Enzymes Flashcards
Explain why enzymes are often referred to as biological catalysts
Enzymes speed up metabolic reactions in your body like digestion.
Explain how enzymes perform their functions
Enzymes have what’s known as an active site where substrate molecules that are complementary in shape can fit in. Two substrates can be condensed by an enzymes to one or one can be hydrolysed into two.
How do enzymes ‘speed’ up a reaction?
The energy required for a reaction to happen is called the activation energy energy. Enzymes reduce the activation energy needed for a reaction to happen so reactions happen faster and more often.
Explain what an E-S complex is and why it lowers activation energy.
When the substrate binds with an enzyme it creates an enzyme-substrate complex. It reduces the activation as two substrates that are joining together are held close together by the enzyme reducing repulsion. Or one molecule that is being broken down has strain put on its bonds by the enzyme which breaks it up much more easily .
Explain the ‘lock and key’ model
Enzymes have a particularly shaped active site which will only bind to substrates that have an exact complementary shape. However scientists noticed that the enzyme would change its shape slightly to accommodate the shape of the substrate due to them not having ‘perfect’ shapes.
Explain the ‘induced fit’ model
Scientists came up with another model to explain this accommodation of enzyme active site shape. The enzyme not only has to change its shape to fit the substrate but has to have its shape changes in the right way.
Explain why an enzyme will only catalyse a reaction of one substrate.
Each enzyme has a specific quarternary structure which determines the shape of the active site. If the active site isn’t complementary with a substrate it won’t be catalysed.
What changes can alter the shape of an enzyme’s active site and why.
Changing the pH level, temperature or a change in the amino acid structure (mutation). This is because these changes can break some bonds in the tertiary structure causing a complete or subtle change in shape which can prevent the enzyme from performing its function. A mutation in the primary structure can change the shape of the tertiary structure rendering it useless.
How do you measure enzyme activity.
You can either measure how much of the product produced by measuring the amount of end product at different times or measure the amount of substrate left at different times. This will help you calculate the reaction rate.
How does temperature effect enzyme activity?
Temperature increases the rate because it provide the molecules with more kinetic energy. This means they move around a lot faster and a successful collision between an enzyme and a substrate is more likely. Also the increase in energy means the substrates will likely have enough or more than the activation energy resulting in a successful collision.
What happens when the temperature increase is too high?
The extra energy can cause the enzymes to vibrate so much that the bonds holding it and it’s active site together can break. This will cause the enzyme to denature as substrates will no longer fit into the active site.
How does pH affect enzyme activity?
Most enzymes usually have an optimum pH of 7 (neutral) but some prefer acidic conditions like enzymes in your stomach. The H+ ions from acids and OH- ions from alkalis can disrupt the ionic bonds in the tertiary structure causing the enzyme to denature.
How does substrate concentration affect enzyme activity?
The higher the substrate concentration, the faster the reaction. More substrates increases the likelihood of one colliding with an enzyme which increases the rate. However, the rate stops at what’s called the saturation point when the enzymes become saturated with enzymes and can’t bind with anymore.
State the how a competitive inhibitor works
Competitive inhibitors have a similar shape to a substrate molecule. They compete to bind with an active site however no reaction takes place. Instead the inhibitor blocks the active site preventing substrates from binding. How much the enzyme is inhibited depends on the concentration of the inhibitor.
State how a non-competitive inhibitor works
Instead of binding to the active site, a NC inhibitor works by binding to the enzyme away from the active site. This changes the shape of the enzyme permanently meaning it can no longer bind with a substrate and concentration of the inhibitor doesn’t affect it at all.
