Enzymes Flashcards
Define an enzyme:
A globular protein produced by a living organism that acts as a biological catalyst in a chemical reaction by reducing the activation energy, without being used up or changed.
What are extracellualr enzymes?
Enzymes that are secreted and catalyse outside cells.
Usually digestion
What are intercellular enzymes?
Enzymes that catalyse inside cells.
What does the enzyme amylase do?
An extra cellular enzyme, secreted by the salivary glands and pancreas, that digests macromolecules that are too big to enter cells which hydrolyses starch into simple sugars.
What does the enzyme catalase do?
Converts hydrogen peroxide (a harmful byproduct of many metabolic reactions) into water and hydrogen.
How do enzymes work?
Enzymes have an active site where a specific substrate can bind to forming an enzyme-substrate complex before releasing products.
How does temperature affect enzymes?
Higher temperatures increase the kinetic energy of the enzyme and so there are more frequent collisions and a higher concentration of enzyme-substrate complexes until the enzyme reaches its optimum temperature and then denatures.
There are less collisions and enzyme active sites get damaged by force of substrate binding.
How does pH affect enzyme action?
A high concentration of H+ ions bond with negative R groups on amino acid groups and enzyme shape is disrupted so enzyme denatures.
At optimum ph enzymes work best.
A high concentration of OH- ions bond with positive R groups on amino acids groups so enzyme denatures.
How does enzyme concentration affect enzyme activity?
When there is a high substrate concentration there are enough substrates to bond with enzymes but it can be enzyme limiting (high rate of reaction). As soon as all the substrates are getting used we become substrate limiting and rate of reaction decreases.
What is a competitive inhibitor?
A molecule that competes with a substrate for the active site.
To increase the rate of reaction we need to increase the substrate concentration.
What is a non-competitive inhibitor?
A molecule that doesn’t compete with the substrate for the active site but prevents bonding.
Increasing the substrate concentration would have no effect.
What are immobilised enzymes?
Enzymes coated or trapped in a agarge which lowers cost and makes them less sensitive to temperature and ph changes.
They also don’t need to be removed from solution and can be used over many times.
What is affinity?
A measure of how strongly substances are attracted to one another.
What is the michaelis-menten constant?
Km is the substrate concentration at half Vmax
What does a higher affinity mean?
A lower substrate concentration is needed to reach Vmax.
