C1.1 enzymes and metabolism

Question 1

describe what happens when temp is raised a bit with enzymes

Answer 1

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

Question 2

descibre what happens when temp at optimim with enzymes

Answer 2

optimum temp- max rate of reaction
balance between enzyme stability and kinetic energy of reactants

Question 3

descibre what happens when temp is over optimum with enzymes

Answer 3

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)

Question 4

describe effect of ph a bit increased in enzymes

Answer 4

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

Question 5

describe effect of ph at optimum in enzymes

Answer 5

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

Question 6

effect of substrate increse a bit in enzymes

Answer 6

increase chance of collisions between enzymes and susbtrates
greater change of forming e-s complexes
increases in rate of reaction

Question 7

effect of substrate increse at optimum a bit in enzyme

Answer 7

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

Question 8

effect of substrate increse after optimum a bit in enzyme

Answer 8

full saturation of the active sites by susbtrate
rate becomes constant for further increase in susbtrate concentration

Question 9

what is metabolism

Answer 9

the sum of all the chemical reactions that occur within living organisms

Question 10

how are metabolic reactions controlled

Answer 10

by specific enzymes, because of enzyme specificity many different enzymes are required by living organisms

Question 11

metabolism can be considered either:

Answer 11

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

Question 12

metabolic pathways

Answer 12

a series of steps from a starter molecule or precursor toward a final end product
each step is catalyzed by a different enzyme

Question 13

describe image of metabolic pathways linear

Answer 13

percursor chemical——>intermediate chemical—–> end product

Question 14

metabolic pathways can either be….

Answer 14

linear or cyclical
anabolic or catabolic

Question 15

describe image of metabolic pathways cyclical

Answer 15

reactant—-> intermediate —-> intermediate—-> reactant + product

Question 16

what are examples of cyclic metabolic pathways

Answer 16

photosynthesis and the krebs cycle of cellular respiration

Question 17

whats an example of linear metabolic pathway

Answer 17

digestion of starch

Question 18

anabolic pathways

Answer 18

build up complex molecules fro. simpler ones they intake energy and involve reduction/ condensation reactions. an example is photosynthesis

Question 19

catabolic pathways

Answer 19

break down complex molecules into simpler ones, they release energy and involve oxidation hydrolysis reactionsan example is cell respiration

Question 20

is heat generation inevitable? and why?

Answer 20

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

Question 21

what do all chemical reactions recquire?

Answer 21

energy to get started as molecules need to collide with enough energy so reactants have bonds broken moecules are reoriented new bonds are formed

Question 22

what is the initial energy input called

Answer 22

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)

Question 23

what are enzymes

Answer 23

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

Question 24

describe the transition state in the progression of a reaction X energy content of molecules graph

Answer 24

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

Question 25

describe the normal activation in the progression of a reaction X energy content of molecules graph

Answer 25

normal activation energy would cause damage to proteins of the cell. Thus, reduced activation energy makes these reactions possible in cell

Question 26

describe the final of a reaction in the progression of a reaction X energy content of molecules graph

Answer 26

after product formed energy released

Question 27

describe endergonic reactions

Answer 27

consume less energy than activation energy

Question 28

describe exergonic reactions

Answer 28

ralse more energy than activation energy

Question 29

descibr eprocess of enzyme- substrate

Answer 29

1. 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
2. realease= enzyme + products leaving active site

Question 30

explain step 1. collsion of enzyme reaction in detail

Answer 30

• 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

Question 31

explain step 2. collsion of enzyme reaction in detail

Answer 31

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

Question 32

explain step 3. collsion of enzyme reaction in detail

Answer 32

products leave active site
enzyme left unchange and can be reused

Question 33

whats a coenzyme or cofactor

Answer 33

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

Question 34

describe path of usage of a coenzyme or cofactor

Answer 34

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

Question 35

what are coenzymes

Answer 35

organic, non- proteic molecules such as NAD+

Question 36

what are cofactors

Answer 36

inorganic molecules such as CU 2+

Question 37

what is the tertiary strucure of enzymes sensitive to and explain

Answer 37

PH, temp, substrate concentration, those are regulate to avoid denaturation
each enzyme has specific envionrmental conditions in which its efficiency is optimum

Question 38

denaturation

Answer 38

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

Question 39

what is the regulation of metabolism controlled by?

Answer 39

the rate of enzyme production and breakdown
the influence of inhibitors

Question 40

explain the rate of enzyme production and breakdown in regulation of metabolism

Answer 40

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

Question 41

explain the influence of inhibitors in regulation of metabolism

Answer 41

inhibitors are compounds that cause enzymes to lose activity either by slowing or stopping the chemical reaction

Question 42

what are the 2 types of inhibitors

Answer 42

reversible or irreversible

Question 43

explain reversible inhibitors

Answer 43

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

Question 44

different types of reversible inhibitos

Answer 44

competitve or non competitive

Question 45

explain irreversible inhibitors

Answer 45

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

Question 46

explain competitive reversible inhibiotrs

Answer 46

a competitive inhibitor molecule occupies the active site and blocks the entry of substances= substrate
inhibitor strucutrally resembles the substrate

Question 47

give example of competitive reversible inhibitor

Answer 47

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

Question 48

explain reversible noncompetitve inhibitos

Answer 48

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

Question 49

what is feedback inhibition and its benefits

Answer 49

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

Question 50

example of non competitive inhibitor

Answer 50

= 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

Question 51

explain the effects of inhibiton on enzyme kinetics

Answer 51

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

Question 52

example of a irreversible inhibitor

Answer 52

= penicillin (antibiotic)
enzyme= transpeptidase
susbtrate= tetra and penta peptidoglycan
product= peptidoglycan cross link

Question 53

explain in detail irreverisble inhibitor penicillin

Answer 53

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