Part 7: Effect Of pH On Enzymes Flashcards
What colour does universal indicator become in the presence of a strong acid?
Red
What colour does universal indicator become in the presence of a weak acid?
Yellow
What colour does universal indicator become in the presence of a neutral substance?
Green
What colour does universal indicator become in the presence of a weak alkali?
Blue
What colour does universal indicator become in the presence of a strong alkali?
Purple
How does the pH falling below the optimum affect enzymes?
If the pH falls below the optimum there are more H+ ions. This affects the amino acids that make up the enzyme and changes the shape of the active site. If it is too acidic and the pH is very low, the enzyme becomes denatured.
How does the pH rising above the optimum affect enzymes?
If the pH rises above the optimum there are fewer H+ ions. This also affects the amino acids that make up the enzyme and change the shape of the active site. If it is too alkaline and the pH is very high, the enzyme becomes denatured.
Why is it important to add the pH buffer to the amylase before adding the starch?
The reaction will start as soon as the enzyme meets the starch. If the buffer is not already in, you will be changing the pH after the reaction has started and the results will not be valid.
Why is it important to incubate the amylase/buffer and starch test tubes separately in the water bath before mixing them?
The reaction will start as soon as the enzyme meets the start- so if they are mixed before reaching the correct temperature, it will change after the reaction has started so the results will be invalid.
Explain why Pepsin and trypsin have different optimum pH levels, with reference to the parts of the digestive system where they are found.
Pepsin’s optimum pH is about 2, so we know that it must be found somewhere acidic (the stomach)
Trypsin’s optimum pH is just above 7, so we know that it must be stored somewhere alkaline (the small intestine).
If jelly contains gelatine (a protein), what type of enzyme must fresh pineapple contain?
Protease
Explain why the jelly with fresh pineapple doesn’t set.
The enzyme in the pineapple (protease) will break down the protein.
Tinned pineapple is heat treated. What has this done to the enzymes? Predict whether jelly with tinned pineapple would set or not.
The enzymes will denature, so the jelly will set.
Explain the effect of hydrochloric acid on the enzymes in a pineapple.
The hydrochloric acid helps the enzymes break down the proteins into amino acids.
Explain the effect of sodium hydroxide on the enzymes in the pineapple.
The sodium hydroxide stops the enzymes from working as protease works better in acidic conditions. Therefore, the jelly will set.
