Factors affecting enzyme action Flashcards
What are the two factors that affect enzyme action?
Temperature and pH
What are the factors that affect the rate of reaction?
Temperature, pH, substrate concentration, enzyme concentration and surface area
If the temperature is increased how does this affect the rate of reaction?
When the temperature is increased the enzymes and substrates gain more kinetic energy. It is this increase in energy which results in more frequent successful collisions between the substrate and the enzymes active site; thus increasing the rate of reaction.
What is the temperature coefficient, Q10, of a reaction measuring?
How much the rate of reaction increases with a 10ºc rise in temperature.
How much does the rate of an enzyme reaction usually increase after the rise of 10c?
The rate of reaction usually doubles.
Explain how temperature denatures enzymes
At high temperatures the bonds holding the protein together vibrate more as they gain kinetic energy. As the intensity of the vibrations increase the bonds begin to strain and then break. When the bonds break the tertiary structure of the protein is changed.
Why does the substrate no longer fit into the active site of the enzyme after it has been denatured?
The tertiary structure of the active site has been changed and so is no longer complimentary of the substrate.
What is meant by the optimum temperature?
It is the temperature in which the enzyme has the highest rate of activity.
What is the most common optimum temperature of the enzymes found in the human body?
40ºc
What is the optimum temperature of thermophilic enzymes?
70ºc
What is the optimum temperature of psychrophilic enzymes?
5ºc
Sketch the graph that describes the difference between the temperature and rate of a reaction
When during a reaction does the temperature, Q10, not apply anymore?
After the enzymes have denatured.
How are enzymes adapted for organisms in extreme cold environments?
The enzymes have flexible structures, especially at the active site
What is the disadvantage of the flexible structure of an enzyme in a cold environment?
They are less stable and easily denature by even slight changes in temperature `
What are thermophiles?
Organisms that are adapted to living in extremely hot environments.
How are enzymes adapted for organisms in extreme hot environments?
The enzymes are more stable due to the increased number of bonds (particularly hydrogen bonds and sulfur bridges).
What actually happens when the pH levels change?
There is a change in the hydrogen ion concentration
When more hydrogen ions are presents what pH level is it?
Low (acid)
When less hydrogen ions are presents what pH level is it?
High (alkaline)
What is meant by the optimum pH?
It is the level of pH where the active sight is in the right shape (optimum hydrogen ion concentration)
What is meant by renaturation?
When the pH strays from the optimum pH and becomes either too alkaline or acidic the enzymes active site becomes altered and the substrate no longer fits. However, if the pH returns to normal then the protein will resume its normal shape.
Sketch the graph for the relationship between pH and the rate of enzyme activity.
What happens to the enzyme when the pH significantly shifts away from the optimum?
The enzyme denatures and so is irreversible
All about interaction
How does the change in pH actually affect the enzyme?
The hydrogen ions interact with the R-groups in the protein, and so by increasing the concentration of the hydrogen ions less interaction occurs between the R-groups inside the protein.
All about interaction
How does very low pH denature an enzyme?
There is a larger concentration of hydrogen ions which means that the R-groups interact with each other less. Due to this the bonds between the R-groups break and change the shape of the enzyme.
+ interaction
How does very high pH denature an enzyme?
There is a low concentration of hydrogen ions which means that there is more interaction between the R-groups. There are more bonds present and so the shape of the enzyme changes.
Where is saliva found?
in the mouth
Where is gastric juices found?
In the stomach
Where are pancreatic juices found?
In the small intestine
What is the name of the enzyme found in the mouth?
amylase
What is the name of the enzyme found in the stomach?
Pepsin
What is the name of the enzymes found in the small intestine?
- Trypsin
- Lipase
- Amylase
- Maltase
What is the optimum pH for the enzymes in the mouth?
Neutral (pH 7)
What is the optimum pH for the enzymes in the stomach?
Acidic (pH 1-2)
What is the optimum pH for the enzymes in the small intestine?
slightly alkaline (pH 8)
What is the function of amylase?
Starch → maltose
What is the function of pepsin?
proteins → polypeptides
What is the function of trypsin?
proteins → polypeptides
What is the function of lipase?
triglycerides → glycerol + fatty acids
What is the function of maltase?
maltose → glucose
The rate of reaction increases up to a maximum point. What is the symbol for this point?
V max
Sketch a graph to show the relationship between the concentration of subrates and the rate of the reaction (include the V max)
