CBSE Class 9 Chapter Wise Notes Structure and Fundamental Unit of Life – Cell
CBSE Class 9 Chapter Wise Notes Structure and Fundamental Unit of Life – Cell:- Here we are going to cover Chapter 1 (CBSE) / NCERT Chapter 5 of Class 9 i.e. CBSE Class 9 Chapter Wise Notes Structural and Fundamental Unit of Life – Cell post. This includes Theory/Detailed Notes of CBSE/NCERT Pattern for 9th Class.
Chapter-1 (CBSE Book)/ NCERT Chapter – 5
- All living beings are composed of cells.
- Robert hook discovered cell.
- Robert hook (1635-1703) developed a compound microscope by using 2 lenses for achieving great magnification.
Theory Notes and Study Material for CBSE Class 9 Chapter – CELL
- The cell is the smallest unit of life. The cell is the most important unit for life, it conducts all the functions and proper working of a living body. If cells are dead in a living body, then the body will not be called a living body. The cell is the basic structural and functional unit of life. If many similar cells are grouped together to perform a particular function is known as TISSUE. It is capable of independent existence and performs essential functions of life. The whole of biology revolves around the activities of cells.
- It consists of an organized mass of protoplasm surrounded by a semi-permeable membrane covering called PLASMA MEMBRANE.
- In an animal cell, the plasma membrane or plasma laguna is the only limiting membrane. However, in plants cells, fungi, and bacteria, a cell is also surrounded by a cell wall.
- A cell is usually microscopic in nature, it is the smallest part of the body in an organism. All organisms start their life as a single cell. Every cell has its own life span. the old and worn or life cells are continuously replaced by new cells.
- Many tissues collectively form an ORGAN.
Discovery of Cell :
- The cell was discovered first by Robert hook. Robert hook saw a cork which was resembling a structure of honeycomb it was consisting small compartments. Cork is a substance that comes from the dead cells of a tree’s bark. Robert discovered a cell first by a self-designed microscope.
FROM THESE ABOVE NOTES, QUESTIONS ARE MAINLY ASKED FROM THE TOPICS: CELL, TISSUE, PLASMA LAGUNA CORK, AND MICROSCOPE. ACCORDING TO THE CBSE/NCERT SYLLABUS. (For Students Extra Knowledge and Help From CBSE Class 9 Chapter Wise Notes Structural and Fundamental Unit of Life – Cell)
Unicellular and Multicellular Organisms
On the basis of the number of cells, there are 3 types of organisms, namely, they are
- Non-cellular organisms
- Unicellular organisms
- Multicellular organisms
- Organisms that do not contain any cell in their body organization, Ex: Virus. They do not have a membrane and are non-living until they reach inside the body of a living organism.
- Those organisms which are having only one cell and this single constitutes a whole organism, for Ex: Amoeba, Bacteria, Paramecium, Chlamydomonas.
- Those organisms in which the body is made up of many cells which group together to perform many functions of the body. Ex: Animals, Fungai, Plants, are all multicellular organisms. All the organisms have arrived from a SINGLE CELL through CELL DIVISION.
FROM THE ABOVE NOTES, QUESTION CAN BE ASKED ON THE TOPICS: ALL 3 TYPES OF ORGANISMS ( NOT IN DETAIL), ACCORDING TO THE LATEST CBSE/NCERT SYLLABUS CLASS 9th. (From CBSE Class 9 Chapter Wise Notes Structural and Fundamental Unit of Life – Cell)
Prokaryotic and Eukaryotic Cells
On the basis of Nucleus Organisation cells have been classified into two main types, namely
- Prokaryotic cells
- Eukaryotic cells
- Such organisms whose cells lack a nuclear membrane are called Prokaryotic cells.
A Well Labeled Diagram of Prokaryotic Cell
- These cells have a chromatic organization of genetic material.
- These cells do not have a well-organized nucleus region due to the absence of a nuclear membrane.
- These cells lap several cytoplasmic organelles like Mitochondria, Lysosomes, Endoplasmic reticulum, Chloroplast, Nucleus Etc.
- In prokaryotes, the chlorophyll is found attached to membrane vesicles and not plastids as in eukaryotes.
- Bacteria, Blue-Green Algae are examples of prokaryotes.
- Organisms whose cells have a nuclear membrane are called eukaryotes.
- In these cells, the genetic materials are made up of two or more DNA molecules.
- The nuclear material is enclosed under a nuclear membrane.
- These cells have a well-developed and organized nucleus.
- These cells have well-developed membrane-bounded organelles such as Mitochondria, endoplasmic reticulum (ER), chloroplast, nucleus, lysosomes, Etc.
- eukaryotic cells occur in plants, animals, Fungai, and protozoa.
NOTE: THE DIFFERENCE BETWEEN THE PROKARYOTIC CELLS AND EUKARYOTIC CELLS ARE VERY IMPORTANT, ACCORDING TO THE LATEST NCERT/CBSE SYLLABUS (from CBSE Class 9 Chapter Wise Notes Structural and Fundamental Unit of Life – Cell)
Cells Shape and Size
- The shape and size of the cell are related to the specified function performed by the organism.
- Most cells have a definite shape.
- Cells may be spindle-shaped (Nucleus of the cell), elongated (Nerve cell), oval-shaped (Red Blood Cells), cuboidal(germ cells), branched (Ostrich ho sides ), and so on.
- The smallest known cell is mitochondria (PPLO). Its size is 0.1-0.5 centimeters.
- The bacterial cell is 0.5-5 millimeters. RBC’s are 7-20 millimeters, human live and kidney cells are 20-30 millimeters and nerve cells are about 90-100 centimeters in size.
Structural Organisation of a Cell
A Well Labeled Diagram of Animal Cell and Plant Cell
1. Cell Membrane
Characteristics of Cell Membrane
- The outermost covering in animal cells is known as the cell membrane, it is present in cells, just next to the cell wall in plant cells.
- It is a selectively permeable membrane. It bounds the semi-fluid content of the cell.
- It is made up of lipids and proteins bilayer. It has fine cores.
- It only allows selectively permeable materials to pass through it.
- It protects the cell from any external injury.
- It maintains the actual shape of the cell.
Characteristics of Cytoplasm
- The space between the nucleus and the plasma membrane is filled with a liquid, which is translucent, amorphous, and colloidal in nature.
- It contains inorganic molecules, water, various cell organelles and organic compounds.
- It helps in the exchange of material between different cell organelles.
- All metabolic activities occur in the cytoplasm. METABOLIC ACTIVITIES SUCH AS SYNTHESIS OF PROTEINS, NUCLEUS DORSALIS, FATTY ACIDS Etc.
3. Endoplasmic Reticulum (E.R)
Structure of Endoplasmic Reticulum
Characteristics of Endoplasmic Reticulum
- It is an interconnected system membrane-lined channels that run through the cytoplasm.
- It may be smooth or rough, depending on the absence or presence of Ribosomes on it.
3.1) Smooth Endoplasmic Reticulum (Smooth E.R)
- The endoplasmic reticulum on which ribosomes are not present that endoplasmic reticulum is known as SMOOTH ENDOPLASMIC RETICULUM.
- The smooth endoplasmic reticulum is smooth in appearance.
3.2) Rough Endoplasmic Reticulum (Rough E.R)
- The endoplasmic reticulum on which ribosomes are present that endoplasmic reticulum is known as rough endoplasmic reticulum, or rough E.R
- The rough endoplasmic reticulum appears rough.
Characteristics of Ribosomes
- The small granules found ether floating in the cytoplasm or attached to the rough endoplasmic reticulum are called ribosomes.
- It helps in the process of protein synthesis.
Characteristics of Mitochondria
- It is of typically f sausage shape or roll-shaped, spherically granule bodies.
- Its outer membrane is double-walled. Its inner membrane is smooth as well as has inner folds.
- It oxides the food to release molecules in the form of ATP.
- It synthesis respiratory enzymes and many amino acids.
Note: THE FUNCTION OF MITOCHONDRIA AND RIBOSOMES ARE VERY IMPORTANT FOR EXAM PURPOSE ACCORDING TO THE LATEST CBSE/NCER SYLLABUS. (From the post CBSE Class 9 Chapter Wise Notes Structural and Fundamental Unit of Life – Cell)
A Well Labeled Diagram of Mitchocondria
6. Golgi bodies (In Animals) / Dictyosoes (In Plants)
Characteristics of Golgi bodies/ Dictyosomes
- The sacks of flattered saps or cisternal are called Golgi bodies.
- It contains vessels, vacuoles, and cutouts.
- They help in the secretion of different enzymes and hormones.
- They help in the storage of secretory products.
- They help in the development of acrosomes.
NOTE: THE DIAGRAM F ANIMAL CELL, PLANT CELL, AND MITOCHONDRIA IS VERY IMPORTANT FOR EXAM PURPOSES ACCORDING TO THE NCERT/CBSE LATEST SYLLABUS. (From the post CBSE Class 9 Chapter Wise Notes Structural and Fundamental Unit of Life – Cell )
Structure of Endoplasmic Reticulum
Characteristics of Nucleus
- A dense spherical cylindrical nucleus is present at the center of a cell.
- It has a nuclear envelope, which has pores to allow the entry and exit of various substances.
- it also contains chromatin which contains DNA.
- It helps to regulate all functions within the cell.
- It contains chromatin fibers that take off all the genetic information in the glass.
Components of Nucleus
The nucleus is comprised of the following parts:
- Nuclear membrane
- Genetic material
Characteristics of nucleolus
- A dense round structure attached to a chromatin fiber at nuclear envelope is known as nucleolus.
- It may be one or more than one in number.
- It helps in the synthesis of proteins by developing RNA molecules.
9. Chromatin Fibers
Characteristics of Chromatin Fibers
- A tangled fibrous mass that condenses to form chromosomes during cell division is known as chromatin fibers.
- It contains chromosomes that have genes to carry hereditary information
Characteristics of Vacuoles
- The fluid-filled membrane-bound spaces which are present at the center of the cell (in plant cell), or floating in the cytoplasm, or absent (in the animal cell) are known as vacuoles.
- In plants, vacuoles are large as well as centered.
- In animals is absent or is found floating in the cytoplasm. In animals, it is very small comparatively.
- It helps the cell to remain turgid.
- It helps in cell elongation.
- It helps in the storage of extra water and extra food substances.
Characteristics of Lysosomes
- Lysosomes are membranous sap bundled off, from Golgi bodies.
- It is a resting membrane that has a covering to protect the cell from digestive enzymes contained in Lysosomes.
- It helps in intercellular digestion.
- It provides energy during starvation.
- It bought about a cellular breakdown during aging.
Characteristics of Granules
- These are small particles, granules, droplets, or crystals.
- They serve as food for cells.
- Example: Starch (in plants), Glucogin (in animals)
NOTE: ALL THE CHARACTERISTICS AND FUNCTIONS OF CELL ORGANELLES ARE VERY IMPORTANT FOR EXAM PURPOSES ACCORDING TO THE LATEST NCERT/CBSE SYLLABUS. (From the post CBSE Class 9 Chapter Wise Notes Structural and Fundamental Unit of Life – Cell)
Organelles Present Only in Plant Cell
1. Cell Wall
Characteristics of Cell Wall
- The outermost rigid, protective, and supportive covering of plant cells (Only) is known as the cell walls.
- The cell wall is mainly composed of cellulose.
- It provides rigidity and shape to the cell.
- It is freely permeable as it allows all the substances to pass through it into the solution.
- It also protects the plasma membrane and other internal organelles and the structure of the cell.
Characteristics of Plastids
Plastids are of three types, namely:
- The double-layered proteinous organelles contain DNA Molecules.
- They have matrix and shape grana which contain chloroplast.
- Chloroplast helps in photosynthesis.
- chromoplast implant color to plants as well as roots.
- Leucoplast help in the storage of food.
Structure of Chloroplast
Organelles Present Only in Animal Cell
Characteristics of Centrosome
- The small naked, Protoplasmic structures are present near the nucleus.
- It consists of 2 small granules called centrioles.
- It regulates cell division.
- It also helps in the spindle formation during cell division.
NOTE: THE DIFFERENCES AND SIMILARITIES BETWEEN PLANT CELLS AND ANIMAL CELLS ARE VERY IMPORTANT AS WELL AS THE DIFFERENCE BETWEEN THE EUKARYOTIC CELLS AND PROKARYOTIC CELLS ARE ALSO VERY IMPORTANT FOR EXAM PURPOSES AS PER THE LATEST CBSE/NCERT SYLLABUS. (From The Post CBSE Class 9 Chapter Wise Notes Structural and Fundamental Unit of Life – Cell )
Movement of Structure In and Out of The Cell
The movement of substance in and out of the cell occurs through the following process:
2. Osmosis = 2.1 endosmosis
= 2.2 endosmosis
- The diffusion of water to a semi-permeable membrane from a reign where water is more concentrated to a reign where it is less concentrated is called Osmosis.
Importance of Osmosis
- It helps in the entry and exit of soil water into roots.
- Osmosis plays a key role in seed germination.
- Cell to cell movement of water occurs through osmosis.
- Living cells remain turgid by osmosis.
- Stomata open and close in response to an increase or decrease in osmotic pressure of the guard cell.
Types of Solutions
The solution in which the concentration of water and solute is the same as in the cytoplasm of the red blood cell (RBC).
- 0.9% = Salt Solution
- 5.1%= Glucose Solution
Are both Isotonic for Red Blood Cells.
- Hypertonic solution is the solution in which the concentration of solute is more and the concentration of water is less.
- Hypertonic solution is the solution in which the concentration of water is more concentrated than the solute.
For the NCERT solutions for this chapter, click on the link below.