Diffusion & Osmosis Experiment

Aim To stimulate osmosis and diffusion within numerous cells contained in varied environments. Apparatus

• 6 beakers • Onion • Iodine Solution • Starch Solution • Concentrated Sugar Solution • Water • Concentrated Salt Solution • Thistle Funnel • Retort Stand • Clamp • Boss Head • Paper Towel • Digital Scales • Dialysis Tubing • Rubber Bands

Method 1. Tie a rubber band very firmly on the end of dialysis tubing and fill it

with concentrated sugar solution to about 2/3 full and then tie the end firmly.

2. Weigh the tubing on a set of digital scales ensuring they are dry (paper towel).

3. Submerge this tubing into approximately 150mL water in a beaker and label the beaker.

4. Repeat steps 1-3 with… • A water tubing in a concentrated sugar solution • Starch solution tubing in an iodine solution • Onion in concentrated salt solution • Onion in water 5. Once this is completed, set up a retort stand with a clamp and boss head. 6. Repeat step 1 for concentrated sugar solution tubing in water but this

time tie it on the end of a thistle funnel firmly. 7. Clamp the thistle funnel and submerge it in 150 mL of water in a beaker. 8. Mark the level of water on the thistle funnel. 9. Observe the changes in the cell and out. 10. Leave them for a day or two and take them out observe and weigh them

being sure to dry them with a paper towel.

Results Start (g) Finish (g)

Concentrated Sugar Solution in Water

20.96 21.31

Water in Concentrated Sugar Solution

20.54 20.41

Starch in Iodine Solution

19.66 20.0

• Onion in concentrated salt solution – it was weak and floppy and losing

water. It had been weakened due to the salt but the cell wall allowed for strong structure.

• Onion in water – it was strong and firm. The outer cores were incredibly tough due to the scarcity to salt and therefore the cell wall could easily keep its shape.

Conclusion Osmosis does occur in all of the environments created. Diffusion is the movement of particles (fluid) from a high concentration to a low concentration, creating a state of equilibrium, moving through a semi-permeable membrane (cell membrane) Semipermeable membranes are membranes that allow some substances through and others not. The substances travel through small pores on the membrane known as stomata. It is found on cell membranes because the cell membranes allows some substances such as water and nutrients through and other not such as large items to go through the pores such as starch. This allowed for many chemical reactions including photosynthesis, as it requires water, carbon dioxide and sunlight that all need to be required to travel through and without these the plant would surely die. Osmosis is diffusion of water and other liquids through a semi permeable membrane while diffusion is any substance. It is essential for plants lives, as they require osmosis to collect water for food and fish require osmosis because as they live in a salt-water environment, like the onion in salt, they will lose water and eventually die or be very weak. To survive and maintain water-balance they require osmosis. For sugar starch to enter and leave cells, they use a process called active transport. Active transport is when cells use up energy from food to move sugars and amino acids inside and to remove wastes such as urea. In this way cells can control exactly which chemicals enter and leave a cell.

Starch Sucrose and Glucose

Starch: Starch is a carbohydrate consisting of a large number if Glucose units joined by glycoside bonds (bond That joins carbohydrate). This polysaccharide (a long carbohydrate molecules joined together by glycoside bonds) is produced by all green plants as and energy store. It is the most common carbohydrate in the human diet and is contained in large amount in foods such as potatoes, wheat, rice and cassava.

Glucose:

Glucose (C6 H12 O6) is a simple monosaccharide (simplest form of sugar).

Glucose is the result of photosynthesis in plants and fuels the plants with

energy. The name "glucose" comes from the Greek word glukus (γλυκύς), meaning

"sweet". The suffix "-ose" denotes a sugar.

Sucrose: Sucrose is the organic compound commonly known as table sugar and sometimes-called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its nutritional role.