BIO-Q1-LESSON-2.pdf

CELL The Fundamental Unit Of Life What is Cell? Cell is the basic Structural and functional unit of living organisms. In other words, cells make up living things and carry out activities that keep a living thing alive. Cell 1 A ll k n own livin g t h in g s...

CELL The Fundamental Unit Of Life What is Cell? Cell is the basic Structural and functional unit of living organisms. In other words, cells make up living things and carry out activities that keep a living thing alive. Cell 1 A ll k n own livin g t h in g s a re ma d e u p o f o n e o r mo re c e lls. Theory 2 A ll livin g c ells arise f rom p re - exist in g c e lls by d ivisio n. Cell theory is a collection of ideas and conclusions from many different scientists over time that describes 3 Th e c e ll is t h e b a sic u n it o f st ru c t u re a n d f u n c t io n in a ll cells and how cells operate. livin g o rga n isms.  Cell Theory Timeline 1674 Anton Van Leeuwenhoek Observed living cell 1665 1883 Robert Hooke Robert Brown Discovered cell Discovered nucleus  Cell Theory Timeline 1835 1839 Felix Dujardin J. E. Purkinje Discovered fluid Named fluid content of content of cell cell as protoplasm 1838 Matthias Schleiden Proposed all plants are made up of cells  Cell Theory Timeline 1845 Carl Heinrich Braun Proposed cell is the basic unit of life 1839 1855 Theodor Schwann Rudolf Virchow Proposed all animals Proposed all cells arise are made up of cells from pre-existing cells  Unicellular Organisms An organism that is made up of only one cell is called as unicellular organism. Euglena Paramecium Yeast  Multicellular Organisms An organism that is made up of more than one cell is called as multicellular organism. Plants Animals Fungus Multicellular Organisms Under Microscope Leaf cells Muscle cells Size of Smallest cell Cells Mycoplasma Size: 0.1 µm Cells vary in size. Most cells are very small (microscopic), some may be very large (macroscopic). Largest cell The unit used to measure size Ostrich egg of a cell is micrometer. Size: 18 cm 1 µm = 1 / 1 0 00 m illi mete r  Size of Cells in Humans Smallest cell Largest cell Longest cell Sperm cell Ovum cell Nerve cell Size: 5 µm Size: 120 µm Size: 1 m  Human RBCs are circular Shape of biconcave for easy passage through human capillaries. Cells Cells vary in shape. Nerve cells are branched to conduct impulses from one Variation depends mainly upon point to another. the function of cells. Some cells like Euglena and Amoeba can change their shape, but most cells have a fixed shape. Human WBCs can change their shape to engulf the microorganisms that enter the body. Structure Compound Of Cell microscope Magnification 2000X The detailed structure of a cell has been studied under compound microscope and electron microscope. Certain structures can be seen only under an electron microscope. Electron The structure of a cell as seen under microscope an electron microscope is called ultrastructure. Magnification 500000X Animal Cell 12 11 1 10 1. Nucleus 2. Golgi body 9 3. Vesicle 4. Plasma membrane 8 5. Mitochondria 6. Cytoskeleton 7. Centriole 8. Lysosome 2 9. Cytoplasm 7 3 10. Rough endoplasmic reticulum 11. Smooth endoplasmic reticulum 4 12. Nucleolus 6 5 Plant Cell 12 11 1 10 1. Nucleus 2. Golgi body 9 3. Vesicle 2 4. Lysosome 5. Plasma membrane 8 3 6. Mitochondria 7. Chloroplast 8. Cell wall 4 9. Vacuole 10. Smooth endoplasmic reticulum 5 11. Rough endoplasmic reticulum 7 12. Nucleolus 6 Bacterial 9 10 Cell 8 1. Capsule 7 2. Cell wall 3. Plasma membrane 6 1 4. Cytoplasm 5. Flagellum 6. Food granule 2 7. Plasmid (DNA) 3 8. Ribosomes 4 5 9. Nucleoid 10. Pili Structure 1. Pl asma Membrane 2. Nucleus Of Cell 3. Cy toplasm A. Cy tosol B. Cell Organelles If we study a cell under a microscope, we would come across three features a) Endoplasmic reticulum in almost every cell: plasma membrane, b) Go lgi bo dy nucleus and cytoplasm. c) Lysosomes All activities inside the cell and d) Vacuoles interactions of the cell with its e) Mi tochondria environment are possible due f) Pl astids to these features. g) Centrosome h) Cy toskeleton Plasma Membrane Extremely delicate, thin , elastic, living and semi-permeable membrane Made up of two layers of lipid molecules Carbohydrates in which protein molecules are floating Thickness varies from 75-110 A˚ Can be observed under an electron microscope only Functions: Maintains shape & size of the cell Protects internal contents of the cell Regulates entry and exit of substances Proteins in and out of the cell Lipids Maintains homeostasis  Cell wall Non-living and outermost covering of a cell (plants & bacteria) Can be tough, rigid and sometimes flexible Pectin Cellulose Made up of cellulose, hemicellulose and pectin May be thin or thick, multilayered structure Thickness varies from 50-1000 A˚ Functions: Provides definite shape, strength & rigidity Prevents drying up(desiccation) of cells Helps in controlling cell expansion Plasma membrane Hemicellulose Protects cell from external pathogens  Nucleus Dense spherical body located near the centre of the cell Nucleus Diameter varies from 10-25 µm Present in all the cells except red blood cells and sieve tube cells Well developed in plant and animal cells Undeveloped in bacteria and blue-green algae (cyanobacteria) Most of the cells are uninucleated (having only one nucleus) Few types of cells have more than one nucleus (skeletal muscle cells)  Nucleus Nucleus has a double layered covering called Nuclear nuclear membrane Nucleolus pores Nuclear membrane has pores of diameter about 80-100 nm Colourless dense sap present inside the nucleus known as nucleoplasm Nucleoplasm contains round shaped nucleolus and network of chromatin fibres Fibres are composed of deoxyribonucleic acid (DNA) and protein histone Chromatin These fibres condense to form chromosomes during cell division Nuclear envelope Nucleoplasm  Nucleus Gene DNA Chromosomes contain stretches of DNA called genes Genes transfer the hereditary information from one generation to the next Chromatin Functions: Control all the cell activities like metabolism, protein synthesis, growth and cell division Histone Nucleolus synthesizes ribonucleic acid (RNA) to constitute ribosomes Store hereditary information in genes Chromatin fibre Chromosome Cytoplasm Jelly-like material formed by 80 % of water Present between the plasma membrane Organelles and the nucleus Contains a clear liquid portion called cytosol and various particles Particles are proteins, carbohydrates, nucleic acids, lipids and inorganic ions Also contains many organelles with distinct structure and function Some of these organelles are visible only under an electron microscope Granular and dense in animal cells and thin in plant cells Cytoplasm  Endoplasmic Network of tubular and vesicular structures which are interconnected with one another Reticulum Some parts are connected to the nuclear membrane, while others are connected to the cell membrane Two types: smooth(lacks ribosomes) and rough(studded with ribosomes) Functions: Gives internal support to the cytoplasm RER synthesize secretory proteins and membrane proteins Rough ER SER synthesize lipids for cell membrane Smooth ER In liver cells SER detoxify drugs & poisons In muscle cells SER store calcium ions Ribosomes  Golgi body Discovered by Camillo Golgi Formed by stacks of 5-8 membranous sacs Incoming Sacs are usually flattened and are called Cis face transport the cisternae Cisternae vesicle Has two ends: cis face situated near the Lumen endoplasmic reticulum and trans face situated near the cell membrane Functions: Modifies, sorts and packs materials synthesized in the cell Delivers synthesized materials to various targets inside the cell and outside the cell Outgoing Produces vacuoles and secretory vesicles Newly Trans face forming transport Forms plasma membrane and lysosomes vesicle vesicle  Nucleus Smooth ER Lysosomes Golgi Body At Work Rough ER Golgi body Plasma Vesicles membrane  Lysosomes Small, spherical, single membrane sac Found throughout the cytoplasm Filled with hydrolytic enzymes Hydrolytic enzymes Membrane Occur in most animal cells and in few type of plant cells Functions: Help in digesting of large molecules Protect cell by destroying foreign invaders like bacteria and viruses Degradation of worn out organelles In dead cells perform autolysis Vacuoles Single membrane sac filled with liquid or sap (water, sugar and ions) In animal cells, vacuoles are temporary, small in size and few in number Tonoplast In plant cells, vacuoles are large and more in number May be contractile or non-contractile Functions: Store various substances including waste products Maintain osmotic pressure of the cell Vacuole Store food particles in amoeba cells Provide turgidity and rigidity to plant cells  Mitochondria Small, rod shaped organelles bounded by two membranes - inner and outer Outer membrane is smooth and encloses the Ribosomes contents of mitochondria Matrix Inner membrane is folded in the form of shelf like inward projections called cristae Cristae Inner cavity is filled with matrix which contains many enzymes Contain their own DNA which are responsible for many enzymatic actions DNA Functions: Synthesize energy rich compound ATP Outer membrane ATP molecules provide energy for the vital Inner membrane activities of living cells Plastids Plastids are double membrane-bound organelles found inside plants and some algae. They are responsible for activities related to making and storing food. They often contain different types of pigments that can change the colour of the cell.  Carrot Pigment: Carotene Chromoplasts Chromoplasts are plastids that Mango produce and store pigments Pigment: Xanthophyll They are responsible for different colours found in leaves, fruits, flowers and vegetables. Tomato Pigment: Lycopene  Potato tubers Food: Starch Leucoplasts Leucoplasts are colourless Maize grains plastids that store foods. Food: Protein They are found in storage organs such as fruits, tubers and seeds. Castor seeds Food: Oil  Chloroplasts Double membrane-bound organelles found mainly in plant cells Outer Usually spherical or discoidal in shape Inner membrane membrane Shows two distinct regions-grana and stroma Grana are stacks of thylakoids (membrane- bound, flattened discs) Thylakoid Thylakoids contain chlorophyll molecules which are responsible for photosynthesis Stroma is a colourless dense fluid Functions: Stroma Convert light energy into chemical energy in the form of food Granum Provide green colour to leaves, stems and vegetables  Centrosome Centrosome is the membrane bound organelle Centrosome present near the nucleus matrix Consists of two structures called centrioles Centrioles are hollow, cylindrical structures Microtubules made of microtubules Centrioles are arranged at right angles to each other Functions: Centrioles Form spindle fibres which help in the movement of chromosomes during cell division Help in the formation of cilia and flagella  Cytoskeleton Formed by microtubules and microfilaments Cell membrane Microtubules are hollow tubules made up of protein called tubulin Microfilaments are rod shaped thin filaments made up of protein called actin Functions: Determine the shape of the cell Give structural strength to the cell Responsible for cellular movements Microtubules Microfilaments Prokaryotic cell Eukaryotic cell 1. Nucleus is undeveloped 1. Nucleus is well developed 2. Only one chromosome is present 2. More than one chromosomes are present 3. Membrane bound organelles are absent 3. Membrane bound organelles are present 4. Size ranges from 0.5-5 µm 4. Size ranges from 5-100 µm 5. Examples: Bacteria and blue green algae 5. Examples: All other organisms Animal cell Plant cell 1. G e n erall y s m a l l i n s i ze 1. G e n erall y l a rge i n s i ze 2. Ce l l wa l l i s a bs ent 2. Ce l l wa l l i s p resent 3. P l a st ids a re a bs ent 3. P l a st ids a re p re sent 4. Va c uo les a re s m a l l er i n s i ze 4. Va c uo les a re l a rger i n s i ze and less in number a n d m o re i n n u m b e r 5. Ce nt r i oles a re p res ent 5. Ce nt r i oles a re a bs ent THANK YOU...