Transport

We’ve already learned that…… cell membranes are described as; selectively permeable what does

this mean?

• The membrane will allow some substances to pass through and will not allow other substances to pass through.

Unit 3 Cellular Transport Learning Intention:Understand that transportation of molecules across the cell membrane helps maintain homeostasisSuccess Criteria: I can … explain the difference between passive and active transportI can… predict the movement of water in osmosisI can… develop a model of endo- and exo - cytosis

Transport Journal

Passive• Define:

3 Types:1.2.3.

Active• Define:

3 Types:1. 2. 3.

Transport Journal

Passive• Define:

3 Types:1.2.3.

Active• Define:

3 Types:1. 2. 3.

Cellular Transport

2 types of transportPassive Transport: – transport across the cell membrane that does not

require energy– molecules move down the concentration gradient– from higher concentration to lower concentration

Active Transport:– Requires energy– Molecules move against the concentration gradient– From lower concentration to higher concentration

Passive Transport

3 Types:1. Diffusion: movement of molecules from higher to

lower concentration

2. Osmosis: movement of water from higher to lower concentration

3. Facilitated diffusion: passive transport in which proteins act as channels

Focus on OSMOSIS• Osmosis is the movement of water across a cell

membrane from an area of higher concentration to an area of lower concentration.

• Osmosis does not require cells to expend energy.

Is osmosis is a type of passive or active transport????

Terms to know• A solution is composed of a solute dissolved in a

solvent.• Example: Salt water– Salt is the solute– Water is the solvent

• In the case of cells, the solutes are organic and inorganic compounds (such as salt), and water is the solvent.

What determines the direction of the water movement in Osmosis?

• The relative concentration of water and solute on the two sides of the cell membrane.

Some Definitions…

• Hypotonic-lower concentration of solutes

• Hypertonic-higher concentration of solutes

• Isotonic-even concentration of solutes

Comparison…

How will the water move in each situation ???

The red arrow is pointing to the solute (such as salt)

In a hypotonic environment, water will enter the cell in order to balance the salt concentration.

(The solute is not doing the moving!!!)

How will the water move in each situation ???

The red arrow is pointing to the solute (such as salt)

In a hypotonic environment, water (blue arrows) will enter the cell in order to balance the salt concentration. (The solute is not doing the

moving!!!)

How will water move in a hypertonic environment???

How will water move in a hypertonic environment???

• Example: Salt Water

• Water will move out of the cell.

Journal: What happens to the cells of a freshwater fish when it is placed in a saltwater tank?

Fish Animal Cells No Cell Walls

Journal: What happens to the cells of a freshwater fish when it is placed in a saltwater tank?

Fish Animal Cells No Cell Walls

How do plant cells deal with osmosis?

• Plant cells have cell wall and most live a hypotonic environment. The cells that make up roots may be surrounded by water. This moves water into the cells by osmosis.

• These cells swell as they fill with water until the cell membrane is pressed against the inside of the cell wall. The water exerts of pressure against the cell wall called turgor pressure.

How do plant cells deal with osmosis?

• In a hypertonic environment, water leaves the cells through osmosis. As the water leaves the central water vacuole, the cells shrink away from the cell walls, and turgor pressure is lost.

• This condition is called plasmolysis, and is the

reason that plants wilt if they don’t receive enough water.

How do unicellular organisms deal with osmosis?

• Because most of them live in a hypotonic environment, water is constantly entering the cells, so they must rid themselves of the excess water. Some of them, such as the paramecia have structures called contractile vacuole which remove the excess water by pumping it out of the cell.

Active Transport

Journal: What was the main difference between active and passive transport?

Active Transport

• Channel proteins also called Cell membrane pumps– Move substances up the concentration gradient

(into an already crowded area)

Active Transport

• Endocytosis: the process by which cells ingest external fluid, macromolecules, and large particles, including other cells.– Pinocytosis: Water– Phagocytosis: Large Particles

Active Transport

• Exocytosis: the process by which a substance is released from the cell through a vesicle that transports the substance to the cell surface and then fuses with the membrane to let the substance out of the cell.

The End!