Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Cell Biology and Signalling > Enzyme Properties > Flashcards

Enzyme Properties Flashcards

1
Q

What are enzymes?

A

Biological catalysts which speed up the rate of a reaction, without altering the final equilibrium between reactants and products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What effect does an enz have as a catalyst on reaction?

A
  • help reaction to reach equ
  • permit cells to make/break covalent bonds at will
  • lowers Ea and inc reaction rate - allow larger prop of random collisions with surrounding mol to kick sub over energy barrier
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is free energy and why is it important?

A
  • Energy needed to do work/drive chem reactions
  • chem reactions proceed only in direction that leads to loss of free energy
  • There has to be release of free energy for reactions to occur
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What has to be put in for reaction to occur and why?

A
  • energy e.g. heat as mol rel stable and can’t be changed to lower energy states without it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the effect of an enzyme on activation energy of reaction?

A
  • Free energy of activation normally quite high
  • Enz make it poss so less energy put in for reaction to progress
  • Quicker rate but not altering equ
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are enzymes responsible for when it comes to foodstuffs?

A

the controlled “combustion” (oxidation) of foodstuffs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the equation for the combustion of propane?

A

5 O2+ C3H8 —> 4 H2O + 3 CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is equation for the combustion of glucose?

A

6 O2 + C6H12 O6 —> 6 H2O + 6 CO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do enz control comb/ox?

A

create series of steps by capturing change in energy (increases as its released from glucose) instead of going from start to finish in one step

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe process of catalysis

A

S binds to enz active site
ESC formed
Catalysis occurs and EPC formed
P released from enz

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which is enz complementary to transition state and why?

A
  • more likely to get P formed as shape of intermediate has better fit for active site than S.
  • Enz stabilises TS
  • when S binds, enz stretch/distort key bonds + weaken it so less Ea needed to break bond at start of reaction
  • cond created in env of active site to lower Ea
  • lower Ea - more mol turned into P in given time
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is substrate specificity?

A

Enzymes will usually catalyse only one type of reaction. A few enzymes are so specific they will act on one substrate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does alcohol dehydrogenase do?

A

oxidises primary alcohols e.g. methanol, ethanol, propanol etc to aldehydes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Where is alcohol dehydrogenase found?

A

In liver

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is group specificity?

A

enz will act on only a few related molecules/sub

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does an enz do if a natural compound can exist in two stereoisomer forms e.g. D-glucose and L-glucose?

A

the enzyme concerned with its metabolism in the cell will usually act only on one isomer.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is specificity determined by?

A

presence of ‘active site’ into which only the substrate of the correct shape and charge can fit.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the active site?

A

a groove or cleft of defined shape in enz in which only the substrate of the correct shape and charge can fit.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What can a group of enzymes present together in one compartment of a cell give rise to?

A

complex and co-ordinated metabolic pathway in which the initial substrate e.g D-glucose is converted through a sequence of specific enzyme catalysed reactions to the product e.g. lactic acid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How does the pathway in which group of enz convert initial S to P work?

A

Enz specific enough so in pathway – only mol it can work on is the one it needs to work on. e.g. Enz 1 only specific to glucose in that form, enz 2 only specific to B etc. Ability to pass on mol – p of 1 enz reaction s of another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What has specificity of enzymes has led to?

A

systematic classification scheme, established by the I.U.B. Commission on Enzymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is systematic classification scheme, established by the I.U.B. Commission on Enzymes?

A

Enzymes are divided into 6 main classes according to the type of reaction they catalyse
Six classes are then further divided into subgroups according to their substrate or source.
Each enzyme is identified by its own individual 4 digit number

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are 6 classes of enz?

A
  1. Oxidoreductases
  2. Transferases
  3. Hydrolases
  4. Lyases
  5. Isomerases
  6. Ligases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What do oxidoreductases do + 3 e.gs?

A

catalyze the transfer of hydrogen atoms and electrons - add O2/remove 2Hs
lactate dehydrogenase
alcohol dehydrogenase
catalase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What do transferases do + e.g?
catalyse transfer of functional groups from donors to acceptors alanine amino transferase
26
What is hydrolases do + e.g?
catalyze the cleavage of bonds by the addition of water (hydrolysis) trypsin
27
What is lyases do + e.g?
catalyze the cleavage of C-C, C-O, or C-N bonds - addition of groups to double bonds or formation of double bonds by removal of groups ATP-citrate lyase
28
What do isomerases do + e.g?
catalyze the transfer of functional groups within the same molecule phosphoglucose isomerase
29
What do ligases do + e.g?
use ATP to catalyze the formation of new covalent bonds | DNA ligase
30
What is IUB name and number for alcohol dehydrogenase?
alcohol : NAD oxidoreductase | E.C. 1.1.1.1
31
What is IUB no. for catalase?
E.C. 1.11.1.6
32
What does lactate dehydrogenase do?
Interconverts pyruvate to lactate | rev reaction – direction in which it goes depends on sub
33
What does alanine amino transferase do?
transfers NH2 group of glutamate to across C=O in py to form l-alanine and the C=O bond in py to bit where NH2 group is in glutamate
34
What does ATP-citrate lyase do?
Catalyses Oxal (4C) accepting (2C) acetate to form citrate (6C)/breakdown of citrate to oxaloacetate + acetate
35
What does trypsin do?
Hydrolyses peptide of gly-lys-val-ala to dipeptides of gly-lys + val-ala
36
What does phosphoglucose isomerase do?
transfers C=O from C1 in glucose-6 phosphate to C2 in fructose-6 phosphate
37
What does DNA ligase do?
Links hydroxyl and phosphate group in nucleotides to form phosphodiester bonds
38
What bio mol are enz?
Proteins
39
What determines shape of active site in enz?
one or more polypeptide chains folding into a complex 3- dimensional shape
40
How is enzyme structure stabilised?
many weak bonds e.g. H-bonds, electrostatic salt links, hydrophobic interactions.
41
What does it mean when enz inactive/denatured?
as weak bonds broken by changing env e.g. by heating/pH giving rise to a disorganised or tangled structure in which the enzyme no longer has any catalytic activity
42
What problem does property of enz structure being stabilised by weak bonds cause but what is adv of this?
makes enzymes very sensitive to changes in their environment u can change enz activity by changing env
43
What does active site of the enzyme contain?
functional groups that stabilize the transition state of the reaction
44
What is “Lock and Key” model for enzyme catalysis?
- enzyme = lock - sub = key - Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme).
45
What is problem with “Lock and Key” model for enzyme catalysis?
- doesn’t explain stabilization of enzyme. - When an enzyme has a substrate enter into its active site, the enzyme will change its shape slightly to match the substrate. - If enzymes were to be specifically designed to fit a substrate, then there would be no need for it to have to adjust its shape. - Nothing much happens – sub just sits in active site
46
What is Induced Fit model of enzyme catalysis?
- amino acid side-chains that are a part of the active site are molded into a specific position. - This position allows the enzyme to start the catalyzing process. E.g. To remove phos from ATP – put ATP into active site – enz changes shape so opp charges meet to catalyse - Also poss change in shape to do with another active site to change shape of that part of mol to make it more/less active
47
What is Modified Lock and Key model?
Enz constrains structure of mol – more likely to bring them into active site e.g. Changing orientation of S1 to bring it closer to S2
48
What does chymotrypsin do?
Cleaves peptide bonds by hydrolysis on the carboxyl side of tyrosine, tryptophan and phenylalanine and of large hydrophobic residues such as methionine
49
What is Phase 1 of chymotrypsin mech?
Enzyme creates nucleophile from serine side-chain. Nucleophile attacks substrate. Covalent intermediate is formed with second product ( PN ) bonded to serine, and first product ( PC ) is released.
50
What is Phase 2 of chymotrypsin mech?
``` Enzyme creates a nucleophile from a water molecule. Nucleophile attacks covalent intermediate, breaking covalent bond to serine. Second product ( PN ) is released. ```
51
What is effect of temperature on enzyme reactions?
- v. Often Increase temp – increase energy of enz mol + sub – chance of them colliding increases - Some point – temp destabilises enz – breakdown of enz structure – enz no longer catalyses - Over normal phys range but enz can have own phys range – some work in boiling water/freezing cond
52
Why is it Enz in cold cond don’t work v. well?
sub mol don’t have much energy – not colliding with active site
53
What is optimum pH?
one where structure (various ionisation of aa) consistent with function
54
What is effect of pH on enzyme reactions?
Diff proteins work at diff pH To do with charges in enz and proteins/aa Charges are to do with level to which proteins/aa protonated (accepted H+) E.g. Something that relies on O- to interact when there’s high conc of H+ in sol – it will accept H+ to form OH and not be able to take part in the reaction or other way around
55
What is Cu2+ cofactor for?
Cytochrome oxidase
56
What is Fe2+/3+ cofactor for?
Cytochrome oxidase, catalase, peroxidase
57
What is K+ cofactor for?
Pyruvate kinase
58
What is Mg2+ cofactor for?
Hexokinase, G-6-phosphatase, pyruvate kinase
59
What is Ni2+ cofactor for?
Urease
60
What is Se cofactor for?
Glutathione peroxidase
61
What is Zn2+ cofactor for?
Carbonic anhydrase, alcohol dehydrogenase
62
What do cofactors do?
inorganic substances (non-protein chemical compound or metallic ion) that are required for, or increase the rate of, catalysis. Involved in moving e-s.
63
What are coenzymes?
- A specific type of cofactor - organic molecules that bind to enzymes and help them function. T - they bind to the active site of the enzyme to form active enzyme and participate in catalysis but are not considered substrates of the reaction. - Donate/accept e-s/H
64
What are 3 e.g. of coenzymes?
NAD+, FAD, ATP
65
What is e.g. of reaction NAD+ involved in?
CH3 CH2 OH + NAD+ ---> CH3CHO + NADH + H+ | catalysed by alcohol dehydrogenase
66
What is e.g. of reaction FAD involved in?
succinate + FAD ---> fumarate + FADH2 (catalysed by succinate dehydrogenase)
67
What is e.g. of reaction ATP involved in?
glucose + ATP ---> glucose-6-phosphate + ADP | catalysed by glucokinase
68
What are isoenzymes?
enzymes with different protein structures which catalyse the same reaction
69
What are 3 properties of isoenzymes?
Coded for by different genes •Different isoenzymes often found in different cellular compartments (cytoplasm or mitochondria), or different amounts in different tissues •Distinct biochemical roles – sometimes found in diff tissues/Respond diff to changes in substrate conc
70
What are e.gs of isoenzymes?
e.g. hexokinase /glucokinase. | Lactate dehydrogenase
71
What is reaction for conversion of py to L-lactate?
pyruvate + NADH + H+ L-lactate + NAD+
72
Why are enz extremely efficient?
Speed up reactions by factor of m/more without themselves being changed e.g. the enzyme catalase catalyses the breakdown of its substrate H2O2 to water at a rate 1014x faster than the uncatalysed reaction at 30C.
73
In which direction do chem reactions proceed?
Direction that leads to loss of free energy which means as reaction progresses - change in free energy from R to P
74
Why does energy have to be put in for a reaction to proceed?
Mol rel stable and can't be changed to lower energy states without initial input of energy
75
What is activation energy?
- Min energy required to start reaction - Energy that boosts mol over energy barrier before it can undergo chem reaction that moves it to lower energy (more stable) state - Normally quite high
76
How do enz lower activation energy?
Bind tightly to substrates + hold them in way that red activation energy
77
Why are enz catalysts?
Lower activation energy of reaction and inc rate of reaction
78
How do enz inc rate of chem reactions?
Allow larger proportion of random collisions with surrounding mol to kick sub over energy barrier
79
What is reaction rate like when there's no enz and why?
- takes long time - activation energy needs to be overcome - energy needs to be put in so stick bends and breaks
80
Why is not much P formed when enz comp to sub?
- sub has to be distorted in particular shape (transition state) for enz to occur - to distort sub - lots of energy needed from random mol collisions - energy almost never exceeds Ea so reaction occurs slowly if at all
81
What is transition state?
Where atoms around bond have altered geometry + e- distribution - state corresponding to highest energy along reaction (at peak of curve) on free energy graph - has more free energy compared to S/P - least stable state

Cell Biology and Signalling (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions