2.1.4- Enzymes Flashcards
what are enzymes?
enzymes are biological catalysts that speed up reactions without changing in anyway themselves.
how does metabolism occur?
it occurs as a result of control and order imposed by enzymes
what reactions do enzymes catalyse?
metabolic reactions at cellular and whole organism level.
what is activation energy?
the level of energy required to enable a reaction to take place, the substrate to become unstable and for products to be formed
how do enzymes have an affect on activation energy and what affect do they have?
- affect= lowers activation energy
- when the substrate is binded to the active site, this puts strains on the bonds in the substrate, so they break easily.
what are the 2 types of cellular enzymes and what are their definitions?
1-intracellular= catalyse reactions in a cell 2-extracellular= catalyse reactions outside of a cell
what is an example of an intracellular enzyme?
catalase
what are the two example of extracellular enzymes?
- amylase
- trypsin
are enzymes proteins, and what type?
yes, globular protein
what type of structure do enzymes have?
a complex/unique tertiary structure, made from a single polypeptide.
-others are made from more than one polypeptide and so have a quarternary structure
what is enzyme specificity?
an enzyme’s active site is specific (specific shape)/complementary for a substrate, so that an enzyme-substrate complex is formed
for a reaction to occur, what must happen between the substrate and enzyme?
when the substrate collides with the enzyme, it must be done at the correct orientation and speed.
what is the shape of the active site determined by?
the complex tertiary structure of the protein that makes up the enzyme
what determines the shape of an enzyme?
the order of the amino acid chain of the protein
what is the LOCK AND KEY hypothesis?
-only the substrate with the correct complementary shape to the active site can fit into the active sit to form a enzyme-substrate complex
who suggested the lock and key and what did he say?
- fischer
- e suggested that both enzymes and substrates were rigid structures that locked into each other very precisely, much like a key going into a lock
what is the INDUCED FIT hypothesis?
when the substrate binds into the active site, the enzyme changes shape to fit around the substrate more closely/tightly
what is the change in enzyme shape in the induced fit theory known as?
conformational changes, which ensure that deal binding arrangement between the enzyme and substrate is achieved
what do the conformational changes maximise?
they maximise the ability of the enzyme to catalyse a reaction
what is enzyme-substrate complex?
when the substrate locks into the active site of the enzyme
what is enzyme-product complex?
when a reaction as occured when the enzyme has broken up the substrate into products.
what are the 4 factors that affect enzyme activity?
- pH
- temperature
- enzyme concentration
- substrate concentration
what is pH?
=the measure of H+ ion concentration,
increased conc=lower pH
what is the effcet of pH on enzyme activity?
- change in pH has an effect on the tertiary structure, as the hydrogen bonds are attracted to the - parts, so they interfere with the bonds which holds the shape and active site
- R groups that are present in the acid in the active site are essential for the function
what is the optimum pH?
the rate at which enzymes work fastest at
what is the shape of the line on the pH and enzyme activity graph?
C with flat ends
what is the effect of temperature on enzyme activity?
- increase temp, the increased kinetic energy of enzymes/substrates
- increased ke= enzymes/substrates vibrate, move faster, resulting in more collisions
- more collisions result in more enzyme-substrate complexes and so an increased rate of reaction
what is the optimum temp in mammals?
37 degrees
what is the effect of enzyme concentration on enzyme activity?
- increased conc= greater chance of collisions, as there is more active sites to bind to
- if conc increases beyond a certain point, there is no effect on the activity
what is the limiting factor of enzyme conc?
when there is more active sites that substrates, the substrate concentration becomes the limiting factor.
what is the effect of substrate concentration on enzyme activity?
-increased conc, increased rate, as there is more enzyme-substrate complex’s are formed
what is the limiting factor of substrate conc?
when substrate conc reaches a certain point, all enzyme active sites are full, and so enzyme concentration becomes the limiting factor.
what is the temperature coefficient?
=when the rate of reaction doubles with a 10 degree increase in temperature
what is the equation for temperature coefficient?
Q10 = R2 / R1
what are conenzymes?
organic factors that don’t bind permanently, but fasciliate the binding
what do coenzymes do?
link different enzyme-catalysed reactions into a sequence during metabolic processes, such as photosynthesis and respiration
what are the key features of coenzymes?
vitamins, such as vitamin B and pantothenic acid
what is an example of a coenzyme?
NAD, is reduced/oxidised, to transfer energy in the form of hydrogen ions (hydrogen acceptor)
what is a cofactor?
= a molecule/ion that helps an enzyme to work (non-protein compound)
what are the three types of cofactors?
1-coenzymes
2-activators
3-prosthetic groups
what is an example of a cofactor?
chloride is a cofactor for amylase
what is an activator?
a type of cofactor that binds to an enzyme/substrate, helping to form an enzyme-substrate complex.
what are prosthetic groups?
a cofactor that permanently attaches to enzyme
why are prosthetic groups essential?
- help enzyme function correctly
- help final 3D shape of enzyme
what are two example of a prosthetic group?
- carbonic anhydrase contains zinc-based pg
- haemoglobin contains p haem group, contains iron, serves as a means of binding oxygen
what are enzyme inhibitors and the two types?
they are substances that slow down the rate of enzyme reaction by affecting the enzyme-substrate complexes
1-competitive
2-non-competitive
what are competitive inhibitors?
- similar in structure to the substrate, so bind to the active site
- this decreased enzyme activity, as it competes with the substrate for the enzyme
- same product amount is produced, but at a slower rate
- the inhibitor keeps the substrate out of active site
what are non-competitive inhibitors?
- binds to the enzymes allosteric site, so changes the shape of the active site to prevent binding
- this decreases the rate, changing the 3D tertiary structure, so the substrate cannot bind
what is reversible inhibition?
when the competitive inhibitor leaves the active site, so that the enzyme can work again
what is irreversible inhibition?
when the non-competitive inhibitor binds to the active site, so denatures the enzyme, meaning that it cannot work again
how are metabolic reactions controlled?
by using the end-product of a particular sequences of metabolic reactions as a non-competitive, reversible inhibitor
why are some non-reversible inhibitors beneficial?
in medical contexts, they can be used to inhibit enzymes that can cause harm.
what is an example of a non-reversible inhibitor as a medical drug and what it does?
- penicillin
- non-reversible inhibition of transpeptidase results in the destruction of bacteria as their cell wall breaks down.
what is another example of a medical drug and what it does?
- aspirin
- non-reversible inhibition of COX, resulting in the reduction of inflammation and provides pain relief
