C1.1 enzymes and metabolism Flashcards
describe what happens when temp is raised a bit with enzymes
increaseses kinetic energy of susbtrate and enzyme
increase chance of collision between enzymes and susbtrates therefore rate increases
low temp has insufficient htemral energy for the activation energy so there is a low rate of reaction
descibre what happens when temp at optimim with enzymes
optimum temp- max rate of reaction
balance between enzyme stability and kinetic energy of reactants
descibre what happens when temp is over optimum with enzymes
rapid decrease in the rate of reaction
destabilises enzymes as the thermal energy disrupts the hydrogen bonds holding the enzyme together
enzyme is denatured (active site loses its shape and activity)
describe effect of ph a bit increased in enzymes
increase in PH (decrease in H+) or decrease in PH (increase in H+)
H+ interact with exposed R groups on active site
changes the charge and solubility of enzyme
enzyme active site changes shape
specifity reduced
decrease in rate of reaction
describe effect of ph at optimum in enzymes
optimum PH= maximum rate of reaction
successful activated E-S complex and therefore reactions occur
moving outside this range results in a dimished rate of reaction
effect of substrate increse a bit in enzymes
increase chance of collisions between enzymes and susbtrates
greater change of forming e-s complexes
increases in rate of reaction
effect of substrate increse at optimum a bit in enzyme
active site begin to become saturated with susbtrate (fully occupied)
new susbtrate must wait for previous reaction to complete and the product to exit the active site
effect of substrate increse after optimum a bit in enzyme
full saturation of the active sites by susbtrate
rate becomes constant for further increase in susbtrate concentration
what is metabolism
the sum of all the chemical reactions that occur within living organisms
how are metabolic reactions controlled
by specific enzymes, because of enzyme specificity many different enzymes are required by living organisms
metabolism can be considered either:
intracellular: occur within a cell such as protein synthesis and cellular respiration
extracellular: occur outside a cell such as cells of pancreas secreting enzymes chemically digest food
metabolic pathways
a series of steps from a starter molecule or precursor toward a final end product
each step is catalyzed by a different enzyme
describe image of metabolic pathways linear
percursor chemical——>intermediate chemical—–> end product
metabolic pathways can either be….
linear or cyclical
anabolic or catabolic
describe image of metabolic pathways cyclical
reactant—-> intermediate —-> intermediate—-> reactant + product
what are examples of cyclic metabolic pathways
photosynthesis and the krebs cycle of cellular respiration
whats an example of linear metabolic pathway
digestion of starch
anabolic pathways
build up complex molecules fro. simpler ones they intake energy and involve reduction/ condensation reactions. an example is photosynthesis
catabolic pathways
break down complex molecules into simpler ones, they release energy and involve oxidation hydrolysis reactionsan example is cell respiration
is heat generation inevitable? and why?
yes it is invetible because mtabolic reactions are not 100% efficient in energy transfer, animals depende on this heat production for maintainence of constant body temp
what do all chemical reactions recquire?
energy to get started as molecules need to collide with enough energy so reactants have bonds broken moecules are reoriented new bonds are formed
what is the initial energy input called
activation energy, which is defined as minimum amount of energy needed to start the reaction, leading to the formation of a high energy intermediate (transition state)
what are enzymes
globular proteins that are employed to catalyse (speed up) chemical reactions in cells, otherwise metabolic reactions would be very slow to sustain life
they speed up rate of chemical reaction, without themselves being used u[
they speed up spontaneous reactions be lowering the activation energy
describe the transition state in the progression of a reaction X energy content of molecules graph
in transition state energy is put into substrate to weaken stubstrate to weaken structure. Allows reaction to occur with minimal amount of additional energy recquired
describe the normal activation in the progression of a reaction X energy content of molecules graph
normal activation energy would cause damage to proteins of the cell. Thus, reduced activation energy makes these reactions possible in cell
describe the final of a reaction in the progression of a reaction X energy content of molecules graph
after product formed energy released
describe endergonic reactions
consume less energy than activation energy
describe exergonic reactions
ralse more energy than activation energy
descibr eprocess of enzyme- substrate
- collision= enzyme+ substrate enetering active site
2.catalysis= enzyme/ substrate complex, enzyme changes shape slightly as substrate enters active site making fit more precise
enzyme/ products complex formed - realease= enzyme + products leaving active site
explain step 1. collsion of enzyme reaction in detail
- enzyme shape includes a pocket called an active site
-the active site is composed of a few amino acids only but interactions between amino acids within the overall 3D structure of the enzyme ensure that the active site has necessary properties for catalysis
-the coming together of substrate molecule and an active site is known as collision, and it is the result of the random movement of molecules
-succesful collisions= the substrate and active site happen to be correctly aligned to allow binding to take place
-sometimes large susbtrate molecules or enzymes can be immobilised by being embedded in membranes to increase the rate of collisions
explain step 2. collsion of enzyme reaction in detail
substrates bind to active site, distinctive shape of activte site is complementary and specific to the substrate like a locke and key
-both enzymes and substrate can slightly shift in shape to better accomodate each other- induced fit theory
due to binding the bonds in the substrate molecule are stressed and become less stable to facilitate the reaction
the binding lowers the overall energy level of the transition state
the activation energy of the reaction is therefore reduced
explain step 3. collsion of enzyme reaction in detail
products leave active site
enzyme left unchange and can be reused
whats a coenzyme or cofactor
non protein component that aids the functioning of an enzyme
they work by removing electrons protons or chemical groups from the susbtrate and passing them to other molecules
describe path of usage of a coenzyme or cofactor
enzyme is inactive until the cofactor or coenzyme is present —–> (activation- able to bind the susbtrate)
enzyme is active when cofactor or coenzyme has bound
what are coenzymes
organic, non- proteic molecules such as NAD+
what are cofactors
inorganic molecules such as CU 2+
what is the tertiary strucure of enzymes sensitive to and explain
PH, temp, substrate concentration, those are regulate to avoid denaturation
each enzyme has specific envionrmental conditions in which its efficiency is optimum
denaturation
permenant or temporary change of protein strucutre fue to breaking of many weak bonds (eg. hydrogen bonds) within the protein molecule causing a change in shape and loss of functionng of the active site
what is the regulation of metabolism controlled by?
the rate of enzyme production and breakdown
the influence of inhibitors
explain the rate of enzyme production and breakdown in regulation of metabolism
sometimes genes are induced only when enzyme product is recquired to catalyze reactions that may occur infrequently
other genes are being transcribed all the time because their enzyme products are in constant demand eg. genes coding for respiratory enzymes
explain the influence of inhibitors in regulation of metabolism
inhibitors are compounds that cause enzymes to lose activity either by slowing or stopping the chemical reaction
what are the 2 types of inhibitors
reversible or irreversible
explain reversible inhibitors
they cause temporary loss of enzyme activity by forming a non-covalent interaction with the enzyme
they can be competitive and non competitive eg. statins
different types of reversible inhibitos
competitve or non competitive
explain irreversible inhibitors
they cause permenant loss of enzyme activity by forming a covalent interaction to a particular group at the active site
an example of irreversible inhibitor is penicillin
explain competitive reversible inhibiotrs
a competitive inhibitor molecule occupies the active site and blocks the entry of substances= substrate
inhibitor strucutrally resembles the substrate
give example of competitive reversible inhibitor
statins is the inhibitor
the process is:
HMG-CoA= susbtrate is conversed into L- mevalonate and eventually into cholesterol
this process uses HMG-CoA reductase (enzyme) and statins competes with HMG-CoA to go into the active site of the enzyme
statins blocks cholesterol synthesis, lowering cholesterol levels in plasma thus reduces risk of cardiovascular diseases
explain reversible noncompetitve inhibitos
they bind to enzyme but not at active site
the inhibitor binds to an “allosteric site” which is any site on the enzyme that is not the active site
binding results in shift of 3D shape of active site, substrate cant fit, active site= non functional
inhibitor does not structurally resemble the susbtrate
what is feedback inhibition and its benefits
feedback inhibition operates where high levels of the end products deactivates enzyme 1 at the beginning of the metabolic pathway
benefit= prevents overproduction of product being made, balances production of product with the energy of the metabolic pathway
once enough of the product is made in high conc it inhibits the pathway of its fomration so that the cell doesnt waste energy on creating a product already has enough of
example of non competitive inhibitor
= isoleucine
initial susbtrate= threorine (amino acid
enzyme 1= threorine deaminase
end product= isoleucine (another amino acid)
once too mcuh isoleucine made, is binds to allosteric site active site of enzyme 1 (threorine deaminase) is no longer able to catalyze conversion of threorine to intermediate A pathwayd is switched off
this is a reversible reaction where if conc of isolecucine decreases to much, allosteric site is emptied enzyme recommences conversion
explain the effects of inhibiton on enzyme kinetics
when the conc of substrate begins to exceed the akiunt of inhibito the max rate of reaction can be achieved however it takes much higher conc of susbtrate to achieve the max rate
takes approximately same conc of enzyme to reach max rate but the max rate is lower than the unhibited enzyme
example of a irreversible inhibitor
= penicillin (antibiotic)
enzyme= transpeptidase
susbtrate= tetra and penta peptidoglycan
product= peptidoglycan cross link
explain in detail irreverisble inhibitor penicillin
cell wall of bacteiral cell is made of peptidoglycan, a molecule composed of long strands of amino polysaccharides running in parallel, strands linked via transpeptidation, using enzyme called transpeptidase, fuses strands together creating stable link between them which increases strength of cellwall
antibiotics like penicillin resmble peptidoglycan chains, inside the bacteria transpeptidase will miskenly bind to penicillin instead of tetra or penta peptidoglycan the binding is permanent and disables the formation of cell wall
as the cross linking fails to occur the cell wall becomes weak and unstable more prone to changes due to osmosis
the cell bursts from osmotic pressure given the gain of water
what are free enzymes
enzymes which are simple added to solutions, are soluble can diffuse in the reaction medium, substrate can be added directly to sultion, more unstable as they can be directly affected by environmental factors
what are immobilized enzymes
enzymes physically or chemically bound to an inert insoluble support, over which a substrate is passed and coverted to products
what are advantages to enzyme immoblisation
ph and temp stability, recyclability, continuos flow operation, product and quality taste, scale up production, sustainability and efficiency
