copy and answer the following eq into your science journal
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Biology February 24, 2014
Copy and answer the following EQ into your science journal.
EQ: How does the structure of the cell membrane aid in its functions of
equilibrium?
It helps cells to maintain homeostasis by controlling what is allowed in and out of the
cell.
Word of the DaySemipermeable
A barrier that permits the passage of some substances but not others.
Here is what is going on this week
• Your workbook, Ch 7 pp 71-84 is due today!
• Prefix/Suffix quiz part 2 on Friday
• Complete the lab in your workbook pp 35-40.
Tonicity
Tonicity is a measure of the
osmotic pressure gradient of two
solutions separated by a
semipermeable membrane
Diffusion is the movement of molecules from a high concentration to a low concentration.
Examples-• Spraying air freshener in a room• The odour of food cooking diffuses throughout
the kitchen and spreads into the next room.
• Osmosis- It is the diffusion of water through a semipermeable membrane from a more dilute solution to a more concentrated solution.
Examples:• Absorption of water by plant roots. • Reabsorption of water by the nephron in
kidneys • Absorption of water by the alimentary canal
— stomach, small intestine and the colon.
Equilibrium• To regulate internal conditions in order to
stay healthy and functioning, regardless of the outside changing conditions.
There are 3 types of situations in which this could vary:
Hypotonic Isotonic Hypertonic
There are 3 types of situations in which this could vary:
1. Hypertonic• In HYPERTONIC solutions, water moves
out of the cell.• Hypertonicity causes cells to shrink.• Plants cells lose water and start to wilt.• The process of water moving out of a cell
is called plasmolysis.• More H2O moves out of the cell.
2. Isotonic• Water DOES or DOES NOT stop moving.• Cells reach a point called Dynamic
Equilibrium in isotonic solutions.• Equal amounts of water are found inside
and outside of the cell.• H2O moves in and out of the cell
equally.
3. Hypotonic• In HYPOTONIC solutions, water moves
into a cell.• Animal cells increase in size and burst or
lyse in these solutions• Bursting of cells is called cytolysis.• Plant cells need this tonicity to be at
homeostasis.• Turgor pressure results from water inside
a plant cell pushing the cell membrane out against the plant’s cell wall.
• More H2O moves into of the cell.
Cells in Solution Models• Each cell has a 10%, or 6% NaCl (salt)
solution in an ENVIRONMENT with either a 3%, 10% or15% salt solution.
• COLOR the cell yellow and the environment light blue.
• Using RED, draw arrows showing the direction of movement of water into or out of the cell. 10%
NaCl
15% NaCl
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