Chapter 5: Enzymes Flashcards
What are enzymes?
Enzymes are protein molecules which act as biological catalysts.
Define catalysts.
A substance that speeds up (or increases the rate of) reactions, without being changed or used up by the reaction.
Why are enzymes important?
They allow reactions to occur which would take too long to occur on their own.
This is why they are essential to ALL living things
List some processes where enzymes are essential.
Digestion (metabolism)
Respiration
Photosynthesis
Muscle and nerve function
DNA replication
Protein synthesis
Cell-Cell communication
How do enzymes control photosynthesis?
They collide with reactants like water and bind to them.
When it is cold, the collisions reduce and photosynthesis slows down
When it is too hot, the enzymes are denatured.
What do enzymes act on?
Molecules known as substrates.
Enzymes are specific for the substrate which they act on, due to their shapes being complementary.
This allows the enzyme to turn the substrate into one or more products
How do enzymes act on substrates?
When an enzyme acts on a substrate, it forms an enzyme-substrate complex which then forms one or more products.
The product is released by the enzyme molecule and the enzyme is then free to repeat the reaction with more complementary substrate molecules.
What are the factors that affect enzymes?
Temperature
pH
How does temperature affect enzyme action?
Increasing the temperature causes the substrate molecules to move faster and collide more frequently with the enzymes active site. This speeds up the number of product molecules formed.
However, this on occurs up to a specific temperature (optimum temp.). After this, the activity levels of the enzyme quickly decline as the enzyme becomes denatured and ceases to function.
State the optimum temperature of enzymes in humans.
37 degrees Celsius
Draw the graph for the affect of temperature on the rate of reaction of enzymes.
How does pH affect enzyme action?
As the pH increases, the enzyme’s activity also increases until it reaches its optimum pH.
After this point, the activity of the enzyme decreases again as they get denatured.
Draw the graph for the affect of pH on the rate of reaction of enzymes.
What happens when enzymes are denatured?
The shape of the active site of the enzyme has been irreversibly damaged and it can no longer catalyse reactions.
At what pH does pepsin work best at?
pH 3
