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First Five

First Five. Silently in your notebook answer the following: The drawing shows the outline of a human cell. Copy the drawing and make two further drawings to show how the cell would appear if it were to be immersed for a few minutes in a solution with:

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First Five

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  1. First Five • Silently in your notebook answer the following: • The drawing shows the outline of a human cell. Copy the drawing and make two further drawings to show how the cell would appear if it were to be immersed for a few minutes in a solution with: • a lower water potential than its own cytoplasm • a higher water potential than its own cytoplasm • Cereal plants were growing in a field. The field was then flooded with sea water. Suggest why the sea water causes plants to die.

  2. Announcements • Quiz: Thursday (M) and Friday (G) on Cell Structure, Specialized Cells, Magnification, Diffusion and Osmosis • Unit Exam: 28th and 29th • Notebook Turn in: 28th and 29th • Late work turn in: 25th

  3. Additional Notes • The cell sap and cytoplasm function as fairly concentrated solutions. • A plant cell in this condition is said to be turgid • If all the cells in the plant are turgid, the plant will be firm and upright and the leaves would be expanded

  4. Plant cells 18 cell wall vacuole cytoplasm and cell membrane The cell absorbs water by osmosis .... ....but the cell wall stops the cell expanding any more

  5. Fresh water fish 14 Trout In fresh water fish, the blood is more concentrated than the surrounding water As a result the fish takes in water by osmosis Not so much through the skin, which is thick, but through the gills which have a very thin membrane

  6. 14 Perch The fish gets rid of the excess water by means of its kidneys kidneys expel excess water ... blood carries water to kidneys gills absorb water by osmosis ...in the form of dilute urine heart

  7. Sea water fish 15 Herring Sea water is a more concentrated solution than the fish’s blood. What will be the osmotic effect ? A sea water fish will lose water by osmosis through its gills. The fish drinks sea water and the gills expel the excess salt from the blood, so keeping its concentration constant

  8. Question 19 What did you notice about the colour of the cell sap in the two cells? Can you suggest an explanation for this?

  9. Osmosis between cells 20 If the concentration of the cell sap is greater in one cell than in its neighbour, water will pass by osmosis from the less concentrated to the more concentrated. cell sap more concentrated cell sap less concentrated

  10. Limp and turgid tissue 21 These cells are short of water; the tissue is limp and the plant is wilting The cells have taken up water by osmosis; the cells are turgid and the tissue is firm

  11. 23 In the growing regions of a plant, the cell walls are not inextensible but are still ‘plastic’ When the vacuole takes in water by osmosis it expands, pushing out on the ‘plastic’ cell wall and increasing the size of the cell. Cell division at a growing point increases the number of cells but cell expansion causes the increase in size. Cell division followed by cell expansion causes growth

  12. Cell extension 3 4 2 1 1 The cell has just divided 2 Vacuoles start to form in one cell 3 The vacuoles absorb water by osmosis and start to extend the cell 4 The vacuoles begin to join up and continue to absorb water and extend the cell 24

  13. Growth in a shoot tip 25 cell division continues these cells will divide vacuoles forming cells absorb water by osmosis and expand

  14. 26 Question 1 In osmosis, water will diffuse through a membrane (a) From water to a concentrated solution (b) From a concentrated solution to a dilute solution (c) From a dilute solution to a concentrated solution (d) From a dilute solution to a more dilute solution

  15. 27 Question 2 Which statements are correct ? (a) The plant cell wall is permeable to water (b) The plant cell wall is selectively permeable (c) The cell membrane is selectively permeable (d) The vacuole contains a solution of salts and sugars

  16. 28 Question 3 Cell sap concentrated solution a c dilute solution b more dilute solution Plant cells Water will tend to move by osmosis (a) from b to a and c, and from c to a (b) from c to a and b, and from a to b (c) From a to b and c, and from c to b (d) From c to b and a, and from b to c

  17. 29 Question 4 Which statements are correct ? (a) A fresh water fish tends to absorb water by osmosis (b) A sea water fish tends to absorb water by osmosis (c) A fresh water fish tends to lose water to its surroundings (d) A sea water fish tends to lose water to its surroundings

  18. 30 Answer The colour intensity in the vacuole of the left hand cell is greater than that in the right This is because the uptake of water by osmosis has diluted the cell sap in the right hand cell

  19. 31 Correct

  20. 32 Incorrect

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