Active Transport SBI 4 U Review Diffusion Osmosis

Active Transport SBI 4 U

Review • Diffusion • Osmosis

Facilitated Diffusion • Protein carrier molecules, located in the cell membrane, can aid in passive transport

Facilitated Diffusion, continued … • Protein carriers speed up the movement of molecules already moving across the cell membrane • Example: glucose diffuses into red blood cells hundreds of times faster than other sugar molecules that have similar properties, why? specialized carrier proteins

Active Transport • When a cell uses its own energy to move materials from an area of low concentration to an area of higher concentration active transport

Without active transport … • Your kidneys would fail to reabsorb needed materials • Your muscles would not contract • Your nerves would not carry impulses

Endocytosis & Exocytosis • How do cells absorb larger molecules? Expenditure of energy is required • Endocytosis process of ingesting materials • Exocytosis process of transporting materials to outside environment

Process of Endocytosis 1. Membrane folds around materials outside the cell 2. Ingested particle is trapped within a vacuole inside the cytoplasm 3. Often lysosomes are used to digest the molecules absorbed by endocytosis

Endocytosis, continued … • Pinocytosis & Phagocytosis • Pinocytosis: cells take up dissolved molecules by engulfing small volumes of the external solution. Ex: small intestine and fat droplets • Phagocytosis: process by which cells engulf solid particles. Ex: white blood cells and microbes • Cellular drinking vs. cellular eating

Exocytosis • Process by which large molecules held within the cell are transported to the external environment • Waste materials are often released this way • Useful materials, like transmitter chemicals emitted from nerve cells are also released by exocytosis

Process of Exocytosis 1. Golgi apparatus holds the secretions inside fluid-filled membranes 2. Small vesicles break off and move toward the cell membrane 3. The vesicles fuse with the cell membrane and the materials is released into the external environment