Cell PDF

The Fundamental Unit of Life  Topics to be Covered Introduction to Cell Cell theory Cell - different shape, size and number Cell Structure Cell Division  Introduction to Cell Cells are the structural, functional, and biological units of all living beings. The entire functio...

The Fundamental Unit of Life  Topics to be Covered Introduction to Cell Cell theory Cell - different shape, size and number Cell Structure Cell Division  Introduction to Cell Cells are the structural, functional, and biological units of all living beings. The entire functioning of living organsims begins from basic unit called cell, that’s why it’s called fundamental unit of life. A cell can replicate itself independently. Hence, they are known as the building blocks of life. ORGAN CELLS TISSUES ORGANS ORGANISM SYSTEM  Discoveries related to Cell Robert Hooke The cell was first discovered and named by ROBERT HOOKE in 1665. Anton Van Leuwenhoek Discovered protozoa and (1674) bacteria, living cell Robert Brown (1831) Discovered cell nucleus Schleiden and Schwann Proposed cell theory (1838, 1839) Purkinje (1839) Protoplasm  Cell Theory All the living organisms are composed of cells The living organisms could be made up of one or more cells The new cells arise from pre- existing cells through the process of cell division Size Number Shape  Cell - different cell number If an organism is made up of a single cell, it is called a unicellular organism (uni: one; cellular: cell). e.g. bacteria, protozoa, etc. The organisms which are made up of more than one cell are called multicellular organisms (multi: many; cellular: cell). e.g. humans, animals, etc. Unicellular Multicellular Bacteria Paramecium Human Animal  Cell - different shape SPINDLE BRANCHED & ELONGATED SPHERICAL  Cell - different size Smallest cell- Mycoplasma (Bacteria) Largest cell- Ostrich egg PPLD (Pleuro- Pneumonia like Organisms)  CELL (Basic structural and functional unit of living organisms) Components Plasma Membrane/ Cell Wall Nucleus Cytoplasm Cell cell Membrane Organelles Rigid outer Has double Fluid content These are Outermost covering of covering lying layered nuclear inside the specialised cell outside the membrane plasma membrane- Permits the entry and plasma having nuclear membrane and bound parts of exit of some materials membrane pores for outside the cell present in (selectively permeable) Present in plants transfer of nucleus cytoplasm only. material and chromosomes. Cell Structure Plasma Membrane or Cell Membrane Outermost covering of the cell and it separates cell contents from external environment. Selectively permeable membrane: - Allows entry and exit of some materials. - Prevents movement of some materials. Allows diffusion of substances like carbon dioxide and oxygen. Regulates movement of substances in and out of the cell. It is made up of lipids and proteins.  Active and Passive Transport Passive Transport Active Transport Substances move from their higher to Substances move from their lower to lower concentration. higher concentration. It requires energy in the form de ATP No energy is required. molecules It is a slow movement It is a rapid movement. Only small molecules or water Movement of large molecules occur molecules are transported passively by active transport.  Osmosis Osmosis is the passage of water molecules across a semi-permeable membrane from a solution with a high concentration to a solution with a lower concentration Types of Osmosis: Endosmosis : The process in which the water molecules / solvent enter into the cell. (Cell Swell) Exosmosis : The process in which the water molecules / solvent move out of the cell. (Cell Shrink)  Diffusion The process of movement of a substance (solid, liquid, or gas) from the region of higher concentration to the region of lower concentration so as to spread uniformly. In the process of diffusion the molecules of the one substance mix with the molecule of the other substance.  DIFFUSION OSMOSIS It is the phenomenon of moving solvent particles across a It is the phenomenon of moving particles from a region of higher semipermeable from a region of low solute concentration to more concentration to a region of lower concentration. solute concentration. It occurs in liquids and gases. It occurs in liquids only. No membrane separation is required here. It requires a semi-permeable membrane. Water is not necessary for movement. Water is the main solvent that moves from one region to another. The flow of constituents is in all directions. The flow of constituents occurs in one direction only. The process can be stopped or we can reverse it by applying an Diffusion is a natural phenomenon that can not be stopped. external force. All the types of substances present in the solution can move from There is a movement of only water or any other substance from a the region of its high concentration to the region of low region of higher concentration of solvent to the region of low concentration. concentration. Example – Addition of ink in water leads to the colouring of the Example – Red blood cells swell up when exposed to water. water. Types of Solutions swell  Endocytosis & Exocytosis Endocytosis Exocytosis  Cell Wall Non-living, rigid outer covering of plant cells composed mainly of cellulose. Provides structural strength, lies outside the plasma membrane. Plasmolysis: Occurs in living plant cells when they lose water through osmosis. Results in shrinkage of cell contents away from the cell wall.  Functions of Cell Wall : Permits plant, fungi, and bacterial cells to resist bursting in hypotonic environments. Cells absorb water by osmosis, leading to swelling and pressure against cell wall. Cell wall exerts equal pressure against swollen cell. Cells with walls can endure greater changes in surrounding medium than animal cells. Plants Present Cellulose Bacteria Present Peptidoglycan Fungi Present Chitin Animals Absent X Virus Absent X  Why cell walls are only present in plants and not animals? (PYQ) Cell wall is present in plants while animals have cell membrane. Cell wall mainly helps the plant to remain rigid and fixed. this helps the plants because they are immobile. the cell wall mainly contains cellulose and other substances, which are the main reasons why the trunks and branches of the trees are strong.  Nucleus The nuclear membrane is double-layered and contains pores for material exchange between the nucleus and cytoplasm. Nucleus contains chromosomes (DNA and Protein) , visible during cell division, which carry genetic information in the form of DNA molecules. DNA (Deoxyribose Nucleic Acid) molecules contain the information essential for constructing & organizing cells. These molecules consist of genes, which regulate cell functions and inheritance, and are visible as chromatin material in non-dividing cells. Chromatin material, visible as an entangled mass of thread-like structures, undergoes organization into chromosomes during cell division. The nucleus plays a central role in cellular reproduction and development by directing chemical activities and determining cell maturity. Cell - origin and cellular structure ribosomes flagella Q. The undefined nuclear region of prokaryotes are also known as (a) nucleus (PYQ) (b) nucleolus (c) nucleic acid (d) nucleoid  Eukaryotes ANIMAL CELL PLANT CELL Cytoplasm- the fluid content enclosed by the cell membrane, contains specialized organelles. Organelles perform specific functions and are enclosed by membranes. Cell Organelles- Eukaryotic cells contain various membrane-bound organelles that carry out various functions in the cell, e.g. Nucleus, Endoplasmic reticulum, Golgi apparatus, Lysosomes, etc. Q. The only cell organelle seen in prokaryotic cell (a) Mitochondria (b) Ribosomes (PYQ) (c) Plastids (d) Lysosomes  Endoplasmic Reticulum The endoplasmic reticulum (ER) forms a network of membrane-bound tubes and sheets within the cell. Rough Endoplasmic Reticulum (RER) Smooth Endoplasmic Reticulum (SER) Appears rough due to ribosomes; sites of protein Smooth appearance; facilitates lipid, enzyme, and synthesis. hormone production. Ribosomes synthesize proteins. No protein synthesis; functions in lipid production. Not involved in lipid production. Facilitates lipid synthesis. No role in enzyme or hormone synthesis. Functions in enzyme and hormone production. No detoxification capability. Crucial in detoxification, especially in liver cells. Q. Lipid molecules in the cell are synthesised by a. Smooth endoplasmic reticulum b. Rough endoplasmic reticulum (PYQ) c. Golgi apparatus d. Plastids  Golgi Apparatus Named after its discoverer, Camillo Golgi. Comprises a system of membrane-bound vesicles arranged roughly parallel to each other in stacks known as cisterns. Facilitates the packaging and transportation of proteins across the cytoplasm. Performs functions such as storage, modification, and packaging of products in vesicles. Traffic police' of the cell Plays a role in the formation of lysosomes.  Lysosomes Lysosomes, filled with digestive enzymes from the RER, act as the cell's waste disposal system. They digest foreign material and worn-out organelles to maintain cell cleanliness. Lysosomes break down complex substances into simpler ones using powerful enzymes. Termed "suicide bags" as they may burst during cellular disturbance, leading to self-digestion. ‘Suicide bags' of the cell Involved in breaking down all organic material, including bacteria and old organelles.  Mitochondria Mitochondria, the cell's powerhouses, have two Cristae membranes: porous outer and folded inner. Inner folds increase surface area for ATP generation, the cell's energy currency. Mitochondria produce ATP, used for cellular activities and mechanical work. They possess their own DNA and ribosomes, ‘Powerhouse' of the cell enabling protein synthesis.  Plastids Plastids, exclusive to plant cells, exist in two varieties: chromoplasts and leucoplasts. Chromoplasts are colored plastids (flowers). Chloroplasts, are chromoplasts, containing chlorophyll, enabling photosynthesis, which regulates atmospheric oxygen levels. Leucoplasts lack coloration and primarily function as storage sites for starch, oils, and protein granules..  Ribosomes Membrane less cell organelle. Involved in synthesis of protein Present in both Prokaryotic and Eukaryotic cell. Q. Which of these options are not the functions of ribosomes? I. It helps in manufacture of protein molecules. (PYQ) II. It helps in manufacture of enzymes. III. It helps in manufacture of hormones. IV. It helps in manufacture of starch molecules. (a) I and II (b) I and III (c) III and IV (d) IV and I  Vacuoles Tonoplast Vacuoles: Storage sacs in cells, small in animals, large in plants. Plant Central Vacuole: Occupies 50-90% of cell volume, filled with cell sap. Functions: Provide turgidity and rigidity to e plant cells, store essential substances. ol Contents: Amino acids, sugars, proteins, and in cu single-celled organisms, consumed food items. Va Specialized Roles: Expelling excess water and wastes from unicellular organisms. Storage Sacs  To Remember Double membrane-bound: Nucleus, Mitochondria, Plastids Single membrane-bound: vacuole, lysosome, Golgi apparatus, endoplasmic reticulum Membrane-less: Ribosome, Centrosome (Centriole)  Feature Plant Cell Animal Cell Cell Shape Square or rectangular in shape Irregular or round in shape Cell Wall Present Absent Plasma/Cell Membrane Present Present Endoplasmic Reticulum Present Present Nucleus Present and lies on one side of the cell Present and lies in the center of the cell Lysosomes Present but are very rare Present Golgi Apparatus Present Present Cytoplasm Present Present Ribosomes Present Present Plastids Present Absent Vacuoles Few large or a single, centrally positioned Usually small and numerous Cilia Absent Present in most of the animal cells Mitochondria Present but fewer in number Present and are numerous Mode of Nutrition Primarily autotrophic Heterotrophic  Cell Division Cell division is the process through which new cells are formed in organisms. New cells formed for growth, cell replacement, and reproduction. Two main types: mitosis and meiosis.  (PYQ) Q. In brief state what happens when (a) Dry apricots are left for sometime in pure water and later transferred to sugar solution? (b) A red blood cell is kept in concentrated saline solution? (c) The plasma membrane of a cell breaks down? (d) Rhoeo leaves are boiled in water first and then a drop of sugar syrup is put on it? (e) Golgi apparatus is removed from the cell? Answer- (a) Dry apricots in pure water: Swell due to osmosis, then shrink in sugar solution due to exosmosis. (b) Red blood cell in concentrated saline solution: Shrinks due to exosmosis caused by water loss. (c) Plasma membrane breakage: Disruption of cell integrity, scattering of cell organelles. (d) Boiled Rhoeo leaves with sugar syrup: No osmosis due to cell death, demonstrating selective permeability. (e) Removal of Golgi apparatus: Impaired protein processing, storage, and secretion. “ be powerhouse of your life ”