Osmosis (T1)

Question 0

Define osmosis…

Answer 0

Osmosis is the movement of water from a less concentrated solution (more dilute) to a more concentrated solution (less dilute)

Question 1

Water moves across all membranes by osmosis. What two things are crucial for osmosis to take place?

Answer 1

• two solutions with different concentrations

- a partially permeable membrane to separate them

Question 2

The level of water on the more concentrated side ……. while the level of water on the less concentrated side …….

Answer 2

The level of water on the more concentrated side rises while the level of water on the less concentrated side falls

Question 3

Osmosis is crucial to plants. Why?

Answer 3

• it is the mechanism by which water and nutrients from the roots moves through their cells
• as the plant cells take in more and more water they become turgid and firm and are able to support and hold the plant upright

Question 4

What is ‘tugor’ and why is it important?

Answer 4

• when plant cells are turgid
• it’s very import to plants as the pressure inside the cells pushes the neighbouring cells against each other
• this provides support to the non-woody parts of the plants and helps hold the stems upright to the leaves can carry out photosynthesis
• it is also important in the functioning of stomata; if a plant loses too much water from its cells the cells become flaccid and the plants wilt. This is a protective actions which cuts down water loss by reducing the exposed surface area of the leaves and closing stomata

Question 5

If a plant loses too much water from its cells what happens and why?

Answer 5

The cells become flaccid and the plants wilt. This is a protective action which cuts down water loss by reducing the exposed surface area of the leaves and closing stomata.

Question 6

What experiments can be carried out to investigate osmosis outside the body of an organism?

Answer 6

• construct an artificially permeable membrane using visking tubing
• fill the visking tube with concentrated sucrose solution, attaching it to a capillary tube and placing the visking tube in a beaker of water
• the level of water in the capillary tube rises as water moves from the beaker to the inside of the visking tube

OR..

• place a drop of sucrose solution on one microscope slide and a drop of tap water on another
• transfer two small squares of inner epidermis from the outer layer of an onion onto each one
• out a drop of the correct solution on top of each an then cover slips
• any excess liquid is blotted up with filter paper
• observe through a microscope for several minutes
• the specimen in water will show turgid cells
• the other will gradually plasmolyse (shrink away from the cell wall due to water loss)
• if the cell is placed in a solution with the same concentration as inside the cell, it will become flaccid