3 enzymes Flashcards

Question

adv of enzyme immobilisation

Answer 1

-enzymes expensive so immobilise so less money & more stable (stability at different temperatures), less likely to denature, and no contamination of substrate -ease of reuse -high storage stability -high SA, insolubility, stability to pH variations eg lactose (galactose + glucose), broken down by lactase

Answer 2

body cant produce lactase=> -bind lactase to inert substance (alginate beads) -beads contain lactase -run milk through beads -lactase hydrolyses lactose -lactose-free milk produced

Answer 3

enzymes = globular proteins that catalyse reactions inside cells (intracellular enzymes) or are secreted to catalyse reactions outside cells (extracellular enzymes) - shape (as well as the shape of the active site of an enzyme) is determined by the complex tertiary structure of the protein that makes up the enzyme and is therefore highly specific

Answer 4

both enzymes and substrates were rigid structures that locked into each other very precisely, much like a key going into a lock

Answer 5

-enzyme and its active site (and sometimes the substrate) can change shape slightly as the substrate molecule enters the enzyme -changes in shape: conformational changes -ensures an ideal binding arrangement between the enzyme and substrate -maximises the ability of the enzyme to catalyse the reaction

Answer 6

Measuring the 📍rate of formation of a product using catalase📍 Measuring the 📍rate of disappearance of a substrate using amylase📍

Answer 7

Hydrogen peroxide is a common but toxic by-product of metabolism - it must be broken down quickly Catalase: an enzyme found in the cells of most organisms that breaks hydrogen peroxide down into water and oxygen Hydrogen peroxide (SUBSTRATE) and catalase are combined and the volume of oxygen generated is measured in a set time The rate of reaction can then be calculated (PRODUCTION OF OXYGEN / CM3) equipment: potato cubes (source of catalase), hydrogen peroxide (w potato in it), conical flask, bung, delivery tube, measuring cylinder, container w/ water to exclude air during oxygen collection

Answer 8

Amylase: a digestive enzyme that hydrolyses starch into maltose and glucose. Amylase functions best at pH 7 and 37℃ (all enzymes operate best under specific optimal conditions) -Amylase and starch (SUBSTRATE) are combined and this reaction mixture is then tested for starch at regular time intervals -done by taking samples from the reaction mixture at each time interval and adding each sample to some iodine solution (starch forms a blue-black colour with this solution) In this way, the time taken for starch to be broken down can be measured -CAN BE repeated under a variety of conditions (e.g. by altering pH or temperature) and the reaction rates can then be compared equipment: pipette, spotting tile [[each well contains 1 drop of iodine solution to test for starch]], amylase + starch solution

Answer 9

-able to measure light absorbance (how much light is absorbed) or light transmission (how much light passes through) a substance -used in any enzyme-catalysed reaction that involves colour change -As colour breaks down the TRANSmission INCreases or light ABSORPtion DECreases and this can be used to measure the rate of the reaction

Answer 10

eg: starch-amylase catalysed reaction as the amylase breaks the starch down into maltose. "Dilution factor of 10" = "10 times less concentrated than one before" 1. COLORIMETER CALIBRATION: important step in a colorimetric investigation. In this case a weak iodine solution can be used to calibrate the colorimeter as the end point (or 100% transmission) 2. PREPARE STARCH SOLUTION OF KNOWN CONCENTRATION (stock solution), from which a range of concentrations are made using serial dilutions 3. w/ calibration + switching on red filter (to maximise the percentage transmission or absorbance), COLORIMETER MEASURES % absorbance/transmission values 4. calibration graph PLOTTED. starch concentration x-axis, percentage absorbance/transmission (y-axis)

Answer 11

-specific optimum temperature – the temperature at which they catalyse a reaction at the maximum rate +Lower temperatures either prevent reactions from proceeding or slow them down this is because: Molecules move relatively SLOWLY at lower temperatures => a lower frequency of successful COLLISIONS that occur between substrate molecules and the active site of the enzyme => less frequent enzyme-substrate COMPLEXES formed. Substrates and enzymes collide with LESS ENERGY, making it less likely for bonds to be formed or broken (stopping the reaction from occurring) ++Higher temperatures speed up reactions this is because: Molecules move more QUICKLY at higher temperatures, higher frequency of successful COLLISIONS between substrate molecules and the active sites of enzymes, more frequent enzyme-substrate COMPLEXES formed. Substrates and enzymes collide with MORE ENERGY, making it more likely for bonds to be formed or broken (allowing the reaction to occur)

Answer 12

📍Bonds (e.g. hydrogen bonds) holding the enzyme molecule in its precise shape start to break -causing TERTIARY structure of the protein and so enzyme to change +permanently damages the active site, preventing the substrate from binding Denaturation has occurred if the substrate can no longer bind. Very few human enzymes can function at temperatures above 50°C. This is because humans maintain a body temperature of about 37°C, therefore even temperatures exceeding 40°C will cause the denaturation of enzymes.

Answer 13

Hydrogen and ionic bonds hold the tertiary structure of the protein/enzyme together => Below and above the optimum pH of an enzyme, solutions with an excess of H+ ions (acidic solutions) and OH- ions (alkaline solutions) can cause these bonds to break This alters the shape of the active site, which means enzyme-substrate complexes form less easily Eventually, enzyme-substrate complexes can no longer form at all atp, complete denaturation of the enzyme has occurred

Answer 14

... indicator of its optimal environment: E.g. pepsin is found in the stomach, an acidic environment at pH 2 (due to the presence of hydrochloric acid in the stomach’s gastric juice) Pepsin’s optimum pH, not surprisingly, is pH 2

Answer 15

Buffer solutions each have a specific pH & maintain this specific pH, even if reaction taking place would otherwise cause the pH of the reaction mixture to change -A measured volume of the buffer solution is added to the reaction mixture -This same volume (of each buffer solution being used) should be added for each pH value that is being investigated

Answer 16

pH, however, does not affect collision rate but only disrupts the ability of the substrate to bind with the enzyme, reducing the number of successful collisions until eventually, the active site changes shape so much that no more successful collisions can occur.

Answer 17

📍higher the enzyme concentration in a reaction mixture = the greater the number of active sites available = the greater the likelihood of enzyme-substrate complex formation 📍As long as there is sufficient substrate available, the initial rate of reaction increases linearly with enzyme concentration 📍If the amount of substrate is limited, at a certain point any further increase in enzyme concentration will not increase the reaction rate as the amount of substrate becomes a limiting factor

Answer 18

📍greater the substrate concentration, the higher the rate of reaction: 📍As the number of substrate molecules increase, the likelihood of enzyme-substrate complex formation increases 📍If the enzyme concentration remains fixed but amount of substrate is increased, past a certain point all available active sites eventually become saturated (ACTIVE SITES SUBSTRATED, start of straight line) and any further increase in substrate concentration will not increase the reaction rate 📍When the active sites of the enzymes are all full, any substrate molecules that are added have nowhere to bind in order to form an enzyme-substrate complex and so the reaction rate will not increase any further until active sites become free again -in the graph below there is a linear increase in reaction rate as substrate is added, which then plateaus when all active sites become occupied so (-

Answer 19

📍every enzyme active site is working continuously. 📍atp substrate molecules are effectively ‘queuing up’ for an active site to become available. 📍 enzyme is working at its maximum possible rate, known as Vmax (V stands for velocity).

Answer 20

1. have a similar shape to that of the substrate molecules and therefore compete with the substrate for the active site + FOR COMP: countering the increase in inhibitor concentration by increasing the substrate concentration can increase the rate of reaction once more (more substrate molecules mean they are more likely to collide with enzymes and form enzyme-substrate complexes before the inhibitor can bind)

Answer 21

2. bind to the enzyme at an alternative site, altering the shape of the active site and therefore preventing the substrate from binding to it +FOR NONCOMP: increasing the substrate concentration cannot increase the rate of reaction once more, as the shape of the active site of the enzyme remains changed and enzyme-substrate complexes are still unable to form despite how many substrate molecules are present

Answer 22

- slow down or stop enzyme activity -Increasing the concentration of an inhibitor reduces the rate of reaction and eventually, if inhibitor concentration continues to be increased, the reaction will stop completely

Answer 23

While a competitive inhibitor will lower the initial rate of reaction (by occupying some of the available active sites), eventually the same amount of product will be produced as would have been produced without the competitive inhibitor (the maximal rate is not affected). -Non-competitive inhibitors lower the initial rate of reaction and the maximal rate of reaction (a LOWER amount of PRODUCT is produced than would normally be produced).

Answer 24

-affects the rate of catalysis -When substrate concentration is fixed (and enzyme concentration is kept constant) the initial rate of reaction is fastest and as active sites become engaged, the reaction rate falls: Michaelis-Menten model -maximal rate or maximal velocity (Vmax) and the Michaelis-Menten constant (Km); values are derived from the reaction rate at different substrate concentrations vmax used to derive Km which is used to compare affinity of diff enzymes for their substrates.

Answer 25

+rate of reaction is measured at different substrate concentrations, producing a graph -looks like (--- with curved stretching a bit wider on y axis -point/line on y-axis where initial rate of reaction is highest (or line a bit above that?), half this value = vmax, follow line to graph, WHERE THAT HITS X-AXIS = Km (substrate conc)

Answer 26

vmax: maximum rate of reaction at saturating substrate concentrations Km: the substrate concentration at ½Vmax. the substrate concentration at which the enzyme works at half its maximum rate. half of the active sites of the enzyme are occupied by substrate molecules. ++higher the affinity of the enzyme for the substrate, the lower the substrate concentration needed for this to occur. This is why the Michaelis-Menten constant is a measure of the affinity of an enzyme for its substrate

Answer 27

INVERSE; enzyme with a high Km has a low affinity for its substrate, & an enzyme with a low Km has a high affinity for its substrate

Answer 28

- act as regulators in metabolic pathways (metabolic reactions must be very tightly controlled +balanced, so that no enzyme can keep uncontrollably generating more of a particular product) -so metabolic reactions can be controlled by using the end-product of a particular sequence of metabolic reactions as a non-competitive, reversible inhibitor +END-PRODUCT INHIBITION: enzyme converts substrate to product. process is itself slowed down as the end-product of the reaction binds to an alternative site on the original enzyme, changing the shape of the active site and preventing the formation of further enzyme-substrate complexes -end-product can then detach from the enzyme and be used elsewhere, allowing the active site to reform and the enzyme's shape to return to an active state -means that as product levels fall, the enzyme begins catalysing the reaction once again, in a continuous feedback loop

Answer 29

Immobilised enzymes: enzymes that have been bound to an inert, stationary and insoluble material such as alginate (ALGINATE BEADS BOUND WITH LACTASE) -substrate is then passed over the immobilised enzyme and the product is collect

Answer 30

📍 no enzyme in product (product is UNCONTAMINATED) & no need to further process or filter the end product 📍-immobilised enzyme can be REUSED multiple times which is both EFFICIENT and COST-EFFECTIVE (enzymes are expensive) 📍Immobilised enzymes have a greater TOLERANCE OF TEMP & PH changes (immobilisation often makes enzymes more STABLE)

Answer 31

Milk: a valuable source of nutrients containing protein, fat and the carbohydrate lactose Lactose: a disaccharide that is broken down into glucose and galactose by lactase enzyme 5-10% of the UK population are lactose intolerant alginate beads containing LACTASE (BOUND WITH LACTASE), lactase breaks lactose down/hydrolyses lactose to glucose & galactose (easily absorbed by lactose intolerant)

3 enzymes Flashcards

(55 cards)