Enzymes & Proteins Flashcards
what are enzymes
biological catalysts, globular proteins that interact with substrates and cause them to react much faster
anabolic and catabolic
ana= builiding up cata=breaking down
metabolism
sum of all the different reaction pathways in a cell or organism
mechanism of enzymes
molecules randomly collide but need right orientation and speed in order for it to be successful.
enzymes help the substrate molecules collide successfully to form products and therefore lower the activation energy
what is Vmax
maximum initial velocity or rate of an enzyme catalysed reaction(highest capacity of enzyme activity0
lock and key theory
active site is specific shaped area on enzymes in which only the right substrate bind
forms enzyme substrate complex , substrates react and form enzyme product complex then the products are released
substrate and R groups of enzyme can react forming temporary bonds holding it together and when products formed bonds break
induced fit hypothesis
Active site changes shape slightly as substrate enters, interaction between substrate & enzyme weak but interactions induce changes in enzymes tertiary structure that strengthen binding and put strain on the substrate. weakens bonds in substrate(lowers activation energy)
intercellular enzymes
enzymes that act inside the cell
extracellular enzymes
nutrients taken from our food cannot directly enter cell plasma membrane so need to be broken down by enzymes into smaller molecules for digestion
single cellular organisms like bacteria/ yeast release extracellular enzymes to their immediate environment to break down larger molecules that can be digested
digestion of starch
1starch broken down into disaccharide maltose by the enzyme amylase which is found in the salivary gland and pancreas
2maltose brown down into monosaccharide glucose by maltase found in the small intestine
glucose can be absorbed by cell lining of digestive system then is absorbed into the bloodstream
digestion of proteins
trypsin is a protease that breaks proteins into smaller peptides which can then be broken down into smaller amino acids. Made in the pancreas and released into the small intestine where it acts on proteins which is then absorbed into cell lining then the bloodstream
how does temperature affect proteins
increase particles Ke
particles move faster and more
collisions
in enzymes more enzyme substrate complex formed
temperature co-efficient q10
measure how much the Ror increases with a 10*c increase in temperature
for enzyme controlled reactions usually taken as 2
denaturing enzymes
at high temps the bonds holding the proteins together vibrate and break causing the tertiary structure to irreversibly change making it lose its complementary function(denatured)
active site changes shape and can no longer for ES complexes so no longer function as a catalyst
what is optimum temperature
the temperature in which enzymes have the highest rate of activity for humans its usually 40*c once enzymes have denatured above optimum temperature the rate of reaction decreases rapidly
q10 no longer efficent
temperature extremes
enzymes adapted for colder temperatures are more flexible mostly at active site (less stable than enzymes at higher temperatures) smaller temp changes denature them
for warmer temperatures enzymes have increased H bonds and disulphide bridges to withstand temperature increase
Ph
acidic conditions have many H+ ions in which react with polar R groups causing their current bonds to break rather than bonding with each other , within a range if the ph returns to normal the enzyme renatures
at extreme changes enzyme irreversibly changed no longer complementary and can no longer act as a catalyst
substrate & enzyme concentration
increasing substrate concentration increases the number of collisions with the active site more ES complexes so higher rate of reaction same with enzymes more active sites available
up until V max where the maximum rate of reaction occurs until another factor is increased
competitive inhibition
similar shape molecule
blocks substrate from active site
cannot carry out function
they compete with each other for the enzyme, this reduces the number of substrate molecules that can bind so slows down the rat of reaction mostly reversible
competitive examples
statins used in the synthesis of cholesterol, prescribed to reduce blood cholesterol concentration( can cause heart disease if too high)
Non competitive inhibition
binds to allosteric site
permanently changes shape of active site
no longer complementary so cannot bind to enzyme
effects of non como
increasing enzyme concentration doesn’t effect the rate of reaction but increasing non competitive inhibitors concentration causes slower rate of reaction less active sites available
examples of irreversible non competitive inhibitors
proton pump inhibitons used to treat long term indigestion( irreversibly block enzyme that secretes H+ ions into the stomach. PPIs vert effective in reduce excessive stomach acid
end product inhibition
product of an enzyme catalysed reaction acts as an inhibitor to the enzyme that made it to maintain concentration levels
what is a cofactor
an inorganic molecule that helps carry out the function of a biological catalyst, may transfer atoms from one reaction to another
What are co enzymes
organic molecules that form a part of the active site on an enzyme
common cofactors
obtained by our diet iron, calcium, chloride ions, zinc ions. Amylase breaks down starch chloride ions needed for the correct formation of the active site
common co enzymes
derived from vitamins class of organic molecule found in the diet. Vitamin B3 used to synthesise NAD, a coenzyme responsible for transfer of H atoms between molecules in respiration
prosthetic groups
Cofactors that are required by enzymes to carry out catalytic function, some cofactors are loosely/ temporarily bound to the enzyme, prosthetic groups are a permanent feature of proteins
precursor activation
most enzymes are produced as inactive precursor enzymes, mainly for enzymes that can cause damage to cells that produce them or the tissues they are released too.
need to undergo a change in tertiary shape to be activated by a cofactor
apoenzyme to holoenzyme
activation of enzymes
sometimes done by action of another enzyme that cleaves certain bonds in a molecule , or changes in conditions that permanently alter the tertiary structure
Eg when stomach acid activates pepsinogen with the H+ (digestive enzyme)
