Cell Transport Structure of the cell membrane Structure

Cell Transport

Structure of the cell membrane:

Structure of the cell membrane: 1. Phospholipid bilayer – hydrophobic tails together 2. Channel proteins – allow certain ions to pass through 3. Carrier proteins – assist larger molecules across the membrane 4. Marker proteins – have carbohydrate chain as sensor

Passive Transport – movement of molecules without using energy 1. Diffusion-molecules move from high to low concentration 2. Osmosis – diffusion of water to speed up diffusion – stir, heat, or increase the concentration

Types of solutions: Hypotonic- high concentration outside the cell, water moves into the cell, cell swells Hypertonic – high concentration inside the cell, water moves out, cell shrinks Isotonic – equal concentration inside and out side of the cell, no change in size

Which type of solution is each cell in?

Examples: 1. Ameba in a pond Hypotonic: - More water outside than inside, water moves into the cell - Uses its contractile vacuole to constantly pump water out of the cell - Cytolysis – cell bursts from internal pressure

Examples: 2. plant roots in moist soil Hypotonic: -water diffuses into the roots -Central vacuole is full, pushes against the cell wall -cell has high turgor pressure (water pressure inside the plant cell)

Examples: 3. plant roots in dry soil Hypertonic: -water diffuses out -Central vacuole shrinks, cell collapses, plant wilts -plasmolysis- loss of turgor pressure

Problems: 1. Why does saltwater dry out cells? Osmosis is the movement of water Inside: 10%salt, 90% water Outside: 20%salt, 80% water Water moves from high to low so it moves out of the cell.

2. Why was salt used to preserve meat? It created a hypertonic environment, drew moisture out of bacteria, and the meat was safe 3. Why does gargling with salt water help ease sore throat pain? It draws water out of the cells, reducing swelling 4. Why do they spray water on vegetables in the grocery store? It creates a hypotonic environment, water diffuses into the cells, keeping them crisp

5. What will happen to the cell in each of the following solutions? the cell is 10% salt Cell is 90% water A) pure water A) Solution is 100% water, hypotonic, water moves in B) 10% saltwater B) Solution is 90% water, isotonic, No change C) 15% saltwater C) Solution is 85% water, hypertonic, water moves out

Another type of passive transport: 3. Facilitated Diffusioncarrier proteins assist larger molecules across a membrane from high to low concentration Glucose enters the cell this way

4. Ion Channels • Ions move through the membrane from high to low concentration through channel proteins • Each protein has a specific shape, fits only one type of ion

Active Transport using energy (ATP) to move molecules from low to high concentration

1. Sodium Potassium Pump: - uses carrier proteins to move 3 Na+ out of the cell and 2 K+ into the cell - this creates a build up of charge, allowing an electrical impulse to jump from nerve cell to nerve cell speed: 450 Na+ out and 300 K+ in each second

2. Endocytosis – cells use energy to ingest fluids or large particles Steps: 1. a pouch forms in the membrane 2. material enters the pouch 3. the pouch pinches off, forming a vessicle. Pinocytosis – ingesting fluid Phagocytosis – ingesting particles or whole cells

Endocytosis Exocytosis

3. Exocytosis – reverse of endocytosis • Substances packaged by the Golgi leave the cell this way