Exchange with the Environment Chapter 2, Section 1 Pages 34-37 How do materials (water & nutrients) get into and out of the cell How are materials moved in and out of the cell? Is there a difference moving small particles as opposed to moving large particles?

particles through the cell membrane Ways to move small particles through the cell membrane Diffusion & Osmosis

The Cell Membrane as the Gate Keeper The cell membrane is made of a bilayer of phospholipids with proteins that grants access of certain material through the cell, while preventing others substance from entering or exiting.

Diffusion p. 34 The movement of particles (molecules) from a area in which they are highly concentrated (more dense) to a area in which they are less concentrated (less dense). Fluid movement

This type of diffusion is called Passive Transport p. 36 High concentration of materials to a low concentration of materials –without energy input from the cell (does it on its own with out help) Passive transport, then, is a type of diffusion which allows materials to enter and exit the cell.

Watch the next Demo Draw what is happening in the demo and explain what is happen using the correct term diffusion.

Did you draw a diagram of an example of diffusion we saw in class. More conc./dense Less conc./less dense

Compare to Egg-cellent Experiment What part of the lab did diffusion occur? ? How do you know that diffusion was happening? Evidence!! ? We could smell the extract. Cells don’t have mouths so they need to exchange materials like wasted, gases, nutrients and so on. They need the membrane to let things our, let thing in, and keep unwanted thing our. The balloon,

Particles moved from areas of Greater (inside the balloon) concentration to areas of lesser concentration (outside the balloon). Particles passed through the Cell Membrane (the rubber of the balloon acted like the cell membrane)

Osmosis is another name for the diffusion of water through a semi-permeable membrane Semi-permeable: Only certain substances can pass through p. 35

Define selectively permeable membrane A membrane that allows only certain materials to cross it Materials pass through pores in the membrane

Osmosis Passive transport The animation to the right shows a transfer of water particles through the Cell membrane

Example of osmosis In this picture a red blood cell is put in a glass of distilled water (all water with no salt or sugar in it).  Because there is a higher concentration of water outside the cell, water enters the cell by OSMOSIS.  In this case too much water enters and the cell swells to the point of bursting open.  In the end pieces of cell membrane are left in the water. http://www.usd.edu/~bgoodman/Osmos.htm

Examples of Osmosis in the Lab What part of the lab did osmosis occur? The potato that soaked in plain water The egg that soaked in colored water. Evidence that osmosis occurred in the potato. There was a greater concentration of water on the outside of the potato than inside. The water moved inside to reach an equilibrium. The potato gained mass and the volume of water was less in the cup.

Osmosis Occurred in the Egg The egg that was soaking in colored water. Water was more concentrated outside the egg than in so the water moved from the area of greater concentration to area of less concentration (inside the egg). The food color molecules were small enough to pass with the water molecules. The mass of the egg increased and a decrease in the volume of water.

Osmosis occurred in the Salt water & syrup There was less water outside of the potato so the water inside (greater concentration) left the potato and went to and area that was less concentrated. The water was more concentrated inside of the egg than in the syrup. There was a decrease in mass of the egg and an increases in volume of the syrup

Why are osmosis & diffusion important?

Why are osmosis & diffusion important? All living things have certain requirements they must satisfy in order to remain alive – maintain homeostasis These include exchanging gases (usually CO2 and O2), taking in water, minerals, and food, and eliminating wastes. These tasks happen at the cellular level. Molecules move through the cell membrane by diffusion

Why are osmosis & diffusion important? All living things have certain requirements they must satisfy in order to remain alive. These include exchanging gases (usually CO2 and O2), taking in water, minerals, and food, and eliminating wastes. These tasks ultimately occur at the cellular level, and require that molecules move through the membrane that surrounds the cell.

Why are osmosis & diffusion important? This membrane is a complex structure that is responsible for separating the contents of the cell from its surroundings, for controlling the movement of materials into and out of the cell, and for interacting with the environment surrounding the cell.

What happens when certain material (molecules) need a little help passing in & out of a cell? They need a little help from a friend!

Active Transport p. 36 A process of transporting particles that requires the cell to use energy. Some proteins actively use energy from the ATPs in the cell to drag molecules from area of low concentration to areas of high concentration

Active Transport Active transport uses energy to send substances against the direction they would travel by simple diffusion: that is from a region of low concentration to a region of high concentration

How do larger particles move into and out of the cell? An active transport process is used to bring large particles into and out of the cell Check out the next slide!!!!!!!!!!! This is not active transport, but it is funny!!!

Endocytosis p. 36 Endocytosis (Endo (within) cytosis (cell) ) is a process in which a substance (e.g. proteins) gains entry into a cell without passing through the cell membrane.

Exocytosis p. 37 Exocytosis (Exo (exit) cytosis (cell) ) is a process in which a substance is exited from the cell without passing through the cell membrane. Examples of things that might be exited include secretion of proteins like enzymes, hormones and antibodies.

The term applied when transporting Exocytosis (another look) The term applied when transporting materials out of the cell. Note the vesicle on the left, and how it fuses with the cell membrane on the right, expelling the vesicle's contents to the outside of the cell

The Cell Membrane (01:01) Introducing the Cell (21:00)

I wonder if we’re thinking the same thing? Oh my gosh! Another worksheet Do the review sheet your teacher is passing out!!! (Page 37)