 Thinking Log  15. The cell membrane only lets certain things in. This is called being ____________ _____________.  16. Does diffusion use energy?

Answers  Thinking Log  15. The cell membrane only lets certain things in. This is called being selectively permeable  16. Does diffusion use energy? No.

TODAY  Complete the transport notes (p. 17)

TRANSPORT IN CELLS

Cells must let in needed materials like oxygen and food molecules. They also must remove waste products such as carbon dioxide and water. The molecules must move through the cell membrane in order to get in or out. The cell membrane is selectively permeable.

Selectively Permeable This means that some substances can pass through the membrane while others cannot. An example of something that is selectively permeable is a window screen. The screen allows fresh air in, while keeping bugs out. When molecules move in and out of cells it is called transport.

Question  Can you think of anything else that is selectively permeable?

One type of transport is diffusion. Diffusion is the main method by which molecules move across the cell membrane. Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration.

Reminder  Concentration is the amount of one substance in another substance or mixture

Diffusion Diffusion happens because molecules are always moving. Molecules bounce off one another and spread each other out. The goal of diffusion is to reach equilibrium (a state of balance—does this sound familiar?).

Draw what the contents of the cell might look like after diffusion. #1 #2

Brainpop--Diffusion Video emistry/diffusion/

Osmosis is a specific type of diffusion. Because water is so important to living things, the movement of water gets a special name…OSMOSIS! Osmosis is the movement of water molecules from an area of higher concentration to an area of lower concentration. Sound familiar? Osmosis and diffusion are the same, except osmosis is the movement of water specifically.

Do we need air freshener? -teacher will spray air freshener in the corner of the room -raise your hand when you SMELL it  Both osmosis and diffusion do not require energy from the cell. They are called passive transport (passive=no energy required).

THAT WAS DIFFUSION IN ACTION!

Active Transport Sometimes a cell needs to move substances the opposite way of diffusion and osmosis. To do this, the cell must use energy. This is called active transport (active=energy required). Which picture is active and which is passive?

Active transport is the movement of molecules from an area of lower concentration to an area of higher concentration. Some substances that are carried into and out of cells this way are calcium, potassium, and sodium. Active transport can happen two different ways: engulfing and transport proteins.

Engulfing means the cell surrounds the substance completely and then forms a vacuole to take up the substance. Transport proteins are found in the cell membrane. Substances can move through the proteins if the cell needs them. Complete the Venn diagram, then vocabulary.

 Note: Stopping here is fine, unless time remains.

Passive v. Active Transport  iocoach/biomembrane1/transport.html iocoach/biomembrane1/transport.html

KEY TERMS TO REVIEW  Concentration: The amount of a particular substance in a given amount of another substance, especially a solution or mixture.  Diffusion: The process by which molecules move from an area of higher concentration to an area of lower concentration.  Equilibrium: State of balance  Selectively permeable: A property of the cell membrane in which some substances are allowed to pass through, while others cannot  Osmosis: The process by which WATER molecules move from an area of higher concentration to an area of lower concentration  Passive Transport: The movement of materials through a cell membrane WITHOUT using cellular energy.  Active Transport: The movement of materials through a cell membrane using energy.