2.4 Enzymes Flashcards
What are enzymes
-proteins made inside cells in the ribosomes
-biological catalysts
What is the tertiary structure
the final shape of an enzyme which is determined by the sequence of amino acids
what are catalysts
substances which speed up biochemical reactions
what can enzymes be affected by
-Ph
-temperature
what is the turn over rate
how fast an enzyme works
what can the active site and shape of substrate be described as
complementary
identify some examples of enzymes
-catalse
-amylase
-pepsin
-lipase
-maltase
-trypsin
where is catalase found and what does it do
in most living organisms that are exposed to oxygen
breaks down harmful hydrogen peroxide
what sort of enzyme is catalyse
intracellular
where is catalase found in eukaryotes
peroxisomes
what sort of reactions do enzymes catalyse
metabolic
identify some extracellular enzymes
amylase
trypsin
why may an enzyme not function
doesn’t have its amino acids in the correct order
why are enzymes specific
they all have differently shaped action sites
define extracellular
excreted onto substance
define intracellular
substrate acted upon inside cells
what is the enzyme product complex
enzyme molecule with product molecules in its action site
what is the enzyme-substrate complex
enzyme molecule with substrate molecules in its active site
what is the product of the enzyme substrate complex
smaller product molecules
what is the product of the enzyme product complex
one larger product molecule
what is the lock and key hypothesis
that the substrate fits perfectly into the enzyme
what is the induced fit hypothesis
the active site is still complementary to the substrate but its active site changes shape to mould around it
what does catabolic mean
breaks down molecules
what does anabolic mean
builds up molecules
what shape are enzymes
globular
what is hydrogen peroxide
a bi product of many metabolic reactions
what is the equation for the break down of hydrogen peroxide
hydrogen peroxide —-> water + oxygen +energy
catalase
what is a limiting factor
factor which can alter the rate of a reaction if all other factors are kept constant
what happens if enzyme concentration increases
-more active sites are available
-more successful collisions
what happens if an enzymes temperature increases
bonds break, tertiary structure unravels, the active site shape is lost and the enzyme denature
how does denaturation by heating happen
heating increases kinetic energy =more collisions
molecules vibrate more so bonds break
substrate is no longer complementary to active site
what are the properties of enzymes
-globular
-soluble in water
-3d tertiary structure
-catalysts
-specific
what is an inhibitor
a substance that reduces or stops a reaction
what is competitive inhibition
substances similar to the substrate which can occupy active sites without triggering reactions inhibiting enzyme activity
what is non-competitive inhibition
inhibitors that can block or change the shape of the active site of an enzyme by binding to the allosteric site
what is substrate inhibition
excess substrate which can compete for the active site, slowing the reaction speed
what is end product inhibition
after the catalysed reaction has reached completion, product molecules stay slightly bound to the enzyme. The enzyme cannot form more of the product than the cell needs
how are metabolic sequences controlled
the product of one enzyme becomes the substrate for the next enzyme catalysed reaction in the metabolic pathway
what happens when the product of the last enzyme catalysed reaction attaches to a part of the first enzyme in the pathway
this binding changes the shape of enzyme 1’s active site, preventing the pathway from running
what is a buffer
something that resists changes in PH
what will you use buffer solutions for in lab investigations
to maintain desired PH for investigating enzyme action at different PH values or to keep the PH constant whilst investigating another factor
how do changes in PH affect bonds within molecules
excess hydrogen ions interfere with hydrogen bonds and ionic forces so the active site of the enzyme will change
how does increasing the concentration of hydrogen ions affect the active site
protons cluster around negatively charged groups
this interferes with the binding
what happens if there is a small change in PH
active site is disrupted
rate of reaction is slow
what happens if the optimum PH is restored
hydrogen bonds reform and the active site shape is restored
what happens at extremes of PH
enzymes denatures
what is the optimum Ph of intracellular enzymes
close to 7
what is the optimum PH of extracellular enzymes
they differ
what is an example of intracellular enzymes + PH
during digestion, amylase that digests starch to maltose works best at a PH of 6.8
what is an example of extracellular enzymes + PH
As food passes in your stomach, hydrochloric acid is secreted giving a low PH. Pepsin works best at values between 1 and 2.
what are coenzymes
organic molecules that bind to enzymes to help them function
what are the 3 types of cofactors
-prosthetic groups
-ions
-coenzymes
what is an example of a coenzyme
-NADP
-Coenzyme A
are coenzymes organic
yes, organic vitamins
what is a coenzymes method of action
binds permanently/not permanently dependant if enzyme contains carbon
what is an example of an inorganic ion factor
chloride ion
what is the method of action of an inorganic ion factor
changes the charge distribution on the surface of the substrate molecule
what is an example of a prosthetic group
zinc
are prosthetic groups organic
no
what is the method of action of prosthetic groups
binds permanently to the active site
what is carbonic anhydrase
an enzyme that catalyses the reaction between CO2 and H2O to form carbonic acid in red blood cells which only functions when a prosthetic group is permanently attached
what are examples of poison inhibitors
-cyanide
-snake venom
what does cyanide do
inhibits respiratory enzymes (cytochrome oxidase) and changes the shape of active site which stops respiration
what does cyanide affect
reactions requiring ATP are no longer supplied so there is no energy which causes cell failure
what does snake venom do
inhibits enzyme (acetylcholinesterase) used to degrade the neurotransmitter acetylcholine
what is the effect of snake venom
stops nerve impulses from being transmitted and stops muscle contraction- leads to flaccid paralysis
what are examples of medicinal inhibitors
-aspirin
-protease
what does aspirin do
contains salicylic acid and binds to enzymes which catalase the formation of prostaglandins
what is the effect of aspirin
prevents the formation of prostaglandins which make nerves more sensitive to pain and swelling
what does protease do
stops protease cutting viral RNA into smaller pieces. The virus can’t inject its RNA into a host cell to replicate
