Biological Molecules and Enzymes Flashcards
What is the structure of carbohydrates, and which chemical elements do they contain?
Complex carbohydrates (e.g. starch / glycogen) are made up of many smaller units (e.g. glucose / maltose molecules). All carbohydrates contain carbon, hydrogen and oxygen atoms.
What is the structure of proteins, and which chemical elements do they contain?
Proteins are made up of long amino acid chains. All proteins contain carbon, nitrogen, hydrogen and oxygen atoms.
What is the structure of lipids, and which chemical elements do they contain?
Lipids are made up of fatty acids and glycerol. All lipids contain carbon, hydrogen and oxygen atoms.
What are enzymes?
An enzyme is a biological catalyst that can increase the speed of a chemical reaction.
How do enzymes work, according to the lock and key hypothesis?
Enzymes are folded into complex shapes that allow smaller molecules to fit into them. According to the lock and key hypothesis, the shape of an enzyme’s active site matches the shape of its substrate molecules. This means that each enzyme is highly specific, and can usually only catalyse one type of reaction
What happens to an enzyme when it denatures?
When an enzyme is denatured, the shape of its active site may change - meaning that the substrate will no longer be able to fit into it.
What two conditions can cause an enzyme to denature?
- Extremely high or low pH conditions.
2. Extremely high or low temperatures.
How is enzyme activity affected by changes in temperature?
- Place a drop of iodine solution into each of the wells of a dimple tile.
- Place 5 test tubes in a rack, and add 5cm^3 of starch solution to each.
- Place another 5 test tubes in the rack, and add 2cm^3 of amylase solution to each.
- Set up a water bath at 20 degrees.
- Place a test tube of starch solution and a test tube of amylase solution in the water bath.
- After five minutes, pour the amylase into the starch. Using a glass rod, add a drop of the mixture to the first well of iodine solution in the dimple tile (it should turn blue-black).
- Start a stopwatch, and test samples of the starch-amylase mixture every minute until the iodine remains yellow.
- Repeat all above stages for multiple temperatures, then record results.
Experiment explained
Amylase is an enzyme that reacts with starch to produce maltose. Iodine changes from yellow to a blue-black colour in the presence of starch. By continously exposing samples of the starch-amylase mixture to the iodine solution, we can tell when all of the starch has been ‘replaced’ by maltose, and how quickly the enzyme has done this. By comparing the reaction speeds at different temperatures, we can discover the optimum temperature of amylase.
How is enzyme activity affected by changes in pH?
- Place a drop of iodine solution into each of the wells of a dimple tile.
- Place 5 test tubes in a rack, and add 2cm^3 of starch solution to each.
- Place another 5 test tubes in the rack, and add 2cm^3 of amylase solution to each.
- Set up a water bath at 35 degrees.
- Mix a test tube of amylase solution with 1cm^3 of a pH buffer in the water bath.
- After one minute, pour the starch solution into this mixture. Using a glass rod, add a drop of the mixture to the first well of iodine solution in the dimple tile (it should turn blue-black).
- Start a stopwatch, and test samples of the starch-amylase mixture every minute until the iodine remains yellow.
- Repeat all above stages for multiple pH levels, then record results.
Experiment explained
Amylase is an enzyme that reacts with starch to produce maltose. Iodine changes from yellow to a blue-black colour in the presence of starch. By continously exposing samples of the starch-amylase mixture to the iodine solution, we can tell when all of the starch has been ‘replaced’ by maltose, and how quickly the enzyme has done this. By comparing the reaction speeds at different pH levels, we can discover the optimum pH of amylase.
Formula for the rate of reaction
Rate of reaction =
(1 / Time taken) x 1000
