Lecture 1, 4, 5: Cell Structure and Functions - Cell Biology PDF

**Lecture 1: Cell Structure and their Functions** Section 1: Cell Structure and Function Learning Objectives: 1. Understand the principle of cell theory 2. Define the main structures and functions of a cell 3. Identify the organelles present in all human cells and learn their function(s)...

**Lecture 1: Cell Structure and their Functions** Section 1: Cell Structure and Function Learning Objectives: 1. Understand the principle of cell theory 2. Define the main structures and functions of a cell 3. Identify the organelles present in all human cells and learn their function(s) [Cell Theory Principles] - small structural and functional building block unit of all plants and animals organisms that carries out life processes. - basic unit of life - cells function relies on structural properties - cells of all organisms are similar in structure and function [Quick Facts] - Trillions of cells in body classified by 200 cell types - Based on specific variations in structure and function Cells common features: - Plasma membrane - Cytosol - Nucleus **[Structures & their functions]** Plasma membrane - Main Function - Barrier separates the cell's contents from its surroundings. - Cell to Cell communication - Controls movement inside and out of cell. - Structure - Thin bilayer of lipids, proteins and some carbohydrates Nucleus - Main Function - Houses DNA - Directs protein synthesis - Structure: - Surrounded by a double layered membrane. Endoplasmic Reticulum - Function - Protein and lipid production - Structure: - Fluid filled membranous system Rough ER: - Function: - synthesizes protein - Structure - Studded with ribosomes Smooth ER: - Function: - packages secretory product into transport vesicles Golgi Complex Main Function - Modifies, packages and distributes newly synthesized proteins. Structure - Stack of flattened, slightly curved membrane enclosed sacs. Lysosomes - Main Function - Breaks down organic molecules w/ Hydrolytic (water) Enzymes - Catalytic - Structure - Small, membrane enclosed degradative organelles Peroxisomes - Main Function - Detoxify using oxidative (oxygen ) enzymes. - Detoxify - Membrane-enclosed sacs Centrioles - Main Function - Form and organize microtubules during assembly... and form cilia and flagella (where are they found?) - Structure - Cylindrical pair of structures at right angle Mitochondria - - Main Function - cell powerhouse, cellular respiration, extracts energy from nutrients and transforms into usable form form, ATP production; - Structure - Rod shaped or oval structure, size of bacteria - outer membrane smooth, inner folded (cristae) - Folding = allows for increased surface area Cytoskeleton: 1. Microtubules: Structure - "bone and muscle of the cell" - composed of tubulin sub-units that create long, slender, hollow tubes Main Functions - Structural component and functional component of cilia and flagella - Maintains assymetrical cell shapes and coordinate complex movements (highway for transport) - Positions cytoplasmic organelles - strategically place organelles for effieciency 1. Microfilaments Structure/Description: - smallest elements of cytoskeleton - intertwined helical chains of actin molecules - Composed of myosin molecules Main Functions - cellular contractile systems (muscle contraction and amoeboid movement) - ex. mechanical siffener for microvilli 1. Intermediate Filaments Structure: - irregular, threadlike protein Function: - help resist mechanical stress - Ex. keratin protein in hair, nails Cytosol "Cell Gel" Contains... Cytosol - Structures: - Intermediary Metabolism Enzymes - Facilitate Intracellular reactions involving degradation, synthesis, and transformation of small organic molecules. - Transport, Sectretory, and Endocytic vesicles: - Transport or store products being moved within, out of, or into the cell, respectively. - Inclusions - Store excess nutrients **Lecture 4: Plasma Membrane** **Plasma Membrane** - also called the ***cell membrane*** - **Main Function**: - Surround every cell (integrity of the cell) - Controls movement of molecules into and out of cell - Ions, waste, nutrients - Cell-Cell communication - **Description:** Spherical cell - **Composed of:** - Thin bilayer composed of proteins and lipids (some carbs). **lipids** called **(Phospholipid molecules)** - Bilayer = Head and Tail (head facing outside, tail facing inside) - The Polar heads = Hydrophilic, negatively charged - The Non-polar tails = Hydrophobic, uncharged; fatty chain tails - Hydrophobic: Water Fearing - Hydrophilic: Water Loving - Why do they hate and love water? - Due to the properties of water (H2O) Oxygen likes to keep electrons in its own orbit = charged, Hydrogen bad at keeping electrons in its orbit = uncharged. Charged layers attract/love water - Phospholipids = twirl, vibrate, move around within their half, exchange places - Never go from ICF to ECF side unless unhealthy - **Function of Bilayer**: to separate Extracellular & Intracellular compartments - Intracellular compartments: Inside the cell (water) - Extracellular compartments: Outside the cell (water) - Fluid Mosaic Model - Fluid: moving, not rigid, Mosaic: not uniform - PL 50x more than proteins, Proteins = more than Half of membrane mass Protein Types (within the Plasma Membrane) - Come in different shapes and sizes due to different purposes / functions - Protein Types - Channels: - Carrier Modules: transfer of specific molecules (glucose) - Docking marker acceptors: - Membrane bound enzymes: - Receptors: signal - Cell adhesion molecules (CAMs): **Lecture 5: Cell to Cell Adhesions** Cell to Cell Adhesions & Junction Types **Cell to Cell Adhesions** - Plasma membrane participate in Cell - Cell adhesions: the holding together / adhering to each other. - 3 Different ways cells ar held together - **Cell Adhesion Molecules (CAMs)** - Membrane proteins that allow cells to hold onto each other - Provide some tissue cohesion as they "velcro" adjacent cells together. - **Extracellular Matrix** - (Extracellular) not inside the cell - Intricate network of fibrous proteins surrounded by interstitial fluid (watery, gel-like substance) composed of complex carbohydrates. - Interstitial Fluid: provides pathway for diffusion of nutrients, waste, and other water-soluble traffic between blood and tissue cells. - Extracellular Matrix Protein - ECM is abundant in Connective tissue, not in epithelial - Fibroblasts: Responsible for making most of the cells (collagen, elastin, fibronectin) in the ECM. - Collagen 1. Description: Cable like fibers 2. Function: Tensile strength (allows cells to not be ripped apart)(integrity of tissue) 3. Most abundant protein in body; half of body protein by weight - Elastin 4. Description: Rubber like protein fibers 5. Function: Stretching and recoil - Fibronectin 6. Description: "function as biological glue" 7. Function: Holds cell in position (promotes cell adhesion) 8. Key Point: Reduced levels relate to tumor metastasis - **Specialized Cell Junctions** - **Desmosomes** (adhering junctions) - additional layer of **STRENGTH** - **Function**: Anchor together two adjacent, non-touching cells - **Facts:** 1. Strongest cell to cell connection 2. Most abundant, can stretch - **Location**: Heart, Skin, Uterus - Cytoplasmic thickening plaque + keratin filament (strong protein) are two structures that make the cell - cell adhesion more rigid (Desmosomes) - **Tight Junctions** (impermeable junctions) - physical removal of space, sowing cells together - **Function:** Adjacent cells binds together to seal off passageway between. - **Location:** found in sheets of epithelial tissue that cover internal cavities 1. Digestive tract - **Facts**: Crohn's disease, IBS, - barrier not intact - **Gap Junctions** (communicating junctions) - forming gap between two cells for better communication. - **Description:** A gap between adjacent cells, linked by small, connecting tunnels. 1. Group of proteins called - **Function:** Allow for ions and small water soluble particles to pass, not large molecules - **Location:** Cardiac and Smooth Muscle - **Use Case:** When a process needs to happen at once, synchronized. (E.g., Heart beat)