chapter 4 - enzymes

Question 1

enzymes

Answer 1

biological catalysts, made of proteins, with a specific active site; they speed up reactions whilst remaining unchanged

Question 2

active site

Answer 2

indented area on the surface of the enzyme with a shape that is complementary to the substrate

Question 3

catalyst

Answer 3

a chemical that speeds up the rate of reaction and remains unchanged and reusable

Question 4

metabolism

Answer 4

the chemical reactions that take place inside living cells or organisms

Question 5

product

Answer 5

a molecule produced from substrates by an enzyme-catalysed reaction

Question 6

substrate

Answer 6

a molecule that is altered by an enzyme-catalysed reaction

Question 7

metabolites

Answer 7

reactants, intermediates and products in enzyme-controlled reactions

Question 8

turnover number

Answer 8

the number of reactions that an enzyme molecule can catalyse per second

Question 9

intracellular enzymes

Answer 9

enzymes that work inside cells

Question 10

function of catalase

Answer 10

protects cells from damage by breaking down hydrogen peroxide into water and oxygen

Question 11

function of ATP synthase

Answer 11

produces ATP

Question 12

function of DNA polymerase

Answer 12

catalyses the synthesis of DNA molecules, duplicates the DNA contents of a cell during division

Question 13

function of carbonic anhydrase

Answer 13

converts CO2 to carbonic acid as its transported by blood cells, adjusts the acidity of an environment to prevent damage to the body

Question 14

extracellular enzymes

Answer 14

enzymes that work outside cells

Question 15

function of amylase

Answer 15

digests starch and breaks it down to maltose

Question 16

function of trypsin

Answer 16

digests proteins into the smaller peptides by hydrolysing peptide bonds

Question 17

function of lipase

Answer 17

digests fats or lipids (triglycerides) into fatty acids and glycerol by hydrolysing ester bonds

Question 18

catabolic reactions

Answer 18

where substrates are broken down

Question 19

anabolic reactions

Answer 19

where substrates are joined to make a larger product

Question 20

effect of temperature on rate of reaction

Answer 20

• increasing temperature increases kinetic energy of molecules
• this increases the amount of collisions and increases the force of the collisions
• more collisions means more substrates that fit into the active site of an ezyme
• leads to an increase in the rate of reaction

Question 21

rate of reactions calculation

Answer 21

1 / time taken to reach end point

Question 22

temperature coefficient

Answer 22

refers to the increase in the rate of a process when the temperature is increased by 10oC

Question 23

optimum temperature

Answer 23

the temperature that gives the enzyme’s maximum rate of reaction

Question 24

denaturation

Answer 24

where the teritary structure of the enzyme is changed to the point that the enzyme no longer works

Question 25

effect of extreme temperature on enzymes

Answer 25

- causes molecule to vibrate - vibrations break the weaker hydrogen and ionic bonds (which maintain the tertiary structure) - tertiary structure changes and active site changes shape - enzyme becomes denatured

Question 26

effect of pH on enzyme activity

Answer 26

- H+ ions interact with negatively charged R- groups of amino acids in the enzyme - this can change the shape of the tertiary structure - interferes with binding of the substrate to the active site

Question 27

cofactors

Answer 27

non-protein substances that bind to enzyme to help ensure enzyme-controlled reactions can take place at an appropriate rate

Question 28

example of inorganic cofactors

Answer 28

amylase won't work unless Cl- ions are present

Question 29

example of prosthetic group

Answer 29

carbonic anhydrase contains a Zn2+ ion

Question 30

reaction that is catalysed by carbonic anhydrase

Answer 30

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3-

Question 31

how do inorganic cofactors work?

Answer 31

work by helping the enzyme and the substrate bind together by affecting the charge distribution or affecting the shape of the ES-C

Question 32

how do coenzymes work?

Answer 32

bind temporarily to the active site; often act as carriers by moving chemical groups between different enzymes and link together enzyme-controlled reactions that need to take place in sequence

Question 33

how do prosthetic groups work?

Answer 33

are permanently, covalently bonded parts of the enzyme molecule

Question 34

enzyme inhibitors

Answer 34

substances or molecules that slow down the rate of an enzyme-controlled reaction by affecting the enzyme molecule in some way

Question 35

enzyme inhibitor if bonds are covalent

Answer 35

irreversible

Question 36

enzyme inhibitor if bonds are hydrogen or ionic

Answer 36

reversible

Question 37

competitive inhibitors

Answer 37

molecules with a similar shape to the substrate; they compete with the substrate molecules to bind to the active site and block it so no substrate molecules can fit in it

Question 38

non-competitive inhibitors

Answer 38

molecules that bind to the enzyme away from its active site which causes a change in the tertiary structure and therefore the active site so the substrate molecules can no longer bind to it

Question 39

allosteric site

Answer 39

the area in which non-competitive inhibitors bind to the enzyme

Question 40

metabolic poisons

Answer 40

interfere with metabolic reactions causing damage, illness or death

Question 41

example of metabolic poison

Answer 41

cyanide - a non-competitive inhibitor of cytochromate c oxidase which catalyses respiration reactions

Question 42

venom

Answer 42

a mixture of toxins and different enzymes

Question 43

example of a venom

Answer 43

phosphodiesterases - interferes with the heart causing a drop in blood pressure

Question 44

end-product inhibition

Answer 44

a reaction in which the end product binds to an enzyme earlier in the sequence which changes the active site and reduces the rate of reaction

Question 45

enzyme activation

Answer 45

where some enzymes (synthesised in an inactive precursor) will not work until they have been altered so that the active site assumes the correct shape. this can be done by: - adding phosphate - removing amino acids - adding a cofactor