Chapter 4 Section 3 Cell Processes

Cells Like all living things, cells must do certain things. – Ex: certain cellular processes and take in needed substances from their surroundings to survive One key component is that cells need to take in food. Then the cell must be able to break down that food into useable energy. If these needs are not met the cell will die.

Question? What do you think will happen when I place a drop of food coloring in water? – The ink quickly begins to spread throughout the water. Why does the food coloring spread throughout the water? – The ink spreads because the molecules that make up the food coloring are moving. – The molecules of all substances are in constant motion.

Diffusion Most molecules move from areas where they are concentrated, to areas where they are less concentrated. Diffusion - is the movement of molecules from areas of greater concentration to areas of lesser concentration.

How do substances pass through the cell membrane? The cell membrane has tiny holes or pores. – The pores are proteins found in the cell membrane. Substances enter and leave the cell by the use of these pores / proteins.

How does the cell membrane regulate the passage of substances into and out of the cell? The size and concentration of a substance determines what can pass through the cell membrane. – If a molecule is too large, it cannot pass through the membrane unless energy is used. – If the concentration of that molecule is the same on the outside of the cell as the inside it will not pass through.

Osmosis Is the diffusion of water through a membrane.

Tonicity Is the measure of osmotic pressure of 2 solutions separated by a membrane. There are three classifications of tonicity that one solution can have relative to another. – Hypertonic – Hypotonic – Isotonic

Hypertonic Is a solution having a greater solute concentration than the cytoplasm. It contains a greater concentration of solutes on the external side of the membrane. When a cell’s cytoplasm is bathed in a hypertonic solution the water will be drawn into the solution and out of the cell by osmosis. If water molecules continue to diffuse out of the cell, it will cause the cell to shrink.

Hypertonic

Hypotonic Is a solution having a lesser solute concentration than the cytoplasm. It contains a lesser concentration of solutes on the external side of the membrane. When a cell’s cytoplasm is bathed in a hypotonic solution the water will be drawn out of the solution and into the cell by osmosis. If water molecules continue to diffuse into the cell, it will cause the cell to swell, up to the point where lysis (explodes) occurs.

Hypotonic

Isotonic A condition where the solute concentration is the same as the solute concentration of another solution with which it is compared.

Osmosis