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52 Cards in this Set
- Front
- Back
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Define active site |
Indented area on the surface of an enzyme molecule with a shape that is complimentary to the substrate molecule |
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Define Catalyst |
CHemical that speeds up the rate of reaction and remains unchanged and is reuseable at the end of the reaction |
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What is Extracellular? |
outside the cell |
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What is intracellular? |
inside the cell |
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WHat is the metabolism? |
the chemical reactions that take place within living cells or organisms |
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What is the substrate? |
molecule that is altered by an enzyme-catalysed reaction. |
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How do metabolic disorders form? |
The instructions for enzymes are encoded in genes if the genes have mutations the sequence of amino acids is altered. altering the tertiary structure and prevent it from functioning making the enyme deficiant. |
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WHy is the enzyme so specific? |
the teritary structure of the active site is crucial as it's shape is complimentary to the shape iof the substrate molecule. so each tpye of enzyme is highly specific in it's function as it can only catalyse a reaction involving a particular type of substrate molecule that fits into it's active site. |
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What is catabolic? |
metabolites are broken down to smaller molecules and release energy |
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What is anabolic? |
energy is used to synthesis bigger molecules from smaller ones. |
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give an example of a intracellular metabolic reaction? |
photosynthesis or respiration |
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Give the features of an intracellular enzyme? |
catalyse reactions in the cell may be located in membranes or free in cytoplasm e.g. lysosomes in vescicles |
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Give the features of extracellular enzymes? |
catayse reactions outside the cell fungal hyphae secrete enzymes that digest complex organic molecules the soluble monomers then absorbed digestive enzymes secreted from cells into digestive system. |
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What are cofactors? |
substances that has to be present to ensure an enzyme-catalysed reaction takes place at the appropriate rate. |
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What is the enzyme substrate complex? |
complex formed by temporary binding of enzyme and substrate molecules during enzyme catalysed reactions. |
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What is a prothetic group? |
a cofactor that is permantly bound by covalent bonds to an enzyme molecule e.g. haem. |
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What prothetic group is important to carbon dioxide being carried in the blood? how? |
The enzyme carbonic anhydrase contains a zinc ion prothetic group to it's active site. this enzyme is found in erythrocytes and catalyses the interconversion of carbon dioxide and water to carbonic acid, which then breaks down to protons and hydrogencarbonate ions. this reaction is reversable doeending on the concentration of substrate or product molecules. |
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What is an enzyme-substrate complex? how does it work? give an example |
during an enzyme catalysed reaction, the enzyme and substrate molecules temprarily bind together to form an enzyme-substrate complex. the presense of certain ions that may tempoarily bind to either sunstrate or the enzyme molecule that may ease the formation of enzyme-sunstrate complex's and therfore increase the rate of reaction. Some cofactors act as co-substrates- they, with the substrate for mthe correct shape to bind to the active site of the enzyme some cofactors change the charge distribution of the surface of the substrate mlecule or that of the enzyme's active site making the temporary bonds in the enzyme- substrate complex easier to form. the enzyme amylase digests starch to maltose and will only function if chloide ions are present. |
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What are coenzymes? Why are vitamins important to the diet? |
coenzymes are small organic non-protein molecules that bind temporarily to the active site of the enzyme molecule, either just before or at the same time that the substrate binds. the coenzymes are chemically changed during the reaction and they need to be recycled to their original state, sometimes by a different enzyme. many coenzymes are derived from water-soluble vitamins. if these vitamins are deficiant in the diet of humans they can cause certain diseases |
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What is an enzyme product complex? |
enzyme molecule with product molecule in it's activew site. the 2 are joined temporarily by non-covalent bonds. |
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how do enzymes used as catalysts |
by providing an alternative pathway with a lower activation energy and doesn't get used up. not used up in reaction each enzyme has a single,specific function catalyising one reaction with one substrate. their globular structure contains a cleft or pocket called the active site. |
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Describe the features of an enzyme |
specific 3D tertiary or Quaternary structure dtermined by gene sequencecing high in alpha helices hydrophobic and hydrophillic R groups Globular Soluble Made of amino acids. |
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What are endotherms? |
enzymes that allow reactiosn to occur at body temperature and by maintaining it. |
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What are ectotherms? |
they don't maintain constant internal temperature, enviroment regulates their temperature. they need to eat less as a result. |
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How do enzymes and substrates come together? |
relies on successful collisionss between enzyme, active site and sunstrate collisions are random and must be between correct enzyme and substrate (complimentary) at the correct angle, at the correct energy |
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give the features of the active site. |
contains 10 amino acids within the cleft, complimentary shape to specific sunstrate the active site and R group on the substrate align. |
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How is product formed from enzyme-catalysed reactions? |
Temp hydrogen bonds hold the substrates in the active site enzyme-substrate complex forms- active site squeezes forming the enzyme-product complex then products are released the enzyme isn't used up. |
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Who proposed the Lock and key method and what is this? |
Fischer, 1894
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What is the induced fit model? how is it different? who proposed it? |
Koshland argued the lock and key doesn't explain how the enzyme-substrate complex is stabalised suggests that the active site isn't rigid and fixed but induces a shape to give it a good fit. So moulds it around the substrate molecule e.g. putting on a glove. it will only accept a hand shape but will mould to the hand. the active site still has a complimentary shape but the subtle changes of the side chains (r groups) make up the active site resulting in a more precise conformatino that exactly fits the sunstrate molecule. this moulding binds more effectively to the active site. an enzyme substrate complex is formed and nono-covalent forces e.g. hydrogen bonds, ionic attractions bind the substrate molecule to the active site- enzyme-substrate complex= stabalised the substrate molecules are then converted to product molecules and now form an enzyme-protein complex. as the product molecules have a slightly different shape from the substrate the complex is destablised from the pressure. they detatch from the active site the enzyme is now free to catalyse another reaction. |
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What are metabolites? |
Reactants, intermediates and products |
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How are the metabolic processes governed by a series of enzyme catalysed reactions? |
In a metabolic pathway the product of one reaction can act as a substrate for the next. if the product builds up, it will feedback (feedback inhibitation) or end product inhibitation ( the desirable product has been reached) if the product is inhibited by feedback it doesn't have to stop everything, only stop that pathway and can activate another. |
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What are the 4 things that affect Enzyme catalysed reactions? |
Ph Conc. Of Enzyme Conc. Of substrate Temperature |
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Explain this graph |
The increase in kinetic energy causes more successful collisions between the substrate and active site of the enzyme so an increase rate in the formation of enzyme - substrate complexes. leading to an increase in product. At the optimum temperature enzyme reaches turnover point which is where all active sites are occupied As temperature increases there is more kinetic energy which causes vibrations within the molecule causing bonds to break. This disrupts the active site and so it is no longer complimentary to the substrate and so the enzyme is denatured. |
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What the the temperature coefficient and how do we measure it? |
Q10- the rate by which a process increases for every change in temperature of 10°C Q10= rate of reaction at (T+10) °C /rate of reaction at T °C For most test tube reactions Q10 = 2 So for every rise in 10°C the rate of reaction doubles until the enzyme passes it's optimum than Q10 drops. |
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Explain this graph are pH reactions reversable? why? why not? |
Interactions between H+ or OH- of the surroundings and amino acid R groups Alpha helices and beta sheets ‘unwound’ Disrupts tertiary structure Interact with amino acids lining active site, active site no longer compliments the substrate Rate of reaction slows at small changes Reversible if change is not too great because original interactions can occur if you hange the PH back. Narrow, optimum, specific pH for every enzyme |
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Explain this graph and why the rise isn't linear |
Increasing enzyme conc increases availability of free active sites Increased chance of successful collisions and formation of ESC, more product formed If substrate conc is limited the reaction will plateau, then stop If substrate conc is increased the rate will increase the rise isn't linear because as more product is formed more gets in the way of the reactions. |
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Explain this graph |
Increasing substrate conc increases chances of successful collisions More ESC, more product Substrate conc id a limiting factorUntil all active sites are occupied- turnover number Adding more substrate will not increase the rate of reaction- it is no longer the limiting factor |
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How do you calculate standard deviation? |
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How do you calculate initial rate of reaction? |
To calculate initial reaction rate a line is drawn at tangent to the steepest part of the curveThe gradient of the line is then calculated
gradient=Change in y/ change in x Rate of reaction is fastest at start due to no product getting in the way. |
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Why is the initial rate of reaction the fastest/ |
At start of reaction all substrate is unreacted
All enzyme active sites are free Chance of successful collisions between enzyme active site and substrate is at its greatest ….so the rate is fastest! |
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Why does the rate of reaction slowly drop after the initial burst? |
As ESCs are formed product is released
The concentration of substrate decreases The chances of successful collisions decreaseThe rate drops |
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Why does it take longer for enzymes in the intestines to start working compared with the ones in the stomach/ |
B has a slower increase because acid comes from the stomach and needs to be neutralised before the enzyme starts working properly.
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Define inhibitor and the 2 types of inhibitor |
A substance that slows the rate of an enzyme catalysed reaction by affecting the enzyme in some way
Competitive non-competitive |
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How do competitive inhibitors work? |
Inhibitor has similar shape to substrate (not the same)
Inhibitor fits into active site- no reaction takes place- due to not having the EXACT shape/R groups that interact w/ molecules lining Active Site. Substrate cannot bind while inhibitor present Level of inhibition depends upon conc of enzyme and inhibitor |
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Why does the graph for competitive inhibitors plateau? |
When it plateus conc of substrate significantly higher than conc of inhibitor so influence of inhibitor is negligible
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How do non-competitive inhibitors work? |
Inhibitor binds to enzyme at allosteric site and distorts tertiary structure and active siteSubstrate cannot bind whilst inhibitor bound
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Why is non-competitive inhibitors so bad for humans? |
Non competitive inhibition can be permanent
The reaction cannot be reversed and the enzyme denatures Cyanide inhibits cyctochrome c, an enzyme involved in respiration Strychnine binds to a glycine receptor in the spine causing convulsions |
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Give an example of good inhibition |
Metabolic pathways are regulated by feedback inhibition This is an example of negative feedback
End product inhibition After catalysed reactions have reached completion , product molecules may stay bound to the enzyme. This means the enzyme cannot form more of the product than the cell needs. This is known as negative feedback. The end of products can also act as non-permanant, non-competitive inhibitors and bind to the enzyme stopping the production so the product doesn’t build up in the cell.
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Why do we have organelles for metabolic activity? |
Metabloic reactions are carried out in particular regions or organelles in the cell. This increases the efficiency of metabloism. Multi-enzyme complexes also do this by keeping Enzymes and substrates in same vicinity and reduces diffusion time.
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how do drugs and toxins work? give some examples |
Many drugs and toxins work through inhibition of enzymatic pathwaysIbuprofen and aspirin inhibit the action of cyclo-oxygenaseThe COX enzyme activates prostaglandins which have a role in our immune responseTheir production leads to inflammation, heat and pain
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What is the balance between a drug being beneficial and the onset of side effects called? |
therapeutic window
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How do snake venom and tetanus work? |
Snake venom and tetanus both cause paralysis They each prevent the release of enzymes that degrade neurotransmitters released at the synapse In the absence of this enzyme no action potential is generated and muscles remain contracted This leads to paralysis and potential death from suffocation
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