enzymes

Question 1

what is a cofactor?

Answer 1

non-protein component of an enzyme required for activity

Question 2

what is a prosthetic group?

Answer 2

non-dissociable cofactor

Question 3

what is a co-enzyme?

Answer 3

dissociable cofactor

Question 4

what is an apoenzyme?

Answer 4

enzyme without a cofactor

inactive

Question 5

what is a holoenzyme

Answer 5

enzyme with a cofactor

active

Question 6

what is heme

Answer 6

enzyme cofactor

porphyrin ring with iron

Question 7

what are the precursors of cofactors and coenzymes?

Answer 7

vitamins

Question 8

what does a lack of B1 cause?

Answer 8

Beriberi

Question 9

what does a lack of vitamin B3 cause?

Answer 9

pellagra

Question 10

what are proenzymes?

Answer 10

inactive form of enzymes

Question 11

how are proenzymes activated?

Answer 11

proteolytic conversion which is irreversible

Question 12

what are common proenzymes?

Answer 12

digestive enzymes
blood clotting enzymes
developmental enzymes

Question 13

what is the prefix of proenzymes?

Answer 13

-ogen

Question 14

what is chymotripsinogen?

Answer 14

proenzyme synthesised in the pancreas

activated by cleaving peptide bonds

Question 15

how is chymotripsinogen activated?

Answer 15

trypsin cleaves bonds to remove a dipeptide (14 and 15)

another dipeptide 147 and 148 are removed

forms A-chymotrypsin which are three chains interconnected by disulphide bonds

Question 16

what is the michaelis-menten equation?

Answer 16

explains the relationship between rate of reaction and substrate concentration

V0 = Vmax[S]/Km + S

Question 17

what is the michaelis constant?

Answer 17

substrate concentration when the reaction rate is half of Vmax

Question 18

what does the michaelis constant show?

Answer 18

a measure of enzyme activity

Question 19

what does a high michaelis constant show?

Answer 19

enzyme has a low affinity for the substrate - lots is needed for it to reach Vmax/2`

Question 20

what are isoenzymes?

Answer 20

different forms of one enzyme catalysing the same reaction (but in different tissues)

Question 21

give an example of an isoenzyme

Answer 21

lactate dehydrogenase

Question 22

name methods that energy can be stored and released

Answer 22

ATP
phosphocreatinine
other nucleotides - GTP
carbohydrates and glycogen
fat

Question 23

describe the structure of ATP

Answer 23

ribose
adenine
three phosphates

Question 24

how is phosphocreatine made?

Answer 24

phosphorylation of creatine using ATP catalysed by creatine kinase

Question 25

what are the uses of biological energy?

Answer 25

transport motility anabolism heat

Question 26

what is an absolute enzyme?

Answer 26

catalyses one type of reaction for a single substrate

Question 27

what is a group enzyme?

Answer 27

catalyses one type of reaction for a group of substrates

Question 28

what is a linkage enzyme?

Answer 28

catalyses one type of reaction for a specific type of bond

Question 29

what do oxidoreductases do?

Answer 29

oxidation and reduction reactions

Question 30

what do transferases do?

Answer 30

transfer of functional groups

Question 31

what do hydrolases do?

Answer 31

hydrolysis

Question 32

what do lyases do?

Answer 32

add/remove groups from double bond without oxidation or reduction

Question 33

what do isomerases do?

Answer 33

rearrange atoms to form isomers

Question 34

what do ligases do?

Answer 34

bond molecules using ATP

Question 35

how is trypsinogen stored?

Answer 35

acinar cells

Question 36

where is chymotrypsinogen cleaved?

Answer 36

in the duodenum

Question 37

what is the reaction rate V?

Answer 37

no of reactions/second catalysed per molecule of the enzyme

Question 38

what is malonate?

Answer 38

competitive reversible inhibitor of succinate dehydrogenase

Question 39

what is irreversible inhibition?

Answer 39

an irreversible inhibitor destroys enzyme activity, usually by bonding with side-chain groups in the active site

Question 40

what is a non-competitve inhibitor?

Answer 40

has a structure different to the substrate | binds to somewhere that isnt the active site and changes the shape of the active site so the substrate cant bind

Question 41

what is an uncompetitive inhibitor?

Answer 41

has a shape different to the substrate | binds to the ES complex so less product is formed and the ES dissociates slowly