Enzymes Flashcards
(40 cards)
What are anabolic reactions?
Building up (synthesis)
What are catabolic reactions?
Breaking down (digestion)
What is metabolism?
The sum of all the different reactions and pathways in an organism.
Explain the term Vmax…
Enzymes can only increase the rate if reaction up to a certain point, maximum initial velocity/rate of the enzyme controlled reaction.
What is collision theory?
For a reaction to happen, molecules need to collide with enough energy and the right orientation, when high temperatures and pressures are applied the speed of the molecules will increase hence the number of successful collisions and the overall rate of reaction.
Why are enzymes described as specific?
They only catalyse one reaction.
Define activation energy…
The minimum amount of energy required for a reaction to take place, enzymes reduce this by forming an enzyme-substrate complex.
Explain lock and key hypothesis.
The substrate fits into the active site (tertiary structure) as it has a complementary shape. An enzyme-substrate complex is formed. The substrate(s) react forming an enzyme-product complex. The R groups interact with the substrate forming temporary binds, putting strain on existing bonds. The product is released and the enzyme remains unchanged.
Describe induced fit hypothesis…
The active site changes shape slightly as the substrate enters (it has a complementary shape). The initial reactions are weak but they induce changes in the enzymes tertiary structure weakening bonds and lowering the activation energy.
What are intracellular enzymes?
Enzymes that act within cells
Give an example of an intracellular enzyme…
Catalayse breaks down hydrogen peroxide (H2O2) a toxic by product of many metabolic reactions into H2O and O2 which prevents dangerous accumulation.
What are extracellular enzymes?
Enzymes that work outside of cells, commonly breaking down polymers.
Explain how starch is broken down by extracellular enzymes…
Amylase (salivary glands and pancreas) breaks starhpch down into maltose. Maltase (small intestine) breaks maltose down into glucose.
Explain how proteins are broken down by extracellular enzymes…
Trypsin (protease) breaks down proteins into peptides by hydrolysis, pancreas/small intestine.
Explain how increasing the temperature changes the rate if reaction…
As the temperature increases the molecules have more kinetic energy hence they move faster and collide more frequently with the enzyme forming more enzyme-substrate complexes increasing the rate if reaction.
What happens at high temperatures to enzymes…
A high temperatures enzymes denature as the binds holding their tertiary structure together vibrate more until they break changing the shape of the active site so the enzyme no longer has a complementary shape to the substrate.
What is Q10/temperature coefficient?
How much the rate of reaction changes with a 10 degrees change in temperature.
What is the usual Q10 of an enzyme controlled reaction?
2
Explain how a changing pH effects the rate of reaction…
Above and below optimum pH, H+ and OH- ions interact with bonds in the tertiary structure changing it hence the active site is no longer complementary, so the enzyme has been denatured, the enzyme can become renatured…
How does substrate concentration change the rate of reaction?
The number of substrate particles in a given area increases meaning a higher collision rate as more active sites are being used so more enzyme-substrate complexes are formed increasing the rate of reaction until the enzyme concentration becomes a limiting factor as Vmax has been reached.
What’s are cofactors?
Small inorganic molecules or ions that help the substrate and active site bind together.
Give an example of a cofactor…
Cl- ions in amylase.
What are coenzymes?
A type of cofactor that is organic, they are changed during a reaction but are recycled during reactions.
What are prosthetic groups?
Tightly bound cofactors that form a permanent part of the enzyme.
