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Transcript
Cellular Transport Cell Borders 1. Cell Wall – Provides support and protection. (In plants!) • Made of cellulose – a tough carb 2. Cell Membrane – Controls what enters and leaves cell. (In ALL cells!) Cell Membrane • Its function is to maintain a balance called homeostasis within the cell. • Remember that the cell membrane is semipermeable or selectively permeable. It controls how, when, and how much stuff enters and leaves the cell. It is picky. Cell Membrane Structure • Phospholipids: arranged in a bilayer with polar phosphate heads out and non-polar fatty-acid tails in (allows the cell to easily separate the outside environment from the inside environment) Cell Membrane Structure • Transport Proteins: move needed substances into and out of the cell that will not easily pass through the phospholipids Cell Membrane Structure • Cholesterol: keeps the fatty-acid tails from sticking together and adds to the fluidity of the membrane • Carbohydrate chains: defines cells characteristics and helps to read chemical signals How is a window screen like a cell membrane? • What are some things that can pass through a window screen? • What are some things that cannot? • Why is it important for a cell membrane to regulate what moves into and out of a cell? Fluid Mosaic Model Solutions and Cellular Transport • Solution: a mixture formed when one substance is dissolved into another substance; ex: Kool-Aid, Jell-o • Solute: the substance being dissolved; ex: Kool-Aid mix, Jell-o mix • Solvent: the substance doing the dissolving; ex: water • Concentration Gradient: the difference in concentrations of solute between two areas • There is a concentration gradient across the cell membrane. Essential Questions • What are the processes of diffusion, facilitated diffusion, and active transport? • What is the effect of a hypotonic, hypertonic, or isotonic solution on a cell? • How do large particles enter and exit cells? 2 Ways to Cross the Membrane • Passive Transport – NO energy is required to move a substance across the membrane. • Movement of solute along/with the gradient; ex: floating in the lazy river • Active Transport – Energy IS REQUIRED to move a substance across the membrane. • Movement of solute against the gradient; ex: trying to swim upstream or against the current Passive Transport - Diffusion • Diffusion - movement of particles from areas of high concentration of solute to areas of low concentration of solute. (water, oxygen, carbon dioxide) • When the concentration is the same throughout, equilibrium is reached. • Temperature and size of molecule affect the rate of diffusion. Passive Transport - Diffusion Passive Transport - Osmosis • Osmosis – the diffusion of water particles across a membrane. • *****Water moves from low solute to high solute.***** • Why is osmosis important for cells? How Osmosis Works in the Cell • Hypotonic - Concentration of solutes outside is lower than it is inside the cell. • Water in How Osmosis Works in the Cell • Hypertonic - Concentration of solutes outside are higher than inside of the cell. • Water out How Osmosis Works in the Cell • Isotonic – Concentration of solutes outside and inside cell are equal. • Equilibrium – water moves in and out at the same rate Passive Transport: Facilitated Diffusion • Facilitated Diffusion – Larger molecules (like glucose, sodium ions, and chloride ions) move across the membrane with the help of protein channels. • Moves from high concentration of solutes to low concentration of solutes– no energy required. Active Transport • Large molecules (glucose) and ions (Na+, K+, Ca+2) pass across the membrane using proteins and ATP ENERGY when moving from low to high concentrations. Active Transport: Exocytosis - Wastes and products are packaged in vesicle by the Golgi and sent OUT of cell Active Transport: Endocytosis – cell membrane forms vesicle and brings things INTO the cell. Types of Endocytosis • Phagocytosis – engulfs by surrounding membrane around solids. • “Phago-” means “to eat” • Pinocytosis – pinches membrane and brings in liquids. • “Pino-” means “to pinch” Odd Man Out • Osmosis • Diffusion • Cell membrane Odd Man Out • Semi permeable • Cell membrane • Phospholipid • Hydrophillic • Protein Channels • Diffusion • Osmosis • Passive Transport • Active transport • Facilitated Diffusion • ATP • Passive Transport • Solute • Water • Solvent • Osmosis • ATP • Active transport • Homeostasis • Hydrophillic • Protein Channels • Solvent • Isotonic Solution • Hypotonic Solution • Isotonic solution • Hypertonic solution • Semi Permeable