4.1 Enzymes

Question 1

what are enzymes

enzymes

Answer 1

biological catlysts that speed up chemical reactions

Question 2

whats the role/affect of enzymes on metabolism at a

cellular level?

Answer 2

catalyse metabolic reactions eg. respiration

Question 3

whats the role/affect of enzymes on metabolism at a

whole organism level?

Answer 3

catalyse metabolic reactions eg. digestion in mammals

Question 4

and an example of each?

enzymes affect both …. and ….

Answer 4

• structure: eg. enzymes involved in production of collagen
• functions: eg. respiration

Question 5

enzymes ply role to catalyse both ….celllular and ….cellular reactions

Answer 5

intra and extra

Question 6

chemicals reactions required for growth are…..

Answer 6

anabolic reactions and a catalysed by enzymes

Question 7

an example of an enzyme that
catalyses intracellular

Answer 7

Catalase
catlalyses the breakdown of hydrogen peroxide a toxic by product o f ceelular reactions into harmless 02 nd h20

Question 8

an example of an enzyme that catalyses extracellular
reactions.

Answer 8

amylase
found in saliva secreeted by slivary glands that catalyses the hydrolysis breakdown of strch into maltose.

Question 9

what determins a enzymes specific active site shape?

Answer 9

its tertiary structure

Question 10

enzymes are …… proteins

Answer 10

globular

Question 11

enzymes work by….

Answer 11

reducing the activation energy
therefore speeding up rate of reaction

how?
1. if two substrate molecules need to be joined the enzyme holds them close reducing the repulsion so bonds form easier
2. if its catalysing a breakdwn fitting in ctive site can form a strain on substrate bond breaks easier

Question 12

lock and key model is only a hypothesis becauase

Answer 12

it dosent give the full story the enzyme and substrate do have to fit together to start with but theres new evidence to show the enzyme substrate complex changed shape slightly to complete the fit this ‘locks’ the substrate even tighter. now modified to the induced fit model

Question 13

state the

induced fit theory

Answer 13

initial interaction is weak but they rapidly induce chnge in tertiary structure enzyme substrate complex changed shape slightly to complete the fit this ‘locks’ the substrate even tighter.

Question 14

what effects

enzyme activity

Answer 14

• pH
• temperature
• enzyme concentration
• substrate concentration

Question 15

how does

temprature influence enzyme activity

two decriptions 2 explnaitions

Answer 15

D1. beween ‘c and ‘c as temp increases so does the rate of reaction
E1. because as temp increases so does kinetic energy so mollecules move faster therefore chance of sucsessful collison increases
D2. as temp goes beyond optimum ‘c the reaction rate decreases before stopping at ‘c
E2. post optimum the amino acids in the enzyme vibrate so much they break the tertiary structure denaturing the active site so no substrate can fit

Question 16

the temperature coefficient (Q10) eqution and explanation

draw graph

Answer 16

Q10=R2 (rate at higher temp)/R1(rate at lower temp)

graph looks like unsymetrical hill slow inclie on left steep on right

value for how much the rate of reaction changes when the temp is raised by 10’c. At temps before optimum this around 2 so rate doubles for every 10 additional degrees

Question 17

how does ph effect enzyme activity

sketch graph

Answer 17

D1. optimum is x’c rate of reaction decrees evenly both sides its bilateraly symetrical
E1. either side the H+ ions and OH- ions found in acids and alkalis can mess up ionic and hydrogen bonds in the tertiary structurt and dnature the enzyme chaniging its active site.

graph looks like bell

Question 18

how does substrate conc effect enzyme activity

draw graph

Answer 18

• part a: reaction tkes place at max rate enzyme is not limiting factor higher conc=more collisions more sucsessful collisions
• part b: until ‘saturation’ aka. all active sites are occupied and dding more substrate will hve no effect
• substrate conc will decrease over time unless more is added

ramp curve plateu. divide into 3 parts

Question 19

how does enzyme conc effect reaction rate?

Answer 19

increase until its no longer the limiting fctor is can plteu if substrate conc is limited

Question 20

whats the source of coenzymes?

Answer 20

vitamins

Question 21

whats an example of a cofactor

Answer 21

Cl- for amylsae

Question 22

what are co-factors

Answer 22

non-protein substances bound to enzymes required for it to function

Question 23

what are the three types of cofactors and there roles/properties

Answer 23

• co-enzymes (organic molecules that participate in the reaction and are changed by it, moving between enzymes theyre recycled source:vitamins)
• ** cofactors** (inorgnic ions help the substrate to bind dont participate in the reaction so aernt used up or changed eg.cl- for amylase)
• prostetic group (tightly permanently bound inorganic molecule bound to active site, eg. ZInc Zn2+ a prosthetic group for carbonic anhydrase in RBC’s)

Question 24

what are the four types of enzyme inhibitors

Answer 24

• compettive
• non competative
• reversible
• ireversible

Question 25

competative inhibitors effect on enzyme controlled reactions

draw graph

Answer 25

• competative inhibitors have similar shape to the substrate and bind to tthe active site although no reaction takes place they block substrate reaching the active site
• if theres high conc of inhibitor it can tke up almost all active sites
• if theres a high enough conc of substate then thgey have better chbce of reaching active site and willl **increase the rate of reaction **

Question 26

non-competative inhibitors effect on enzyme controlled reactions

draw graph

Answer 26

• bind to enzyme away from the active site known as the **allosteric site **
• this causes the active site to change shape so substrate can no longer bind
• increasing substrate conc wont change reaction rate

Question 27

reversible inhibitors

Answer 27

weak hydrogen bonds or weak ionic bonds they can be removed

Question 28

ireversible inhibitors

Answer 28

strong covalent bonds cant be removed from the enzyme

Question 29

metabolic poisons are often enzye inhibitors eg:

Answer 29

• Cyanide
• Arsenic
  both inhibit enzymes tht catalyse respiration reactions so cells die

Question 30

some medical drugs are enzyme inhibitors

Answer 30

• antiviral drugs eg HIV inhibit reverse transcriptase which catalyses the replication of viral dna so prevents the virus from replicating
• antibiotics eg. penecilin inhibit the enzye wich catalyses the formation ofproteins in bcteri cell walls so they burst

Question 31

the role
of end-product inhibition

Answer 31

metbolic pathways are regulated by end-product inhibition

metabolic pathway:series of connected metbolic reactions the product of the first reaction takes part in the second and so on each reaction ctalysed from a different enzyme

often the enzyem is inhibited by the product they form knon as product inhibition

its way of controlling how much product is made.

Its reversible so can start again

Question 32

How can enzyme inhibition help protect cells?

Answer 32

enymes are sometimes synthesised as inactive presecursos in metabolic pathways to prevent them causng damage to cells eg. protease are sythesised as inactive precursors to stop them being active in the cell theyre made in tvv 6d m9i mi