FB 4 enzymes onwards Flashcards
what are anabolic reactions
building up
what are catabolic reactions
breaking down
what is the metabolism
all the different reactions and reaction pathways
what is the Vmax
enzymes can only increase rates of reaction to a certain point
(maximum initial velocity)
what are extracellular reactions and give example
act outside of cells and are secreted
as all reactions require substrates which need to be constantly supplied to cells but some (like polymers like proteins and polysaccharides) are too large to enter cells so must be broken down first.
single celled and multicellular use extracellular enzymes to make use of nutrients
fungi produce extracellular enzymes that work outside the body
amylase and trypsin are both involved in digestion in humans
describe the mechanism of an enzyme reaction
for reaction to happen, molecules need to collide with right orientation when high temperatures and pressures are applied the speed of molecules increases along with number of successful collisions and RoReaction
enzymes lower the activation energy as they help the molecules collide successfully
(specific tertiary structure)
what is enzyme specificity
many different enzymes are produced by organisms as each enzyme catalyses one biochemical reaction
what is the lock and key hypothesis
idea that the tertiary structure of an enzymes has an active site which is complementary to the shape of a specific substrate molecule.
>when substrate bound to active site an enzyme substrate complex is formed
>substrate/s reacts and product/s are formed
>enzyme is unchanged
>substrate held in a way by enzyme that R groups and atom groups are close enough to interact
what is the lock and key hypothesis
idea that the tertiary structure of an enzymes has an active site which is complementary to the shape of a specific substrate molecule.
>when substrate bound to active site an enzyme substrate complex is formed
>substrate/s reacts and product/s are formed
>enzyme is unchanged
>substrate held in a way by enzyme that R groups and atom groups are close enough to interact forming temporary bonds and puttings strain on the bonds in the substrate
what is the induced fit hypothesis
> active site of enzymes actually changes shape slightly as the substrate enters
more accepted idea/model
initial reaction between enzyme and substrate is weak but these weak interactions rapidly induce chnages to the tertiary structure which strengthen binding and putting strain on the substrate molecule
> this weakens bonds and lowers activation energy
what is the effect of pH on enzyme reaction
> hydrogen bonds and ionic bonds between R groups hold the protein in precise 3D shape
(these bonds resulted from interactions between polar R groups in the amino acids forming the primary structure)
> active site only right shape at certain H+ion concentration. if pH returns to optimum the enzyme returns to normal by renaturation
denaturation= substrates can no longer bind to active site
the more H+ ions the less the R groups are able to interact. bonds break and shape of enzyme changes.
very narrow range of pH
eg)pepsin works at pH 2
amylase pH 7 trypsin,lipase,maltase and amylase pH 8
what is the effect of temperature on enzyme reaction
> increases the KINETIC ENERGY of the particles
particles move faster and collide more frequently
enzymes work at an optimum temperature
what is the effect of enzyme concentration on enzyme reaction
rate of reaction increases to its Vmax
at this point all active sites are occupied and no more enzyme substrate complexes can form
what is the effect of substrate concentration on enzyme reaction
> more collisions with active site and more enzyme substrate complexes form and reaction increases
how is a serial dilution carried out
just read
The sample/culture is taken in a test tube and six test tubes, each with 9 ml of sterile diluents, which can either be distilled water or 0.9% saline, are taken.
A sterile pipette is taken.
1 ml of properly mixed sample/culture is drawn into the pipette.
The sample is then added to the first tube to make the total volume of 10 ml. This provides an initial dilution of 10-1.
The dilution is thoroughly mixed by emptying and filling the pipette several times.
The pipette tip is discarded, and a new pipette tip is attached to the pipette.
Now, 1 ml of mixture is taken from the 10-1 dilution and is emptied into the second tube. The second tube now has a total dilution factor of 10-2.
The same process is then repeated for the remaining tube, taking 1 ml from the previous tube and adding it to the next 9 ml diluents.
As six tubes are used, the final dilution for the bacteria/cells will be 10-6 (1 in 1,000,000).
what is the temperature coefficient
Q 10- how much the rate of reaction increases with a 10 degree rise in temperature
calculated by taking to rate of reaction at two temperatures
why do some enzymes need coenzymes, cofactors and prosthetic groups
some need non-protein helper molecules which can either transfer atoms/groups between reactions or may form part of the active site of the enzyme.
if a cofactor is organic/contains carbon its a coenzyme
what is Cl- a cofactor for
amylase
breaks down starch and contains a Cl- ions needed for active sites specific shape
what is the prosthetic group for carbonic anhydrase
Zn2+
what are a common source of coezymes
vitamins
eg) B3 is used to synthesise NAD which transfers H+ions in respiration
alcohol dehydrogenase needs NAD+ to accept hydrogen produced when ethanAl is produced by ethanOl
what are thermophiles and psychrophiles
thermo- hot springs
psychro- cold
where are many inorganic cofactors obtained
obtained from the diet as minerals eg) Zinc, Iron, calcium and chloride
what is a prosthetic group
tightly bound/ form permanent structure of the protein eg) Fe ion prosthetic group for haemoglobin
or Zinc Zn2+ ions that form part of carbonic anhydrase structure which is needed for the metabolism of CO2
how do cofactors work
chnage the tertiary shape of an enzyme to activate the active site as many enzymes are in an inactive formcalled ‘inactive precursor enzymes’ or apoenzymes
active enzymes are called holoenzymes
why are some enzymes kept in inactive form until needed
could cause damage in active form in cells when not needed
-they change the 3Y structure caused by action of another enzyme which changes the pH/ temperature which can then activate the precursor enzyme (proteases)
eg) inactive pepsinogen released into stomach tp digest proteins and the acidic pH activates the enzyme pepsin
this adaption is to protect the body from the digestive action of pepsin
what are precursor enzymes also called if they change the conditions like pH or temp which changes tertiary structure change an actives another precursor enzyme
zymogens or proenzymes
how does blood clotting coagulation cascade work
blood clotting process only begins onceplatelets aggregate on sides of tissue damage
this releases clotting factors like factor X
factor X is dependent on cofactor vitamin K for activation
prothrombin» thrombin (a protease)» soluble fibrinogen»» insoluble fibrin fibres
insoluble fibrin fibres together with platelets help blood clot
competitive inhibition binds to…
non-competitive inhibition binds to..
-active site of enzyme mostly temporarily apart from aspirin
decreases RoR but doesnt change Vmax
-allosteric site of enzyme changing the 3Y struct so active site changes shape. enzyme cant carry out function at all
does change V max lowers
example of competitive inhibitors
- statins which are used to syntheise cholesterol and are regularly prescribed to people to reduce blood cholesterol as high levels cause heart disease
- aspirin- irreversibly inhibits the active site of COX enzymes, preventing synthesis of prostaglandins and thromboxane which are chemicals that produce pain and fever.
example of non-competitive inhibitors
proton pump inhibitors treat long term indigestion
they irreversibly block enzyme system that secretes H+ ions into stomach so reduce production of stomach acid.
what is end product inhibition and ATP example
product of a reaction acts as an inhibitor to the enzyme that produces it which acts as a negative feedback mechanism.
>eg ATP which regulates ATP production in metabolic pathway of respiration
ATP binds to allosteric site of PFK preventing the addition of a phosphate group to glucose meaning it isnt broken down and ATP not produced at same rate
when ATP used up less is bound to PFK so enzyme PFK is able to add second phosphate group to glucose and respiration continues and more ATP produced.
why are membranes important
- compartmentalisation- vital as it stops incompatable reactions
- keeps environment suitable for chemical reactions same
- allow for cell signalling and are sites of cell communication
what is the function of phospholipids
> outersurface of hydrophilic heads interact with water
movement of phospholipids in membrane causes movement of other components
what is the function of cholesterol
maintains membrane stability and fluidity
without this would be rigid and solid and phospholipids group too closely
what is the function of glycolipids
cell markers/ antigens
>cell recognition by cells of the immune system
important in phagocytosis
what is the function of glycoproteins
receptors to cell signals
>when chemical binds to receptor it sets off a direct response in cell cascade of events
> act as receptors for neurotransmitters like acetylcholine to trigger/prevent impulse transmission to next neurone
receptors for peptide hormones like insulin and glucagon which affect uptake of glucose
what are the factors affecting membrane structure and permeability
> temperature-makes more fluid and loses structure and breaks down completely
carrier and channel proteins will also be denatured at high temps so membrane permeability affcected
> solvents- many organic solvents are less polar than water like alcohols , organic solvents will dissolve membranes (which is why alcohols used in antiseptics)
non-polar alcohol molecules can enter membrane disrupting the membrane.
> can stop nerve impulses being transmittted for example
what is diffusion
the net overall movement of particles from a region of higher concentration to a region of lower concentration through a partically permeable membrane
passive process
what is facilitated diffusion
channel proteins which polar molecules and ions can pass through
these membranes are selectively permeable and are specific to 1 molecule or ion
what is active transport
requires energy against the concentration gradient
how do beta blockers work
bind to cell receptors like glycoproteins
factors effecting the rate of diffusion
temperature-
concentration difference-
factors effecting the rate of diffusion
temperature- higher the temperature the higher the rate of diffusion
concentration difference- the greater the difference in concentration the faster the rate of diffusion because overall movement from higher conc. to lower is larger.
what is bulk transport
another form of active transport
where larger molecules like hormones and enzymes are too big to move through channels or carrier proteins
>moved into and out of cell by bulk transport
eg) endocytosis
what is endocytosis
bulk transport of material into cells
>2 types: phagocytosis (solids) and pinocytosis (liquids)7
1) cell surface membrane invaginates when it comes into contact with material to be transported.
2) membrane enfolds the material until evntually the membrane fuses forming a vesicle
3) vesicle moves off into cytoplasm for eg) further processing within the cell like vesicles with bacteria move towards lysosomes to be digested by enzymes
what is exocytosis
reverse of endocytosis. vesicles form on Golgi apparatus move toward and fuse with cell surface membrane and are then released outside cell
which energy is required for these processes
ATP required for movement of vesicles along cytoskeleton, changing shape of cells to engulf materials and the fusion of cell membranes as vesicles or as they meet at cell surface membrane
what are the effects of different water potentials on plant cells and animal
higher water potential of external solution»_space;»»water enters cell
»»>swells and becomes turgid»»protoplast pushed against cell wall
same for animal
in animals too much can swell and burst cell or little shrivels
if animal cell placed in solution with lower water potential than cytoplasm it will LOSE water and shrink
