Chapter 4.1 Flashcards
Why are enzymes used?
- possible to speed up the rate of reaction of important reactions with temperature and pressure, but this would DAMAGE cell components
So enzymes are used instead
What are enzymes?
Enzymes are biological catalysts
- they increase the rate of reaction without being used up in Biolocial organisms
- globular proteins
What types of reactions do enzymes do? (2)
Where can these be? (Examples) (2)
-Where in bacteria
ANABOLIC = building up in growth molecules from smaller
CATABOLIC (thing catalyse) = breaking down reactions
2) BOTH INTRACELLULAR - reactions for cells such as respiration (fats,Ayse for hydrogen peroxide in cells )
OR EXTRACELLULAR- reactions outside cells like digestion (trypsin for proteins analyse for starch in mouth ) or even outside organism (in bacteria / fungi)
Describe enzyme structure + how catalysations Hallen and why are enzymes highly specfic
- they have an active site, which is where the substrate binds to, determined by tertiary structure
- for the enzyme to work substrate has to fit exactly in (complimentary)
- thus an enzyme substrate complex can be formed and the reaction catalysed
- or else it can’t, thus enzymes are highly specific .
Briefly say Why do enzymes speed up rate of reaction
- enzyme Substrate complex allows for the activation energy to be lowered so overall more reactants can react in successful collisions
- there are two ways
What is the lock and key hypothesis (1)
What happens at each step + remember what complexes made!
In the same way a key will only fit into one lock, the substrate only complimentary and can only fit into one enzyme
- when bound an enzyme substrate complex is formed
- then substrate reacts and products are formed
- this makes aN ENZYME PRODUCT COMPLEX
- THEN PRODUCTS RELEASED
- now Enzyme unchanged can do another reaction again
(Again bonds made put strain / atom groups of substrate held close enough so reaction happens)
What is the induced fit hypothesis!
What happens
- Also shows how high specfic I enzymes are. They have to be able to make the active site of the enzyme change shape exactly to fit their complimentary shape too!
- it works by initial Interactions between enzyme and substrate being weak, but these interactions rapidly cause change in enzyme tertiary 3D structure, that then STRENGHTENS BINDING
- these strengthend bonds between enzyme and substrate now put a strain on substrate bonds, lower activation energy etc
- enzyme substrate = enzyme product complex = split
(Again atom groups Of substrate held close enough so react)
How does the binding of enzyme to Su rate actually lower activation energy (like what actually happens)
Anabolic and catabolic / both
1) FOR ANABOLIC enzyme substrate complexes ensure that RIGHT ATOM groups of substrate are held CLOSE ENOUGH to react, this means any repulsion received is reduced and they can bond easily
2) FOR CATABOLIC Active Site of Enzyme R- groups can also interact with he substrate, creating TEMPORARY BONDS, which puts a strain on the bonds in THE SUBSTRATE, which can weaken the bonds and thus LOWER THE ACTIVATION ENERGY NEEDED SO RATE KF REACTION INCREASES.
Example of extra cellular enzyme - starch digestion
WHat enzymes + where + why (2 steps)
1) begins in mouth , amylase (produced in saliva and from pancreas) breaks down starch into maltose, a disaccharide
2) then small intestine , where maltose broken down into glucose by maltase
- now glucose small enough to enter cell
Example of extracellular enzyme trypsin
What is it Where it made + where it works
Tyrpsin is a type of protease
- catalysed polypeptides into smaller peptides which then broken into amino acid
- trypsin produced in pancreas , and digested in small intestine
- then amino acid can be absorbed by bloodstream
What happens if you increase temperature on rate of reaction for enzymes substrate (key words!)
1) increase to optimum
2) increase past optimum
1) increasing temperature of reaction environment increases rate of reaction
- this is because reactants gain KINETIC ENERGY
- so they VIBRATE , with all more energy (so greater proportion to be at activation energy) and thus collide frequently , leading to SUCCESSFUL COLLISIONS
- thus rate of reaction increases
2) However this only happens until an optimum temperature
- this is the temperature at which the rate of reactions is highest, (no longer limiting but)
- . Past the optimum temperature an increase in temperature can cause ATOMS AND BONDS TO VIBRATE MORE, THUS PUTTING STRAIN ON BONDS LIKE HYDROGEN (or ionic etc) BONDS CAUSING THEM break between R groups in the tertiary structure of a protein .
- This breakage of the bonds causes changes in the 3D structure of the protein, and thus the active site of the enzyme CHANGES
- thus the active site is no longer COMPLIMENTARY TO THE SUBSTRATE , the enzyme is DENATURED AND a complex can’t be made so rate of reactions decrease until all enzyme denatured …
- this Is IRREVERSIBLE
What happens if you DECREASE temperature on rate of reaction for enzymes substrate
-decreasing temperature does not denature the enzyme, and decrease of reaction is not that rapid , here there is less kinetic energy and less proportion of reactants with activation energy essentially, so rate of reaction will be low due to infrequent successful collisions
More on optimum temps on how much temp needs to change for it
- only a small change past optimum temperature is needed for RAPID denaturation , because only a small change in tertiary structure is needed to ruin 3d steucture So no longer COMPLIMENTARY
- Q10 don’t work after denatured
- optimum temp is different for different, could be low could be high
Q10.?
What is it normally for enzyme controlled reactions here
Just a measure of how much the rate of reaction changes with an increase of 10° of temperature.
- here it is increased temp / old temp rate of reaction x 100
2 = doubles every 10°
2) It is normally 2!, but after denaturation this would not apply
- this assumes everything is constant too
How do enzymes deal with extreme temps? In terms of structure
- in cold, structures tend to be less stable so that a small change in temp will denature them, so they have to keep cold
- high temps like for thermphiles will have very stable structures such as high proportions of HYDROGEN BONDS AND
DISULFIDE BRIDGES , which makes them more RESISTANT to temperature changes
Why does PH cause a change in structure in an enzyme?
2 ways
Check summary
- Enzymes are held by various bonds including hydrogen and ionic bonds in r groups of tertiary structure
- high ph= low h+ vice verca
1) hydrogen ions interact with polar and charged r groups. So changing concentration of H+ ions changes the DEGREE OF THIS INTERACTION.
2) ALSO the interaction of hydrogen ions with r groups also affects interaction of R groups with each other
= THUS
- TOO MUCH hydrogen ions, the less r groups can interact with each other
- and TOO LITTLE hydrogen ions= less r groups CAN react with each other
Thus this leads to BONDS BREAKING and thus 3d structure changing, changing active site and so on
-3) as a result enzymes change with PH can only work in a NARROW RANGE (where they can renature too )
Summary
1) amount of H+ ions changes degree of interaction between hydrogen ions and polar / charged r groups, which changes structure
2) amount of h+ ions determine how much other r groups can interact with each other: too much / too little cause little interactions causing bonds to break and 3d structure to change etc
How does pH have effect on enzyme
1) deviating a bit from optimum
2) deviating a lot from optimum
- increasing or decreasing pH towards optimum pH will cause rate of reaction to increase
- however past this pH the structure changes of teritary so active site is altered and rate of reaction decreases.
- HOWEVER, if the pH returned to optimum it will RENATURE and return to higher rates of reaction !
2) however if you take it beyond optimum pH too much , structure of enzyme is IRREVERSIBLY CHANGED, so it cannot renature
- thus enzyme has DENATURED and rate of reaction decreases as substrate no longer complimentary , complex can’t be made etc
When does rate of reaction highest and why
How to work out
Initial # this because at the start you have the highest amount of substrate molecules , over time you will lose some so you will lose rate of reaction
2) draw gradient from 0!!!
