Unit 1 Cell Biology Topic 4 Enzymes From

Unit 1 – Cell Biology Topic 4 - Enzymes

From the last topic you should remember that the code held in the order of DNA bases is used to produce proteins This section focuses on a particular group of proteins called Enzymes

What you need to know. . . -What are enzymes? -Where are enzymes found? -What kind of reactions do enzymes help take place? -What biotechnology industries are enzymes used in?

Enzymes allow chemical reactions to occur within cells at low temperatures (eg 370 C) 3 cell processes this includes are Respiration, Photosynthesis and Digestion

Enzymes are molecules which speed up chemical reactions, without being changed in the process Enzymes are found in every cell and are made of proteins. Enzymes can build-up and break-down molecules.

Substrate (what the enzyme acts on) Enzyme Product (What is produced from the reaction)

Amylase An enzyme found in your saliva. It helps the breakdown of a large molecule called starch into small sugar molecules

The amylase is involved in the reaction but is not used up

Experiment Set up the following: Test tube 5 ml Starch solution + 0. 5 ml Amylase

Dimple tile Add 2 drops of the starch and amylase mixture to each dimple

Test 1 dimple each minute for the presence of starch using 1 drop of Iodine turns blue/black in the presence of starch

When all the starch has been broken down add 10 drops of Benedicts reagent to the test tube and place the tube in a waterbath at 700 C Benedicts reagent turns brick red/orange if sugar is presence

Results Iodine – over a short time the iodine no longer turns black – the amylase has broken down all the starch Benedicts – The starch and amylase mixture turns orange with the benedicts reagent – The amylase has produced the sugar Maltose

Enzymes have a shape which is complementary to the substance it is helping react. (Their shapes match) This is why enzymes are specific, their shape only matches to one substrate Eg. Amylase only breaks down starch Pepsin only breaks down protein

As well as breaking down molecules, some enzymes can help build up bigger molecules from smaller ones. We call these synthesis reactions.

Phosphorylase An enzyme found in plants which builds up starch from small glucose molecules It can be extracted from potatoes as long as all the potato starch is removed

Glucose-1 phosphate Phosphorylase Starch

Experiment Dimple tile Row 1 Row 2 Row 3 1 2 3 4

Add the following to the dimples in each row Row 1 – 2 drops potato extract + 2 drops glucose-1 -phosphate Row 2 – 2 drops potato extract + 2 drops water Row 3 – 2 drops water + 2 drops glucose 1 -phosphate

Test the first dimple in each row with Iodine (has starch been produced? ) Repeat every 5 minutes for the second, third and fourth dimple

Results Shade in the dimple if iodine turns black Row 1 Row 2 Row 3 1 2 3 4

Conclusion The starch is only produced when the substrate (Glucose-1 -phosphate) and the enzyme phosphorylase (from the potato extract) are present

Effect of temperature on Enzymes Most enzymes work best at body temperature (370 C) Above this temperature, the heat affects the enzyme and its shape is permanently changed – it is denatured

A denatured enzyme no longer fits substrate – the enzyme doesn’t work

Experiment Pineapple contains an enzyme Bromelain which breaks down proteins Tinned pineapple is heat treated to destroy microbes which might make the pineapple go off Gelatine is a protein found in jelly which makes the liquid jelly set

Set up 2 petri dishes, one labelled fresh and one labelled tinned Add enough jelly to each dish to cover the base Add a segment of fresh or tinned pineapple to the appropriate labelled dish

Leave to set overnight

Results Fresh pineapple contains the enzyme which breaks down the gelatine and the jelly does not set Tinned pineapple allows the jelly to set as the enzyme breaking down the gelatine is destroyed

Enzymes in industry Enzymes can be added to washing powders to help break down biological stains such as grass, blood, food stains etc on clothes These are Biological detergents They work best at low temperatures, around 30 -400 C

Experiment Photo film has a plastic base layer and a light sensitive layer held on by a protein glue

Setup as follows: Tube A Tube B 20 ml Bio detergent 20 ml Non. Bio detergent Place both tubes into warm water for 30 minutes

Results The Biological detergent contained enzymes which broke down the protein glue and separated the light sensitive layer from the plastic

Cheese making also uses an enzyme called Rennet It causes milk to clot, giving solid curds to make cheese and liquid whey. It is obtained from the stomachs of calves or from genetically engineered bacteria

Check test questions 1 – Name the biological substance which speeds up chemical reactions in cells but isn’t use up in the process

2 – What term refers to the fact that enzymes only act on one substrate eg. Enzymes are _____ 3 – What enzyme breaks down starch molecules into smaller sugars?

4 – What physical property of an enzyme means that it can only work on one substrate? 5 – Why do enzymes in washing detergents help to save money? (Problem solving)

Check test questions 1 – Name the biological substance which speeds up chemical reactions in cells but isn’t use up in the process Enzymes

2 – What term refers to the fact that enzymes only act on one substrate eg. Enzymes are _____ Specific 3 – What enzyme breaks down starch molecules into smaller sugars? Amylase

4 – What physical property of an enzyme means that it can only work on one substrate? Their shape 5 – Why do enzymes in washing detergents help to save money? (Problem solving) They work at low temperatures – don’t have to use energy to heat water up as much