Chapter 1, Lesson 4 The Cell in Its Environment – pg. 28 How Do Materials Move Into and Out of Cells?

How Do Materials Move Into and Out of Cells? Lab Activity (with your pod): 1. Fill beaker ½ way with cold water. Place the beaker on the desk and allow it to sit until there is no movement in the water. 2. Add one drop of food coloring to the water. 3. Observe for a few minutes and write down changes you notice on p. 28 in the margin. 4. Bring materials back & wait to discuss with class

What is going on???? Words you may have used to describe: Starts as a glob of color in the middle Color spreads out slowly After a while, the color became more equal throughout

What must move into & out of a cell? (p. 28) Oxygen Water Food Particles (salts & sugars) Carbon dioxide Waste materials **Highlight/underline those!

Importance of the Cell Membrane Structure: Double layer of lipid molecules lined up side by side Selectively permeable: some substance can cross the membrane while others cannot Substances can move in & out of a cell by passive transport or active transport

Check out 3 of the 5 molecules that all living things have!!! Carbohydrates Lipids Proteins

Figure 1, p. 29…do it now please! In what way is the cell membrane like a gatekeeper? Answer: It is in charge of controlling who comes in or out of the cell!

Diffusion & Osmosis: Forms of Passive Transport (p. 30) Passive Transport: the movement of dissolved materials across a cell membrane without using the cell’s energy Fun example: riding a bike down a hill

What about the molecules? P. 30 Molecules are always moving! They bump into each other Over time, as molecules continue colliding and moving apart, they become less concentrated (crowded) Eventually, the molecules spread evenly throughout the space Ouch! That kinda hurt!

DIFFUSION (the definition) The process where molecules move from an area of higher concentration to an area of lower concentration.

Figure 2…take a look at this Diffusion A drop of food coloring in a plate of gelatin gradually spreads as molecules of the dye diffuse. How would the third plate look if diffusion continues?

Figure 2…take a look at this Diffusion A drop of food coloring in a plate of gelatin gradually spreads as molecules of the dye diffuse. How would the third plate look if diffusion continues? You should have a picture of dye spread in a wider circle

Diffusion & Osmosis: Forms of Passive Transport (p. 30) Link to eyeball science: http://kitchenpantryscientist.com/edible-eyeballs-a-diffusion- experiment-for-halloween/

Here is a little water critter – a Paramecium (found in pond water) Think about this… Here is a little water critter – a Paramecium (found in pond water) nucleus Contractile vacuole

Think about this… All living things need oxygen – a Paramecium doesn’t have lungs to breathe in oxygen so it gets it from the water.

Think about this… What is water made of? Hydrogen and Oxygen!!!

DIFFUSION Think about this… So, how does the oxygen get INTO the Paramecium’s body? DIFFUSION

Think about this… Diffusion is one form of passive transport because the concentration of oxygen is higher outside the paramecium than it is inside of it. So…oxygen moves easily into the cell

p. 30: 2nd paragraph Unicellular organism in pond: Make a quick sketch of this in the margin on page 30.

How about an example for us

Osmosis p. 31 The diffusion of water molecules across a selectively permeable membrane Cells cannot function properly without water Form of passive transport Read 2nd paragraph & Figure 3, Effects of Osmosis…let’s do that

Figure 3 – Effects of Osmosis The top picture shows a healthy plant cell – water moving in and out through the cell membrane. The 2nd picture shows how the cell membrane has pulled away from the cell because too much water is lost. Can this happen to us too? YEP – think about being stranded on a desert island – no fresh water.

Castaway! The movie https://www.youtube.com/watch?v=z7Rv_7k WfBc

Take out your egg lab and do your question of the day…

IN YOUR BODY…the big deal

Other Real Life Examples… Leech or Slug murder Salt on a leech or slug will kill it because their skin has no protective barrier to it. Water leaves their cells to balance out the salt.

Another real life example…

If the cells have lost water…

What are the two types of passive transport we talked about? Diffusion and Osmosis Diffusion – molecules going from crowded to less crowded places Energy not needed Does not involve water Osmosis – Diffusion of water Water molecules going from crowded to less crowded places What does passive transport mean again? Movement of molecules across a membrane without needing energy

Active Transport Movement of materials across a cell membrane using cellular energy Molecules move from areas of lower concentration to higher concentration Proteins move these molecules across the cell membrane – (see figure 4) Substances that do this include calcium, potassium, and sodium

Crossing the Cell Membrane - figure 4 (pg. 32) Molecules move into and out of a cell by means of passive or active transport. Complete the boxes, and describe where the concentration of each substance is high or low.

Crossing the Cell Membrane - figure 4 (pg. 32) Passive Active Crossing the Cell Membrane Molecules move into and out of a cell by means of passive or active transport. Complete the boxes, and describe where the concentration of each substance is high or low. Osmosis Diffusion

Assess Your Understanding 1a Use diffusion to tell what happens when you drop a sugar cube into water. Sugar dissolves; molecules collide moving from high concentration to low concentration

Assess Your Understanding 1b Draw an arrow to show the overall direction water will travel as a result of osmosis. (The yellow line is the cell membrane)

Assess Your Understanding 1c Active transport depends on to move molecules across the cell membrane. Proteins

Assess Your Understanding 1d How does active transport differ from passive transport? Active transport uses cell energy in moving materials into or out of cells; passive transport does not.

Got it??? Now I know that the key function of the cell membrane is to… Regulate the materials that move into and out of cells