ch4 experiments

Question 1

h2o2 presence of catalase test: what is the purpose of stoppering

Answer 1

to trap any gas released from hydrogen peroxide so that they can be collected for testing

Question 2

h2o2 presence of catalase test: why should the tube be loosely capped

Answer 2

loosely cap to ensure safety as under high pressure the stopper can pop out and injure your eye (we’re testing for presence, not the amount anyways)

Question 3

h2o2 presence of catalase test: purpose of the control?

Answer 3

to show that any oxygen released by the h2o2 in the other setups is due to the presence of tissue added into that setup

Question 4

h2o2 presence of catalase test: why do we test the test tubes with glowing splints

Answer 4

to test whether the gas released by the h2o2 is o2, as glowing splint relights in the presence of o2

Question 5

h2o2 presence of catalase test: setup with measuring cylinder / rubber tubing
how does the experiment work

Answer 5

the breakdown of h2o2 is catalysed by catalase in the tissue extract releasing oxygen gas that will accumulate in the boiling tube and rubber tubing
the volume of o2 gas will be delivered to the measuring cylinder filled w water and displace the water in the measuring cylinder
water level in the measuring cylinder will fall
the volume of o2 gas collected can be found by the reading of the volume of water displaced by the gas in the measuring cylinder

limitations: o2 must be accumulated to a certain level before the water is displaced

Question 6

h2o2 presence of catalase test: setup with measuring cylinder / rubber tubing
limitations?

Answer 6

o2 gas must accumulate to a certain level before it is displaced -> measurement isn’t too accurate

Question 7

h2o2 presence of catalase test: setup with pipette / rubber tubing
how does the exp work

Answer 7

the breakdown of h2o2 is catalysed by catalase in the tissue extract releasing oxygen gas that can accumulate in the pipette that is closed bit a clip
the volume of o2 gas released by the reacting mixture will displace the reacting mixture inside the pipette
causing the level of the reacting mixture in the pipette
the volume of oxygen gas release can be measured by the volume of reacting mixture being displaced in the pipette

Question 8

h2o2 presence of catalase test: setup with pipette / rubber tubing
major source of error?

Answer 8

a lot of the o2 gas released by the reacting mixture is not collected by the pipette

Question 9

h2o2 presence of catalase test: ink
how does the experiment work

Answer 9

the difference in gas pressure controls the movement of the ink
if it moves up the pressure in the test tube is higher than the air pressure
the oxygen gas released by the reacting mixture will increase the air pressure inside the boiling tube that will become higher than atmospheric pressure
the colour ink is being pushed up by the higher air pressure inside the boiling tube
the volume of oxygen gas released can be measured by the distance moved by the color ink multiplied by the cross sectional area of the lumen of the pipette (company will tell you the diameter of the lumen of the pipette

Question 10

h2o2 presence of catalase test: important CVs?

Answer 10

mass / dimension of each tissue
duration of immersion in h2o2 solution
volume / conc of h2o2 solution
temp
pH

Question 11

h2o2 presence of catalase test: how does the mass / dimension of each tissue affect the exp results

Answer 11

the larger the mass of the tissue, the larger the amount of catalase contained inside the tissue
the more active sites of catalase available to bind with hydrogen peroxide
the higher the chance of successful collision between catalase and hydrogen peroxide to form enzyme-substrate complex
the higher the rate of breakdown of hydrogen peroxide to form oxygen

Question 12

h2o2 presence of catalase test: how does duration of immersion affect the results

Answer 12

the longer each tissue is immersed in hydrogen peroxide
the higher the chance of successful collision between catalase and hydrogen peroxide to form enzyme-substrate complex
the higher the rate of breakdown of hydrogen peroxide to form oxygen

Question 13

h2o2 presence of catalase test: how does the volume / conc of h2o2 affect the results

Answer 13

the volume / concentration of hydrogen peroxide solution as the substrate
the higher the chance of successful collision between catalase and hydrogen peroxide to form enzyme-substrate complex
the higher the rate of breakdown of hydrogen peroxide to form oxygen

Question 14

how are proteins formed

Answer 14

a polypeptide chain is formed by joining many amino acids through condensation reactions
attraction forces between the side chains of amino acids in the same polypeptide chain causes the polypeptide chain to coil and fold in a specific way into a 3D structure / conformation of protein
Sometimes, polypeptides combine with other polypeptides to form a protein

Question 15

when are enzymes denatured

Answer 15

at high temps (not extreme temps)

Question 16

why do we only compare initial rates of reaction for enzymatic rate of reaction experiments

Answer 16

we only compare initial rate of reactions (as this is usually the enzyme’s maximum possible working rate under the conditions of the exp)