Enzymes and Digestion

  • Created by: Riya2105
  • Created on: 02-02-20 15:49

Cell Organisation- Cells and Tissues

Cells are the basic building blocks that make up all living organisms. Specialised cells carry out particular functions. The process by which cells become specialised for a particular job is known as differentiation. These specialised cells from tissues, which form organs, which from organ systems.

A tissue is a group of similar cells that work together to carry out a particular functions. In mammals, examples of tissues include muscular tissues, which contract to move whatever it's attached to. The glandular tissue makes and secretes chemicals like enzymes and hormones. The epithelial tissue covers some parts of the body. 


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Cell Organisation- Organs and Organ Systems

An organ is a group of tisses that work together to perform a certain function. For example, the stomach is made up of muscular, epithelial and glandular tissue. The muscular tissue contracts and relaxes to move the stomach wall so that it can churn up the food. The glandular tissue produces digestive juices to digest food. The epithelial tissue covers the inside and outside of the stomach.

An organ system is a group of organs working together to perform a particular function. For example, the digestive system breaks down food and absorbs it. It is made up of the glands, the stomach, the small intestine, the liver, the large intestine and the pancreas.

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Enzymes are catalysts produced by living things. A catalyst is a substance which increases the speed of a reaction without being changed or used up in the reaction. Enzymes are all large proteins and all proteins are made up of chains of amino acids. Every enzyme has an active site with an unique shape that fits onto the substance involved in a reaction. This is because, for the enzyme to work, the substrate has to fit into its active site. If the substrate doesn't match the enzyme's acticve site, then the reaction won't be catalysed. Increasing the temperature of the reaction can cause the enzyme to become denatured. All enzymes have an optimum temperature which the enzyme works best at. Also, all enzymes have an optimum pH that they work best at and it's often neutral pH 7.

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Investigating Enzymatic Reactions

1) Put a drop of Iodine solution into every well of a spotting tile

2) Place a bunsen burner on a heat-proof mat, and tripod and gauze over the Bunsen burner. Put a beaker of water on top of the tripod and heat the water until it is 37°c.

3) Use a syringe to add 1cm^3 of amylase solution and 1cm^3 of a buffer solution with a pH of 5 to a boiling tube. Using test tube holders, put the tube into the beaker of water and wair for five minutes. 

4) Next use a different syringe to add 5cm^3 of a starch solution to the boiling tube.

5) Immediately mix the contents of the boiling tube and start a stop watch. Use continuous sampling to record how long it takes to for the amylase to break down all of the starch. When the iodine solution remains browny-orange, starch is no longer present

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Enzymes and Digestion

Carbohydrases convert carbohydrates into simple sugars. Amylase is an example of a carbohydrase. It breaks down starch into maltose and other sugars. Amylase is made in the salivary glands, the pancreas and the small intestine.

Proteases convert proteins into amino acids. Proteases are made in the stomach, the pancreas and the small intestine.

Lipases convert lipids into Glycerol and fatty acids. Lipases are made in the small intestine and the pancreas.

Bile is made in the liver and is stored in the gall bladder before it is realeased in the small intestine. The hydrochloric acid in the stomach makes the pH too acidic for enzymes to work properly in the small intestine and therefore the bile is released to neutralise the acid and make conditions alkaline. It emulsifies fats which gives it a much larger surface area, making digestion faster.

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Food tests- Sugars and Starch

You can use Iodine solution to test for starch. Make a food sample and transfer 5cm^3 of your sample to a test tube. Then add a few drops of iodine solution and gently shake the tube to mix the contents. If the sample contains starch, the colour of the solution will change from browny-orange to blue-black.

You can use the Benedict's test to test for sugars. Prepare a food sample and transfer 5cm^3 to a test tube. Then, prepare a water bath so that it is set to 75 degrees. Add some Benedict's solution to the test tube using a pipette. Place the test tube in the water bath using a test tube holder and leave it in there for 5 minutes. If the food sample contains reducing sugar, the colour of the solution in the test tube will change from blue to green, yellow or red.


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Food tests- Proteins and Lipids

You can use the biuret test to test for proteins. Prepare a sample of your food and transfer 2cm^3 of your sample to a test tube. Add 2cm^3 of biuret solution to the sample and mix the contents of the tube by gently shaking. If the food sample contains protein, the solution will change from blue to pink or purple.

You can use the sudan III test to test for lipids. Prepare a sample of the food you're testing and transfer about 5cm^3 into a test tube. Use a pipette to add 3 drops of Sudan III stain solution to the test tube and gently shake the tube. Sudan III stain solution stains lipids. If the sample contains lipids, the mixture will separate out into two layers. The top layer will be bright red. If no lipids are present, no separate red layer will form at the top of the liquid.

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