Enzymes

Question 1

Enzyme

Answer 1

Biological catalyst that are globular proteins ( tertiary structure)
‘biological’ Because they are made of living cells/ produced bi cells
Speed up chemical reactions without changing themselves

Question 2

metabolism

Answer 2

Refers to all the reactions of the body
Reactions occur in sequences called metabolic pathways

Question 3

Anabolic reactions

Answer 3

Building up muscle eg. Protein synthesis

Question 4

Catabolic reactions

Answer 4

Breaking molecules down eg. Digestion

Question 5

properties of enzymes

Answer 5

• Speed up reactions
• Not used up
• Not changed
• High turnover number eg. catalyses many reactions per second
• Specific (One enzyme per type of reaction)

Question 6

Site of enzyme action

extra. intra

Answer 6

Extracellular - enzymes outside the cell
Intracellular - enzymes that act inside the cell

Question 7

active site

enzme ac

Answer 7

Enzyme acts on its substrate which makes temporary bonds at the active site forming enzyme - substrate complex
when a reaction is complete, products are released, leaving enzyme unchanged and active site is ready to receive another substrate molecule

Question 8

lock and key model

Answer 8

Substrate is imagined fitting into the active site as a key fits into a lock
Shape of lock and key are specific to each other

Question 9

induced fit model

Answer 9

Enzyme active site forms a complementary shape to the substrate after binding

Question 10

activation energy

Answer 10

Minimum energy required to start a chemical reaction

Question 11

How enzymes work

Answer 11

Work by modifying substrate so the reaction requires a lower activation energy when substrate enters active sites
Shape of molecule alters, allowing reactions to occur at lower temperatures

Question 12

Rate of production
Percentage increase in Mass

Answer 12

RoP- increase in mass/time
PinM- actual increase/ initial x100

Question 13

As temp increase up to OPT TEMP

Answer 13

Enzymes and substrate gain kinetic energy
Greater chance of collisions between enzyme active site and substrate (successful collisions’)
therefore more enzyme-substrate meaning complexes formed meaning greater rate

Question 14

Above optimum temp

Answer 14

becomes denatured
Enzyme gains too much kinetic energy
H bonds holding active site together break causing active sites to change shape
therefore substrate cannot enter active sites so no enzyme-substrate complexes are formed
Eventually reaction stops

Question 15

at low temp

Answer 15

Enzyme is inactivated as molecules have very low kinetic energy
Shape is unchanged and the enzyme will Work again if temperature is raised

Question 16

Effect of pH on rate of reaction

Answer 16

Enzymes wwork with a narrow pH range
Small pH changes cause small reversable changes
Large pH changes causes enzymes to denature
the changes on amino acid side chains of Enzymes active site is affected by hydrogen and hydroxide ions
a buffer will maintain pH, prevent changes, would alter rate or denature above a certain poin

Question 17

At low pH

Answer 17

excess H+ ions are attracted to negative charges and neutralies them

Question 18

at high pH

Answer 18

excess OH- ions neutralise the positive charge
Disrupts the ionic and hydrogen bonds maintaining shape of the active site- denatured
No enzyme - substrate complexes form and enzyme activities lost

Question 19

substrate conc

Answer 19

Rate of reaction increases as concentration of substrate increases- more enzyme - substrate complexes formed
Beyond a certain point the rates no longer increases as conc of enzyme becomes a limiting factor

Question 20

enzyme conc

Answer 20

Rate of reaction increases as enzyme conc increases as there are more active sites for substrate to bind to
Increase in concentration beyond a certain point has no effect on the rate so substrate concentration becomes a limiting factor

Question 21

enzyme inhibition

Answer 21

• Decrease in enzyme controlled action rate by another substance
• Inhibitor combines with an enzyme and prevents it from forming an enzyme - substrate complex

Question 22

Competitive inhibition

Answer 22

• Have molecular shape complimentary to active sites and similar to substrate
• Compete for active site meaning blocked entry for substrates
• Rate in which product is formed decreases
• higher conc of competitive inhibitor lowers rate
• increasing substrate conc increases rate
  EG. malonic acid competes with succinate for active site of Succinate dehydrogenase

Question 23

non competive inhibitor

Answer 23

• Doesn’t bind to active sites, binds to enzyme at ‘allosteric site’ doesn’t compete with substrate
• Binding to non-competitive inhibitor changes shape of active site preventing binding of substrate
• Enzyme substrate complexes not formed
• Increasing substrate conc has no effect on rate
  EG. Cyanide attaches to enzyme cytochrome oxidase to inhibit respiration

Question 24

immobilised enzymes

Answer 24

Enzymes are immobilised when they are fixed, bound or trapped on an inert matrix eh. Alginate beads/ microfibrils
gel membrane- membrane bound enzmes are more accessible to substrate

Question 25

alginate beads

Answer 25

Packed into glass columns and substrate added to the top of column
As it flows down its molecules bind to enzyme molecules active site both on the bead surface and inside as substrate molecules diffuse in
Product absorbed at the bottom

Question 26

Advantages of immobilised enzymes

Answer 26

• Recovered at the end of reaction so can be reused
• Increase stability than enzymes in free solution, so can work at a wider range of temperatures and pHs before denaturing
• Products are not contaminated with enzyme
• Multi-enzyme reaction become possible

Question 27

Use of immobilised enzymes

Answer 27

• Detergent industry
• Lactose free milk
• Biomedical applications
• Textile industries

Question 28

Biosensors

Answer 28

Association of biomolecule with a transducer
EG. Glucose oxidase binds glucose, producing electric current detected by the electrode

Question 29

transducer

Answer 29

Turn the chemical signal into an electrical signal

Question 30

Advantages of biosensors

Answer 30

• Specific to the substrate they are testing for
• Can detect my new traces of biologically important molecules
• Gives quantitative results

Question 31

reducing flow rate

Answer 31

increases contact time with enzme and substrate/ more digestion
more SC/ more E-S complexes