Exchange Processes

Question 1

What is the definition of diffusion?

Answer 1

The net movement of particles from an area of high concentration to an area of lower concentration

Question 2

What is the definition of osmosis?

Answer 2

The net movement of water particles across a semi permeable membrane from an area of high water potential to low water potential

Question 3

What is the definition of active transport?

Answer 3

The net movement of particles across a semi permeable membrane from an area of low concentration to high concentration against the concentration gradient

Question 4

Why does active transport require a carrier protein?

Answer 4

Because is it is not passive and it goes against a concentration gradient so needs more energy

Question 5

What would happen to a potato chip placed into a high sugar solution?

Answer 5

The water in the potato would move out through active transport and the potato would shrink and loose mass

Question 6

What is a semi permeable membrane?

Answer 6

A membrane with small holes that allows some particles to pass through but not others that are too large

Question 7

What is an example of where osmosis is used in nature?

Answer 7

How water keeps plant cells turgid

Question 8

What is an example of where diffusion is used in nature?

Answer 8

How oxygen leaves a leaf

Question 9

What is an example of where active transport is used in nature?

Answer 9

How minerals get into root hair cells

Question 10

What is the method for the osmosis practical?

Answer 10

1. Label 6 boiling tubes 0, 0.2, 0.4, 0.6, 0.8 and 1.0 mol
   dm-3
2. Place 20cm3 of each solution into the correct boiling
   tube.
3. Using a cork borer cut 6 cylinders from the plant material. Make sure you
   remove any peel.
4. Use a scalpel, ruler and tile to cut all of the cylinders to the same length
   (approximately 2cm long). Work quickly to prevent the tissue drying out.
5. Roll the cylinders on a paper towel to remove any excess moisture. Do not
   squeeze the cylinders.
6. Measure the mass of each chip and record these initial masses in a suitable
   table.
7. Place one cylinder of known mass into each of the salt solutions. You could
   record the initial mass on the boiling tube to ensure you do not get them mixed
   up.
8. When told to remove the cylinders from the salt solution and blot dry in
   the same way as you did in stage 5.
9. Measure the mass of each cylinder and record these final masses in your
   table.
10. Calculate the change in mass and then calculate the percentage change in
    mass

Question 11

Why are cells so small?

Answer 11

The smaller the cell the easier it is to get oxygen to the cytoplasm by diffusion

Question 12

How are alveoli adapted for gas exchange?

Answer 12

They have walls which are only one cell thick
They have lots of capillaries
They give lungs a really big surface area