Moving Materials into and out of the Cell

•Cells need to receive materials:• water

• nutrients

• oxygen for the mitochondria

• carbon dioxide for chloroplasts

•Cells need to dispose of materials• carbon dioxide from the mitochondria

• other wastes resulting from cellular metabolism

• excess water ( especially cells that live in fresh water)

•There are two ways in which cells receive and dispose of materials:

• Passive transport

• Active transport

•Passive transport:

• does not require an input of energy

•Active transport:• requires an input of energy

•There are two kinds of passive transport:

•diffusion

•osmosis

•Diffusion: the random movement of molecules from areas of higher concentration to areas of lower concentration

• Basically molecules tend to move from where they are more crowded to where they are less crowded. They do this because of their own kinetic energy and random movement.

•Osmosis: the diffusion of water through a membrane

• Osmosis is just a special kind of diffusion. Like regular diffusion, the water molecules tend to move from where they are more crowded to where they are less crowded. It has a special name because of the importance of water to living cells.

•In order to understand diffusion and osmosis, it is necessary to understand solutions.

•Solution: a type of mixture in which one or more substances are dissolved in another substance

•Examples of solutions

•salt water

•pancake syrup

•cola

•air

•A solution includes at least one solvent and at least one solute. Salt water is a solution, in which salt is the solute and water is the solvent.

•Solute: the dissolved substance

•Solvent: the substance in which the solute is dissolved

•Solution: the solvent plus the solute

•The solvent and the solute are not chemically bonded to each other. The solvent and solute each have their own molecules which can be separated without using any chemical reactions.

•Cells placed in solutions:

•If a cell is placed in a solution, the solution may be hypertonic, hypotonic, or isotonic to the cell.

•Hypertonic Solutions

• If the solution is hypertonic to the cell, there is a higher percentage of solute in the solution than in the cell.

• This also means that there is a higher percentage of water in the cell than there is in the solution.

• Notice that the water(solvent) is the opposite of the solute. If you have more dissolved stuff, you have less water and vice versa.

•So ......, if you place a cell such as an egg in a hypertonic solution, will water go out of the egg or into the egg?

•Hypotonic Solutions:

• If the solution is hypotonic to a cell such as an egg, it means that there is a lower percentage of solute in the solution than there is in the egg.

• This means that there is a higher percentage of water in the solution than in the egg.

•So ....., will more water move into the egg or out of the egg?

•Isotonic Solutions:

• If a cell is placed in an isotonic solution, the percentage of solute outside the cell is the same as the percentage of solute inside the cell.

• This means that the percentage of water(solvent) is also the same on the inside as the outside.

•So ....., if you place an egg in an isotonic solution and check the mass the next day, what result could you expect?

• Identify each of the following as hypertonic, hypotonic, or isotonic to the egg:

• Vinegar:

• Pancake syrup:

• Distilled water:

•www.youtube.com/watch?v=AYNwynwaALo