Cell Membranes and transport of Materials

Do Now: Shipwrecked A shipwrecked sailor is stranded on a small desert island with no fresh water to drink. She knows she could last without food for up to a month, but if she didn’t have water to drink she would be dead within a week. Hoping to postpone the inevitable, her thirst drove her to drink the salty water. She was dead in two days. Why do you think drinking the saltwater killed her faster than not drinking any water at all?

Introduction

The Cell Membrane

Plasma Membrane (aka Cell Membrane) Phosopholipid Bilayer Called the Fluid Mosaic Model Selectively Permeable

Selectively Permeable If a membrane is selectively permeable only certain things can pass through

Selectively Permeable Only certain materials can go in and out of the cell

The Cell Membrane is Selective: Things that passively cross: Non-Polar Molecules (O2 & Co2) Small Molecules (Water) Things that actively cross: Polar Molecules (Na+, K+, Cl-) Large Molecules (glucose, starch)

Types of Transport Passive (no ATP) Active (requires ATP)

Passive Transport Passive Diffusion Osmosis Facilitated Diffusion

Movement of materials that DOES NOT require energy (ATP) Passive Transport Movement of materials that DOES NOT require energy (ATP)

What is happening here???

DIFFUSION The passive movement of material from an area of high concentration to an area of low concentration

The number of a substance in a specific area Concentration The number of a substance in a specific area

High Concentration Low Concentration

High Concentration Passive Transport Low Concentration

Factors Affecting Diffusion Concentration—diffusion always goes from high concentration to low concetration Temperature—the higher the temperature, the faster diffusion occurs Molecular Size—the bigger the molecule, the longer diffusion takes

The diffusion of water through a selectively permeable membrane OSMOSIS The diffusion of water through a selectively permeable membrane

Osmosis—another look…

No net movement of water in or out of the cell Isotonic Solution No net movement of water in or out of the cell

Hypotonic Solution Water moves from the solution into the cell causing it to swell or break (lysis)

Hypertonic Solution The water moves out of the cell into the solution, causing the cell to shrink

Types of Solutions

Why doesn’t the plant cell shrivel up?

Explain what is happening in this cartoon…

Procedures Your teacher has cut three potato pieces for your group; measure and record the diameter of each potato core. Using the balance, measure and record the mass of each potato core.

3. Place one potato core in the cup with solution A and label this cup “Solution A". Place the second core in the cup with Solution B and label the cup “Solution B". Place the third core in the cup with solution C and label this cup “Solution C". 4. Cover the top of each cup with a piece of aluminum foil. Fold the aluminum foil down along the sides of the cup so that it cannot fall off easily. 5. Allow the cups to sit for a day.  STOP HERE

Lab – Diffusion & Osmosis Cover Page: title, picture, name/date/section Title – “The effects of IV on DV? Intro – Use all key terms in intro Diffusion - Osmosis Selectively permeable - Passive transport Concentration Problem – “What are the effects…?” Hypothesis – Leave ~ 5 lines… Data:

COVER PAGE Create a cover page for today’s lab Title: Diffusion and Osmosis Name, Date, Period Picture

Intro In this lab we will study osmosis by ______________. Osmosis is movement of water from a region of _____ water concentration to a region of _______ water concentration. Diffusion, on the other hand, is movement _________. The potato has a ______-_________ membrane, so it only lets certain things through. The ____ in the water will be too big to pass through the ___________, so water will either enter or exit the cell to reach _____________.

Hypothesis If the potato swells, then the water moved (in/out), so the solution had (more/less) sugar than the potato. This would mean the solution is (isotonic/hypertonic/hypotonic) to the potato.

Data Solution A Solution B Solution C Day 1 Day 2 Change Length Mass Appearance

Facilitated Diffusion Diffusion that is helped by proteins in the membrane

Facillitated Diffusion

Diffusion vs. Facillitated Diffusion

Active Transport Active Pumps Membrane Movements Endocytosis Exyocytosis

Active Transport Movement of materials from low concentration to high concentration using a protein carrier that requires energy (costs ATP)

High Concentration Active Transport Low Concentration