Cheater 3: Enzymes

Question 1

Enzymes are

Answer 1

Biological catalysts that speed up rate of metabolic reactions

Question 2

What type of proteins are enzymes

Answer 2

Tertiary

Question 3

Surgically enzymes are _ proteins nature being _ because of _

Answer 3

Globular
Soluble
Hydrophilic R groups outside of 3d coil shape

Question 4

2 types of enzymes, description and examples

Answer 4

Intracellular- secreted within cells, eg rubisco atp synthase
Extracellular- outside cell, eg pancreatic lipase, pepsin

Question 5

What is lock and key hypothesis

Answer 5

Both enzyme and substrate are rigid/ don’t change shape

Question 6

Definition of active site

Answer 6

Region, usually depression/cleft in the surface of an enzyme, to which substrate can bind to

Question 7

Shapes of active site substrate are

Answer 7

Complementary, not same!

Question 8

Explain the lock and key model

Answer 8

Random movement of enzyme and substrate brings the substrate into active site. A enzyme-substrate complex-bond-is temporarily formed. R groups of amino acids in active site interact with substrate. This breaks substrate apart. Enzyme-product complex briefly formed before product molecules leave.

Question 9

What happens to an enzyme after changing substrate to products

Answer 9

It is unchanged, ready bind with another substrate

Question 10

Which theory has replaced lock and key hypothesis

Answer 10

Induced fit hypothesis

Question 11

What is the induced fit hypothesis

Answer 11

Both active site-most time and substrate-some time change shape

Question 12

What is activation energy

Answer 12

Extra energy needed by the substrate to be converted into products

Question 13

2 ways in which activation energy can be provided

Answer 13

Heating

Enzymes

Question 14

How can heating increase rate

Answer 14

Increase energy of reactants/substrate

Question 15

How do enzymes provide activation energy

Answer 15

Lower it

Question 16

Reason enzymes lower Ea and how

Answer 16

Temperature can’t always be raised to give activation energy. And hence enzymes decrease it of the reaction which they catalyse.

They hold the substrate in such a way that molecules can react more easily to convert to products

Question 17

Which enzyme is involved in basic H2O2 breakdown

Answer 17

Catalase

Question 18

2 ways in which rate of reaction can be calculated

Answer 18

1) amount of substrate disappeared
2) amount of product formed
PER UNIT TIME

Question 19

Rate and time are _ proportional

Answer 19

Indirectly

R α 1/t

Question 20

H2O2 is toxic. State it’s breakdown equation

Answer 20

H2O2–>H2O+O2

Question 21

State the trend in the breakdown of H2O2 and reason for the same

Answer 21

• •• reaction begins very fast. As soon as enzyme and substrate mixed bubbles of O2 released quickly and large volume of it collected in first mins ••• because when they’re first mixed there are a large no of substrate molecules. Virtually every enzyme has substrate in active site •••
• •• rate of O2 released gradually slows and eventually stops ••• because substrate is being used up and enzyme is waiting for substrate to hit active site as fewer substrate is there

Question 22

Rate of reaction depends on

Answer 22

How many enzymes enzymes can covert the substrate into product and release it

Question 23

Which part of curve is best to calculate rate

Answer 23

Initial

Question 24

Briefly explain 3 methods to calculate rate of reaction

Answer 24

1) gradient of straight line
2) gradient of tangent
m=Δy/Δx
3) Check volume produced in first 30s and multiply by 2 to get for 60s ie a min

Question 25

Which factors affect rate of enzyme catalysed reaction

Answer 25

Enzyme concentration Substrate concentration Temperature pH

Question 26

When investigating effect enzyme concentration what should be kept constant

Answer 26

Substrate concentration | Volume of setup, done by adjusting water

Question 27

Why do all graphs meet though at different times for diff enzyme conc

Answer 27

Substrate amount is same so product made will also be same

Question 28

Why is it best to use in it all rate to compare enzyme concentrations

Answer 28

Once reaction is under way with different zym concentrations amount of substrate in each reactions varies bcos it's converted at different rates. Only in the beginning can we be sure that rate differences are caused ONLY by zym conc

Question 29

Reaction rate is _ proportional to enzyme conc

Answer 29

Directly

Question 30

Why is rate α zym conc | And how does initial rate increase with zym conc and under what condition

Answer 30

More the enzyme, more active sites available for substrate. | And as long as there is plenty of substrate initial rate increases linearly with enzyme conc

Question 31

What breaks down starch to maltose

Answer 31

Amylase

Question 32

Why is it difficult to identify rate of the course of reaction of starch breakdown

Answer 32

Both starch and maltose are colorless

Question 33

How can we measure rate of starch breakdown

Answer 33

Rate at which starch disappears by taking samples at known times and adding iodine. Using a colorimeter to measure intensity of blue-black color as a measure of amount of starch left Plot graph for starch left against time to calculate initial rate

Question 34

For graphs of enzyme conc while measuring O2 formation of starch disappearance, which graphs will be at the top and bottom

Answer 34

Formation : highest conc will be top with highest rate of production Disappearance : highest conc will be inside with highest rate and hence reaching minimum sooner

Question 35

How are enzyme conc vs rate graphs (formation of disappearance)

Answer 35

Linear

Question 36

Effect of substrate conc is normally measured with reference to

Answer 36

Product formation

Question 37

State the explanation for the graph of substrate vs initial rate

Answer 37

As substrate conc increases initial rate also increases. However, if substrate is increased further, it would not be as though there is mores substrate and hence more often bind to active site. Instead, as enzyme conc is constant, there is a point where every active site is occupied and cannot work faster as substrates are queuing up for vacant active sites

Question 38

What does Vmax indicate and when is it achieved

Answer 38

Maximum rate of enzyme catalysed reaction When all active sites are bound to substrate. Enzyme is saturated with substrate

Question 39

What is Km

Answer 39

Michaelis Menten constant | Substrate concentration at which half of maximumrate of reaction, 1/2Vmax, is achieved

Question 40

What 2 things does Km tell us

Answer 40

* half the active sites of given conc of enzyme are saturated with substrate * gives info about affinity os enzyme for substrate ie Km α 1/affinity of e-s

Question 41

How to calculate Vmax?

Answer 41

Since Vmax is achieved at infinite substrate conc it is impossible to accurately measure Vmax from graph. Instead of plotting [s] on X axis and [v] on y axis, we plot 1\[s] and 1/[v] and thus 1\infinity=0. DOUBLE RECIPROCAL PLOT Is straight line, easier to understand 1/Vmax is y intercept (where [s]=0 ie infinity). And from there calculate Vamx

Question 42

What is turnover rate

Answer 42

Rate at which substrate molecules are converted to product per unit time.

Question 43

What is carbonic hydrase and where is it found

Answer 43

H2CO3 Fastest enzyme to remove 600,000 CO2 molecules from repairing tissue In RBC

Question 44

Significance of Vmax and Km values (6)

Answer 44

* make computer models of biochemical pathways. Behavior of cells to predict reaction pathway and how enzymes will interact. Consequences of changing conditions (temp, ph, inhibitor) can be built in model * presense of enzyme for diff substrate compared quantitatively * understand what affects enzyme efficiency and design better catalysts with genetic engineering * performance of a commercially important enzyme from diff organisms compared * calculation can be applied to other fields (eg biochemistry, antibody-antigen engineering) * knowing Km means proportion of active site occupied by substrate can be calculated for any substrate conc (for scientists^)

Question 45

What is optimum temperature

Answer 45

Temp at which enzyme catalyses a reaction the maximum rate

Question 46

How is rate at high and low temp

Answer 46

H- enzyme and substrate molecules move faster and collide more. Frequently so substrate is converted to products more often L- reaction is very slow bcos substrate does not often collide with active site hence binding is rare

Question 47

What is the optimum temp

Answer 47

Rate highest at 40°C

Question 48

What happens after optimum temp

Answer 48

Structure of enzyme vibrates so energetically that hydrogen bonds holding it in precise shape begin to break

Question 49

Enzyme losing shape and activity is called _ and is _

Answer 49

Denaturation | Irreversible

Question 50

State the chain of bacteria which thrive at higher optimum temps

Answer 50

Thermus Aquaticus (bacteria) ---> Taq polymerase (enzyme) 75-80°C ---> PCR-polymerase chain reaction (gene/DNA amplification)

Question 51

Human enzymes optimum temp is _. Our body is kept at _ to ensure _ reactions occur at _ to their _ rate. Slight rise in temp is dangerous because enzymes would _

Answer 51

``` 40°C 37°C Enzyme catalysed Close to Maximum Denature ```

Question 52

What happens to amino acid when pH decreases/increases and is neutral

Answer 52

Decrease ie acidic Amine NH2 ionised to NH3+ Increase ie alkaline Carboxylic acid ionised ti COO- Neutral ie 7 Net charge=0

Question 53

What in general explains why enzymes change with pH changes

Answer 53

They are proteins so the ionic bonds of their amino acids are disturbed causing overall charge

Question 54

Optimum ph

Answer 54

7 max rate

Question 55

what is pH

Answer 55

Measure os concentration of Hydorgen ions in a solution

Question 56

How exactly does pH affect enzymes

Answer 56

Interacts with R groups of amino acids by affecting ionisation (+/-) of groups which in turn affects 3d arrangement of enzyme. Shape of active site changes and therefore reduce chance of substrate fitting

Question 57

pH changes are _ just like temp changes

Answer 57

Irreversible

Question 58

Function of a buffer

Answer 58

Has particular pH | Maintains it's pH even when reactions cause pH changes

Question 59

Method to prepare immobilized enzymes

Answer 59

Enzyme mixed with sodium alginate solution Little droplets of this mixture then added ti solution of calcium chloride Na and CaCl2 react ti form jelly which turns each droplet into bead with enzyme which is immobilized

Question 60

What is competitive inhibition

Answer 60

- Inhibitor has similar shape to substrate and fits into active site. - Is reversible and can be achieved by increasing conc of substrate - Increase in Km, but Vmax unchanged

Question 61

Graphs of competitive inhibitor | Recall graphs

Answer 61

As substrate conc increases competitive inhibitor and no inhibitor rates increase. But substrate rate is more In reciprocal, 1/v value is same so they intersect same place at Y axis However 1/km is less for no inhibitor

Question 62

What is non competitive inhibition

Answer 62

* Shape of inhibitor not similar to substrate * Inhibitor binds to some other part of enzyme, allosteric site, rather than active site * While inhibitor is bound, it disrupts normal arrangement of hydorgen bonds and hydrophobic interaction holding enzyme in 3d shape. Distortion ripples across molecules to active site making it unsuitable to substrate * Reversible * Decreases Vmax, Km unchanged

Question 63

How are graphs of non competitive inhibitor and non inhibitor ie substrate

Answer 63

As [S] increases both V increase but non competitors is less than substrate In reciprocal plot Substrate has higher 1/Vmax, but intersect X axis at 1/Km

Question 64

What is feedback mechanism?

Answer 64

Eg S1>e1>P1>e2>P2>e3>P3 to S1 is e1 As levels of P3 rise e1 inhibition increases. So less P1 is made and hence less P2, P3. As P3 level falls, function of e1 increases so Ps are produced again ti restart cycle. This end product inhibition finely controls levels of P3 between narrow upper and lower limits.