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BDS year 1 - biochemistry > enzymes + inhibition > Flashcards

enzymes + inhibition Flashcards

1
Q

how many times can enzymes increase the Ror

A

1013 faster

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2
Q

what is a coenzyme

A

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

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3
Q

what is a prosthetic group

A

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

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4
Q

what is zymogen

A

inactive precursor of enzyme

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5
Q

what is a haloenzyme

A

protein WITH coenzyme pr ions needed for activity

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6
Q

what is a apoenzyme

A

protein WITHOUT coenzyme or ions needed for activity,

labile (easily altered) to heat

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7
Q

where are lysosomes commonly found

A

saliva
tears
tissue fluids
nasal mucus

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8
Q

what do lysosomes do

A

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

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9
Q

how does lysosome cause bacteria lysis

A

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

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10
Q

when do lysosomes work the fastest

A

near neutral pH

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11
Q

another name serine protease?

A

proteolytic enzymes

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12
Q

how and why proteolytic enzymes secreted in the body

A

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

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13
Q

name 3 zymogen forms of serine protease

A

trypsinogen
chymotrypsinogen
pepsinogen

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14
Q

how do you activate pepsinogen

A

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

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15
Q

how you do activate trypsinogen

A

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

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16
Q

how long is chymotrypsin and how is it held together

A

245 AA

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

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17
Q

how is chymotrypsinogen activated

A

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

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18
Q

where are the active sites that come together in chymotrypsin

A

Asp102
His57
Ser195

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19
Q

name 3 enzymes which are used to cut polypeptide chain

A

trypsin
Chymotrypsin
elastase

20
Q

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

A

cuts next to = basic R groups
Lysine + Arginine

bottom of the pocket

21
Q

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

A

cuts next to = hydrophobic R groups
Tyrosine + Phenylalanine

hydrophobic pocket

22
Q

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

A

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

small pocket so large R groups don’t fit

23
Q

what is Michaelis - mention equation + what does it show

A

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

24
Q

what happens as the substrate conc increases

A

increases For

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

25
Q

when is the fastest rate of reaction

A

Vmax

26
Q

what does Km mean

A

substrate conc at half Vmax

27
Q

what does a small Km value mean

A

tight binding between enzyme + substrate

28
Q

what happens as enzyme conc increases

A

increases Ror

eventually all substrate converted to product –> Ror decreases to 0

29
Q

what happens as the temp increases

A

increases energy + more frequent collisions

but if at too high temp, active site change shape so Ror decreases quickly

30
Q

what happens if pH moves away from optimum pH

A

Ror decreases suddenly

31
Q

why are enzyme inhibitors important

A

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

32
Q

what are diff types of enzyme inhibitors

A

reversible + irreversible

33
Q

how does a irreversible inhibitor work

A

substance causes irreversible inactivation to enzyme

involves forming or breaking of covalent bonds in enzyme

34
Q

give a example of irreversible inhibition

A

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

35
Q

how does reversible inhibition work

A

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

36
Q

describe steps in how competitive inhibition works

A

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

37
Q

how are Vmax and Km affected in competitive inhibition

A 
Vmax = doesn't change bc can be reversed using high conc of substrate 
Km = increases bc affinity between substrate + enzyme decreases
38
Q

give a example of competitive inhibition

A

malonate comp inhibitor of succinate for succinate dehydrogenase

39
Q

describe steps in how non-competitive inhibition works

A

inhibitor binds to another site on enzyme not active site

can bind to free enzyme + ESC

40
Q

how are Vmax and Km affected in non-competitive inhibition

A 
Vmax = decreases --> binding stops the reaction
Km = stays same as substrate can still bind to enzyme, same affinity
41
Q

give 2 examples of non-comp inhibition

A

AMP inhibits fructose 1,6 bisphosphate

Alanine inhibits pyruvate kinase as converts phosphoenol pyruvate to pyruvate –> alanine

42
Q

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

A

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

43
Q

how may types of reversible inhibition ae there + name them

A

3
comp
non-comp
uncomp

44
Q

what are the type of allosteric effctors

A

negative + positive

45
Q

how do positive allosteric effectors work

A

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

46
Q

how do negative allosteric effectors work

A

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

BDS year 1 - biochemistry (14 decks)

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