Class 11 Cell Structure and Function

Class 11 cell is a part of NCERT Biology class 11. Cells are the atoms of human bodies. They form the basis of living organisms. New cells also arise from pre-existing cells. In simple terms, they can be defined as the structural and functional unit of life. The study of cells is known as cytology. Anton Van Leeuwenhoek was the first to describe a live cell. It also forms an important part of the class 11 syllabus, and if you prepare well, you can get high marks in it. In this blog, we will discuss class 11 cell in detail.

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Types of Cells

According to class 11 cell, cells are primarily of two types – Eukaryotic and Prokaryotic Cells.

Eukaryotic Cell	Prokaryotic Cell
Cells are larger in size.	Cells are smaller.
Presence of well-defined nucleus and membrane-bound organelles.	Absence of well-defined nucleus and membrane-bound organelles.

Prokaryotic Cell

The main features of the prokaryotic cell are mentioned below.

• Blue-green algae, mycoplasma and bacteria represent them.
• Vary in shape and multiply rapidly.
• Genetic material is naked.
• Absence of cell organelles.
• Presence of cell wall surrounding the cell membrane except in Mycoplasma.
• Ribosomes are attached to the cell membrane having two subunits 50s and 30s that form the 70s ribosomes together and act as protein synthesis sites.
• Polyribosomes are those ribosomes that attach to RNA to form a chain.
• Reserved materials like cell inclusion bodies are present in the cytoplasm.

Eukaryotic Cell 

The main features of the eukaryotic cell are mentioned below. 

• Eukaryotic Cells are found in Fungi, Protista, Plants and Animals.
• The cytoplasm is divided into compartments because of the presence of membrane-bound organelles.
• Presence of a well-organised nucleus bound by a nuclear membrane.
• Genetic material arranged in chromosomes.
• Plant cells have a cell wall in addition to the membrane. They have a large central vacuole, which is absent in animal cells.
• Characteristic presence of centrioles in animal cells.

Cell Structure

Now that we know about the two kinds of cells, let’s discuss each part of the cell part as discussed in class 11 cell in length now!

Cell Membrane

The cell membrane is an important part of the cell. Its various features are mentioned below. 

• Composed of lipids that are made up of phosphoglycerides and arranged in a bilayer. Protein compounds were also discovered later on.
• Proteins are present as – integral protein that remains buried in the membrane and peripheral protein that lies on the surface.
• The protein movement across the bilipid layer is possible because of the quasi-fluid nature of the membrane, as proposed by Singer and Nicholson.
• The primary function of the plasma membrane is to ensure transport of substances.

Cell Wall

The characteristics of the cell wall are mentioned below. 

• Present in plants and algae.
• The cell wall in plants is made up of cellulose, hemicellulose and pectin.
• The algal cell wall is composed of cellulose, galectins and minerals.
• The primary cell wall in plants is incapable of growth, it soon transforms into a secondary cell wall in mature plants.

The Endomembrane system consists of endoplasmic reticulum, Golgi bodies, lysosomes, and vacuoles.

Endoplasmic Reticulum

According to class 11 cell, the endoplasmic reticulum is involved in some of the most important processes. They are mentioned below.  

• Smooth ER – Involved in lipid synthesis and does not bear ribosomes on the surface.
• Rough ER – Performs protein synthesis and secretion and bears ribosomes on the surface.

Golgi Apparatus 

According to class 11 cell, the golgi apparatus is another important part of the cell. They are listed below. 

• Site of synthesis of glycoproteins and glycolipids.
• Involved in packaging of material and transporting.
• Consists of flat, disc shaped cisternae stacked parallel.

Lysosome

The chapter on class 11 cell mentions the membrane bound structure. It is rich in hydrolytic enzymes – lipase, protease etc that are capable of digesting proteins, carbohydrates and fats.

Vacuoles

Vacuoles have a special role to play in the functions of the cell, according to class 11 cell.

• Membrane bound structures.
• Contains sap, excretory products and water.
• Present as food vacuole or contractile vacuole.

Mitochondria

Next in class 11 cell, the mitochondria is also an essential part of the cell structure. Its features are mentioned below. 

• Found in sites of aerobic respirations.
• Produce cellular energy in the form of ATP.
• The matrix contains circular DNA molecules, RNA molecules, ribosomes and components of protein synthesis.

Plastids

The plastids are another important part of the cell structure. They are mentioned in class 11 cell. The many features of the plastids are mentioned below. 

• Found in plant cells.
• Semi-autonomous organelles, having their own genetic material.
• Are of three types depending upon the type of pigment found. They are: 
  Leucoplasts: Colourless plastids of varied shape with stored nutrients.
  Chromoplasts: Yellowish or reddish in appearance because of the a.  presence of soluble fats.
  Chloroplasts: Double membranous structures. The inner membrane is known as the stroma. Thylakoids present in the stroma as stacks known as grana. The stroma contains enzymes for protein synthesis.

Centrosome

Next in class 11 cell, is the centrosome, which is an important part of the cell structure. Its features are mentioned below. 

• Contains two cylindrical structures called centriole.
• Central part of the centriole’s hub peripheral fibril is called spokes.

Nucleus

Moving further in the cell structure according to class 11 cell, is the nucleus. It performs certain important functions. 

• It has highly extended nucleoprotein fibres called chromatin, nuclear matrix and nucleoli.
• Chromatin material rearranges into chromosomes during cell division.
• Consist of histone and proteins.
• The centromere or the primary constriction of each chromosome on the discs of which kinetochores are present.
• On the basis of the position of the centromere, chromosomes can be divided into – metacentric, submetacentric, telocentric and acrocentric.
• Some chromosomes have non-staining secondary constriction, that gives a small fragment called a satellite.

Must Read: Biology Project for Class 11

So, this was all about the cell structure as described in class 11 cell. We hope these notes help you prepare well for your upcoming exams. Choosing the right stream after class 12th plays a pivotal role in shaping your career. If you want to pursue biology after 12th but not do MBBS, Get in touch with our Leverage Edu experts who will help you choose the right courses after class 12th Biology and guide you every step of the way. Sign up for a free session today!