Enzymes Flashcards
What is an Enzyme and what is its function
Enzymes are globular proteins, they act as catalysts (speed up metabolic reactions).
Whats the difference between intracellular and extracellular enzymes and give an example?
Intracellular enzymes work inside cells eg. Catalase which converts hydrogen peroxide to oxygen and water.
Extracellular enzymes are ones that work outside cells such as digestive enzymes amylase and trypsin which are released into digestive system.
What does specificity of an enzyme refer to?
Its ability to catalyse only one reaction/ type of reaction.
What does the lock and key theory state?
Only one particular substrate molecule will fit into the active site of the enzyme molecule due to the shape of the active site.
What causes the shape of the active site?
the specific sequence of Amino acids which produces a specific tertiary structure - the 3D shape of the molecule.
What is the activation energy?
The amount of energy required to set off the reaction (and break the bonds in the substrate molecule.)
How does an enzyme catalyse a reaction (speed up the reaction)
They lower the activation energy required for the reaction to occur.
maExplain the Induced fit theory.
- The active site of the enzyme molecule does not have a perfectly complementary shape to the substrate.
- When the substrate moves into the active site, it interacts with the active site and interferes with the bonds that hold the shape of the active site
- As a result the shape of the active site is altered to give a perfect fit to the shape of the substrate.
- This changes the shape of the active site, which also affects the bonds of the substrate making them easier to break or make so reducing the activation energy.
Describe the course of an enzyme controlled reaction.
- In and enzyme controlled reaction the substrate is complementary to the enzymes active site, therefore the substrate enters the enzymes active site combining to form the enzyme substrate complex (ESC)
- This destabilises and strains the bonds in the substrate forming an enzyme product complex.
The product then finally leave the the active site and enzyme is free to take up another molecule.
What affect does pH have on the condition of the enzymes.
Optimum pH - the pH they work at best.
When the pH is too high (acidic ) or too low the enzyme will not function properly and denature this is because:
1.hydrogen ions that cause acidity affect the interaction between R groups in the tertiary of the enzyme therefore the hydrogen and /or the ionic bonds break.
- This affect the tertiary structure so the shape of the active site is altered, the shape will no longer be complementary to the substrate molecule so the enzyme substrate complex will no longer form.
What is the affect of low temp on enzyme activity?
- Molecules have little kinetic energy
- They collide infrequently with the substrate molecule and activity is reduced.
What is the affect of increasing temperate on enzyme activity.
As the temperature rises:
- Molecules gain more kinetic energy
- They collide more frequently with the substrate molecules and more likely to have sufficient energy to overcome the required activation energy.
What happens to enzymes if the temperature is too high?
- Increased kinetic energy causes enzymes to vibrate, causing vibration within the protein molecule, so hydrophilic and hydrophobic interactions , as well as hydrogen and ionic bonds break within the the tertiary structure break.
This changes the 3D structure of the of the protein so the enzyme loses its shape, becoming denatured.
Active site no longer fits.
What is the affect of enzyme concentration on Enzyme activity
As there are more enzymes available there are more active sites available, there is greater likelihood of collisions between enzyme and substrate molecules, more interactions per second means higher rate of reaction .
What is the affect of substrate concentration on enzyme activity?
1.If the substrate concentration is high, there is a greater chance of successful collisions between the enzyme active sites and substrate molecules,
- As the substrate concentration increases, so does the rate of reaction. If the number of enzyme molecules is limited, the rate of reaction plateaus once all the enzyme active sites are fully occupied as enzymes are working at maximum rate. Therefore further increases in substrate concentration will have no effect as enzyme concentration will then be the limiting factor
