Lec 5 PDF - Cytoplasmic Organelles

Lec8: ‫ مريم علي حسين‬:‫إعداد‬ Cytoplasmic Organelles Cytoplasmic organelles are specialized metabolically active structures within the cytoplasm, known as organelles. They play essential roles in maintaining cellu...

Lec8: ‫ مريم علي حسين‬:‫إعداد‬ Cytoplasmic Organelles Cytoplasmic organelles are specialized metabolically active structures within the cytoplasm, known as organelles. They play essential roles in maintaining cellular functions and survival. Organelles can be classified into: 1. Membranous Organelles: These organelles are composed of membranes similar to the cell membrane and include:  Mitochondria  Endoplasmic Reticulum (ER) Found cytoplasm  Golgi Apparatus  Lysosomes  Secretory Vesicles  Coated Vesicles  Peroxisomes 2. Non-Membranous Organelles: These organelles lack membranes and include:  Ribosomes  Proteasomes  Centrioles Ribosomes Ribosomes are small, spherical, non-membranous particles (20-30 nm) assembled in the nucleus. They are responsible for protein synthesis. Ribosomes exhibit unique features in their structure, location, and function, enabling the production of specialized proteins to meet cellular needs. Ribosome Location in the Cell: 1  Lec8: ‫ مريم علي حسين‬:‫إعداد‬ 1. Free Ribosomes: Found in the cytoplasm, producing proteins that function within the cell, such as enzymes and structural proteins. 2. Bound Ribosomes: Attached to the rough endoplasmic reticulum (Rough ER) and produce proteins destined for: o Cellular membranes o Extracellular secretion (e.g., hormones) o Vesicular bodies like lysosomes - Ribosome Structure: Ribosome  Composed of two subunits: 1. Large Subunit (60S): Responsible for forming peptide bonds between amino acids. 2. Small Subunit (40S): Reads mRNA sequence and translates codons.  Both subunits consist of: 1. Ribosomal RNA (rRNA) 2. Ribosomal proteins Endoplasmic Reticulum (ER) The ER is a network of interconnected channels and sacs enclosed by a membrane, found in eukaryotic cells’ cytoplasm. It surrounds a space called the cisterna. Despite appearing separated in sections, high-resolution microscopy reveals connectivity throughout the cell. 2  Lec8: ‫ مريم علي حسين‬:‫إعداد‬  Found in all eukaryotic cells except mature red blood cells (Mature Erythrocytes). ⑪morise  Absent in prokaryotic cells.  Composed of a complex, membrane-lined network of flattened sacs, tubules, vesicles, and cisternae.  Extends from the plasma membrane to the nuclear envelope.  Forms 30-60% of the total endomembrane system Types of Endoplasmic Reticulum: 1. Smooth Endoplasmic Reticulum (SER) Characteristics:  Lacks ribosomes on its membrane, giving it a smooth appearance.  Often located near the plasma membrane and may connect to it.  Contains few flattened sacs, with higher concentrations of tubules and vesicles. Functions: 1. Lipid Production. 2. Detoxification. 3. Calcium Storage. 4. Metabolism (Metabolism of carbohydrates and lipids). 2. Rough Endoplasmic Reticulum (RER) Characteristics:  Studded with 80S ribosomes on its outer surface, giving it a rough appearance under an electron microscope. These ribosomes are responsible for protein synthesis.  Directly connected to the nuclear envelope’s outer membrane, facilitating the rapid transfer of mRNA to ribosomes. 3  Lec8: ‫ مريم علي حسين‬:‫إعداد‬  It consists of interconnected flattened sacs (Cisternae) that form a vast network.  It plays a vital role in the synthesis and processing of proteins, making it an essential element in maintaining cellular functions..Functions: 1. Protein Synthesis: revein o Primary site for synthesizing o Translation occurs on ribosomes attached to the RER. 2. Protein Transport: o Proteins are transported to the SER or Golgi Apparatus for further modifications and final destinations. The structure and relationship of the nuclear envelope, rough, and smooth endoplasmic reticulum. Golgi Apparatus The Golgi apparatus is a cellular organelle first discovered by the scientist Camillo Golgi, who observed dense, network-like structures close to the nucleus, which were later named Golgi bodies. It consists of parallel stacks of flattened membrane-bound sacs known as cisternae, typically 6-8 in number, each 0.5-1.0 µm in diameter. Components: 1. Cis Face (Proximal): 4  Lec8: ‫ مريم علي حسين‬:‫إعداد‬ o Faces the ER and receives transport vesicles containing unmodified proteins. 2. Trans Face (Distal): o Faces the plasma membrane and exports secretory vesicles containing modified proteins to their destinations. Functions: 1. Protein Modification: o Adds sugar groups (glycosylation) to proteins from the ER. o Modifies lipids and forms glycolipids. 2. Packaging and Transport: o Packages proteins into vesicles for transport to the plasma membrane or for secretion. 3. Lysosome Formation: o Assembles hydrolytic enzymes and forms lysosomes. 4. Exocytosis: o Produces secretory vesicles containing proteins for secretion. Golgi Apparatus golgi Revein 5  Lec8: ‫ مريم علي حسين‬:‫إعداد‬ Secretory Granules: Membranous organelles are found in secretory cells. They store substances such as proteins, hormones, enzymes, or other materials prepared for secretion. Structure: 1. Membrane: o Enclosed by a double lipid bilayer that isolates the contents from the cytoplasm. 2. Contents: o It contains highly concentrated secretory materials, such as: o - Digestive Enzymes as found in pancreatic cells. o - Hormones as found in endocrine cells. o - Mucins as found in goblet cells. The contents are often in an inactive state (Inactive Precursors) that are activated upon secretion. Functions: 1. Storage 2. Secretion 3. Protection. Secretory Granules 6  Lec8: ‫ مريم علي حسين‬:‫إعداد‬ Peroxisomes: Membranous organelles surrounded by a single membrane that separate their contents from the cytoplasm are small, round or oval in shape, and play a vital role in cellular metabolism, particularly in relation to fat breakdown and detoxification. They are also known as oxidative organelles due to their role in oxidative reactions. Peroxisomes are M found in all eukaryotic cells, but they are particularly observed in cells that need to detoxify (such as liver cells) and in cells that oxidize fatty acids (such as adipose cells). Functions: 1. Detoxification. 2. Synthesis of plasmalogens 3. Lipid Metabolism: (Beta-oxidation). Peroxisomes Lysosomes: Lysosomes are membrane-bound organelles containing hydrolytic enzymes that are essential for breaking down biomolecules and cellular waste. They function as the cell’s "digestive system." Types of Lysosomal Activity: 1.Primary Lysosomes: Recently formed from the Golgi Apparatus and contains inactive enzymes. 1.Secondary Lysosomes: 7  Lec8: ‫ مريم علي حسين‬:‫إعداد‬ It is formed when elementary particles fuse with vesicles containing substances that need to be digested. 3. Residual Bodies : Contain materials that have not been fully digested Functions: 1.Intracellular Digestion 2. Cellular Recycling (Autophagy ) 3.Waste Removal Lysosomes Centrosome : The centriole is a cylindrical cellular structure composed of a set of microtubules. It is typically found in animal cells, consisting of a pair of centrioles arranged vertically, each made up of nine pairs of microtubules organized in a cylindrical shape, with each pair consisting of three microtubules, giving the centriole its unique shape. The centriole plays an important role in the process of cell division, as it helps in the formation of spindle fibers that organize the distribution of chromosomes. division 1. cell Hagella org. 2 3 Citascrotuble 8  Lec8: ‫ مريم علي حسين‬:‫إعداد‬ Proteasomes Proteasomes are cylindrical, hollow protein complexes found in the cytoplasm and nucleus of eukaryotic cells, approximately 15 nanometers long and 11 nanometers in diameter. They are an essential part of the Ubiquitin-Proteasome System (UPS), responsible for maintaining protein balance within the cell by breaking down damaged or obsolete proteins in a process called intracellular protein degradation.. Functions: Breaksown protei is 1. Protein Degradation. 2. Cell Cycle Regulation. Proteasomes Mitochondria a powerhoue Mitochondria are double-membrane-bound organelles, usually round or oval, found in the cytoplasm of most eukaryotic cells with a clear nucleus. Red blood cells (erythrocytes) do not have mitochondria, while liver and muscle cells contain hundreds or thousands due to their high metabolic activity. The primary function of mitochondria is to generate large amounts of energy in the form of adenosine triphosphate (ATP), the main energy source for cells. Unlike other organelles, mitochondria can reproduce through binary fission. Creates att 1. storage 2.. 3 Calciumanites Thermag 9 n.  Lec8: ‫ مريم علي حسين‬:‫إعداد‬ Functions: 1. Energy Production: Generates ATP for cellular energy. 2. Calcium Homeostasis: Stores calcium to regulate cell signaling. 3. Programmed Cell Death (Apoptosis): Helps control cell death. 4. Stem Cell Regulation: Plays a role in stem cell management. 5. Thermogenesis: Produces heat. 6. Cell Growth: Supports cell growth and division. Structure: 1. Outer Mitochondrial Membrane: Contains porin proteins that allow small molecules "Less than 5 kilodaltons" to pass through. 2. Intermembrane Space: Located between the inner and outer membranes, containing enzymes like adenylate kinase for energy-related reactions. 3. Inner Mitochondrial Membrane: Has folds called cristae that increase surface area for energy production. It contains components for the electron transport chain and ATP synthesis. 4. Cristae Space: The space within the inner membrane where energy production processes occur. 5. Mitochondrial Matrix: The innermost space containing mitochondrial DNA, ribosomes, and enzymes necessary for the Krebs cycle and fatty acid oxidation. Cytoskeleton 10  Lec8: ‫ مريم علي حسين‬:‫إعداد‬ The cytoskeleton is a complex network of protein fibers that extend throughout the cytoplasm of eukaryotic cells. It plays an essential role in supporting the cell’s shape and organizing internal processes such as organelle movement, cell division, and cell movement. Components: The cellular structure consists of three main types of protein fibers: microfilaments, intermediate filaments, and microtubules. 1. Microfilaments: Thin fibers made of actin protein, 6-8 nanometers in diameter. o Functions:  Maintains cell shape.  Facilitates cell movement through extensions like pseudopodia.  Participates in cell division (cytokinesis). 2. Intermediate Filaments: Medium-sized fibers, approximately 8-10 nanometers in diameter, composed of proteins like keratin, lamins, desmin, neurofilament proteins, vimentin, and glial filaments. o Functions:  Provides mechanical support and withstands physical stress.  Anchors the nucleus and other organelles.  Facilitates cell communication through intercellular junctions. 3. Microtubules: Hollow tubes about 25 nanometers in diameter, made of tubulin protein. o Functions:  Provides structural support and shape.  Transports organelles within the cell using motor proteins like kinesin and dynein.  Assists in cell movement through cilia and flagella. 11 ‫‪Lec8:‬‬ ‫إعداد‪ :‬مريم علي حسين‬ ‫‪12‬‬