Moving Cellular Materials https://www.youtube.com/watch?v=4Eo7JtRA7lg

Why do things move into or out of cells? In order to survive and function properly, cells must take in nutrients and get rid of wastes. Cell membranes do not allow all substances to pass through them. They are selectively permeable. (Selecting is choosing.)

selectively permeable when some substances can pass through the cell membrane, while other substances cannot permeable ex. air impermeable ex. a wall

Remember the cell membrane? It is the outer layer of a cell which controls the movement of dissolved molecules into and out of the cell. It is kind of like a screen—what can pass through a screen?

Air, light, water, etc.

Cell membrane- The membrane enclosing a cell is made up of two lipid layers called a "bilipid" membrane.

The cell membrane is made up of lipids that fit together kind of like bristle blocks.

Why do things move into cells? Just like you, cells need certain materials to live. Actually, you need these materials because your cells need them. Cells need oxygen, nutrients from food, and other substances. These materials must pass through the cell membrane to get into the cell.

Why do things move out of cells? Just like you, cells produce wastes. Actually, the wastes you remove from your body are the wastes your cells produced. Some of these wastes are carbon dioxide and urea. These materials must pass through the cell membrane to get out of the cells and into your blood. Your blood takes them to a place where they can get out of your body.

How do materials move through the cell membrane? Some materials move through the cell membrane by passive transport. This means the cell does not use energy to move these substances in or out. They just let it happen. Some materials move through the cell membrane by active transport. This means the cell must use energy to move these substances in or out.

Active or Passive Transport Which way things move through a cell membrane depends on: (1) the size of the particles (S, M, or L) (2) the path taken through the membrane (diffusion, transport proteins, endocytosis or exocytosis), and (3) whether or not energy is used (passive or active)

Three types of passive transport diffusion (O2 and CO2) osmosis (diffusion of H2O) facilitated diffusion

Diffusion (diagrams A-E) Diffusion is the random movement of molecules from an area where they are crowded (in high concentration) to an area where they are less crowded (a lower concentration). Examples: perfume spreading in a room; food coloring spreading in a beaker of water (diagram A) This happens because the molecules are moving and bouncing off of one another.

A. Diffusion

DIFFUSION (Watch the blue molecules) ROOMBA

E. Diffusion Diffusion animation cell membrane high concentration low

B. Molecules leaving a cell by diffusion Cell membrane Outside cell Inside cell

C. Molecules leaving a cell by diffusion Cell membrane diffusion Outside cell Inside cell

D. The small (red) molecules have reached equilibrium Cell membrane Outside cell Inside cell EQUILIBRIUM

Equilibrium (diagram D) When the concentration of molecules is the same inside and outside the cell, equilibrium has been reached. The molecules keep moving in and out of the cell, but they move in and out at the same rate. This means when molecules move into the cell, the same number of molecules move out of the cell, therefore the concentration stays the same in both places.

D. The small (red) molecules have reached equilibrium Cell membrane Outside cell Inside cell EQUILIBRIUM

Examples of molecules that diffuse through cell membranes 1. Oxygen 2. Carbon dioxide 3. Water

Osmosis Osmosis is the diffusion of water through a cell membrane. If cells are surrounded by water that contains some dissolved substances, water will diffuse out of the cells. This happens because the water is more highly concentrated in the cell than outside the cell. (see diagram G)

F. Cells in Solutions animation What could happen?

Amoeba Sisters Osmosis

Facilitated Diffusion (diagrams G-K) Some molecules are too big to diffuse normally through the cell membrane. Facilitated diffusion is where protein channels (openings) in the cell membrane allow these larger molecules to get through. It is still passive transport, just with a larger opening.

Air, light, water, etc.

Larger things can get in Like a doggy door Larger things can get in

Openings in the cell's membrane are made up of certain proteins whose function is to control the movement of food and water into the cell.

Facilitated Diffusion video

G. facilitated diffusion high concentration low concentration

I. Facilitated Diffusion Cell membrane Protein channel Outside cell Inside cell

J. Facilitated Diffusion Cell membrane diffusion Protein channel Outside cell Inside cell

K. Facilitated Diffusion Cell membrane diffusion Protein channel Outside cell Inside cell EQUILIBRIUM

Diffusion alone is not enough to move all of the dissolved materials into or out of a cell. Sometimes materials must move against a concentration difference (like a salmon going upstream).

Active transport is when a cell uses energy to move materials into areas where they are more concentrated. (From a low concentration to an already high concentration.)

What are the three types of active transport? active transport by transport proteins endocytosis exocytosis

Active transport by transport proteins Transport proteins force molecules to move in the opposite direction of diffusion. Molecules move from an area of lower concentration to an area of higher concentration.

Active transport by transport proteins This happens when a cell needs more of a substance, but the concentration is higher inside the cell than it is outside the cell. This requires the cell to use energy.

L. Active transport by transport proteins low concentration high concentration

active transport Cell membrane Outside cell Inside cell

Endocytosis (diagram M) Molecules too big to pass through the cell membrane by diffusion or transport proteins can be taken in by endocytosis. Endocytosis is where the cell membrane surrounds the substance to bring it in.

M. Endocytosis

Endocytosis (diagram M) An animal-like protist called an amoeba gets its food that way. Endocytosis and Exocytosis Animation

Exocytosis Molecules too big to pass through the cell membrane by diffusion or transport proteins can be removed by exocytosis. Exocytosis is where substances inside the cell are moved to the cell membrane and the cell membrane opens up to let them out.

N. Exocytosis

Exocytosis Amoebas get rid of wastes this way. Endocytosis and Exocytosis Animation Review

Size comparison of a cell Cell communication (mousetrap) Cell transport Cell transport through membrane

A. diffusion or osmosis

B. facilitated diffusion

C. Active Transport through transport proteins Textbook page 79

D. Endocytosis (into)

E. Exocytosis (exit)

Question 1 What is diffusion? Diffusion is the type of passive transport in which molecules in a more dense area randomly move to an area that is less dense until equilibrium is reached.

Question 2 _______ is the diffusion of water through a cell membrane. The answer is osmosis. Cells contain water and are surrounded by water. These water molecules move by diffusion into and out of cells.

Question 3 Which letter corresponds with facilitated transport? A B C

Question 3 B. Facilitated transport is the type of passive transport that occurs when substances are so large they can enter the cell only with the help of transport proteins in the cell membrane.

Question 4 Which letter corresponds with the transport in which the cell membrane lets a larger item into the cell? A B C D E

Question 4 D. Endocytosis is the process of taking substances into a cell by surrounding it with the cell membrane.

diffusion or osmosis high concentration low concentration

facilitated diffusion high concentration low concentration

Active transport by transport proteins low concentration high concentration

Cell membrane- The membrane enclosing a cell is made up of two lipid layers called a "bilipid" membrane. The lipids that are present in the cell membrane are called "phospholipids."