Cell - The Unit of Life Class 11th Chapter 8 PDF

# Cell - The Unit of Life ## Cell Theory: * Formulated by Schleiden & Schwann (Botanist & Zoologist, respectively) * Modified by Rudolf Virchow * "All living cells are made up of cells and its products. All new cells arise from pre-existing cells." ## Cell Types: * **Prokaryotic Cells:** * *...

# Cell - The Unit of Life ## Cell Theory: * Formulated by Schleiden & Schwann (Botanist & Zoologist, respectively) * Modified by Rudolf Virchow * "All living cells are made up of cells and its products. All new cells arise from pre-existing cells." ## Cell Types: * **Prokaryotic Cells:** * **Fundamental, structural & functional unit of life.** * Discovered by Robert Hooke (dead cells) and Antonie van Leeuwenhoek (live cells) * **Cell Envelope:** * **Glycocalyx:** * Capsule (outer) * Slime layer (middle) * S-layer (innermost) * **Cell Wall:** * Peptidoglycan (thick) * Gram Positive (takes up stain) * Gram Negative (does not take up stain) * **Plasma Membrane:** * Semipermeable * Mesosomes: infolding of plasma membrane for DNA replication and respiration. * Chromatophores: containing pigments, help in photosynthesis. * **Nucleoid:** * Genetic material * Circular, double-stranded DNA * **Plasmid:** * Extra chromosomal DNA * **Flagella:** * Helps with locomotion * **Fimbriae:** * Helps in adherence * **Pili:** * Helps in conjugation * **Eukaryotic Cells:** * **Plasma Membrane:** * Bilayer of phospholipid * Phosphoglycerides * Carrier Proteins * Channel Proteins * Cholesterol * **Cell Wall:** * Fungi: chitin & protein * Algae: cellulose, galactans, mannans * **Endomembrane System:** * Organelles work in coordinated fashion * **Endoplasmic Reticulum:** * **Rough ER:** * Membrane continuous with nuclear envelope * 80S ribosomes attached * Protein synthesis * permeable * **Smooth ER:** * Lack ribosome * Lipid synthesis * Absent in plants * **Golgi Bodies:** * Dictyosome stacks * Present in cytoplasm * Cis convex * Trans convex * Formation: * Packaging * Glycosylation of proteins * Lipid synthesis * Glycoprotein synthesis * **Lysosomes:** * Single membrane * pH - 4-5 * Hydrolytic enzymes * Formed by Golgi bodies * Contain: * Protease * Lipase * Carbohydrase * **Mitochondria:** * "The powerhouse of the cell" * Outer membrane * Inner membrane (less permeable) * Infoldings (cristae) * ATP synthesis * Kreb's cycle * F0-F1 particles * Number depends on activity of the cell * Semi-autonomous as it replicates on its own * **Vacuole:** * Single membrane * Plants: large central vacuole, tonoplast & maintains rigidity * Animals: small vacuoles, contractile (Amoeba) - for excretion, osmoregulation and gaseous buoyancy * Food vacuole: engulfs food (in protists) * **Plastids:** * Exclusively present in plants and euglenoids * **Leucoplast:** * Colorless * Amyloplast: stores amylase, amylopectin * Elaioplast: stores oils * Aleuroplast: stores protein * **Chromoplast:** * Colorless * Contains xanthophyll and carotenoids * **Chloroplast:** * Contains chlorophyll * Green pigament * Photosynthesis * Found in mesophyll cells * **Nucleus:** * Control center * Contains genetic material * Double membrane bound * Has nuclear pores * Contains nucleolus: site of rRNA synthesis * **Cytoskeleton:** * Network of protein filaments * Provides mechanical support, shapes and motility * Present in the cytoplasm * **Cilia/Flagella:** * 9+2 arrangement * Peripheral microtubule doublets * Central microtubule doublet * Radial spokes * Central sheath * **Centrosome & Centriole:** * Spindle microtubule * Hub: triplet microtubule * Interconnected bridges ## Cell Transport: * **Fluid Mosaic Model:** * Singer and Nicolson (1972) * Quasi-fluid nature * Phospholipids show "flip-flop" movement * **Cell Transport:** * **Active Transport:** * ATP expenditure * Uphill (against concentration gradient) * **Passive Transport:** * No ATP expenditure * Downhill (along concentration gradient) * **Simple Diffusion:** * No special proteins needed * **Facilitated Diffusion:** * Requires special proteins ## Summary: This document describes various aspects of the cell, including general cell theory, the difference between prokaryotic and eukaryotic cells, the various organelles present in each type of cell, and the different types of cell transport. It also includes diagrams and information about different structures and function.