Cells And Movemnet Of Molecules Flashcards
How does water travel up a plant
Through xylem vessels to the leaves
What keeps the leaves of a plant firm and outstretched
Xylem in the veins. The leaves are lignified and the fully turgid cells push against each other and create pressure
What makes the leaves wilt
Water moves out of the cell by osmosis so the cell is flaccid and there is no pressure in the cell
What are the affects of osmosis on animal cells
Because there is no cell wall there is never any internal pressure . Normally in blood cells they are surrounded by a plasma of the same water concentration as the cytoplasm so no osmosis occurred . When the plasma is diluted water enters the cell by osmosis causing them to swell and burst.
What happens when a plant cell is in a turgid state
Pressure and water concentration in cell increase its water potential until it equals that of the water outside . Cell is now turgid and there is no net water movement
What is active transport
Active transport is when a substance moves against the concentration gradient e.g from. A low concentration to a high concentration . This is called active transport because this movement requires energy. Energy is used to pull a particle through a protein against the direction of diffusion
What is xylem
Lignified cell walls
What is diffusion
The tendency of particles of liquid and gases to move apart by kinetic energy from a region of their own high concentration into a region of their own lower concentration until there is no difference in the concentration in the volume occupied.
What is osmosis
Form of diffusion. The diffusion of solvent, water across a selectively permeable E.g a cell membrane. Because it because it can occur in both directions osmosis is often expressed as the next diffusion of water across the membrane. Water tends to defuse down its own concentration gradient
What is water potential
It is a measure of a tendency to donate water to its surrounding- usually by diffusion down waters own concentration gradient
Why do plant cells not swell up and burst like animal cells
I plant cells have walls around them so they cannot swell up and burst through uptake of water by osmosis when placed in distilled water. Plant cells oppose their own continuous swelling in water because of the pressure on the cell contents enclosed by the cell-surface membrane Exerted by its wall. When a plant cell is turgid the cell wall pushes back against the cytoplasm and opposes any further osmotic uptake of water through the cell-surface membrane
What affects a cells water potential
A cells water potential may be dependent only on it solute concentration , as in animal cells or it may also depend on the pressure exerted on the cell’s water by a cell wall
What is it called when two solutions have the same Solute concentrations
Isotonic
What is called when a solution has a greater solute concentration than another
The solution with the lower concentration is said to be hypertonic to it.
What is plasmolysis
When the vacuole loses water so the cytoplasm pulls away from the cell wall .in a playsmolysed cell the wall is limp and there is no internal pressure , and the cell Sap has the same water concentration as the external solution. The cell has a greater water potential than the surrounding liquid and water moved out by osmosis . The sorrounding solution has crossed the cell wall and now surrounds the cell membrane .Hypertonic
