enzymes + inhibition

Question 1

how many times can enzymes increase the Ror

Answer 1

1013 faster

Question 2

what is a coenzyme

Answer 2

small organic AA that participates in enzyme catalysed reaction + stable to heat

Question 3

what is a prosthetic group

Answer 3

coenzyme that covalently/firmly bound to enzyme –> not removed by dialysis

Question 4

what is zymogen

Answer 4

inactive precursor of enzyme

Question 5

what is a haloenzyme

Answer 5

protein WITH coenzyme pr ions needed for activity

Question 6

what is a apoenzyme

Answer 6

protein WITHOUT coenzyme or ions needed for activity,

labile (easily altered) to heat

Question 7

where are lysosomes commonly found

Answer 7

saliva
tears
tissue fluids
nasal mucus

Question 8

what do lysosomes do

Answer 8

protects against sensitive bacteria –> causing lysis of bacteria + losing cell content

Question 9

how does lysosome cause bacteria lysis

Answer 9

hydrolyses beta 1-4 bond in glycol chain between N-acetyl glucosamine (NAG) + N-acetyl muramic acid (NAM)

Question 10

when do lysosomes work the fastest

Answer 10

near neutral pH

Question 11

another name serine protease?

Answer 11

proteolytic enzymes

Question 12

how and why proteolytic enzymes secreted in the body

Answer 12

secreted as zymogens (inactive form ) then activated by gut

bc they needed for digestion of proteins - but the can work in human body - so harmful

Question 13

name 3 zymogen forms of serine protease

Answer 13

trypsinogen
chymotrypsinogen
pepsinogen

Question 14

how do you activate pepsinogen

Answer 14

pepsinogen –> pepsin
gastric gland: chief cells produce pepsinogen + parietal cells produce HCl
pepsinogen –> pepsin by HCl

Question 15

how you do activate trypsinogen

Answer 15

pancreatic zymogens –> trypsinogen –> trypsin
trypsinogen –> trypsin by Enterokinase in cell walls of cells in duodenum
trypsin activates more zymogen like chymotrypsinogen

Question 16

how long is chymotrypsin and how is it held together

Answer 16

245 AA

5 disulphide bonds between different parts of structure + folds into 3D globular structure

Question 17

how is chymotrypsinogen activated

Answer 17

trypsin cleaves/cuts bond between Arg15 + 16
Pi-chymotrypsin cuts at Leu13 + removes dipeptide
Pi-chymotrypsin cuts at Tyr146 + removes another dipeptide
A chain = 1-13 alpha Chymotrypsin
B chain = 16-146
C chain = 149-245
3 parts of chain held by disulphide bridge

Question 18

where are the active sites that come together in chymotrypsin

Answer 18

Asp102
His57
Ser195

Question 19

name 3 enzymes which are used to cut polypeptide chain

Answer 19

trypsin
Chymotrypsin
elastase

Question 20

where does trypsin cut next to and what are its pocket properties

Answer 20

cuts next to = basic R groups
Lysine + Arginine

bottom of the pocket

Question 21

where does chymotrypsin cut next to and what are its pocket properties

Answer 21

cuts next to = hydrophobic R groups
Tyrosine + Phenylalanine

hydrophobic pocket

Question 22

where does elastase cut next to and what are its pocket properties

Answer 22

cuts next to - small R groups
Glycine, Alanine, Valine

small pocket so large R groups don’t fit

Question 23

what is Michaelis - mention equation + what does it show

Answer 23

V (initial velocity) = Vmax (max velocity) / Km (substrate conc at half Vmax) + S (substrate conc)

Question 24

what happens as the substrate conc increases

Answer 24

increases For

eventually active sites of enzymes become saturated, so Ror stays the same

Question 25

when is the fastest rate of reaction

Answer 25

Vmax

Question 26

what does Km mean

Answer 26

substrate conc at half Vmax

Question 27

what does a small Km value mean

Answer 27

tight binding between enzyme + substrate

Question 28

what happens as enzyme conc increases

Answer 28

increases Ror | eventually all substrate converted to product --> Ror decreases to 0

Question 29

what happens as the temp increases

Answer 29

increases energy + more frequent collisions | but if at too high temp, active site change shape so Ror decreases quickly

Question 30

what happens if pH moves away from optimum pH

Answer 30

Ror decreases suddenly

Question 31

why are enzyme inhibitors important

Answer 31

gain info on enzyme active site shape + amino acid at active site gain info on chemical mechanism of reaction/ regulation or control of pathway

Question 32

what are diff types of enzyme inhibitors

Answer 32

reversible + irreversible

Question 33

how does a irreversible inhibitor work

Answer 33

substance causes irreversible inactivation to enzyme | involves forming or breaking of covalent bonds in enzyme

Question 34

give a example of irreversible inhibition

Answer 34

diisopropylphosphofluoridate permanently inactives serine protease by forming covalent bond with serine AA in active site

Question 35

how does reversible inhibition work

Answer 35

substance binds to enzyme active site to inhibit but can be reversed involves formation of non-covalent bonds

Question 36

describe steps in how competitive inhibition works

Answer 36

inhibitor competes with substrate for same active site in enzyme only binds to free enzymes reduces amount of free enzymes available for substrate binding Ror decreases

Question 37

how are Vmax and Km affected in competitive inhibition

Answer 37

``` Vmax = doesn't change bc can be reversed using high conc of substrate Km = increases bc affinity between substrate + enzyme decreases ```

Question 38

give a example of competitive inhibition

Answer 38

malonate comp inhibitor of succinate for succinate dehydrogenase

Question 39

describe steps in how non-competitive inhibition works

Answer 39

inhibitor binds to another site on enzyme not active site | can bind to free enzyme + ESC

Question 40

how are Vmax and Km affected in non-competitive inhibition

Answer 40

``` Vmax = decreases --> binding stops the reaction Km = stays same as substrate can still bind to enzyme, same affinity ```

Question 41

give 2 examples of non-comp inhibition

Answer 41

AMP inhibits fructose 1,6 bisphosphate | Alanine inhibits pyruvate kinase as converts phosphoenol pyruvate to pyruvate --> alanine

Question 42

describe steps in how uncompetitive inhibition works + how are Vmax and Km affected in uncompetitive inhibition

Answer 42

inhibitor binds only to ESC Vmax = decreases inhibitor stops reaction Km = decreases --> tighter binding between enzyme + substrate bc when inhibitor binds, substrate can't move out

Question 43

how may types of reversible inhibition ae there + name them

Answer 43

3 comp non-comp uncomp

Question 44

what are the type of allosteric effctors

Answer 44

negative + positive

Question 45

how do positive allosteric effectors work

Answer 45

increased Ror binds to allosteric site + makes substrate bind more tightly to enzyme --> higher affinity Vmax increases + Km decreases

Question 46

how do negative allosteric effectors work

Answer 46

decrease Ror binds to allosteric site + changes shape of active site so substrate can't bind to it Vmax decreases + Km increases