Enzymes

Question 1

finish the sentence
Enzymes are all______ ______ with ______ ______ which has a ______ or ______ area which has a ______ ______ ______ called an ______ ______ where the ______ takes place.

Answer 1

Enzymes are all tertiary proteins with globular shape which has a pocket or cleft area which has a specific 3D shape called an active site where the reaction takes place.

Question 2

What do enzymes act as and what does this mean

Answer 2

Biological catalysts which are proteins that speed up metabolic reactions without being used up

Question 3

What do enzymes provide and how do they do this

Answer 3

an alternative pathway during a reaction because they are specific so can only catalyze one shape of substrate

Question 4

finish the sentance
Enzymes are important in ______ as they ______ ______ into ______ e.g p_____ into a_____ a______.

Answer 4

Enzymes are important in digestion as they hydrolyse polymers into monomers e.g polypeptides into amino acids.

Question 5

write out the reaction and its biological importance
lactase

Answer 5

lactose —-> glucose + galactose
hydrolysis of mil sugar (disaccharide)

Question 6

write out the reaction and its biological importance
catalase

Answer 6

hydrogen peroxide —-> water + oxygen
H2O2 toxic by product of metabolism must be removed

Question 7

write out the reaction and its biological importance
RUBISCO

Answer 7

RuBP + CO2 —-> glycerate phosphate
fixes CO2 from atmosphere in photosynthesis

Question 8

write out the reaction and its biological importance
ATPsynthase

Answer 8

ADP +Pi —-> ATP
energy requiring process - active transport

Question 9

write out the reaction and its biological importance
Glycogen Synthetase

Answer 9

Glucose —-> glycogen
converts glucose to a storage compound glycogen (polysaccharide)

Question 10

define activation energy

Answer 10

the extra energy that is required to enable a reaction to occur is known as the activation energy.

Question 11

enzymes and activation energy

Answer 11

enzymes are able to lower the activation energy of a reaction to allow it to proceed more quickly at lower temperatures in the body so that molecules can be broken down and new ones formed.

Question 12

name the two enzyme action models and note which one is more widely accepted and why

Answer 12

lock and key
induced fit is more widely accepted because it tells us how the substrate is hydrolysed

Question 13

Describe the induced-fit model of enzyme action and how an enzyme acts as a catalyst

Answer 13

1. Substrate binds to the active site/enzyme
2. Active site changes shape (slightly) so it is complementary tosubstrate
3. so distorting/breaking/forming bonds in the substrate
4. which reduces activation energy

Question 14

describe how temperature effects enzyme activity in detail

Answer 14

RofR very slow at low temps as enzyme and substrate
molecules have little kinetic energy
therefore few enzyme substrate collisions form
as temp increases K.E of substrate and enzyme molecules increases
so more successful collisions between enzyme and substrate
so more ES complexes form
RofR reaches V max - optimum temp of enzyme reaction
increasing temp further means molecules vibrate causing weaker bonds to break
h-bonds, ionic bonds holding enzyme 3d shape together break
tertiary structure changed which can alter shape of AS
fewer ESCs form and RofR decreases
enzyme is denatured

Question 15

describe how PH effects enzyme activity in detail

Answer 15

Above and below optimum PH the h-ions can interfere with R-group interactions between amino acids as H+ will cluster around negatively charged R groups and disrupt the H-bonds and ionic bonds which maintain tertiary structure of a protein and the shape of the active site.
reduces Rof enzyme controlled reaction as fewer ESCs form
in extreme PH changes enzyme denatures H+ conc alters charges around active sitewhich may affect binding of substrate to active site in induced fit hypothesis
h-bonds, ionic bonds holding enzyme 3d shape together break
tertiary structure changed which can alter shape of AS
no ESCs form and RofR falls to zero

Question 16

define limiting factor

Answer 16

a variable that prevents V max from being achieved. If it increases then the rate of process will increase

Question 17

describe effect of increasing substrate conc on the rate of an enzyme catalyzed reaction

Answer 17

conc of enzyme stays constant and conc of substrte increases
no of collisins between ES molecules will increase
more ESCs forming
rate of reaction is high
point will be reached where all enzyme active sites will be full
so increasing substrate conc will not increase RofR further
so remains at V max
conc of enzyme is LF

Question 18

describe effect of increasing enzyme conc on the rate of an enzyme catalyzed reaction

Answer 18

as enzyme conc increases there are more active sites available
greater chance of substrate colliding with active site
more enzyme substrate complexes can be formed
all substrate molecules occupying AS
initial rate of reaction will increase
further increase in enzyme conc will not increase RofR further
conc of substrate limits further increase in RofR

Question 19

define enzyme inhibition

Answer 19

Enzyme inhibitors reduce the RofR. There are two types of inhibitors , competitive inhibitors and non competitive inhibitors.

Question 20

Describe how a non-competitive inhibitor can reduce the rate of an enzyme-controlled reaction

Answer 20

Attaches to the enzyme at a site other than the active site
Changes (shape of) the active site
(So active site and substrate) no longer complementary
so less/no substrate can fit/bind;

Question 21

Describe how a competitive inhibitor can reduce the rate of an enzyme-controlled reaction

Answer 21

Competitive inhibitors have a similar shape to the substrate molecule
have a complementary shape to active site
enter active site and bind with it forming EIC and prevent ESC forming
no of ESCs form reduced and RofR falls

Question 22

finish the sentence
Many ______ do not ______ ______ with the ______ ______ or away from the ______ ______ so are not permanent and are described as ______ ______. Others permanently ______ to the ______ ______ or away from the ______ ______ and are therefore ___-______.

Answer 22

Many inhibitors do not permanently bind with the active site or away from the active site so are not permanent and are described as reversible inhibitors. Others permanently bind to the active site and are therefore non - reversible.