Page 1 :
Cell theory, ●, ●, ●, , ●, , ●, ●, ●, ●, ●, , ●, , ●, ●, , ●, , ●, , All living organisms are made up of a fundamental unit of life called-cell., The cell is a Latin word for “a little room”., The scientist Robert Hooke saw a little room in the cork (the bark of a tree) that, resembled the structure of a honeycomb. The use of the word “Cell” to describe, These units is used till this day in Biology as” Cell Biology”., The Compound Microscope consists of an eyepiece,objective lens and condenser to, observe a cell after putting a drop of Safranin (for plant cell) and methylene blue (for, animal cell)., The scientist Leeuwenhoek saw free living cells in the pond water for the first time. (, father of microbiology)., The scientist Robert Brown discovered the nucleus in the cell., The cell theory states that all the plants and animals are composed of cells, it was, proposed by Schleiden and Schwann., The cell theory was further expanded by Virchow by suggesting that “all cells arise, from the pre-existing cells”., The cells differ in size, shape, structure Types of cells: Onion cells, Smooth muscle, cell, Blood cells, Bone cell, Fat cell, Nerve cell, Ovum, Sperm etc. Each kind of cell, performs a specific function., A single cell may constitute a whole organism as in Amoeba, Chlamydomonas,, Paramecium and Bacteria; these are called unicellular organisms. Whereas in, multicellular organisms (Human beings) division of labour is seen., The features in almost every cell are the same: Plasma membrane, nucleus and, cytoplasm., Plasma membrane: It is the outermost covering of the animal cell., - It is called a selectively permeable membrane (because it prevents movement of, some materials)., - It helps in diffusion and osmosis, Diffusion: movement of substance from high concentration to low concentration. Eg;, exchange of carbon dioxide or oxygen with an external environment., , Osmosis: it is the passage of water from the region of high water concentration to a, region of low water concentration through a selectively permeable membrane., , (a) The cell gains water, if the medium surrounding the cell has a higher water, concentration (Hypotonic solution) than the cell., (b) The cell maintains the same water concentration as the cell (Isotonic solution),, water crosses the cell membrane in both directions.

Page 2 :
Cell theory, , ●, , ●, , ●, , ●, , ●, , ●, , ●, , (c) The cell loses water, if the medium has lower water concentration (Hypertonic, solution) than the cell., The cell engulfs food is called endocytosis and ejects solid is called exocytosis., Amoeba acquires food through endocytosis and excretion of solid is called, exocytosis., The cell wall is a rigid outer covering composed of cellulose. It provides structural, strength to plant cells., When a living cell loses water, there is shrinkage of contents of a cell away from the, cell wall. This phenomenon is called plasmolysis., The cell walls permit the cells of plants, fungi and bacteria to withstand very dilute, (Hypotonic) external media without bursting., The Nucleus: It is a dark colored, spherical or oval, dot-like structure near the centre, of a cell called Nucleus., The nucleus plays a central role in cellular activities/reproduction., The chromatin material gets organised into chromosomes., The chromosomes contain information for inheritance of features from parents to, next generations in the form of DNA( DeoxyriboNucleic Acid ) and protein molecules., The functional segments of DNA are called genes., In some organisms like the Bacteria nucleus is not covered by a nuclear membrane., Hence it is called a prokaryote.The organisms with cells having a nuclear membrane, are called eukaryotes., Differences between prokaryotes and eukaryotes, Prokaryotes, , Eukaryotes, , Size: generally small (1-10 µm), Nuclear region: Not well defined, and not surrounded by a nuclear, membrane & known as nucleoids., Chromosome: Single, Membrane-bound cell, organelles absent, Eg- bacteria, blue green algae etc., , Size: generally large. (5-500 µm), Nuclear region: Well defined and, surrounded by a nuclear membrane, Chromosome: More than, one chromosome, Membrane-bound cell, organelles present, Eg- fungi, plant cells and animal cells., , Cell organelles: Every cell has a fluid matrix (other than nucleus) called cytoplasm., The nucleus and cytoplasm are together called protoplasm., The protoplasm term was coined by Purkinje., It has important cell organelles: Endoplasmic Reticulum (ER), Golgi apparatus,, Lysosomes, Mitochondria, Plastids, and vacuoles., Endoplasmic Reticulum (ER): It is a large network of membrane –bound tubules, and vesicles. There are two types of Endoplasmic Reticulum, - Rough Endoplasmic Reticulum(RER) It looks rough because Ribosomes are, attached to its surface. They are the sites of protein synthesis., - Smooth Endoplasmic Reticulum(SER) It looks smooth because Ribosomes are, not attached to its surface. They are the sites of fat molecules synthesis., SER-help in the functioning of enzymes and hormones to carry out biochemical, activities., SER-detoxifies many poisons and drugs from the cell.

Page 3 :
Cell theory, ER serves as a channel for the transport of material between various regions of the, cytoplasm and the nucleus., Proteins and fat molecules produced by ER help in membrane biogenesis., ● Golgi apparatus: It was first described by a scientist Camillo Golgi. It is a system of, membrane bound vesicles called cisterns. Its functions include the, storage,modification and package of cell products. The complex sugars are made, from simple sugars in the Golgi apparatus. It is also involved in the formation of, lysosomes., ● Lysosomes: They contain membrane-bound sacs with powerful digestive enzymes, (enzymes are made by RER) to digest the worn-out cell organelles. When the cell, gets damaged, lysosomes may burst and the enzymes digest their own cell, hence, called as “Suicidal bags of a cell”. It is a waste disposal system of the cell., ● Mitochondria: It is covered by a double membrane. Outer membrane is very porous, and the inner membrane is deeply folded., These folds create a large surface area for ATP (Adenosine Triphosphate), molecule synthesis., ATP is the energy currency of a cell; hence the Mitochondria are called the, PowerHouse of a Cell., Mitochondria have their own DNA and Ribosomes; therefore they can make their, own proteins., ● Plastids: They are present only in plant cells. There are two types., -Chromoplasts (Colored Plastids): Chromoplasts are plastids and contain, carotenoids. They lack chlorophyll. Carotenoid pigments are responsible for different, colours like yellow, orange and red colour imparted to fruits, flowers, old leaves,, roots, etc., -Chloroplasts (Green Plastid): Green pigmented and useful in Photosynthesis and, also contains various other pigments like yellow or orange etc., -Leucoplasts (White or colourless plastids; stores materials such as oils, proteins,, fats etc. ), Plastids are also covered by a double membrane. The matrix is called Stroma, seat, for enzymatic actions., Plastids have their own DNA and Ribosomes; therefore they can make their own, proteins., ● Vacuoles: Storage sacs for solid or liquid contents., They are small in size in animals while plants are large, and may occupy 50-90 % of, the cell volume., Helps to provide turgidity and rigidity to the cell. Many substances like amino acids,, sugars, organic acids and proteins are stored in vacuoles. In Amoeba food vacuole is, specialised to play an important role., ● Cell: It is the fundamental structural unit of living organisms, helps in respiration,, obtaining nutrition and clearing waste material or forming a new protein., Differences between Plant cell and Animal Cell, ANIMAL CELL, , PLANT CELL

Page 4 :
Cell theory, Cell wall absent, Plasma membrane is the outer layer which, provides turgidity to the cell, Vacuoles are small in size, Plastids are absent, Nucleus lies in the centre., , Cell wall present, Cell wall is the outer layer which gives, rigidity and turgidity to the cell, Vacuoles are big in size, Plastids are present, Nucleus lies on one side, , 1. All living organisms are composed of a fundamental unit called…………. ( Cell), 2. Who discovered the nucleus in the cell……………………….( Robert Brown), 3. Who saw the free living cells for the first time……………..( Leeuwenhoek), 4. Name two unicellular organisms …………….. ………………..( Amoeba,, Chlamydomonas,), 5. Write two differences between prokaryotes and eukaryotes……………..( Nuclear, region/ Chromosome), 6. What are the two types of ERs ……. ( RER/ SER), 7. What are the functions of Golgi Bodies? (It includes the storage, modification and, package of cell products. The complex sugars are made from simple sugars in the, Golgi apparatus)., 8. What are the types of plastids (Chromoplasts,Leucoplasts), 9. Which are the substances stored in vacuoles? (Substances like amino acids, sugars,, organic acids and proteins are stored in vacuoles), 10. What would happen if the plasma membrane ruptures or breaks down?(The rupture or, breakdown of a cell's plasma membrane signals that the cell has been injured, and in, this case, the damaged cell's lysosomes may burst, causing the digestive enzymes, inside those lysosomes to eat their own cell. The cell will die as a result of this.), 11. What would happen to the life of a cell if there was no Golgi apparatus?(The, preservation, modification, and packaging of products in particles are all tasks of the, Golgi apparatus. All types of storage, modification, packaging and dispatch of, materials within and beyond the cell would be impossible if there was no Golgi, apparatus for the cell.), 12.What is active transport?(The movement of molecules across a membrane in cells, against a concentration gradient with the help of ATP units is called active transport), 13.What do you mean by a nucleoid?(In prokaryotes and lower organisms like bacteria,, the nuclear region of the cell may be poorly defined because of the absence of a, nuclear membrane. Such an undefined and incipient nucleic region containing only, naked nucleic acids without any membrane covering them is called a nucleoid.), 14.How do substances like CO₂ and water move in and out of the cell?(Gases like CO₂ and, O₂ move in and out of the cell by diffusion from their higher concentration to lower, concentration. Water enters the cell by endosmosis through a semi-permeable plasma, membrane from its higher concentration to lower concentration. Similarly, water, moves out of the cell by exocytosis when a cell is placed in a hypertonic solution.), 15. Why is the cell called the structural and functional unit of life? (Because shape and size, of cells are related to specific functions they perform. Cells constitute various, components of plants and animals.), 16.Which structure present in the nuclear region of a living cell bears, genes?(Chromosomes is the structure present in the nuclear region of a living cell, which bear genes)