Hello!!!

What you think we’d land up if we zoom inside a person till last point?

Yes…, you guessed it right, today we’re going to talk about the cells!!

In this you’ll learn about cells that make up all living organisms.

 At the end of this you’ll be able to…,

• Define a cell
• Identify the parts of a cell
• Identify different cell organelles

Welcome to the guided tour of the cell, let’s zoom in!

An organism, is made of different organ system, organ system are formed by the interaction of various organs, an organ is collection of tissues and tissues are formed by the similar kind of cells.

Do you know what is cell??

Cell is called as building blocks of life as cell is the fundamental and structural unit of all living organisms. Every living organism weather big or small is made up of tiny units called cells. Mainly there are two types of cells namely, prokaryotic and eukaryotic cells. The eukaryotic cells are further divided into animal cells and plant cells.

You might be wondering!! If,  cell is the basic unit of organism how come you have never seen before. Because, a cell is so small which we can’t see through our naked eyes.

But, today we are able to know about cells as we can see cells through microscope.

Fun fact!!!: Microscope magnifies the objects so that you can see even the small things clearly.  Did you know who discovered the cell?

Robert Hooke, an English scientist, with the help of microscope, first discover the cell in 1665, by examining slices of cork from the bark of a tree.

Now, let’s take a look at the detailed structure of an animal eukaryotic cell. Here, you’ll come across the cell membrane, cytoplasm, nucleus and cell organelles.

Let’s get a closer view of the cell membrane or the plasma membrane. It’s a bilayer living membrane and made of phospholipids and proteins. Plasma membrane is a selectively permeable or semi-permeable, as it allows the only some substances in and out of the cell. Hence, it’s also called as gate keeper of the cell.

Do you know how the substance move in and out of the cell? There are mainly two types of movement, active transport and passive transport. Passive transport includes simple diffusion, facilitated diffusion and osmosis which do not require energy expenditure. This transport allows the movement of smaller molecules like co2 and o2. Active transport includes the active transport and vesicular transport requiring cellular energy for their transportation across the membrane. Active transport is further divided into symport and antiport. Vesicular transport is divided into exocytosis and endocytosis.

The fluid content between the nucleus and the plasma membrane is called cytoplasm. The nucleus along with the cytoplasm forms the protoplasm. Let’s take closer look at cytoplasm, it’s a clear, thick, jelly-like material with water, organic compounds and organelles. The liquid part of the cytoplasm are called cytosol. Cytosol protects and supports the organelles that perform different metabolic functions.

Now, let’s look into the cell. This is the control unit of the cell called the nucleus. Nucleus have a nuclear membrane which is double layered. Nuclear membrane is pores to allow the substance to enter and leave the cell. It separates nucleoplasm or nuclear sap or karyolymph from cytoplasm. Nucleoplasm contains chromatin network intacted with the nuclear membrane and also nucleolus, proteins and enzymes. Chromatin network made of nucleotides and proteins contains genetic information required for the normal function of cell. Nucleus also plays a major role in cell division.

Did you know cell have different organelles? Let’s explore them now.

The protein synthesis site of the cell called endoplasmic reticulum (ER). It’s an irregular, double tubular network continuous with the nuclear membrane from inside. There are two types of ER, i.e., rough ER and smooth ER. Rough ER have ribosomes on it while ribosomes are absent on smooth ER. Rough ER synthesizes protein while smooth ER synthesizes lipids and fats.

Have you seen small spherical granules in cells? These are ribosomes, found scattered in the cytoplasm or found attached to the endoplasmic reticulum. These are naked and have no membrane. Ribosomes are made up of proteins and RNA containing two subunits of 60s and 40s and synthesizes proteins.

Here is another organelle for storing and transportation of proteins across the cytoplasm called Golgi apparatus. These are stacks of flattened membrane bound sac or vesicles called cisterns. Vesicle containing soluble proteins produced by ER fused with dictosome are transported across the cytoplasm to different organelles or diffused outside the membrane by Golgi apparatus.

There is the power house of the cell called mitochondria. It’s a double layered, rod shaped cells present in higher number inside the cell. Mitochondria contains its own DNA, ribosomes, proteins and enzymes. The important enzyme ATP synthase which produces ATP, intern the function of mitochondria is said to be producing ATP or energy.

The vesicle like structure found here are lysosomes which keeps the life factory clean. Usually absent in plants but present in animals they contains 40 different types of enzymes. These enzymes destroy injured or old organelles and foreign substances like bacteria. Interestingly lysosomes are known as suicide bags. When cells gets damaged lysosome burst and enzyme digest the cell.

Would you like to summarize this journey?

We went into the cell and there was a gatekeeper, the cell membrane. Through semi-permeability we went inside and found ourselves swimming in some clear cytoplasm and asked who’s running this cell, found talking to the nucleus. We went inside nucleus to ask the information about the cell and found stored information on chromosome. After exiting from nucleus found ourselves into a stretching so far, was a thin and wavy network of endoplasmic reticulum. We went inside the cell, trying not to get packed and get sorted by the Golgi apparatus and asked who makes protein here and found its ribosome. We were feeling happy and pretty fine, till lysosome engulf and throw us out of the cell.

So when you go inside a cell, remember what you see, if you ever feel confusion, remember active transport is opposite of diffusion.