Enzymes Flashcards
what are reactions catalysed by
enzymes
what are enzymees
biological catalysts
what type of protein are enzyme
globular
what do enzymes do
interact with a substrate molecules causing them to react at much faster rates without the need for harsh environment conditions
what are chemical reactions required growth called
anabolicw
where is energy released from
large organic molecules (glucose)o
how is energy released from large organic molecules
in metabolic pathways consisting of catabolic reactions (breaking down reactions)
how are these large organic molecules obtained
from the digestion of food
what is the specificity of the enzyme
each enzyme catalyses one biochemical reaction
what is activation energy
energy needs to be supplied for most reactions to start
what can enzymes help with
for molecules collide successfully and reduce the activation energy required
describe the lock and key hypothesis
only a specific substrate can fit into an enzyme’s active site
when the substrate is bound to the active site, an enzyme-substrate complex is formed
- the substrate then react and the product is formed in an enzyme-product complex
- the product is then release, leaving the enzyme unchanged and able to take part in subsequent reactions
what puts strain on the bond in the substrate
the substrate is held in such a way by the enzyme that the right atom-groups are close enough to react, the R-groups within the acitve site of the enzyme will also interact with the substrate forming temporary bonds
what is an induced-fit hypothesis
the active site of the enzyme actually changes shape slightly as the substrate enters
describe the initial intereaction between the enzyme and substrate in induced-fit hypothesis
it is relatively weak but these weak interactions rapidly induce changes in the enzymes tertiary sturcture that strengthen binding, putting strain on the substrate molecule
what are intracellular enzymes
enzymes that act within cells
give an example of intracellular enzymes
the synthesis of polymers from monomers, making polysaccharides from glucose, requires enzymes
catalase helps break down hydorgen peroxide
what supplies raw materials (substrates)
nutrients
what form are nutrients in
polymers such as proteins and polysaccharides
why do nutrients need to be broken down intosmaller components
they are too large to enter through the cell-surface membrane
how are these nutrients broken down
by enzymes through the process of digestion (extracellular enzymes)
what are extracellular enzymes
they work outside the cell that made them
how do single-celled organisms use extracellular enzymes
eg. bacteria and yeast, release enzymes into their immediate environment, extracellular enzymes break down the larger molecules (proteins) produce smaller molecules (amino acids and glucose) are absorbed by the cell
how do multicellular organisms use extracellular enzymes
the large molecules still have to be digested so smaller molecules can be absorbed into the bloodstream, from there, they are transported around the body to be used as substrates in cellular reactions
example of extracellular enzymes in multicellular organisms
involved in digestion in humans are amylase and trypsin
describe the first step of the digestion of starch
Starch polymers are partially broken into maltose, which is a disaccharide. The enzyme involved in this stage is called amylase. amylase is produced by the salivary glands and the pancreas, it is released in saliva into the mouth, and in pancreatic juice into the small inestine.
describe the second step of the digestion of starch
maltose is then broken down into glucose, which is a monosaccharide. the enzyme involved in this stage is called maltase, maltase is present in the small intestine
describe digestion of proteins
trypsin is a protease (type of enzyme that catalyses the digestion of proteins into smaller peptides, whcih can then be broken down further into amino acids by proteases.) Trypsin is produced in the pancrease and released with the pancreactic juice into the small intestine, the amino acids produced are absorbed by the cells lining the digestive system and then absorbed into the bloodstream
what biological molecule forms an enzyme
protein
what are the monomers that form proteins
amino acids
describe how the structure of proteins determines enzyme activity
specific 3D shape, tertiary structure, active site binds to substrate and catalyses reaction
explain how catabolism and anabolism are related to metabolism
catabolism is breaking down of molecules, anabolism is building of molecules, reactions involve breaking down and building of molecules
explain lock and key, and induced-fit
both models substrate interact with R-groups in active site binds leading to bond strain in substrate molecule, lock and key substrate is complementary to active site, induced-fit active site is flexible, it changes shape as substrate binds, closer fit between active site and substrate
are enzymes more likely to come into contact with the substrate at a high or low temperature
high
what needs to happen for an enzyme to catatlyse a reaction
they must come into contact with the substrate and the enzyme must be the right shape
what can an enzymes structure be affected by
temperature and pH
describe temperature of being an effect of enzymes
increasing temperature increases kinetic energy in particles
so the particles more faster and collide more frequently so an increase in rate of reaction
what is the temperature coefficient Q10
a measure of how much the rate of reaction increases with a 10oC rise in temperature
in an enzyme controlled reaction this is taken as 2 so it doubles
describe denaturation from temperature
at high temps the bonds holding the protein together vibrate more
as the temp increases the vibrations increase until the bond strain and then break
this results in a change in the precise tertiary structure of the protein and the enzyme has been denatured
what happens when an enzyme has been denatured
the active site changes shape and is no longer complementary to the substrate so the substrate no longer fits into the active site and the enzyme will no longer function as a catalyst
what is the optimum temperature
the enzyme has the highest rate of activity and the temperatures can vary, many enzymes in the human body have an optimum temperature of 40oC
what happens when an enzymes temperature increases over its optimum temperature
it decreases in rate of reaction rapidly
what happens to an enzymes rate of reaction when it hasn’t reached optimum yet
it decreases in rate of reaction but not as rapid as it hasn’t denatured yet
give examples of extremely cold environment
deep oceans, high alititudes and polar regions
give properties of enzymes that are adapted to the cold
tend to have more flexible structures mainly at the active site
making them stable than enzymes that work at higher temperatures
describe thermophiles
organisms adapted toliving in very hot environments
enzymes present in these organisms are more stable than other enzymes
this is because they will have an increased number of bonds, mainly hydrogen bonds
what does a chnage in pH also mean
a chnage in hydrogen ion concentration, more hydrogen ions are present in low pH environments
what is optimum pH
active site will only be in the right shape at a certain hydrogen ion concentration
describe bonding in proteins
hydrogen and ionic bonds between amino acid R-groups hold proteins in their precise 3D shape
these bonds result from interactions between the polar and charged R-groups present on the amino acids forming the primary structure
what is renaturation
if pH returns to optimum after denaturing the protein will resume its normal shape and catalyse reaction agin
will enzyme renature if pH changes significantly
no
when pH is low are R-groups able to interact with each other as much
no, it leads tobond breaking and shape of enzyme chnaging
what enzyme is present in saliva
amylase (pH 7-8)
what is function of amylase
turns starch into maltose
what enzyme is present in the stomach
pepsin (pH 1-2)
what is the function ofpepsin
turns proteins into polypeptides
what enzymes are present in pancreatic juice
trypsin, lipase, amylase, maltase (pH 8)
what is the function of trypsin
turns proteins into polypeptides
what is the function of lipase
turns triglycerides into glycerol and fatty acids
what is the function of maltase
turns maltose into glucose
what does a high concentration of substarte lead to
a higher collision rate with the active sites of enzymes and the formaiton of enzyme-substrate complexes, rate of reaction increases
what does a high cocnentration of enzyme lead to
increase number of available active sites in a particular area or volume
what happens when the rate of reaction increases up to (Vmax) maximum
all of the active sites are occupied by susbtrate particles and no more enzyme-substrate complexes can be formed until products are released from active sites
why is it important that cellular condiitons are kept within narrow limits
so that enzyme activity is not delayed, ensure it is at a rate fast enough to sustain living processes
why cant reactions happen too fast
lead to the build up of excess products
what can enzymes be activated by?
cofactors
what can enzymes be inactivated by
inhibitors
what are inhibitors
molecules that prevent enzymes from carrying out their normal function of catalysts
what are the two types of inhibitors
competitive and non competitive
how comeptitive inhibitors work
a molecule that has a similar shape to the substrate can fit into the active site, this blocks the substrate from entering the active site
what happens when a substrate and inhibitor molecules present in a solution
will compete with each other to bind to the active sites of the enzymes catalysing the reaction, reducing the number of substrate molecules binding to active sites (slows rate of reaction)
is a competitive inhibitor effect reversible
yes as it is only temporary (apart from aspirin)
what is the effect on rate of reaction with competitive inhibitors
reduces rate of reaction for a given concentration of substrate, does not change Vmax
whats an example of competitive inhibitor
statins - used in synthesis of chloesterol
aspirin - irreversible
how does a non competitive inhibitor work
inhibitor binds to the enzyme at a location called allosteric site
this causes the tertiary structure of the enzyme to change (active site changes)
how does a non competitve inhibitor effect rate of reaction
increasing concentration of enzyme or substrate will not overcome the effect of a non competitive inhibitor, increasing concentration of inhibitor decreases rate of reaction
what is the end product inhibition
enzyme inhibition that occurs when the product acts an a inhibitor to the enzyme that produces it
example of non competitive inhibitors
prton pump inhibitors used to treat long term indigestion, irreversibly block an enzyme system responsible for secreting hydrogen ions into the stomach
what is end product inhibition an example of
non competitive inhibiotr
describe respiration
a metabolic pathway resulting in production of ATP, glucose is broken down in a number of steps
what is a cofactor
a non protein substance that bounds to enzymes in order for some of them to work
what are inorganic factors
- they work by helping the enzyme and substrate bind together
- thye dont directly participate in the reaction so arent used up or changed in any way
- eg. chloride ions are inorganic cofactors for the enzyme amylase
what are organic cofactors (Coenzymes)
- they participate in the reaction and are changed by it
- they often act as carriers moving chemical groups between different enzymes
- eg. vitamins
what are prosthetic groups
when a cofactor is tightly bound to the enzyme
give an example of a prosthetic group
zinc ions are prosthetic group for carbonic anhydrase and are a permanent part of the enzymes active site
whats the name of when enzymes are produced in an inactive form
inactive precursor enzymes
why does a cofactor need to be added to a precursor protien
they often need a change in tertiary structure mainly to the active site to be activated
what is the precursor protein called before a cofactor is added
apoenzyme
what is the precursor protein called after a cofactor is added
holoenzyme
what is the word equation for the reaction controlled by catalase?
hydrogen peroxide -> water + oxygen
why is it important to keep all the cylinders the same size in the practical effect of substrate concentration on rate of enzyme controlled reaction
the surface area must be controlled as the surface area affects the speed at which substance can reach the active site
explain the shape of the graph from the effect of substrate concentration on the rate of an enzyme controlled reaction
as the concentration of the hydrogen peroxide increases, there is more substrate available to bind with the active site of catalase via complementary binding, increases each volumes
state 2 limitations of the effect on substrate concentration
cannot control temperature and cannot control the concentration
how to change these limitations
leave cylinders in a water bath at room temp
use solution of enzyme catalase of known volume and concentration
