CBSE Class 9 Science Revision Notes Chapter 5

CBSE Class 9 Science Revision Notes Chapter 5 – The Fundamental Unit of Life

A cell requires energy and utility which is provided by the contributions of many organelles. The concept of transport of materials in and out of the cell by processes like osmosis and diffusion is crucial from an exam point of view. 

Understanding the fundamentals is the first step toward getting better grades in biology. The concepts of a cell’s structure, function, and the organelles that carry out these functions are examined in CBSE Class 9 Science Chapter 5 – The Fundamental Unit of Life Revision Notes by Extramarks. It will be simple to memorise some of the chapter’s fundamental ideas if students carefully read and comprehend these notes. They can consult these notes for a thorough review. 

Class 9 Science Chapter 5 Notes

Introduction to Class 9 Science Chapter 5 Notes

The formation of the cell served as the starting point for the continuous evolution of species. When cells divide, they create multicellular and unicellular animals that are vital components of the ecosystem. Students can find out all the information about defining a cell and its appropriate functions in Chapter 5 of CBSE Class 9 Science: The Basic Unit of Life Revision Notes by Extramarks. The definition, many cell types, the structure and operation of the cell and its organelles, as well as the significant distinction between plant and animal cells, are among the key points covered by subject matter experts in their explanation of these ideas. The notes are written in simple language, making them essential for an instant memory boost.

Definition and Structure of a Cell

The cell was discovered by Robert Hooke in 1665, after which Robert Brown took his discovery forward by discovering the nucleus in 1831. The cell may be defined as the structural and functional unit of life since it provides structure to the body and performs all functions at the grassroots level. 

Cell Theory: This theory suggests that all living organisms are consisting of cells. New cells arise from pre-existing cells. 

Types of Cells

Cells may be either prokaryotic or eukaryotic.

1. Prokaryotic cells – Primitive cells, consisting of no true nucleus and incomplete nature, are called prokaryotic cells. These are usually seen in unicellular organisms like blue-green algae, archaebacteria, etc. Organisms with this type of cell are called prokaryotes. 
2. Eukaryotic cells – Advanced cells, which consist of a true nucleus and organelles, are known as eukaryotic cells. These cells are complete and are found in both unicellular and multicellular organisms. These cells are not seen in blue-green algae and bacteria. Organisms with this type of cell are called eukaryotes. 

Cell Organelles

Cell organelles are those components within a cell that perform its day-to-day activities to keep it operative. A cell has the following organelles, which are crucial for its functioning. 

• Endoplasmic reticulum – This is an organelle that allows the interpretation of genetic information present in the nucleus, and appears membrane-like. Two types of Endoplasmic reticulum, namely RER (Rough ER) and SER (Smooth ER) are observed. The functions of these are as follows:

1. Rough endoplasmic reticulum: Contains ribosomes for protein synthesis. 
2. Smooth endoplasmic reticulum: Lacks ribosomes but can perform functions of detoxifiers and lipid metabolites. 

• Golgi apparatus – This organelle transports and packs proteins across the cytoplasm, and thus, is called the ‘post office’ of the cell. 
• Lysosomes – Lysosomes perform the function of defence by targeting foreign objects and releasing potent enzymes that help in killing intruders. These are also called suicide bags.
• Mitochondria – Mitochondria generate ATP and thus are called the powerhouse of the cell. Mitochondria have their DNA called mtDNA. 

Proper revision of this chapter provides students with an upper hand while preparing for the examinations. The concepts explained in these notes help students with a quick recap of the chapter. The Class 9 Science Chapter 5 Notes can be accessed anytime by students from Extramarks, enabling them to source error-free and reliable materials without having to look elsewhere.