enzymes basics Flashcards
define ‘enzyme’
a biological catalyst which increases rate of reaction
- globular proteins
how do enzymes increase rate of reaction?
provides an alternate reaction pathway with a lower activation energy
describe the active site of an enzyme
- binds to complementary substrate
- specific shape
describe the lock and key mechanism
enzyme = lock
substrate = key
must collide perfectly
- The products of the reaction are then released and it is now an enzyme-product complex
describe the induced fit mechanism
active site changes shape slightly to fit the substrate forming an enzyme substrate complex
- R groups in the active site interact with the substrate to form temporary bonds
- there is a change in tertiary structure
- strain is put on the substrate bonds and they are weakened
why is the induced fit mechanism better?
it is more likely that the active site will change slightly when there are frequent fast collisions, rather than a perfect collision
what is an intracellular enzyme?
enzymes that act within cells
what is an extracellular enzyme?
enzymes released from cells to break down nutrients
what is an anabolic reaction?
built up
- growth, synthesis
what is a catabolic reaction?
break down
what is an example of an intracellular enzyme?
catalase
how do enzymes affect structure?
they are involved in collagen production
how do enzymes affect function?
processes such as respiration or photosynthesis
Why must enzymes be in an aqueous environment?
It allows both the enzyme and the substrate the ability to move and therefore collide with one another allowing for enzyme-substrate complexes
What is the structure of an enzyme?
- Globular protein: has a 3D, spherical shape + water soluble due to positioning of hydrophilic R group
- Has an active site: which has a very specific shape where the complementary substrate binds to
What effect does an increase in temperature (from 10 to 30 c) have on the rate of a reaction?
Kinetic energy is increased which increases the number of successful collisions, therefore more enzyme-substrate complexes are formed and the rate of reaction increases
What is meant by optimum temperature?
When enzyme activity is at its highest
What happens when the temperature is raised too high (40 to 60 c) on the rate of a reaction?
- increase of energy means vibrations are produced which break the bonds that hold the enzyme together
- the enzyme denatures, meaning there is now an irreversible change to the shape of the active site, and so enzyme activity and rate of reaction decreases
What does the temperature coefficient show in a reaction?
It shows how much the rate of the reaction changes when the temperature is raised by 10 degrees
What is the formula for the temperature coefficient?
Q10 = rate at higher temperature / rate at lower temperature
What is meant by optimum pH?
The pH the enzyme works best at
What happens as you move away from the optimum pH on a graph?
The enzyme begins to denature (the H+ and OH- ions found in acids and alkalis break the ionic and hydrogen bonds that hold the enzymes tertiary structure together, resulting in it changing shape. Therefore enzyme activity decreases.
Explain the effect of having few substrate molecules on rate of reaction.
Few substrate molecules mean there are many active sites free and able to be reacted, and so an increase in substrate concentration will increase the rate of reaction
Explain the effect of having more substrate molecules on rate of reaction.
When there are more substrate molecules, all the active sites are engaged in catalysts. This therefore produces the maximum rate of reaction
Explain the effect of having an excess of substrate molecules on rate of reaction.
An excess of substrate molecules means all active sites are engaged in catalysis and so an increase in substrate concentration will not change the rate of reaction
what is meant by ‘enzyme specificity’?
enzymes only fit with a complementary substrate which has the exact shape to fit the active site
how will the substrate changing shape slightly assist enzyme action
it puts a strain on the bonds and they can break more easily
how do small molecules join to form polysaccharides? (3 marks)
- peptide bonds
- condensation reaction
- water removed
why does the structure of an enzyme molecule allow them to be detected in solution using the biuret test? ( 1 mark)
enzymes are globular and water soluble
