Chapter 3 - Movement Of Substances Flashcards
Define concentration gradient.
Concentration gradient is the difference in concentration between 2 regions.
How is a concentration gradient related to diffusion?
Particles will diffuse down their concentration gradient. The steeper the concentration gradient, the faster the rate of diffusion.
What happens if the water potential of 2 regions is the same?
Water molecules are constantly moving in and out of the cell. If the water potential is the same, there is no more net movement if water molecules, and dynamic equilibrium is reached.
Define osmosis.
Osmosis is the net movement of water molecules from a solution of higher water potential to a solution of lower water potential, through a partially permeable membrane.
What is the standard format of answering a question relating to osmosis?(3)
1) compare water potential
2) NET MOVEMENT of water molecules move in or out the cell by OSMOSIS.
3) Effect
Define water potential.
The tendency of water molecules to move from one place to another is known as water potential.
How does the concentration of the solution relate to water potential?
A dilute solution has a higher water potential while a concentrated solution has a lower potential.
What happens when a plant cell is placed in water?
Water has a higher water potential than the plant CELL SAP. Net movement of water molecules moves into the cell by osmosis. Vacuole increases in size and press contents against cell wall. Cell swells up and becomes firm and turgid.
What happens when a plant cell is placed in a concentrated sugar solution?
Cell sap has a higher water potential compared to the concentrated sugar solution. Net movement of water molecules moves out of the cell by osmosis. Cytoplasm and cell surface membrane pulls away from the cell wall. Cell is now plasmolysed and becomes soft and flaccid.
What happens when an animal cell is put in water?
Water has a higher water potential than cytoplasm of cell. Net movement of water molecules moves into the cell by osmosis. The cell bursts.
What happens when an animal cell is placed in a concentrated sugar solution?
Cytoplasm has a higher water potential than concentrated sugar solution. Net movement of water molecules move out by osmosis. Cell crenates.
Why is turgor important in plants?
Turgor plays an important role in maintaining the shape of soft tissues in plants. It keeps herbaceous (non-woody) plants firm and upright. Loss of turgidity causes the plant to wilt.
Why does a plant wilt and what can be done?
Plasmolysis causes tissues to become soft and flaccid. When cells of a plant becomes flaccid, the plant wilts. Water may be added to the soil to dilute the soil solution. This causes water molecules to enter the plant cells and keeps the plant firm and upright.
How does the surface to volume ratio affect diffusion?
The greater the surface area to volume ratio, the faster the rate of diffusion. As a cell becomes bigger, its surface area to volume ratio decreases.
How are cells adapted for the absorption of materials? List 1 example.
They have an increased surface area to volume ratio. For example, epithelial cells have a folded cell membrane.
