Enzymes Flashcards
(45 cards)
What type of molecules are enzymes?
Enzymes are globular proteins that act as biological catalysts.
Describe the structure of an enzyme.
Enzymes have a specific 3D structure with an active site formed by folded chains of amino acids held by hydrogen bonds, ionic bonds, and disulfide bridges.
Define the term complementary.
Complementary refers to the specific fit between the enzyme’s active site and its substrate, like a lock and key.
What do enzymes do?
Enzymes speed up biochemical reactions by lowering the activation energy required for the reaction.
What is meant by the term biological catalyst?
A biological catalyst is a substance, like an enzyme, that increases the rate of a chemical reaction in a living organism without being consumed.
Why are many different enzymes needed for different reactions?
Different enzymes are needed because each enzyme has a specific active site that only fits particular substrates.
How do enzymes lower activation energy?
Enzymes lower activation energy by binding to substrates at their active sites, forming an enzyme-substrate complex and stabilizing the transition state.
What is the difference between catabolic and anabolic enzymes?
Catabolic enzymes break down large molecules (e.g., amylase breaking down starch). Anabolic enzymes build larger molecules (e.g., DNA polymerase synthesizing DNA).
What is an enzyme-substrate complex?
An enzyme-substrate complex is the temporary structure formed when a substrate binds to the enzyme’s active site.
Describe the lock and key hypothesis.
The lock and key hypothesis states that the enzyme’s active site is a specific shape that perfectly fits the substrate, like a key fitting into a lock.
Describe the induced fit hypothesis.
The induced fit hypothesis suggests that the enzyme’s active site changes shape slightly to fit the substrate more snugly when it binds.
How do the lock and key hypothesis and the induced fit hypothesis differ?
The lock and key hypothesis suggests a rigid active site, while the induced fit hypothesis suggests a flexible active site that changes shape to fit the substrate.
What are the limitations of the lock and key hypothesis?
Limitations include not explaining enzyme flexibility, wide substrate interactions, and how enzymes lower activation energy by stabilizing the transition state.
What is the difference between intracellular and extracellular enzymes?
Intracellular enzymes function inside cells, while extracellular enzymes are secreted outside cells and function in external environments like digestion.
Name an intracellular enzyme and its function.
Catalase, which breaks down toxic hydrogen peroxide into water and oxygen inside cells.
Name an extracellular enzyme and its function.
Amylase, which breaks down starch into maltose in the digestive system.
what is the effect of substrate concentration on enzyme activity
the higher the substrate concentration, the more frequent collisions meaning a higher rate of reaction. This is only up until Vmax is reached when the enzymes become the limiting factor so no more reactions happen.
what is the effect of enzyme concentration on enzyme activity
the higher the enzyme concentration, the more frequent collisions meaning a higher rate of reaction. This is only up until Vmax is reached when the substrates become the limiting factor so no more reactions happen.
why does enzyme activity increase with temperature?
the heat gives the enzymes more kinetic energy so there are more frequent collisions between the active site of the enzyme and the substrate, increasing the rate of reaction
what happens to enzyme activity when the temperature increases past the optimum?
the rate of reaction decreases because the enzymes become denatured as the hydrogen bonds between them start to break causing the tertiary structure of the enzyme to change. this change of the tertiary structure alters the active site so the enzymes can no longer bind to their substrate, making them denatured and non-functioning. Once an enzyme has denatured it can’t be renatured as the tertiary structure has been changed too much.
what is the temperature coefficient (Q10)
ROR at temperature X + 10 degrees / ROR at temperature X
what is pH?
how many hydrogen (H+) ions are present
low pH= high concentration of hydrogen ions
high pH= low concentration of H+
what are the average optimum pH’s for intracellular and extracellular enzymes?
intracellular= 7.3 - 7.4
extracellular= function at different pH’s in the same organism
how does pH effect enzyme activity?
large changes in pH disrupts the hydrogen and ionic bonds - disrupting the active site. Hydrogen ions interact with polar charged R groups. The more hydrogen ions present (low pH) the less R-groups are able to interact with each other so the bonds break and the shape of the enzyme changes. The reverse is true when fewer hydrogen ions are present. This means the shape of the active site will change as the pH changes and therefore it will only function within a narrow pH range
