Cell unit

• Cell theory emphasised the unity underlying the diversity of forms of living organisms
• Cell theory highlighted the cellular organisation of all life forms
• Cell theory created a sense of mystery around living phenomena, requiring integrity of cellular organisation for living phenomena to be demonstrated or observed
• Physico-chemical approach and cell-free systems can be used to study and understand physiological and behavioural processes
• Reductionist Biology is a physico-chemical approach to study and understand living organisms
• G.N. Ramachandran was an outstanding figure in the field of protein structure
• G.N. Ramachandran discovered the triple helical structure of collagen and the allowed conformations of proteins through the 'Ramachandran plot'
• G.N. Ramachandran was born on October 8, 1922, and passed away on April 7, 2001
• All living organisms are composed of cells and products of cells
• All cells arise from pre-existing cells
• Eukaryotic cells have membrane-bound organelles, while prokaryotic cells lack them
• Ribosomes are non-membrane-bound organelles found in all cells
• Prokaryotic cells have a cell wall surrounding the cell membrane except in mycoplasma
• Prokaryotic cells lack a well-defined nucleus and have naked genetic material
• Prokaryotic cells may have small circular DNA outside the genomic DNA called plasmids
• Most prokaryotic cells have a three-layered cell envelope consisting of glycocalyx, cell wall, and plasma membrane
• Bacteria can be classified into Gram-positive and Gram-negative based on their response to staining procedures
• Prokaryotic cells may have inclusions like phosphate granules, cyanophycean granules, and glycogen granules
• Ribosomes in prokaryotes are about 15 nm by 20 nm in size and are made of 50S and 30S subunits
• Ribosomes in prokaryotes form 70S prokaryotic ribosomes when the 50S and 30S units are present together
• Inclusion bodies in prokaryotic cells store reserve material in the cytoplasm and are not bound by any membrane system
• Prokaryotic cells do not have a membrane system and contain phosphate granules, cyanophycean granules, and glycogen granules in the cytoplasm
• Gas vacuoles are found in blue-green and purple and green photosynthetic bacteria
• Eukaryotic cells include protists, plants, animals, and fungi
• Eukaryotic cells have membrane-bound organelles that compartmentalise the cytoplasm
• Eukaryotic cells have an organised nucleus with a nuclear envelope
• Eukaryotic cells have complex locomotory and cytoskeletal structures
• Genetic material in eukaryotic cells is organised into chromosomes
• Plant cells have cell walls, plastids, and a large central vacuole, which are absent in animal cells
• Animal cells have centrioles, which are absent in almost all plant cells
• Cell membrane is mainly composed of lipids and proteins
• Cell membrane has a fluid mosaic model structure
• Cell membrane is selectively permeable and allows passive transport of molecules through simple diffusion and osmosis
• Cell membrane requires carrier proteins for the transport of polar molecules
• Active transport across the cell membrane is an energy-dependent process, e.g., Na+/K+ Pump
• Cell wall is a non-living rigid structure that forms an outer covering for the plasma membrane of fungi and plants
• Cell wall gives shape to the cell, protects it from damage and infection, and helps in cell-to-cell interaction
• Endomembrane system includes endoplasmic reticulum (ER), Golgi complex, lysosomes, and vacuoles
• Endoplasmic reticulum (ER) divides the intracellular space into luminal and extra luminal compartments
• Rough endoplasmic reticulum (RER) is involved in protein synthesis and secretion