topic 4 enzymes

Question 1

what are enzymes

Answer 1

globular proteins eith complex and unique tertiary structure
known as biological catalysts bcs they increase the rate of a chemical reaction without being used up in the reaction itself

Question 2

are enzymes soluble or insoluble and why

Answer 2

soluble bcs the are globular proteins so have hydrophilic amino acids on their surface and hydrophobic in the centre

Question 3

what do all chemical reactions require

Answer 3

a certain amount of energy to react - activation energy

Question 4

how do enzymes increase the rate of reaction

Answer 4

lower the activation energy

Question 5

2 categories of enzymes

Answer 5

• intracellular enzymes- act within the call that produces them
• extracellular enzymes- act outside the cell that produces and secretes them

Question 6

example of intracellular emzyme

Answer 6

catalayse
catalyses the breakdown of hydrogen peroxide into oxygen and water which prevents the accumulation of toxic hydrogen peroxide inside cells

Question 7

examples of extracellular enzymes

Answer 7

• amylase- secreted in salivary glands, pancreas, and small intestine to break down starch into maltose
  -trypsin- secreted by pancreas into the small intestine to break down proteins into smaller polypeptides

Question 8

what level of structure determines the enzymes active site

Answer 8

tertiary structure

Question 9

what is special about the active site

Answer 9

it is complementary to the substrate

Question 10

what happens for a enzyme- substrate to form

Answer 10

temporary binds form between the R groups within the active site and the substrate. These binds lower the activation energy to help break down the substrate into products

Question 11

lock and key model

Answer 11

the substrate fits perfectly into the enzymes active site

Question 12

induced fit model

Answer 12

the substrate does not fit perfectly into the enzymes active site. As the substrate enters the enzyme the active site changes shape slightly. This puts a strain on the substrates binds which lowers the activation energy

Question 13

how do u measure the rate of reaction at any point on a graph

Answer 13

draw a tangent and calculate the gradient

Question 14

what does the rate of an enzymes controlled reaction depend on

Answer 14

the frequency of successful collisions between the substrate molecules and the active site

Question 15

how do changes in temperatures or pH denature enzymes

Answer 15

-bonds start to break chaing thr tertiary structure
- active site changes so that the substrate no longer fits so enzymes substrates cannot be formed

Question 16

different factors that affect the rate if enzymes controlled reaction

Answer 16

-tempreture
-pH
- substrate conecentration
- enzymes concentration

Question 17

how temperature effects enzyme controlled recations

Answer 17

-as temp increases molecules have more kinetic energy so more collisions and more enzyme substrate complexes
-max collision rate is reached at optimum temp
- after optimum temp too much kinetic energy causes the active site to change and denature bcs the molecules are vibrating more rapidly causing bonds to break so tertairy structure changes

Question 18

tempreture coefficient

Answer 18

a value that shows how much the rate of reaction changed when the tempreture increased by 10c

Question 19

the formula are tempreture coefficient

Answer 19

Q10 = rate of reaction at temp x + 10c (higher temp) / rate of reaction at temp ( lower temp)

• usually has a value of around 2 bcs the rate of reaction generally doubles when temp is increased by 10
  this does not apply above the optimum temp

Question 20

how does hydrogen ions lower the rate of reaction

Answer 20

the hydrogen ions can bond with the R groups of the amino acids in the protein including amino acids within the active site which form temporary bonds to the substrate which prevent the substrate from binding to the R groups it reduces the rate of reaction

Question 21

how can hydrogen ions denature a enzyme

Answer 21

hydrogen ions bond with the R group on amino acids in the rest of the enzyme which can break bonds holding the tertiary structure changing the shape of the active site

Question 22

how does pH affect rate of reaction

Answer 22

below the optimum pH rate of reaction is low or zero in acidic conditions H+ ions break ionic/ hydrogen bonds and denature enzymes
maximum rate is at optimum pH
above optimum rate of reaction is low or zero. In alkaline conditions OH- ions break ionic bonds or hydrogen bonds and denature enzymes

Question 23

is the rate of reaction directly proportional to the substrate concentration

Answer 23

yes

Question 24

how does substrate concentration affect the rate of reaction

Answer 24

ror increases as substrate concentration increases bcs more substrates can form enzyme-substrate complexes
as concentration increases or plateus this is the saturation point which is when all active sites are occupied by a substrate and enzyme concentration becomes the limiting factor

Question 25

is the rate of reaction directly proportional to the enzyme concentration

Answer 25

yes

Question 26

how does enzyme concentration affect the rate of reaction

Answer 26

ror increases as enzyme concentration increases bcs more enzymes can form enzyme-substrate complexes as concentration increases or plateus all substrate molecules available are being acted upon and substrate concentration becomes the limiting factor

Question 27

inhibitors

Answer 27

molecules that bind to enzymes to reduce their activity

Question 28

reversible inhibitors

Answer 28

these form weak bonds w the enzyme

Question 29

irreversible inhibitors

Answer 29

these form strong bonds w the enzyme, bind permanently to the active site

Question 30

2 categories of inhibitors

Answer 30

competitive- bind to the active site non competitive - bind away from the active site

Question 31

competitive inhibitors

Answer 31

-similar shape to substrate -prevents substrate from binding -most are reversible

Question 32

example of competitive inhibtior

Answer 32

malonate which is similar to succinate which is the substrate for the enzymes involved in respiration

Question 33

lots of _____ are competitive inhibitors

Answer 33

drugs methotrexate- used to treat certain cancers, reversible competitive inhibitor of an enzyme found in human cells penecillin- used to treat bacterial infections- inhibitor of an enzyme involved in the synthesis of bacterial cell walls, irreversible

Question 34

how are most competitive inhibitors overcome

Answer 34

by increasing substrate concentration

Question 35

non competitive inhibitors

Answer 35

bind at the allosteric site and changes tertiary structure of the enzyme so that the active site is no longer complementary to the substrate

Question 36

end product inhibitor

Answer 36

-regulates metabolic pathways by reducing the rate of reaction -the final product inhibits the first enzyme -if the level of product needed increases the level of product decreases and therefore less inhibition of the first enzyme -non competitive inhibition BCS takes [lace through the allocation site

Question 37

cofactors

Answer 37

non protein substances that bind to enzymes to increase their activity ( chemicals that function w enzymes in partnership)

Question 38

example of cofactor

Answer 38

cl- cofactor for enzyme amylase found in digestive system where it catalyses the hydrolysis of starch to the disaccharide maltose the substrates are water and starch

Question 39

2 types of cofactors

Answer 39

-coenzymes-organic cofactors usually derived from vitamins -prosthetic groups- cofacters that are tightly bound to enzymes