Enzymes and digestion Flashcards
What is an enzyme?
A biological catalyst that speeds up the rate of reaction without being used up.
What is a substrate?
The substance on which an enzyme acts and that is changed in the reaction.
What happens to a substrate during a reaction?
It is either broken down or built up, producing a product.
What is an enzyme-substrate complex?
The binding of a substrate to the active site of the enzyme.
How do enzymes reduce activation energy?
By holding the substrate in the correct position.
What are metabolic reactions?
Chemical reactions in the body that can be sped up by enzymes.
What are the main properties of enzymes?
- Made of proteins (amino acids)
- Each has an active site
- Specific to one type of substrate
- Unaffected by the reaction they catalyse
- Work best in specific environments (temp and pH)
- Can be denatured by excessive conditions.
What is the active site of an enzyme?
A depression used to hold a substrate in place.
What does the lock and key theory describe?
The specificity of enzymes, where the enzyme and substrate are complementary.
What does it mean for an enzyme to be denatured?
The shape of the active site changes so that it is no longer complementary to the substrate.
How does pH affect enzyme activity?
Extreme pH levels interfere with bonds holding the enzyme together, changing the shape of the active site and potentially denaturing the enzyme.
What is the optimum pH for most enzymes?
Normally pH 7.
How does temperature affect enzyme activity at low temperatures?
Substrate particles move slowly, reducing the chance of collision with the enzyme’s active site.
What happens to enzyme activity as temperature increases?
Substrates gain kinetic energy, moving more and increasing the likelihood of successful collisions, but excessive heat can cause denaturation.
What enzyme is found in celery that breaks down hydrogen peroxide?
Catalase
Catalase is an enzyme that catalyzes the decomposition of hydrogen peroxide into water and oxygen.
What happens when washing up liquid is added to the measuring cylinder containing catalase and hydrogen peroxide?
Oxygen makes bubbles and becomes foam
This foam allows for the measurement of the products produced during the reaction.
How can the pH be changed in an experiment involving catalase?
By adding different pH buffer solutions
This allows for the investigation of the effect of changing pH on enzyme activity.
What is a more reliable method to collect gas produced in the catalase reaction?
Using a gas cylinder
This method is more reliable than measuring the height of the foam.
What does amylase break down starch into?
Maltose
Amylase is an enzyme that catalyzes the hydrolysis of starch into maltose.
What color indicates the presence of starch when iodine is added?
Bluey black
If starch is broken down by amylase, the iodine will remain browny orange.
What safety procedures should be followed when conducting experiments with iodine?
Wear safety goggles and wash skin with water and soap if contact occurs
Iodine is an irritant, and safety precautions help prevent injuries and reactions.
What happens to the rate of reaction as enzyme concentration increases?
The rate of reaction increases
More enzyme molecules increase the chances of successful collisions with substrates.
What limits the rate of reaction when substrate concentration increases?
Plateaus occur when there are not enough substrate particles
Eventually, all enzymes may reach full capacity, preventing further increases in reaction rate.
What are the main functions of the mouth in digestion?
Chewing, mixing with saliva, and amylase action
Teeth chew the food, the tongue helps mix it, and amylase begins starch digestion.
