Cells - Session 1

The cell is the basic building-blocks of life. Similar to the fact that bricks are used to build a house, cells are the building-blocks that make up living things. They come in different shapes and sizes. Cells work together to form tissues, organs, and ultimately entire organisms. A cell is like a tiny unit that has everything it needs to carry out its functions. Some examples of cells are nerve cells and muscle cells. Muscle cells make up the muscles. Nerve cells are found in our brain.

We have studied that all living things are made up of cells. Cells perform various important functions. For example, during summer skin cells help in sweating. Sweating maintains our body temperature during summer. Muscle cells help us in movement. Red blood cells make up blood. Red blood cells carry oxygen to different parts of our body.

Cells are extremely small structures that can only be seen with special tools called microscopes. Microscopes help scientists observe cells by making them appear bigger. Cells exist in many living things, including plants, animals, and bacteria. Without microscopes, we would not be able to see these tiny building-blocks of life.

When we look at cells under a microscope, we see different parts. The cell membrane surrounds and protects the cell. It decides what goes in and out of the cell. Different kinds of structures are found inside the cell. These structures have various functions inside the cell. These structures are also called organelles. Some examples of organelles are nucleus, mitochondria, and ribosomes.

Unicellular organisms are living things that consist of a single cell. They can survive and perform all necessary life functions with similar to one cell. Unicellular organisms are like a house with no rooms, where everything happens. They eat, grow, reproduce, and carry out all their activities within that single space. An example of unicellular organism is bacteria.

Multicellular organisms are made up of many cells that work together as a team. These cells specialize in different tasks. They collaborate to ensure the proper functioning of the organism. Multicellular organisms are like large houses with different rooms. Each room has a specific purpose, such as a kitchen for eating, a bedroom for sleeping, and a bathroom for hygiene. Similarly, different cells in multicellular organisms have distinct roles and work together to maintain the survival of an organism. Some examples of multicellular organisms are plants, animals and human.

Let us understand the structure of a cell. The outer layer of the cell is called the cell membrane. It encloses organelles in a cell. Cell membrane is a protective layer of the cell. It is made up of a double layer of special material called phospholipid. Phospholipid bilayer looks like a sandwich.

A Phospholipid has two parts. One part is called the head. Other part is called the tail. The head of phospholipid has the ability to attract water. It is also called the hydrophilic head. The term hydro means water and the term philic means attract. So the term hydrophilic means water attracting. The tail of the phospholipid repels water. It is also called hydrophobic tail. The term hydro means water and phobic means repel. So the term hydrophobic means water repelling.

The hydrophilic heads of both layers of phospholipid face outward. The hydrophobic tails of both layers of phospholipid face inward to each other. Some other molecules are also embedded within the phospholipid bilayer. These molecules are called proteins. They help in the transport of material into and out of the cell.

The cytoplasm is a gel like substance that fills the inside of a cell. It is a fluid that surrounds all the structures within the cell, such as the nucleus and other organelles. Imagine the cytoplasm as a soup inside the cell. It is made up of water, proteins, salts, and other molecules that support the activities of the cell.

The Nucleus is one of the organelles found in a cell. The nucleus is like the control center of a cell. It is a circular structure that acts as the command center of the cell. The nucleus is surrounded by a protective covering called thenuclear envelope. It acts like a wall. It separates the nucleus from the rest of the components of the cell. The nucleus also contains a smaller structure called the nucleolus. The nucleolus is involved in making ribosomes. Ribosomes are organelles found in a cell.

Inside the nucleus, there is a substance called chromatin. Chromatin contains genetic material of the cell called the DNA. The DNA in the nucleus is like a set of instructions that tells the cell what to do. It determines how the cell grows, functions, and looks. The DNA determines the traits of an organism, such as its eye color, height, and other characteristics.

Mitochondria is another organelle found in a cell. Mitochondria are the powerhouses of the cell. They are responsible for producing energy. They are small, bean shaped structures that generate ATP. ATP is the primary source of energy for a cell.

Think of the mitochondria as tiny generators within the cell. They convert nutrients from the food we eat into usable energy. This energy is crucial for the cell to carry out its various functions and activities. The number of mitochondria within a cell can vary depending on the energy requirements of a cell. Cells with high energy demands, such as muscle cells, tend to have a larger number of mitochondria compared to other types of cells.

Mitochondria consist of an outer membrane and an inner membrane. The inner membrane is organized into folds known as cristae. Cristae makes available a larger surface area for energy production. A gel like substance is seen inside the mitochondria. This gel like substance is called the matrix. Matrix contains DNA and other important molecules. Mitochondria has its own DNA. It helps in various cellular processes for energy production.