Enzymes Flashcards
How do enzymes work?
Enzymes are biological catalysts that speed up reactions. The substrate fits into the enzyme’s active site like a “lock and key,” where the reaction occurs.
What is meant by enzyme specificity?
Each enzyme has a specific active site shape that only fits one type of substrate.
How can enzymes be denatured?
High temperature or extreme pH can change the shape of the enzyme’s active site, making it no longer fit the substrate.
What factors affect enzyme activity?
Temperature, pH, and substrate concentration.
How does temperature affect enzyme activity?
Enzyme activity increases with temperature up to the optimum. Beyond that, enzymes denature and activity drops.
How does pH affect enzyme activity?
Each enzyme has an optimum pH. Too high or too low can denature the enzyme’s active site
How does substrate concentration affect enzyme activity?
Higher substrate concentration increases reaction rate until all active sites are full (saturation point).
What is the core practical to investigate enzyme activity and pH?
- Set up a water bath at 37°C (body temperature is the optimum for most enzymes).
- Add 1 cm³ of amylase to a test tube.
- Add 1 cm³ of buffer solution (to control the pH).
- Place the test tube in the water bath for 5 minutes to allow the enzyme to reach the right temperature.
- Add 1 cm³ of starch solution to the test tube and start the stopwatch.
- Every 10 seconds, use a pipette to take a drop of the reaction mixture and place it on a spotting tile with iodine.
- Observe the colour change , Iodine turns blue-black if starch is still present.It stays orange-brown when starch is fully broken down.
- Record the time taken for iodine to stop changing colour – this is when the starch has been fully digested.
- Repeat with different pH buffer solutions to compare how pH affects enzyme activity.
Why is it important to control variables in enzyme experiments?
To ensure the results are valid and only the independent variable is affecting the outcome.
Why are repeats important in enzyme experiments?
They help identify anomalies and increase reliability of results.
How do you plot a graph of an enzyme reaction?
With independent on x axis and dependant on the y axis.e.g temp on the x axis and enzyme activity on the y
How do you calculate the rate of an enzyme reaction?
Rate = 1 ÷ time (for time-based reactions), or measure product formed per second.
What role do enzymes play in digestion?
They break down large molecules into smaller soluble molecules like:
• Carbohydrases → sugars
• Proteases → amino acids
• Lipases → fatty acids and glycerol
What is the core practical for identifying food molecules using reagents?
•Starch → Iodine turns blue-black
•Reducing sugars → Benedict’s turns brick-red when heated
•Proteins → Biuret turns purpl
•Fats → Ethanol gives a cloudy layer
What is the role of amylase?
Breaks starch into sugars.
What is the role of protease?
Breaks proteins into amino acids.
What is the role of lipase?
Breaks fats into fatty acids and glycerol.
What does bile do?
Neutralises stomach acid and emulsifies fats.
What does iodine solution test for and what is the result?
- It tests for starch
- The colour changes from orange-brown to blue-black if starch is present.
What does Benedict’s solution test for and what is the result?
- It tests for reducing sugars like glucose
- The colour changes from blue to green, yellow, orange, or brick-red when heated, depending on the amount of sugar present.
What does Biuret solution test for and what is the result?
- It tests for protein
- The colour changes from blue to purple if protein is present.
What does the ethanol test check for and what is the result?
- It tests for fats and lipids
- A cloudy white emulsion forms if fat is present.
What does Universal Indicator test for and what are the colours?
- It tests the pH level of a solution
- It turns red in strong acid (pH 1), green in neutral (pH 7), and purple in strong alkali (pH 14).
What is phenolphthalein used for and what are the colour changes?
- It is used to monitor pH changes, especially in lipase enzyme practicals
- It is pink in alkaline solutions and turns colourless when the solution becomes acidic.
