Grade 12 General Biology 1 Lesson 8 PDF

Grade 12 General Biology 1 LESSON 8 TRANSPORT ACROSS MEMBRANES TOPIC  OBJECTIVES Explained the transport mechanisms in cells Differentiate endocytosis from exocytosis REVIEW FLUID MOSAIC MODEL (Singer & Nicolson, 1972) FUNCTIONS:...

Grade 12 General Biology 1 LESSON 8 TRANSPORT ACROSS MEMBRANES TOPIC  OBJECTIVES Explained the transport mechanisms in cells Differentiate endocytosis from exocytosis REVIEW FLUID MOSAIC MODEL (Singer & Nicolson, 1972) FUNCTIONS: 1. Protection 2.Cell Shape 3. Compartmentalization 4.Cell Recognition 5.Cell Function 1. Phospholipid bilayer 2. Proteins 3. Carbohydrates 4. Cholesterol 2013 NOBEL PRIZE IN PHYSIOLOGY OR MEDICINE James E. Rothman Thomas C. Sudhof Randy W. Schekman Discoveries of machinery regulating vesicle traffic, a major transport system in our cells MEMBRANE TRANSPORT The transport of different molecules and substances is one of the most important function of the cell membrane MEMBRANE TRANSPORT Refers to the movement of particles across or through a membranous barrier (cell membrane) WHY IS MEMBRANE TRANSPORT IMPORTANT? 1. Cell Homeostasis: Membrane transport helps maintain a stable internal environment (homeostasis) by regulating the movement of ions, nutrients, and waste products in and out of cells. 2. Nutrient Absorption: Cells need to absorb essential nutrients, such as glucose and amino acids, to function properly. Membrane transport mechanisms allow for the selective uptake of these molecules. 3. Waste Removal: Transport processes help expel waste products and toxins from the cell, preventing buildup that could be harmful. 4. Signal Transduction: Membrane transport plays a key role in cell signalling. Receptors on the cell membrane can trigger internal responses when specific molecules bind to them, affecting various cellular activities. 5. Energy Production: In processes like cellular respiration, transport mechanisms are vital for moving ions across membranes, which is essential for generating ATP, the energy currency of the cell. 6. Cell Communication: Membrane transport is involved in the communication between cells. For example, neurotransmitters are released from one cell and bind to receptors on another, requiring specific transport mechanisms. 7. Cell Growth and Division: Proper membrane transport is necessary for cell growth and division, as it ensures the availability of materials needed for these processes. Overall, membrane transport is fundamental to the survival and functioning of cells, allowing them to interact with their environment and maintain their integrity. What are the materials being transported by the cell membrane?  water fearing Lipids are non-polar – no charge Water mixes with hydrophilic compounds Lipids have no charge, water cannot by sticking to their charged groups. stick or mix with it AQUAPORINS  What are the factors that can affect membrane transport? 1. MEMBRANE PERMEABILITY - If the lipid bilayer is tightly packed, the lesser the permeability - Temperature and pH (higher temperatures tend to increase membrane permeability, while extreme pH levels can disrupt the membrane's structure, affecting its permeability)  TEMPERATURE *In Higher Temperatures, the lipid molecules in the membrane become more fluid. This can make the membrane more permeable, allowing substances to pass through more easily. *In Lower temperatures, the membrane becomes less fluid and more rigid. This can decrease permeability, making it harder for substances to cross the membrane.  pH Acidic or Alkaline Conditions: Changes in pH can affect the charge of molecules and proteins in the membrane. For instance, extreme pH levels can denature proteins, which may disrupt the structure of the membrane. This can increase permeability or even cause the membrane to break down. Neutral pH: At a neutral pH, the membrane typically maintains its integrity, helping to control what enters and exits the cell 2. Size and charge of the particles or solute - Smaller size and uncharged particles – easily transported - Bigger size and charged particles are hard to transport and needs support or facilitator 3. Transmembrane solute concentration - refers to the difference in the concentration of substances (like ions or nutrients) on either side of a cell membrane. This difference plays a crucial role in how substances move in and out of cells. - High concentration = faster transport TRANSPORT MECHANISMS PASSIVE ACTIVE SIMPLE PRIMARY DIFFUSION ACTIVE SECONDARY OSMOSIS ACTIVE FACILITATED BULK DIFFUSION TRANSPORT  PASSIVE TRANSPORT -Does NOT require energy or ATP -It’s driving force is usually kinetic energy. The concentration gradient moves from an area of (high concentration lower concentration) TYPES OF PASSIVE TRANSPORT 1. SIMPLE DIFFUSION - solute molecules pass directly through a membrane from a region of high concentration to a region of low concentration TYPES OF PASSIVE TRANSPORT 1. SIMPLE DIFFUSION - Particles that can pass through are small, uncharged molecules and lipid soluble molecules Example of Simple Diffusion: Gas Exchange in Lungs: When you breathe in, oxygen from the air (high concentration) diffuses into your blood - capillaries (low concentration) to the alveoli of your lungs. This process happens naturally without any energy. TYPES OF PASSIVE TRANSPORT 2. OSMOSIS - Diffusion of solvent molecules through a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration TYPES OF PASSIVE TRANSPORT 2. OSMOSIS - If there is high concentration of solute, the solvent will follow since the cell aims for equilibrium or balance TYPES OF PASSIVE TRANSPORT 2. OSMOSIS - This is important in cell biology because cells are permanently immersed in fluids. TYPES OF SOLUTIONS UNDER OSMOSIS  SOLUTE SOLUTE SOLUTE=SOLVENT SOLVENT SOLVENT PLASMOLYSIS OR CRENATION, HEMOLYSIS OR SHRINKING OF SWELLING CELLS Example of OSMOSIS: *Saltwater and Freshwater Fish: When a freshwater fish is placed in saltwater, water moves out of the fish's body (where there’s a higher water concentration) into the saltwater (where there’s a lower water concentration). This can cause the fish to become dehydrated. Conversely, if a saltwater fish is placed in freshwater, water will flow into its body, which can be harmful if not managed * Drying fish TYPES OF PASSIVE TRANSPORT 3. FACILITATED DIFFUSION - Movement of molecules through a semi- permeable membrane from an area of high concentration to an area of low concentration with the aid of transport molecule TYPES OF PASSIVE TRANSPORT 3. FACILITATED DIFFUSION - Examples are hydrophilic molecules like polar molecules, ions, small nonpolar molecules Different facilitator of diffusion a. Channel Proteins -membrane proteins that forms pores or channels which serves as passageway for ions (charged particles) to cross the membrane -each ion have their own channel proteins Example: Aquaporins – water channel proteins (aqua – water , porins – pores) Different facilitator of diffusion b. Gated-Channel Proteins -membrane proteins that opens a gate allowing molecules to pass through the membrane -Can be opened or closed in response to stimuli (voltage, mechanical stress) – senses like touch, vibrations, pressure Different facilitator of diffusion c. Carrier proteins -carry ions or molecules across the membrane by undergoing a conformational change upon binding Examples of molecules transported are: Glucose and amino acids ACTIVE TRANSPORT -requires the use of energy or ATP -The concentration gradient moves from an area of (low concentration …………higher concentration) TYPES OF ACTIVE TRANSPORT 1. PRIMARY ACTIVE Transport - Uses energy - With membrane protein transporters (ion pumps, ion channels, ATPases) - Na, K, Mg and Ca 1. PRIMARY ACTIVE Transport Example: Sodium – Potassium Pump Pump 3 sodium -out 2 potassium – in To maintain electrochemical gradient especially the neurons. More sodium out maintaining the voltage since outside of the cell needs to be more positively charge and must remain positively charged to prevent neurons from detecting the unbalanced voltage. TYPES OF ACTIVE TRANSPORT 2. SECONDARY ACTIVE Transport - Uses potential energy often from electrochemical potential difference as ions are pumped in and out of the cell - Also known as couple transport of cotransport TYPES OF ACTIVE TRANSPORT 2. SECONDARY ACTIVE TRANSPORT - The electrochemical difference build up from ATP energy is used to pump the second molecule. 2 molecules are transported. 2. SECONDARY ACTIVE Transport Types of Transporter molecules a. Symporter - Substrates move in the same direction b. Antiporter - Substrate moves in the opposite direction TYPES OF ACTIVE TRANSPORT 3. BULK TRANSPORT - Requires energy - Movement of large materials into or out of the cell by way of vesicles. 3.1 ENDOCYTOSIS - Cells take in substances from outside of the cell by engulfing them in a vesicle - Purpose: a. Taking in nutrients b. Capturing pathogens or other foreign substances c. Disposal of old or damaged cells TYPES OF ENDOCYTOSIS 1. PHAGOCYTOSIS -”cell eating” -cell engulfs large particles using pseudopodia and encloses it in a vesicle called phagosome PHAGOCYTOSIS TYPES OF ENDOCYTOSIS 2. PINOCYTOSIS -”cell DRINKING” -drinks the extracellular fluid with dissolved small molecules -the cell membrane encloses around the fluid and seals itself to form a vesicle non- specific transport TYPES OF ENDOCYTOSIS 3. Receptor- Mediated -cell membrane contains receptor proteins use to engulf specific target molecules 3.2 EXOCYTOSIS - Secretory vesicles within the cell fuses with the plasma membrane releasing its content into the extracellular space Purpose: a. Secretion of cell products b. Removal of toxins and other waste products  END OF LESSON 8