Fundamental Unit of Life One Shot in 20 Mins | Class 9th Science Chapter-5 | Vedantu Class 9

Summary

The script is a biology lesson focusing on cells, the basic unit of life. It covers cell theory, the discovery of cells and their structures like the nucleus and cell organelles. The teacher explains the difference between prokaryotic and eukaryotic cells, the function of the plasma membrane and cell wall in动植物, and the processes of osmosis and cell division. The lecture also touches on the roles of various cell components like the endoplasmic reticulum, Golgi apparatus, and mitochondria, emphasizing their importance in cell function and life overall.

Takeaways

• 📚 The session aims to revise the entire chapter on 'Fundamental Units of Life' in just 20 minutes through mind mapping.
• 🌿 Cells are the structural and functional units of life, responsible for forming the body's structure and performing all life processes.
• 👩‍🔬 Robert Hooke discovered cells in 1665, observing dead cells (cork cells) with a self-made microscope.
• 🔬 Antonie van Leeuwenhoek discovered living cells in 1674, examining water from a pond and observing living cells with a microscope.
• 🧬 The nucleus was discovered inside cells by Robert Brown in 1831, which was a significant step in understanding cell structure.
• 🌱 The term 'protoplasmic' was coined by J. Goodyear in 1839, referring to the living substance within cells.
• 🌳 The cell theory was proposed by Schleiden and Schwann in 1838-1839, stating that all plants and animals are composed of cells.
• 🔬 The modified cell theory by Virchow explained that new cells arise from pre-existing cells, not from a non-cellular environment.
• 🔬 Prokaryotic cells are primitive cells without a defined nucleus or nuclear membrane, whereas Eukaryotic cells have a defined nucleus and other organelles.
• 🌱 Plant cells have a cell wall and cell membrane, whereas animal cells only have a cell membrane, which is selectively permeable and controls the entry and exit of molecules.
• 💧 Osmosis plays a crucial role in the movement of water and other molecules through the selectively permeable cell membrane.

Q & A

What is the basic structural and functional unit of life?

The cell is the basic structural and functional unit of life. It is the building block of all living organisms, performing various functions that contribute to the overall function of the body.

Who discovered cells and in what year?

Cells were discovered by Robert Hooke in 1665. He defined cells as the structural and functional units of life using his self-designed microscope.

What is the difference between prokaryotic and eukaryotic cells?

Prokaryotic cells are primitive cells without advanced structures like a nucleus. They have a simple nucleus without a nuclear membrane and usually have a single chromosome. In contrast, eukaryotic cells have a well-defined nucleus with a nuclear membrane and contain multiple chromosomes and complex organelles.

What is the function of the plasma membrane?

The plasma membrane, also known as the semi-permeable membrane, controls the entry and exit of molecules. It allows certain substances like oxygen and water to pass through while preventing others like foreign materials from entering the cell.

What is the process of osmosis and its role in the cell?

Osmosis is the movement of water through the plasma membrane from an area of high concentration to an area of low concentration. This process is crucial for maintaining the balance of water inside and outside the cell.

What are the three types of solutions related to osmosis?

The three types of solutions related to osmosis are hypertonic, isotonic, and hypotonic solutions. Hypertonic solutions have a higher concentration of water outside the cell, causing cells to shrink. Isotonic solutions have similar water concentrations inside and outside the cell, resulting in no net movement of water. Hypotonic solutions have a higher concentration of water inside the cell, causing cells to swell.

What is the function of the cell wall in plant cells?

The cell wall in plant cells provides structural support and protection. It is made of cellulose and is freely permeable, allowing the cell to maintain its shape and withstand external pressure.

What is the nucleus and its role in the cell?

The nucleus is an organelle within the cell that contains the genetic material. It is surrounded by a double membrane and contains a dark structure called nucleolus. The nucleus is responsible for controlling the cell's activity and plays a crucial role in cell division by helping in the replication and distribution of chromosomes.

What are ribosomes and their function?

Ribosomes are cellular structures that are involved in protein synthesis. They are often referred to as the protein factories of the cell because they synthesize proteins necessary for various cellular functions.

What is the endoplasmic reticulum and its function?

The endoplasmic reticulum is a network of membranes within the cell that plays a role in the synthesis of proteins and lipids. It has two types: rough endoplasmic reticulum, which is studded with ribosomes and involved in protein synthesis, and smooth endoplasmic reticulum, which lacks ribosomes and is involved in lipid synthesis.

What is the Golgi apparatus and its role?

The Golgi apparatus is an organelle involved in modifying, sorting, and packaging proteins and lipids for transport to other parts of the cell or secretion outside the cell. It is often referred to as the cell's 'post office'.