enzymes Flashcards
Enzymes are…
Enzymes are globular proteins that catalyse thousands of metabolic reactions.
Metabolism is…
What are the two different types of reactions?
Metabolism is the name given to chemical (metabolic) reactions of life.
Anabolic (larger built up from smaller molecules) and catabolic (larger molecules broken down)
A catalyst is…
A catalyst is a molecule that speeds up a chemical reaction but remains unchanged at the end of the reaction.
What must happen for a reaction between two molecules to occur?
There must be an effective collision between them. The molecules must collide with each other in the right way and the right speed.
What are the features/functions ? of an enzyme
- Required in small amounts
- Lowers the activation energy
- Remain unchanged at the end of the reaction
- Specific in action
- Affected by temperature and pH
_____ ____ is an energy barrier that has to be overcome before the reaction can happen. Enzymes work by lowering the _____ ____ required to activate the reacting molecules.
Activation energy is an energy barrier that has to be overcome before the reaction can happen. Enzymes work by lowering the activation energy required to activate the reacting molecules.
Why are enzymes highly specific (ie only catalyse only one type of reaction)?
The active site where the substrate molecule binds has a precise shape and distinctive chemical properties. Only particular substrate molecules can fit into a particular active site.
(tldr an enzyme is specific due to the unique 3D shape at the active site)
Explain the “lock and key” hypothesis.
An enzyme works by binding onto its substrate molecule at a specially formed pocket, active site, in the enzyme.
- As the enzyme and substrate form a complex, the substrate is raised in energy to form a transition state and then breaks down into products + unchanged enzyme
“Lock and key” hypothesis in an equation?
E + S –> E-S complex –> Pr + E
Explain catalysis by “induced fit”.
At the active site, arrangement of certain amino acid molecules in the enzyme exactly matches certain groupings of substrate, enabling E-S complex to form.
What are the 3 key steps of an enzymatic reaction?
- The shape of the active site of the enzyme is specific and complementary to the shape of the substrate. The E-S complex is formed.
- Interactions between enzyme and substrate molecules strain/weaken chemical bonds within the substrate. Thus, lowering the activation energy.
- When the reaction between substrate and enzyme is completed, products no longer fit into the active site and are released. Enzymes are also released.
Factors affecting enzyme reaction: temperature
1. describe at low/increasing temperatures BEFORE the optimum
Enzymes are inactive at low temperatures due to low kinetic energy, the frequency of effective collisions is low.
As temperature increases, kinetic energy of the E and S molecules increases, increasing the frequency of effective collisions between E and S active sites, which increases the rate of reaction and products formed.
Factors affecting enzyme reaction: temperature
2. describe at optimum temperature
All enzyme active sites are saturated when enzyme activity is at its highest.
Factors affecting enzyme reaction: temperature
3. describe at increasing temperatures AFTER the optimum
High temperatures break the bonds that keep the enzyme protein in its specific shape.
The active site loses its original shape and is no longer complementary to the substrate.
The enzyme is denatured and loses its catalytic function.
Factors affecting enzyme reaction: pH
1. describe at the optimum pH
Enzyme maintains its specific 3D conformation and so the enzyme active site is complementary to the substrate.
Enzyme binds the substrate(s) to form the E-S complex. Substrate is converted to products.
