Quiz: Enzymes Flashcards
Define enzyme
A protein originating from living cells and capable of producing certain chemical changes in organic substances by catalytic action.
Define active site
The part of an enzyme that interacts with substrate during catalysis.
Define catalyst
Substance that causes or accelerates a chemical reaction without itself being affected.
Define activation energy
Least amount of energy required to activate atoms or molecules to a state in which they can undergo a chemical reaction.
Define substrate
The substance acted upon by an enzyme.
Describe the function of an enzyme
They speed up reactions by providing an alternative reaction pathway of lower activation energy.
Explain the “lock and key” model of enzyme action.
Enzymes begin chemical reactions when the substrate binds with the active site. The active site has a unique shape that matches with the specific substrate’s shape.
The lock is the enzyme, while the key is the substrate. The key hole would be the active site. Keys that do not fit their specific locks don’t make them work, but keys that do fit make them work perfectly.
How does excess heat affect an enzyme?
Excess heat will denature an enzyme and will cause it to lose its shape and its function. The active site of a denatured enzyme cannot combine with its substrate and no reaction will take place.
List 5 ways enzymes are used in medicine and industry.
Milk processing; detect blood sugar level; fruit juice; production of high fructose syrup; breaking down hydrogen peroxide into hydrogen and water.
How are enzymes named?
The name of the enzyme is formed by dropping the suffix (at the end of the word) and then adding “ase” to the root.
Iodine tests for what type of substance?
Starch.
What is the color of a positive iodine test?
Purple
Name 1 substance that yields a positive iodine test.
Starch.
Name 1 substance that yields a negative iodine test.
Sucrose
What color iodine test shows low amylase activity? Explain why.
Yellow. Because starch is still present.
What color iodine test shows high amylase activity? Explain why.
Dark purple. Because starch is not present, but amylase is.
Describe the chemical composition of starch.
It is a polysaccharide composed of glucose molecules.
What is curd?
A soft, white substance formed when milk sours, used as the basis for cheese.
What is whey?
The watery part of milk that remains after the formation of curds.
What is the role of rennin in cheese making?
Rennin is used to hydrolyze milk proteins, which curdles the milk.
What temperature increases enzyme activity?
When temperature is increased by 10%, the enzyme activity will increase (boiling).
What temperature decreases enzyme activity?
Lower temperatures decrease enzyme activity.
What level of enzyme concentration increases enzyme activity?
Increasing concentration will increase enzyme activity.
What level of enzyme concentration decreases enzyme activity?
Decreasing concentration will decrease enzyme activity.
What pH increases enzyme activity?
If the pH is at its base point, enzyme activity will increase.
What pH decreases enzyme activity?
If the pH is too acidic, the enzyme activity will decrease.
