Diffusion + Osmosis + AT

Question 1

Why did the student blot the potato cylinders dry when he removed them from the sugar solutions?

Answer 1

-remove any excess liquid
- water will increase the weight of potatoes, decreasing accuracy

Question 2

how is active transport and diffusion used in the process of absorbing glucose into the bloodstream

Answer 2

If there is a lot of glucose in the villi, it will use diffusion to absorb into the bloodstream (moving from an area of high concentration to an area of low concentration). If there is more glucose into the bloodstream, the use of active transport (moving from an area of low concentration to an area of higher concentration) will move the remaining glucose in the villi into the bloodstream.

Question 3

What is diffusion?

Answer 3

Diffusion is when particles of a gas or fluid spread out, resulting in a net movement from an area of high concentration to low concentration.

Question 4

What is osmosis?

Answer 4

Osmosis is diffusion of water particles from a dilute (high conc. of water) to a concentrated solution through a partially permeable membrane.

Question 5

What is active transport?

Answer 5

Active transport is the movement of substances from an area of LOWER concentration to an area of HIGHER concentration

It requires energy from respiration (not passive)

It works against the concentration gradient

Question 6

Describe how diffusion is used in humans

Answer 6

• Diffusion is used in humans during respiration. The alveoli has thin walls and a good blood supply. It exchanges oxygen into the bloodstream for carbon dioxide.

Question 7

State 3 factors that affect the rate of diffusion

Answer 7

• Temperature
• Surface Area
• Concentration gradient

Question 8

What does hypertonic and hypotonic mean?

Answer 8

Hypertonic means the outside solution has a higher concentration of solute than inside the cell (meaning the cells will move out)

Hypotonic means the outside solution has a lower concentration of solute than inside the cell (meaning the cells will move in)

Question 9

How is the respiratory system adapted to maximise gas exchange

Answer 9

Large amount of aveoli for increasing surface area

Thin walls to reduce diffusion distance

Good blood supply to maintain concentration gradient

Question 10

What happens to the cell when it is placed in a hypertonic solution?

What happens to the cell when it is placed in a hypotonic solution?

Answer 10

Flaccid - it shrinks/shrivels

Turgid - it swells and can potentially burst as water enters

Question 11

How do you do the osmosis potato practical?

Answer 11

1. Use a cork borer to cut five potato cylinders of equal diameter.
2. Use a scalpel to ensure they are the same length.
3. Measure and record in a table the mass of each cylinder.
4. Measure 10cm3 of 2.0M salt solution and pour into a boiling tube.
5. Repeat Step 4 with different amounts of salt solutions and pour them into different boiling tubes, ensuring they are labelled with the different concentrations.
6. Add equal amounts of distilled water into each boiling tube.
7. Add one potato cylinder into each tube.
8. Record initial masses of potato cylinders into a table
9. Leave them for 15 minutes
10. Slowly take the cylinders out of the boiling tube and blot dry with a paper towel.
11. Measure and record into the table the new masses of the cylinders
12. Calculate change in mass and percentage change in mass of each cylinder
13. Record this onto a graph.