Movement Of Substances Across The Plasma Membrane In Everyday Life

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In comparing two solutions with different solute concentrations: •The solution with higher solute concentration is said to be hypertonic (‘hyper’:more) •The solution with a lower solute concentration is hypotonic (‘hypo’: less) •Solutions in which the concentration of solute are equal are said to be isotonic (‘iso’: equal)

Animal and plant cells in an isotonic solutions

• An isotonic solution is a solution in which the concentration of solute is equal to that of the cytoplasm of the cell • Water diffuses into and out of the cell by osmosis at equal rates • Therefore there is no net movement of water across the plasma membrane [no net gain or net loss of water] • The cells retain their normal shape

The shape of animal & plant cells after being placed in an isotonic salt solution

Animal and plant cells in a hypotonic • Solutions whichsolutions contain a higher

concentration of water than that of the cytoplasm are called hypotonic solutions • Hypotonic solutions contain lower concentration of solute than the cell • Since the concentration of water is higher outside the cell, there is net movement of water from outside of the cell into the cell by osmosis • The cells gains water, swells and the

The effects of hypotonic solutions on animal cells

1. When red blood cells are immersed in a hypotonic solution, water diffuses into the cells by osmosis 2. This is because the solution outside the cells is less concentrated 3. The cells start to swell 4. If the solution s extremely hypotonic, that is consists of distilled or pure water the cells may swell up and eventually burst 5. The plasma membrane of red blood cells is too thin and delicate to withstand the osmotic pressure which develops within the cells 6. This causes the plasma membrane to rupture and the contents are released to surroundings 7. This condition is called haemolysis

Net movement of water into red blood cells

The effects of hypotonic solutions on plant cells 1. When plant cells are immersed in a hypotonic solution water diffuses into the large central vacoule by osmosis 2. The solution outside of the cell is less concentrated than the inside of the cell 3. The large central vacoule expands, causing the cell to swell 4. In this condition, the cell is said to be turgid and firm as a result of the net flow of water into the cell 5. The plant cell does not burst because the rigid cell wall is strong enough to resist the increasing pressure within 6. The swelling plant cell in a hypotonic creates turgor pressure within the cell. This pressure prevents the cell from taking I too much water and bursting as an animal cell would 7. Turgor pressure is very important to plant cells as it supports and maintains the shape of the cells

Animal and plant cells in a hypertonic solutions • Hypertonic solutions contain a higher concentration of solute than that of the cell • Since the concentration of water is higher within the cell, there is a net movement of water from the inside to the outside of the cell. As a result water leaves the cell. • This causes the cell to shrink or shrivel as its internal pressure

The effects of hypertonic solutions on plant cells • When plant cells are immersed in a hypertonic solution, water diffuses out of the large central vacoule by osmosis • Both the vacoule and cytoplasm lose water to the surroundings and shrink. The plasma membrane pulls away from the cell wall • This phenomenon is called plasmolysis, a shrinking of the cytoplasm due to osmosis • The plant cell becomes flaccid and less turgid • The flaccidity of plant cells leads to wilting in plants • If plasmolysis persists, death of plant cells may result • However a plasmolyed plant cell can b can become turgid again by immersing the cell in a hypotonic solution like pure water. Water is taken up by osmosis and the cells become turgid again

The effects of hypertonic solutions on animal cells • When red blood cells are immersed in a hypertonic solution, water diffuses out of the cell by osmosis • The solution outside the cell is more concentrated • The cells lose water to the external environment, shrivel and the plasma membrane crinkles up. • The red blood cells are said to have undergone crenation.

The shape of animal & plant cells after being placed in an hypertonic salt solution

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