2.4 enzymes Flashcards
what are enzymes
biological catalysts that speed up the rate of reactions without being used up
what is the active site of an enzyme
area on the surface which is complementary to the shape of the substrate molecules
what is a catalyst
chemical/ substance that speed up the rate of reaction without being used up/changed
what is the turnover number
the number of reactions that an enzyme molecule can catalyse per second
what is an extracellular enzyme and exapmles
works outside of cells
amylase, trypsin
what is an intracellular enzyme and examples
made and retained in the cell
catalase
what are metabolites
the reactants, intermediates and products
what is a catabolic reaction
metabolites are broken down into smaller molecules and release energy
what is an anabolic reaction
energy used to synthesise larger molecules
what is metabolic/metabolism
the chemical reactions that that place inside cells
what is a product and substrate
molecule produced from substrate molecules
molecule altered by an enzyme
what does catalase do, consist of and where is it found
protects the cell from damage from reactive oxygen by breaking down hydrogen peroxide
4 polypetide chains and a haem group (iron)
vesicles
what does amylase digest, where is it produced and acts
starch into maltose
pancreas/salivary glands
acts in the mouth
what does trypsin do, where is it produced and acts
digests proteins into smaller peptides by hydrolysing peptide bonds
pancreas
acts in the lumen of small intestines
describe the induced fit model and how it releases products
the active site and substrate still have a complementary shape
when binded the active site changes shape so it fits around the substrate more closely forming an enzyme substrate complex
products have been converted it forms an enzyme product complex which detaches due to difference in shape from the active site released
what is an enzyme substrate complex
enzyme with substrate molecule in its active site bound by non covalent bonds
what is a enzyme product complex
substrate is built up or broken down into a product in its active site bound by non covalent bonds
describe the lock and key model forming smaller products
active site is a fixed shape and complementary to substrate
temporary hydrogen bonds hold substrate and enzyme together forming enzyme substrate complex
substrate broken down into smaller products
describe the lock and key model forming larger products
two smaller substrates fit into active site, forms an enzyme substrate complex
bonds form between substrate molecules forming an enzyme product complex
larger product leaves the site
describe the induced fit hypothesis
substrate and active site are complementary
active site changes shape of the side chains (R groups) slightly to have a closer fit
how do enzymes lower the activation energy
specific active site to substrate
brings the molecules close without excessive heat
so activation lowers and rate of reaction speeds up
identify the factors impacting rate of enzyme activity
temperature
pH
enzyme concentration
substrate conc.
how does temperature speed up metabolic reactions
gains kinetic energy so molecules move faster
increases rate of successful collisions
rate of ES complexes increases so the ROR increases
up to the maximum point/ optimum temperature
how are enzymes denatured by temperature
heat makes molecules vibrate which breaks weak bonds holding the tertiary structure of enzymes active site
ROR decreases as substrates no longer fit
as more heat applied the active site irreversibly changes and is no longer complementary
reaction no longer takes place = denatured
what is temperature coefficient Q10
increase in rate of reaction when temperature increases by 10 degrees
what does Q10=2 mean
ROR doubles as increased by 10 degrees
what is pH
indicates whether a subtance is acidic, alkaline, or neutral
what is a buffer
something that resists changes in pH
how does change in pH impact enzymes
increases concentration of hydrogen ions (positive)
attracted to negative ions on active site
H+ interfers with hydrogen bonds and ionic forces holding tertiary structure
causes it to change shape
ROR decreases as substrate no longer fits
what happens when enzymes optimum pH is restored
bonds reform and active site shape restored
what is a competitive inhibitor
inhibition of an enzyme where the inhibitor has a similar shape to the substrate
competes for the enzymes active site
blocks it and prevents formation of enzyme substrate complexes
what is a non competitive inhibitor
inhibition of an enzyme where the competitor molecule attaches to the allosteric part of the enzyme/ not the active site
changes the shape of the active site so substrate is no longer complementary and no more ES complexes forming
what is a reversible inhibitor
inhibitor can be released to resume enzymes function
what happens to the rate of reaction with a competitive inhibitor
competes directly with substrate molecule
reduces the rate of ES complexes forming and products being formed
slower ROR
how can you reverse the effects of competitive inhibitors
increase the concentration of substrates
more chance of enzyme colliding with substrate
what happens to ROR with a non competitive inhibitor
the maximum rate reduces
what is end product inhibition
enzyme catalased reactions are regulated by product molecules staying tightly bound to the enzyme so no more can be formed
how do presence of organelles increase efficiency of metabolic reactions
enzymes are bound to organelle membranes
name two metabolic poisons that act as enzyme inhibitors
cyanide
snake venom
what is cyanide made of, what does it do and how
inhibits aerobic respiration and catalase
when ingested KCN is hydrolysed to produce hydrogen cyanide a toxic gas that dissolves into H+ and CN- ions
binds irreversibly to enzyme in mitochondria
inhibits final stage of respiration
what does snake venom do
inhibits enzyme acetylcholinesterase (AChE)
which brekas down neurotransmitter ACh
if inhibited it causes muscle contraction/ paralysis as ACh stays bound to receptors on muscle membrane
name medicinal drugs that act as medicinal inhibitors
aspirin
ATPase inhibitors
ACE inhibitors
Protease inhibitors
nucleoside reverse transcriptase inhibitors
what are cofactors
non protein substance that enzymes require in order to function properly
what are coenzymes
organic cofactors that bind temporarily to active site of enzyme
Accept or donate hydrogen ions
contain carbon
what are inorganic cofactors
inorganic molecules that help substrate and enzyme bind together but dont get directly used in reaction
name the cofactor that is permanently bound to enzyme
prosthetic groups
name the prosthetic group in carbonic anahydrase
zinc ion
name the cofactor in amylase
chloride ion
what happens to coenzymes during reactions
bind to enzyme
continually recycled to original state
act as a carrier between enzymes
name a source of coenzymes
vitamins
NAD is derived from vitamin B3
name a source of cofactors
minerals
State the difference between cofactors and coenzyme
cofactors = a non-protein component to help enzymes carry out their functions
Coenzymes = organic cofactors
explain what happens when substrate concentration increases
more ESC can form
more product form
ROR increases
explain what enzyme concentration does
more active sites available
more successful collisions
more ESC can form
