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

**Lecture 1: Cell Structure and their Functions** **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...

**Lecture 1: Cell Structure and their Functions** **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. Nucleus - Main Function - Houses DNA Endoplasmic Reticulum Rough ER: synthesizes protein Smooth ER: packages Golgi Complex - Main Function - Modifies, packages and distributes newly synthesized proteins. Lysosomes - Main Function - Breaks down organic molecules w/ - Hydrolytic (water) Enzymes - Catalytic Peroxisomes - Main Function - detoxify using oxidative (oxygen ) enzymes Centrioles - Main Function - Form and organize microtubules during assembly... and form cilia and flagella (where are they found?) Mitochondria - Main Function - cell powerhouse, cellular respiration, extracts energy from nutrients and transforms into usable form form, ATP production; know the structure - outer membrane smooth, inner folded (cristae) Folding = allows for increased surface area **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): **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)