biological molecules pt 2 Flashcards
what are enzymes?
enzymes are globular proteins that act as a catalyst.
what must be satisfied for a chemical reaction to take place such as
sucrose + water —-> glucose + fructose?
the sucrose and water molecules must collide with a sufficient amount of energy to alter the arrangement of their atoms to form glucose and fructose
the free energy of the products muss be less than that of the substrates
many reactions require an initial amount of energy to start. the minimum amount of energy to start the reaction in this way is called the activation energy.
what is the structure of an enzyme like?
being globular on shape it is clear that an enzyme is made from a 3D formation of proteins. a specific region of the enzyme is functional, this is known as the active site. the active site is composed if a small number of amino acids. the molecule upon which the enzyme acts is called the substrate. this fits neatly into the depression and forms an enzyme substrate complex. the substrate is temporarily held in place by temporary bonds that form between the amino acids in the active site and groups on the substrate.
what is the induced fit model of an enzyme?
this is a model that shows the reaction between an enzyme and a substrate. it shows that the enzyme is flexible and can hold itself around the substrate like glove. as it changes shape it puts a strain in the substrate molecule. this strain distorts a particular bond/bonds in the substrate and consequently lowers the activation energy needed to break the bond.
what must happen for an enzyme to work?
the enzyme must come into physical contact with its substrate
have an active site which fits the substrate.
what are the two events that are usually measured in an enzyme catalyzed reaction?
the formation of the products of the reaction
the disappearance of the substrate
what is the explanation of a volume over time graph?
at first there is a lot of substrate but no product
it is easy for substrate molecules to come into contact with empty active sites on the enzyme molecule.
all enzyme active sites are filled at any given time and the substrate is rapidly broken down into its products
the amount of substrate decreases while it is broken down while the amount of product increases.
as the reaction progresses there is more and more product and less and less reactant
it becomes more and more difficult for the substrate molecules to come into contact with the enzyme molecules because there are fewer substrate molecules and also the product molecule might get in the way preventing the substrate from reaching the active site
it therefore take s longer for the substrate molecule to be broken down so subsequently it also means that the production of product is slower so both graphs therefore tail off
the graphs flatten out when all of the substrate has been used up.
what happens when there is a rise in temperature.
a rise in temperature means that there is an increase in kinetic energy in the molecules. the molecules therefore move around more rapidly and so collide with each other more often. this means that there are more effective collisions and so there is more enzyme substrate complexes formed and so the rate of reaction increases.
what happens when the temperature is two great?
the hydrogen bonds along with other bonds begin to break resulting in the enzyme along with its active sites changing in their shape. at first the substrate fits less easily into the active site slowing the rate of reaction. at a certain point the enzyme has changed so much that it stops working all together. it is now said to be denatured (permanent)
why may have our body temperatures evolved to be 37 degrees?
although higher body temperatures would increase the metabolic rate slightly, the advantages are offset by the additional energy that would be needed to maintain that temperature
other protein, may be denatured at higher temperatures
at higher temperatures, any further rise in body temperature, for example during weakness would denature enzymes.
how does the pH effect how an enzyme works?
a change in pH alters the charges on the amino acids that make up the active site of the enzyme. as a result the substrate can no longer become attached to the active site of the enzyme so the enzyme substrate complex can not be formed
depending on how significant the change in pH is, it may cause the bonds maintaining the enzyme’s tertiary structure to break. the active site therefore changes shape.
describe an enzyme concentration vs a rate graph
as the enzyme concentration increases the rate increases until at a certain point (B) when as the enzyme concentration increases there is n change in rate. this is because at the beginning the limiting factor is the enzyme where as at the end it is the substrate
explain an enzyme concentration vs a rate graph
at the beginning the enzyme is the limiting factor as there is not enough active sites to hold all of the substrate. as more enzymes are added the rate increases. the the substrate molecules outnumber the enzyme molecules so they can’t all get into an active site to make an enzyme substate complex. when more enzymes are added there are more active sites so more ESCs can form
at B the substrate becomes the limiting factor. when are enzyme is added the rate stays the same. this is because the enzyme molecules outnumber the substrate molecules so there is an excess number of active sites.
describe a substrate concentration vs rate graph
as the substrate concentration increases the rate o reaction also increases until at B when the substrate concentration increases the rate of reaction does not change
explain an substrate concentration vs a rate graph
at the beginning there are too few substrate molecules to fill up all of the available active sites. as more substate is added the rate increases. this is because more active sites are subsequently filled up until all active sites are filled ups at B.
at B the addition of further substrate molecules as no effect as the enzyme is the limiting factor. as all the active sites are occupied at any one time so there is therefore no increase in rate of reaction.
