Osmosis
Plants use osmosis to prevent wilting.

Osmosis

This Biology quiz is called 'Osmosis' and it has been written by teachers to help you if you are studying the subject at middle school. Playing educational quizzes is a fabulous way to learn if you are in the 6th, 7th or 8th grade - aged 11 to 14.

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Osmosis refers specifically to the movement of water molecules through partially permeable membranes, and in this middle school Biology quiz we take a close look at how the process works. Partially permeable membranes allow water molecules to pass through them in both directions, and this is how osmosis occurs.

If there are solutions of different concentrations on opposite sides of the membrane, it is important that you realize that water molecules are passing through in both directions. It is a special case of diffusion as it involves only water molecules and a partially permeable membrane. To understand it properly involves your knowledge of the particle theory of matter (kinetic theory - atoms and molecules are constantly in motion).

Because there are more water molecules in a less concentrated solution than a more concentrated solution, more of them will be crossing through the membrane at any given time. The result of this is that the more concentrated solution will gain water molecules from the less concentrated one. You have probably seen this happening in lessons at school where a concentrated sugar solution in placed into a tube made from a partially permeable membrane or by placing a piece of potato into a glucose solution. The level of the concentrated sugar solution rises as it gains water molecules whereas the piece of potato shrinks since it loses water to the glucose solution surrounding it.

Eventually the concentrations will become equal. At this point, there will be the same number of water molecules passing through the partially permeable membrane in both directions. Equilibrium has been reached and so in practical terms, osmosis stops as there is no further change in concentration, but you must remember that the water molecules are still passing through the cell membranes.

1.
Osmosis takes place in which of the following?
Roots
Hair
Soil
The atmosphere
Water is taken up by root hair cells from the soil as there is a concentration gradient from soil to the root hair cell
2.
Water molecules move...
down the concentration gradient
along the concentration gradient
against the concentration gradient
nowhere
Along the gradient is always marked as incorrect in exams
3.
Plants use osmosis to prevent...
respiration
photosynthesis
wilting
excretion
Plant cells become flaccid when they are short of water. Osmosis makes them turgid once more
4.
Osmosis is the movement of which molecules?
Oxygen
Hydrogen
Any
Water
Osmosis is only about water molecules
5.
In living organisms, the partially permeable membrane is the...
nucleus
cell membrane
chloroplast
bacterium
This contains the cytoplasm and when there is a concentration gradient between the outside of the cell and the cytoplasm, osmosis occurs, restoring the equilibrium
6.
Osmosis takes place in this important structure.
Alveolus
Villus
Nephron
Artery
Water is reabsorbed by osmosis in the nephrons of the kidneys, keeping the blood plasma at the right concentration to avoid the lysis (bursting) of the red blood cells in particular
7.
Dilute means...
a little solute and a lot of water
a lot of solute and little water
concentrated
the same
Dilute means weak and watery. A small amount of solute, e.g. salt, dissolved in a lot of water
8.
Water molecules move from...
dilute to a more dilute solution
dilute to a more concentrated solution
concentrated to a more dilute solution
concentrated to a less concentrated solution
It is a special case of diffusion as it involves a movement of only water particles from a higher concentration to a lower concentration across a partially permeable membrane
9.
Potato cylinders are put into a strong sugar solution. After an hour they are...
bigger
smaller
the same
sweet potato
Water leaves the potato cells by osmosis, so the potato cylinders shrink in size due to water loss
10.
Why is osmosis not the same thing as diffusion?
A partially permeable membrane is needed for osmosis
A partially permeable membrane is needed for diffusion
Osmosis involves oxygen only
Diffusion involves water only
True diffusion occurs when two substances are in direct contact with one another, here they are physically separated by the partially permeable membrane

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