents. One example of how the Golgi body works is in the production of lysosomes. Lysosomes are organelles that contain digestive enzymes that break down cellular waste and damaged organelles. The Golgi body packages these enzymes into vesicles and transports them to the cell membrane, where they are released. 

Fun fact: The Golgi body has been nicknamed the “post office” of the cell because it packages and sorts proteins and lipids and sends them to other parts of the cell.

8.  Lysosomes

A lysosome is a type of organelle found in the cells of animals and plants. It is a membrane-bound sac that contains hydrolytic enzymes, which are enzymes capable of breaking down large molecules into smaller ones. Lysosomes are involved in a variety of cellular processes, including digestion of macromolecules, intracellular trafficking, and autophagy, which is the process of breaking down and recycling cellular components. An example of a lysosome's function is in the digestion of proteins. When a cell takes in a protein molecule, it is digested by proteins contained in the lysosome. These proteins, called lysosomal hydrolases, break down the protein into its component amino acids, which can then be used by the cell for other purposes. In addition to digestion, lysosomes also help with cellular recycling, by breaking down and recycling cellular components that are no longer needed. Lysosomes are found in all cells, but their size and number may vary depending on the type of cell. For example, cells that are involved in digestion, such as those of the digestive system, contain many lysosomes.

 Fun fact: Lysosomes are sometimes referred to as the “cell’s stomach” because of their role in breaking down and digesting large molecules.

9. Ribosome

A ribosome is a small, organelle-like particle found in all living cells. It is composed of two subunits, the larger subunit and the smaller subunit. These subunits are composed of proteins and ribosomal RNA (rRNA). Ribosomes are responsible for the production of proteins within a cell, a process known as translation. The larger subunit of the ribosome is responsible for recognizing the sequence of codons that make up a gene, while the smaller subunit binds the transfer RNA (tRNA) molecule that carries the amino acid that is being added to the growing protein chain. The smaller subunit is also responsible for the catalysis of peptide bond formation between two amino acids. Ribosomes are essential for all forms of life, from bacteria and archaea to plants and animals. Ribosomes are found in all three domains of life and are incredibly important for the production of proteins that are essential for life. 

A fun fact about ribosomes is that they can be found in a variety of sizes and shapes, depending on the organism. For example, ribosomes in the mitochondria of animals are much larger than the ribosomes found in bacteria.

10.  Vacuole

A vacuole is a membrane-bound organelle found in a variety of single-celled and multicellular organisms. It is a large, enclosed compartment filled with water, enzymes, and other molecules that a cell needs to survive. The primary function of a vacuole is to store and transport molecules, allowing them to move freely within the cell. Vacuoles also play an important role in maintaining a cell’s shape and structure. Vacuoles can be found in both plant and animal cells, although they are more prominent in plant cells. In plant cells, vacuoles make up to 95% of the cell’s volume, while in animal cells, they make up only 5-10%. Vacuoles are filled with a variety of different molecules, including proteins, lipids, sugars, ions, and other small molecules. Vacuoles can be used for a variety of different functions, including storage, waste disposal, and defense. They can also be used to transport molecules from one part of the cell to another. For example, proteins can be transported from the endoplasmic reticulum to the vacuole, where they can be broken down and used for energy. 

Fun Fact: Vacuoles can also be used to store toxins produced by the cell to defend itself against predators!

The components of a cell that are not listed in the question are :

1. Cytoskeleton - a network of protein fibers that provides structural support and shape to the cell.
2. Centrioles - organelles that play a role in cell division.
3. Cilia and flagella - structures that allow cells to move.
4. Microfilaments - thin protein fibers that make up the cytoskeleton and play a role in cell division.
5. Microvilli - small, finger-like projections on the cell surface that increase the surface area for absorption or secretion.
6. Nucleolus - a structure within the nucleus that is involved in the production of ribosomes.
7. Peroxisomes - organelles that detoxify harmful substances and break down fatty acids.
8. 
   
9. Pinocytotic vesicles - small, membrane-bound vesicles that are involved in the uptake of liquids by the cell.
10. Secretory vesicles - small, membrane-bound vesicles that store and transport molecules that are secreted by the cell.
11. Cytosol - a gel-like fluid that fills the cell and contains dissolved ions, molecules and organelles.

Types of Cell : Prokaryotic & Eukaryotic Cells

There are two main types of cells: prokaryotic and eukaryotic.

1. Prokaryotic cells : Prokaryotic cells are the simplest type of cell and are typically smaller than eukaryotic cells. They do not have a true nucleus or membrane-bound organelles. Examples of prokaryotic cells include bacteria and archaea.

Bacteria are single-celled microorganisms that can be found in a wide variety of environments, including soil, water, and the human body. They can be classified based on their shape (coccus, bacillus, spiral), as well as their metabolic properties (aerobic, anaerobic, facultative). Archaea are also single-celled microorganisms, but they are more closely related to eukaryotic cells than to bacteria. They can be found in extreme environments such as hot springs, deep sea vents, and salt flats.

2. Eukaryotic cells : These cells are more complex than prokaryotic cells and contain a true nucleus as well as membrane-bound organelles. Eukaryotic cells can be further divided into different types based on their characteristics and functions. Some examples include:

• Animal cells : Animal cells are typically smaller than plant cells and lack a cell wall. They have a variety of organelles, including a nucleus, mitochondria, and lysosomes. Animal cells also have specialized structures such as cilia and flagella that allow them to move.

• Plant cells: Plant cells are typically larger than animal cells and have a cell wall that provides structural support. They also have a variety of organelles, including a nucleus, mitochondria, and chloroplasts. Chloroplasts are unique to plant cells and are responsible for photosynthesis.

• Fungal cells : Fungal cells are eukaryotic cells that have a characteristic cell wall composed of chitin. They can be single-celled or multicellular. They have a variety of organelles, including a nucleus, mitochondria, and endoplasmic reticulum. Fungi play an important role in the ecosystem, breaking down dead plant and animal material, and forming symbiotic relationships with other organisms.

• Protist cells : Protist cells are eukaryotic cells that are not classified as animal, plant or fungi. They can be single-celled or multicellular, and are found in a wide variety of environments, including freshwater, marine and terrestrial environments. They have a variety of organelles, including a nucleus, mitochondria, and chloroplasts (in some cases).

3. Specialized cells :

• Neurons : These are cells that transmit electrical signals in the nervous system. They have a complex structure, including a cell body, dendrites, and an axon.

• Muscle cells: These cells are specialized for contraction and are responsible for movement. They can be further divided into three types: skeletal, smooth, and cardiac muscle cells.

• Epithelial cells: These cells line the surfaces of organs and glands, and form the skin. They have unique properties such as tight junctions that help to maintain the barrier function of the cell.

• 
  

• 

• Blood cells : These cells circulate through the blood and have specific functions such as carrying oxygen and fighting infection. They can be further divided into three types: red blood cells, white blood cells, and platelets.

• Stem cells : These cells have the ability to differentiate into various types of cells and can be used to repair and regenerate tissues. They can be found in various tissues such as bone marrow, blood and the brain. They can be further divided into two types: embryonic stem cells and adult stem.

Extras :

★ Difference between Plants and Animals Cell

Plant and animal cells are both eukaryotic cells, but they have some significant differences in terms of their structure and function.

1. Cell wall: Plant cells have a cell wall that surrounds the cell membrane. The cell wall is made of cellulose and provides structural support and protection. Animal cells do not have a cell wall.

2. Chloroplasts: Plant cells have chloroplasts, which are organelles that are responsible for photosynthesis. Animal cells do not have chloroplasts.

3. Mitochondria: Both plant and animal cells have mitochondria, which are organelles that are responsible for producing energy in the form of ATP.

4. Vacuoles: Plant cells have one large central vacuole that stores water, sugars and other molecules. Animal cells have smaller, membrane-bound vacuoles that perform similar functions.

5. Cytoskeleton: Both plant and animal cells have a cytoskeleton, which is a network of protein fibers that provides structural support and shape to the cell.

6. Cell size: Plant cells are typically larger than animal cells.

7. Movement: Animal cells have specialized structures such as cilia and flagella that allow them to move, while plant cells do not have such structures.

8. Reproduction: Plant cells reproduce through cell division and growth, while animal cells reproduce through the process of mitosis and meiosis.

Overall, while plant and animal cells share many similarities, the presence of a cell wall, chloroplasts, and large central vacuoles in plant cells and the absence of these structures in animal cells are key differences that set them apart from one another.

★ Difference between Prokaryotic and Eukaryotic Cells

Prokaryotic and eukaryotic cells are the two main types of cells, and they have several key differences in terms of their structure and function.

1. Nucleus: Eukaryotic cells have a true nucleus, which is a membrane-bound organelle that contains the cell's genetic material. Prokaryotic cells do not have a true nucleus; instead, their genetic material is found in a region of the cell called the nucleoid.

2. Membrane-bound organelles: Eukaryotic cells have a variety of membrane-bound organelles, such as the mitochondria, endoplasmic reticulum, and Golgi apparatus, that perform specific functions. Prokaryotic cells do not have membrane-bound organelles.

3. Size: Prokaryotic cells are typically smaller than eukaryotic cells.

4. Cell wall: Prokaryotic cells have a cell wall that surrounds the cell membrane, while eukaryotic cells do not have a cell wall.

5. Cytoskeleton: Eukaryotic cells have a cytoskeleton, which is a network of protein fibers that provides structural support and shape to the cell. Prokaryotic cells do not have a cytoskeleton.

6. Cilia and flagella: Eukaryotic cells have specialized structures such as cilia and flagella that allow them to move, while prokaryotic cells typically do not have such structures.

7. Reproduction: Prokaryotic cells reproduce through binary fission, which is a form of asexual reproduction, while eukaryotic cells reproduce through mitosis and meiosis.

8. Metabolism: Prokaryotic cells can have a wider range of metabolic processes, and they can survive in extreme environments like high temperature, high salinity, high radiation, and low oxygen.

Overall, while prokaryotic and eukaryotic cells share many similarities, the absence of a true nucleus and membrane-bound organelles in prokaryotic cells, and the presence of these structures in eukaryotic cells are key differences that set them apart from one another.

In conclusion, cells are the basic building blocks of life and come in a variety of forms. Prokaryotic cells, such as bacteria, are the simplest type of cell, while eukaryotic cells, such as plant and animal cells, are more complex and contain a true nucleus as well as membrane-bound organelles. Each type of cell has its own unique characteristics and functions, which are essential for maintaining the balance of life. We have discussed the different components of cells, types of cells, and the differences between prokaryotic and eukaryotic cells. The study of cells is a vast and ever-evolving field, and new discoveries are being made all the time. We hope that this blog has provided a comprehensive overview of cells, and has sparked an interest in further learning about this fascinating topic. Remember that the better understanding of cells, the better we can understand our own body and the environment around us

Thank you so much for reading, hope you understand well. Please give your feedback in comment section and also comment Next topic.