Ultrastructure of prokaryotic and eukaryotic cells

Ultrastructure of prokaryotic and eukaryotic cells

1. CELL BIOLOGY Dr. Nathiya T Assistant Professor Department of Technology KJC

2. Ultrastructure of prokaryotic and eukaryotic cells

3. 1. Structure of Prokaryotic Cells: Cell Envelope: Prokaryotes have a cell envelope composed of three layers: Cell Wall: Provides shape, protection, and prevents the cell from bursting due to osmotic pressure Cell Membrane: A lipid bilayer that controls the movement of substances in and out of the cell Capsule (optional): A slimy outer layer that provides protection and assists in attaching to surfaces

4. Cytoplasm: The cytoplasm contains a gel-like substance called the cytosol, where various metabolic reactions occur Ribosomes: Small structures responsible for protein synthesis. Prokaryotes have smaller ribosomes compared to eukaryotes Nucleoid Region: This is the region where the prokaryotic DNA is located. It is not enclosed within a nuclear membrane Plasmids (optional): Small circular DNA molecules that exist separately from the main chromosome Pili/Fimbriae: Thin, hair-like appendages that help bacteria adhere to surfaces, facilitate conjugation (transfer of genetic material), or aid in motility Contd …

5. Flagella: Long, whip-like appendages that allow bacteria to move in liquid environments Endospores: Tough, dormant structures formed by some bacteria to withstand harsh conditions and facilitate survival Inclusions: Storage structures within the cytoplasm that accumulate nutrients or reserve materials, such as glycogen granules or lipid droplets Gas Vesicles: Gas-filled structures found in certain aquatic bacteria, enabling them to float or regulate buoyancy Contd …

6. 2. Structure of Eukaryotic Cells: Eukaryotic cells are more complex and have a true nucleus and membrane-bound organelles that perform specific functions Here are the key features of eukaryotic cell ultrastructure: Nucleus: The nucleus contains the genetic material (DNA) organized into chromosomes It is surrounded by a double membrane called the nuclear envelope, which has nuclear pores for communication with the cytoplasm

7. Cell Membrane: Like prokaryotes, eukaryotic cells have a cell membrane that separates the cell from its environment and regulates the movement of substances Cytoplasm: The cytoplasm is a gel-like substance where various cellular activities occur Endoplasmic Reticulum (ER): A network of interconnected membranous tubules involved in protein synthesis and lipid metabolism. There are two types: rough ER (with ribosomes attached) and smooth ER (without ribosomes) Golgi Apparatus: Stacked membranous sacs responsible for processing, modifying, and sorting proteins and lipids synthesized in the ER Mitochondria: Known as the powerhouse of the cell, mitochondria produce energy through cellular respiration and have their own DNA Contd …

8. Lysosomes: Vesicles containing enzymes that break down waste materials, cellular debris, and foreign substances Vacuoles: Larger in plant cells, vacuoles store water, nutrients, and waste products. Animal cells have smaller and fewer vacuoles Chloroplasts (in plant cells): These organelles contain chlorophyll and perform photosynthesis, converting sunlight into chemical energy Cytoskeleton: A network of protein filaments (microtubules, microfilaments, and intermediate filaments) that provides structural support, helps in cell movement, and facilitates the transport of organelles Centrioles: Paired cylindrical structures involved in cell division and organization of the cytoskeleton. Found in animal cells and some protists Contd …

9. Cilia: Short, hair-like structures projecting from the cell surface involved in movement or the movement of surrounding fluids. Found in various eukaryotic cells Cell Junctions: Specialized structures that connect cells together, such as tight junctions, gap junctions, and desmosomes, facilitating cell adhesion and communication Microvilli: Finger-like projections on the surface of some cells, particularly in the epithelial lining of organs, increasing surface area for absorption Nucleolus: A distinct region within the nucleus where ribosomal RNA (rRNA) synthesis and ribosome assembly take place Peroxisomes: Membrane-bound organelles involved in various metabolic processes, including the breakdown of fatty acids and detoxification of harmful substances Contd …

10. Glyoxysomes : Specialized peroxisomes found in plant cells involved in the conversion of stored lipids into carbohydrates during germination Contractile Vacuole: A specialized vacuole in certain protists responsible for regulating water balance and expelling excess water from the cell Nematocysts: Stinging organelles found in cnidarians (such as jellyfish and corals) used for defense and capturing prey Secondary Lysosomes: Formed by the fusion of lysosomes with other vesicles or endocytic compartments for further breakdown and recycling of cellular components Contd …

11. Difference between prokaryotic and eukaryotic cells

12. Thank you