D2.3

Question 1

Osmosis in Cells without Cell Walls

Crenation?

Answer 1

• Shrinking of the ANIMAL cell, as animals lack a cell wall and are thus able to shrink dramamtically/become visably crinkled.

Question 2

Osmosis in Cells without Cell Walls

Contractile Vacuole?

Answer 2

• An adaption in unicellular aquatic organisms to prevent them from swelling and bursting
• It collects water from cytoplasm/interior and empities it back to environment
• Allows them to survive in hypotonic environments

Question 3

Osmosis in Cells without Cell Walls

Describe HyPERtonic solutions.

Tonicity always refers to TWO environments

Answer 3

• The environment that has a HIGHER solute conc. is hypertonic.
• Solution around cell contains more solutes than cell itself.

Question 4

Osmosis in Cells without Cell Walls

Describe HyPOtonic solutions.

Answer 4

• The environment that has a LOWER solute conc. is hypotonic.
• Environments with low solute conc. that are less than the natural solute conc. of the cell.

Question 5

Osmosis in Cells without Cell Walls

What is the structure and function of aquaporins?

Answer 5

• Aquaporins are protein channels that allow for faster movement of polar water through the amphipathic cell membrane.
• Without them, H2O would move slowly through non-polar tails.
• Made of 6 helical protein chains.

Question 6

What is the consequence of Animal cells being sumberged in a hypertonic solution?

Answer 6

• Water will leave the cell to try to reach an equilibrium of solute conc.
• Causes cell to have a lower volume of water and shrink in cell/shrivel; CRENATION.

Question 7

Osmosis in Cells without Cell Walls

What is the consequence of Animal cells being sumberged in a hypotonic solution?

Answer 7

• Water will move into the cell to achieve homeostasis/equilibrium between solute conc. of the cell & environment.
• Cytoplasm will fill with water - swell, and because of no cell wall, could lose structure and burst; LYSIS/LYSE.

Question 8

Osmosis in Cells without Cell Walls

Explain contractile vacuoles in Paramecium

Single celled freshwater protist

Answer 8

• Paramecium’s environment is hypotonic, thus it has a contractile vacoule to assist.
• When water enters the cell its moves into the contractile vacuole
• When vacoule is full, it merges with cell membrane to release water by exocytosis

Question 9

Osmosis in Cells WITH cell walls

What is Hydrostatic pressure?

Answer 9

• The pressure that a fluid exerts in a confined space, against the boundary of the space.
• Occurs in PLANT CELLS due to the presence of CELL WALLS which create a firm boundary.

Question 10

Osmosis in Cells WITH cell walls

What is Tugor Pressure?

Answer 10

• The specific hydrostatis pressure inside plant cells
• The result of water entering the cell, filling the vacuole, and it swlling so that is pushes the cytoplasm against the wall.
• This pressure in the vacuole causes it to strain on the wall –> tugor pressure

Question 11

Osmosis in Cells WITH cell walls

What is Plasmolysis?

Answer 11

• In hypertonic solutions water LEAVES the cytoplasm of cell causing the cell membrane to shrink in.
• The cell wall stays in place, so the cell membrane detaches from the wall.

Question 12

Osmosis in Cells WITH cell walls

What is the cause of tugor pressure in plant cells?

Answer 12

• Occurs in hypotonic envrionemnts when the low solute conc. in the environment causes water to enter the plant cells/vacuoles & swells, putting pressure of the rigid cell wall.

Question 13

Osmosis in Cells WITH cell walls

What are the consequences to plant cells in hypertonic solutions?

Answer 13

• Cells will lose water to equalise the high solute environment which has a lower water potential.
• The turgor pressure in a hydrated plant gives it a higher water potential so water moves out of plant cells
• This causes the cytoplasm to shrink in/PLASMOLYZED/ the membrane detaches but the wall stays in place
• Plant wilts

Question 14

Osmosis in Cells WITH cell walls

What are the consequences to plant cells in hypotonic solutions?

Answer 14

• Plant cells gain water in the vacoule and it swells, building turgor pressure and therefore low water potential.
• There should be higher water potential, casuing water to move in
• The cell is TURGID, but does NOT burst dye to the presence of a cell wall.
• As plants become turgid, water potential increases due to storage in vacuoles – eventually becomes same as envrionment.

Question 15

Water Potential

Define Water Potential

Answer 15

• The potential energy of water per unit volume - AKA: the potential for water to move.
• Higher water potential –> more likely water to move/diffuse to a new environment.
• Pure water has a water potential of 0

Question 16

Water Potential

What is solute potential?

Both plant and animal cells affected

Answer 16

• An absolute quantifiable measure of the amount of solute.
• The amount of solute dissolved impacts free energy of water (ability to flow/water potential).

Question 17

Water Potential

What is Pressure Potential

Only for plant cells

Answer 17

• The numerical representaiton of the turgor pressure inside the cell
• When pressure is exerted on water, its more likely to move, so pressure increases water potential

Question 18

Water Potential

What is the equation for Water Potential?

Answer 18

• Considers how solutes reduce water’s freedom to move while turgor pressure increases its liklihood to move.
• Equation: Sum of solute potential (negative value) + pressure potential (positive value).

Note it animal cells & solutions, there’s no pressure potential so water potential=solute potential

Question 19

Water Potential

Flow of water/predicting water movement?

Answer 19

• Water moves from hypotonic to hypertonic
• Water always moves from an area of higher water potential to an area of lower water potential

Question 20

Water Potential

Explain water potential from roots to leaves in plants.

Answer 20

• Water potential decreases moving from the roots to the leaves.
• The high water potential in soil means water moves into root cells.
• Then the lower water potential further up the plant aids in pulling water up against gravity.

Note, the lower water potential moving up is in part due to transpiration