Grade 9 Science Chapter Notes on The Fundamental Unit of Life PDF

Grade 09 'S Science Chapter Notes JU BY  'S Chapter Notes JU The Fundamental Unit of Life BY Class 09 121  Topics to be Covered Introduction to Cell 1.1 Definition 1.2 Basic Characteristics...

Grade 09 'S Science Chapter Notes JU BY  'S Chapter Notes JU The Fundamental Unit of Life BY Class 09 121  Topics to be Covered Introduction to Cell 1.1 Definition 1.2 Basic Characteristics of Cell 1.3 Cell Discovery 1.4 Cell Theory Microscopes 2.1 Simple Microscope 'S 2.2 Compound Microscope 2.3 Parts of Compound Microscope JU Types of Cells 3.1 Prokaryotic Cell BY 3.2 Eukaryotic Cell Cells of Different Sizes and Shapes 5 Basic Components of a Eukaryotic Cell 5.1 Nucleus 5.2 Cytoplasm 5.3 Cell Membrane 122  Topics to be Covered 6 Cell Membrane 6.1 Structure and Function 6.2 Permeability 6.3 Types of Transport: Active and Passive 7 Cell Wall 7.1 Cell Wall in Plant Cell 8 'S 7.2 Cell Wall in other Organisms Cells in Different Solutions JU 8.1 Hypotonic Solution 8.2 Hypertonic Solution BY 8.3 Isotonic Solution 9 Cell Organelles 9.1 Endoplasmic Reticulum 9.2 Golgi Body 9.3 Mitochondria 9.4 Chloroplast 9.5 Vacuole 9.6 Ribosome 9.7 Lysosome 10 Cell Division 10.1 Mitosis 10.2 Meiosis 123  Mind Map Nucleus Prokaryotic Eukaryotic Cell Cytoplasm Cell Cell Membrane Cell Types of Cells Components 'S JU Cell: The Fundament BY al Unit of Life Cell Organelles Cell Division Mitosis Meiosis 124  1. Introduction 1.1 Definition A cell is defined as the smallest, basic unit of life that is responsible for all of life's processes. Cells are the structural, functional, and biological units of all living beings. 1.2 Basic Characteristics of Cell 'S JU BY A Typical Animal Cell Stores hereditary information Capable of reproducing Acquires and utilises energy Site of various bio-chemical reactions Able to respond to stimuli 125 1.3 Cell Discovery Examined a thin slice of cork and observed tiny compartments which he called "cells" Cork is obtained from the bark of a tree and contains dead plant cells. Robert Hooke A Dutch lens maker who improved 'S the design of microscopes. JU Observed the first living cells and called them "animalcules" Anton Van BY Leeuwenhoek 1.4 Cell Theory The cell theory was given by Schleiden and Schwann, which was later modified by Rudolf Virchow. The three postulates of cell theory are: ✓ All living organisms are composed of one or more cells. ✓ Cell is the basic structural and functional unit of living organisms. ✓ All cells arise from pre-existing cells. 126  2. Microscopes A microscope is an instrument that magnifies small objects, thus revealing details too small to be seen by the naked eye. 2.1 Simple Microscope 2.2 Compound Microscope A single lens 'SMultiple lenses JU Total magnification is Total magnification is product limited to one lens of objective lens and eyepiece BY Used to magnify the size Used to magnify and of small objects study micro-organisms 2.3 Parts of a Compound Microscope Eyepiece Adjustment Knob Objective Lens Glass Slide Mirror/ Light Source 127  3. Types of Cells Regardless of the complexity as well as type of organism, cells are mainly divided into two categories. Mentioned below are the distinctions between the 2 major types of cells - 3.1 Prokaryotic 3.2 Eukaryotic Cell Cell Absent Present and Nucleus 'S Instead, they have a nucleoid surrounded by a nuclear JU region in the cell membrane BY Size ranges from Size ranges from Cell Size 0.2 μm - 2.0 μm 10 μm – 100 μm in in diameter. diameter. Ribosomes Present Present Membrane- bound cell Absent Present organelles Bacteria Plant Examples and Archaea and Animal cell 128  4. Cells of Different Sizes and Shapes Cells of Different Sizes Blue Whale’s Neuron 25 –30 m Amoeba Mycoplasma Ostrich’s Egg 0.01- 0.1 mm 'S 0.0002 mm 130-170 mm JU Cells of Different Shapes BY Shape of a cell depends on the function of the cell. Neuron Red Blood Cell Muscle Cell Branched- To Biconcave Discs- Spindle Shaped- connect with To maximise the To align properly other neurons oxygen carrying & to contract & capacity relax with ease 129 5. Basic Components of a Eukaryotic Cell 5.1 Nucleus Contains the hereditary material of the cell, the DNA which is organised as chromosomes Controls growth and metabolic activities of the cell Surrounded by the nuclear envelope that separates the DNA from the rest of the cell 5.2 Cytoplasm 'S Thick, jelly-like substance present inside the cell membrane and JU external to the nuclear membrane Mainly composed of water, salts, proteins and suspended cell BY organelles Site for most of the bio-chemical reactions 5.3 Cell membrane Flexible, living and selectively permeable membrane Outermost layer of the animal cells Present in both plant and animal cell 130  6. Cell Membrane Phospholipid Bilayer 'S Transport Protein JU 6.1 Structure and Functions BY Structure: The cell membrane is made up of lipids and proteins. Phospholipids are the main component of the cell membrane, and they are arranged in 2 layers called the phospholipid bilayer. The lipid bilayer is embedded with proteins that help in transport of certain substances. Functions: Encloses the components of the cell and protects it Monitors what goes in and out of the cell 131 6.2 Permeability Selectively Freely Impermeable Permeable Permeable 'S JU Selected No Particles All Particles Particles BY There are 3 types of membranes: impermeable, selectively permeable and freely permeable. Impermeable membrane: No particles can move across the membrane. Selectively permeable membrane: Only selected molecules are allowed to cross the membrane. Freely permeable membrane: All the molecules are allowed to pass through it without any resistance. 132 6.3 Types of Transport Based on energy requirements, transportation of molecules in living systems can be of two following types: Active Transport Passive Transport Movement of molecules Movement of molecules across the membrane against their concentration gradient 'Sacross the membrane down their concentration gradient without the use JU by using cellular energy of energy. in the form of ATP. BY Carrier proteins are Carrier proteins are not required. required. Large molecules and Molecules like oxygen and ions need active carbon dioxide can pass transport to cross through the membrane by the membrane. passive transport. Example- Uptake of Example- Diffusion of minerals and ions by plant gases in alveoli roots 133  7. Cell Wall 7.1 Cell Wall in Plant Cell The outermost layer in plant cells Responsible for maintaining the rigid structure and providing mechanical strength to the plant cell Cell Wall 'S Composed of cellulose JU 7.2 Cell Wall in other Organisms BY Fungi Algae Bacteria Chitin Cellulose Peptidoglycan 134  8. Cell in Different Solutions 8.1 Hypotonic Solution If the medium surrounding the cell has a higher water concentration than the cell, meaning that the outside solution is very dilute, the cell will gain water by osmosis. 8.2 Hypertonic Solution 'S JU If the medium has a lower concentration of water than the cell, meaning it is a very BY concentrated solution, the cell will lose water by osmosis. 8.3 Isotonic Solution If the medium has exactly same water concentration as the cell, there will be no net movement of water across the cell membrane. 135  9. Cell Organelles An organelle is a subcellular structure that has one or more specific jobs to perform in the cell, much like an organ does in the body. 9.1 Endoplasmic Reticulum 9.2 Golgi Body 'S JU Transportation system of Consists of smooth BY eukaryotic cell flattened membrane- RER bound, sac-like Ribosomes attached to structures called its membrane. cisternae Synthesis proteins and Packages materials enzymes synthesised in the cell SER and transports it Ribosomes are not Involved in the attached to its formation of membrane. lysosomes Synthesises lipids and steroids 136  9.3 Mitochondria 9.4 Chloroplast Structure: Structure: Double-membrane organelle found in eukaryotic cell 'S Double-membrane organelle found in all higher plants JU Contains smooth outer Contains grana which membrane and an inner are stacks of disc- BY membrane with shaped structures infoldings called cristae known as thylakoids Has its own DNA and Stroma is ribosomes to make the homogenous proteins matrix which contains grana, various enzymes, DNA, and ribosomes. Function: Function: Helps to generate energy Site of in the form of ATP photosynthesis in plants 137  9.5 Vacuole Plant Cell Animal Cell Vacuole Membrane-bound cell organelle present in the cytoplasm and filled with a watery fluid containing various substances 'S In plant cells, vacuoles store food, water and excretory products. As vacuoles are full of the cell sap, they JU provide turgidity and rigidity to the cell. Animal cells contain one or more vacuoles, and their size is relatively smaller as compared to the plant cell vacuole. BY 9.6 Ribosome 9.7 Lysosome Site of protein synthesis Contains hydrolytic In prokaryotic cell enzymes that break ribosomes are found in down complex molecules the cytoplasm. into simpler ones In eukaryotic cell Performs digestion of ribosomes are found as foreign bodies, breaks particles attached to down a damaged RER and suspended in organelle and disposes the cytoplasm. off toxic wastes out of the cell 138  10. Cell Division 10.1 Mitosis 2n Mitosis occurs in Parent somatic cells Cell Only one nuclear division occurs Results in two diploid daughter 2n Daughter 2n cells Cells Chromosome 'S number remains same JU 10.2 Meiosis BY Parent 2n Cell Meiosis occurs in 1st germ cells Nuclear Division Two nuclear divisions occur 2n 2n 2nd Results in four Nuclear haploid daughter Division cells Chromosome number is reduced to half n n n n Daughter Cells 139