chp 6 Flashcards
(116 cards)
1
Q
Enzymes are ?
A
biological catalysts
2
Q
wdym by enzymes ?
A
proteins in their final correct 3d structure
3
Q
in which structure is the enzymes useful ?
A
tertiary or quaternary
4
Q
how to catalysts increase rate of reaction ?
A
lowering activation energy
5
Q
wt do we call the little push of energy that starts a chemical reaction ?
A
activation energy
6
Q
why does the enzyme lower the activation energy ?
A
so the reaction can start more easily and happen faster
7
Q
do enzymes change the total energy released or used in the reaction ?
A
no
8
Q
main function of enzymea ?
A
enzymes speed things up
9
Q
wdwm by ground state ?
A
a stable , low energy form
10
Q
wt do we call the highest energy point in the reaction ?
A
transition state
11
Q
what is the least stable form in a reaction ?
A
transition state
12
Q
wt is the special area called in the enzyme ?
A
active site
13
Q
wt do we have inside the active site that helps reaction happen ?
A
amino acid side chain
14
Q
wt do the amino acids use to hold and orient the substrate ?
A
- ionic bonds
- hydrogen bonds
- hydrophobic interactions
15
Q
2 common enzymes ?
A
pepsin and trypsin
16
Q
who help enzymes ?
A
cofactors like small organic ions ( mg, zn ) and
coenzymes like organic molecules ( often from vitamins )
17
Q
wt do we call the part of the enzyme that is inactive alone ?
A
apoenzyme
18
Q
wt do we call the complete active enzyme , and wt does it consist ?
A
holoenzyme , apoenzyme + cofactors / coenzymes
19
Q
do enzymes obey the laws of thermodynamics ?
A
yes
20
Q
wt is the usual concentration of enzymes ?
A
low concentration
21
Q
example of oxidoereductases ?
A
dehydrogenase
22
Q
oxidoereductases needs wt ?
A
NADH OR FADH2 as coenzymes
23
Q
examples of transferases ?
A
aminotransferase
kinase
24
Q
transferases needs wt ?
A
ATP and Mg2+ as cofactor
25
hydrolases examples?
peptides
esterase/lipase
26
example of lyases ?
decarboxylase
27
examples of isomerases
racemase
geometric ismoerase
structural ismoerase
28
ligases needs wt ?
ATP
29
example of ligases ?
carboxylase
30
alcohol dehydrogenase wt type of enzyme class ?
oxidoreductase
31
hexokinase wt ype of enzyme class
transferase
32
chymotrypsin wt type of enzyme class
hydrolase
33
pyruvate decarboxylase wt type of enzyme class
lyase
34
alanine racemase wt type of enzyme class ?
ismoerase
35
pyruvate carboxylase wt type of enzyme class ?
ligase
36
which enzyme class uses NAD+
oxidoreductase
37
when can molecules become products
only molecules that reach transition state can become products
38
how is enzyme related to speed , transition state ,Ea ?
enzymes speed up reactions by stabilizing the transition state which lowers activation energy
39
how do enzymes make reactions faster ?
1- proximity and orientation
2- electrostatic
3- acid base catalysis
4- covalent catalysis
40
explain proximity and orientation effects ?\//
enzymes hold the substrate close and in the right position
41
2. Electrostatic Effects
explain it
The charges inside the enzyme help stabilize or attract the substrate ( like using magnet to guide the substrate into the right spot
42
3. Acid-Base Catalysis
explain it
The enzyme can donate or take H⁺ (a proton) to help break or form bonds
43
name an amino acid that can act like acid or a base
histidine, lysine and aspartate
44
Covalent Catalysis
explain
A side chain in the enzyme temporarily bonds to the substrate to form a reactive intermediate then lets go once the job is done
45
in which part of the enzymes the reaction happens ?
active site
46
active sites are made from wt ?
amino acids
47
wt are the two kinds of amino acids in the active site
catalytic amino acids
non catalytic amino acids
48
wdym by catalytic amino acids
they help in the reaction , these can donate or accept protons or form temporary bonds
49
catalytic amino acids should havewt ?
charged or polar aide chains
50
examples of catalytic amino acids
histidine , aspartate , lysine
51
histidine , aspartate , lysineare example of wt amino acids ?
catalytic AA
52
wdym by non catalytic amino acids
these dont directly help in the reaction but they help by holding the substrate in the right position or stabilizing the transition state
53
wt do we call the helpers of an enzyme ?
cofactors
54
cofactora can be like wt ?
metal ion like sodium , potassium , magnesium , calcium , zinc , iron , copper
55
wt are the jobs of the metals cofactors
alkali metals ( Na , K ) and alkaline earth metals (Mg , Ca ) help hold the enzymes shape or structure
transition metals ( Zn , fe , Cu ) help speed up the reaction they participate directly in the reaction
56
Which of the following amino acids is most likely to act as a catalytic residue?
A) Leucine
B) Histidine
C) Valine
D) Alanine
B
57
Which of the following best describes the role of histidine in general acid-base catalysis?
A) It provides hydrophobic interactions with the substrate
B) It acts as a proton donor or acceptor depending on the pKa
C) It always forms a covalent bond with the enzyme
D) It stabilizes the metal ion cofactor
b
58
A reaction involves stabilization of a positively charged transition state. Which amino acid side chain would be most helpful?
A) Aspartate
B) Leucine
C) Serine
D) Phenylalanine
A
59
What distinguishes proximity/orientation effects from electrostatic effects in enzyme catalysis?
A) Electrostatic effects require ATP, while proximity does not
B) Proximity/orientation helps bring substrates together in the right position; electrostatics stabilize charges
C) Electrostatics involve metal cofactors, proximity does not
D) They are both the same type of effect
B
60
Which of the following would most likely be used in covalent catalysis?
A) A nonpolar side chain like valine
B) A nucleophilic side chain like serine or cysteine
C) A hydrophobic patch of the enzyme
D) An amino group of alanine
B , covalent catalysis needs a nucleophile — something that attacks a substrate.
Amino acids like serine, cysteine, or lysine have lone pairs that can form temporary covalent bonds with the substrate
61
What does transition state stabilization by an enzyme lead to?
Lower activation energy
62
Which feature of the active site is MOST responsible for enzyme specificity?
A) It contains water to help binding
B) It changes shape randomly
C) It is complementary in shape and charge to the substrate
D) It repels the substrate until ATP is used
c
63
What are coenzymes?
they are organic helper molecules that some enzymes need to work properly
64
wt are Non-protein helpers
cofactors
65
coenzymes are usualyy taken from where ?
covitamins enzymes
66
example of coenzyme ?
Nad+
67
Fad is an example of wt ?
coenzyme
68
diff bw cofactor and coenzyme ?
Cofactor = like a metal bolt that holds the enzyme in the right shape 🧩
🌿 Coenzyme = like a tool that helps the enzyme do the reaction
69
Relationship of coenzyme and cofactors
All coenzymes are cofactors,
But not all cofactors are coenzymes.
70
Why do enzymes need coenzymes?
ecause:
Coenzymes bring extra functional groups that the enzyme's amino acids don’t have.
They help with chemical reactions that the enzyme can’t do alone.
71
Thiamine (B₁) wt does its coenzyme form ?
Thiamine pyrophosphate
72
Thiamine pyrophosphate function
Helps with decarboxylation (removal of CO₂) and aldehyde transfer
73
Riboflavin (B₂) wt does its coenzyme form ?
FAD and FMN
74
FAD and FMN func
Helps with redox reactions (oxidation & reduction)
75
Pyridoxine (B₆)coenzyme form
Pyridoxal phosphate
76
Pyridoxal phosphate func
Helps with amino group transfer
77
NAD and NADP is coenzyme of which vitamin
Nicotinic acid (Niacin)
78
NAD and NADP func
Also helps with redox reactions
79
Pantothenic acid wts the coenzyme
COENZYME A
80
coenzyme a func
Helps with acyl group transfer (important in metabolism)
81
biotin is the coenzyme form of who
biotin
82
biotin function
Helps with carboxylation (adding CO₂ to molecules)
83
Folic acid coenzyme form
Tetrahydrofolic acid
84
Tetrahydrofolic acid function
Helps with one-carbon group transfers
85
Vitamin B₁₂ coenzyme form
Deoxyadenosylcobalamin, methylcobalamin
86
Deoxyadenosylcobalamin, methylcobalamin function
Helps with intramolecular rearrangements
87
Vitamin C (Ascorbic acid) function
Believed to help with hydroxylation (adding OH groups)
88
Vitamin C (Ascorbic acid) coenzyme form
unknown
89
wdwm by holoenzyme ?
is the complete , active form of an enzyme
90
apoenzyme + cofactor gives us wt ?
Holoenzyme (active enzyme)
91
enzymes work the best wt which temp ?
37
92
if temp increases wt happens to the enzyme
works faster because molecule collide more but if its too hot it denatures
93
If the pH is too acidic or too basic wt happens to the enzyme ?
it can alter the shape of the enzyme.
94
enzyme is measure with wt ??
IU
95
Specificity constant (kcat/Km)
measure of efficiency: how fast and how tightly the enzyme binds
96
1. Sequential Reactions wt happens in it ?
All substrates must bind before any product is released.
97
two types of . Sequential Reactions
Ordered: substrates bind in a specific sequence.
Random: substrates can bind in any order.
98
2. Double-Displacement Reactions (Ping-Pong)
wt happens here
The enzyme binds one substrate, changes form, and releases the first product before binding the second substrate.
99
2. Double-Displacement Reactions (Ping-Pong)
is common in which enzyme ?
Common in transferase enzymes.
100
🔹 Enzyme Inhibition wt happens in it ?
Inhibitors slow down or stop enzyme activity
101
🔹 Enzyme Inhibition
importnt for wt ?
Regulating metabolism
Drug action/therapeutics
102
two types of enzyme inhibtion
Reversible Inhibition , Irreversible Inhibition
103
Reversible Inhibition how does it work ?
can be undone by increasing substrate or removing inhibitor.
104
Irreversible Inhibition wdwm
Inhibitor forms a covalent bond with enzyme → permanent inactivation.
105
🔸 2. Irreversible Inhibition
used i n wt ?
Used in some drugs and poisons.
106
which inhibition is not reversible by adding substrate
Uncompetitive
107
wdwm by cooperative binding
meaning that when one substrate binds, it makes it easier for more to bind
108
wdwm by Compartmentation
Reactions happen in different places inside the cell to keep things organized and safe.
109
What is Enzyme Induction?
Enzyme induction means the cell starts making an enzyme only when it’s needed.
110
There are 2 types of effectors in allosteric regulation
Homotropic: Substrate is also the effector.
Heterotropic: Different molecule acts as effector.
111
allosteric has two models wt are they ?
conceerted model and sequential model
112
wdwm by concerted model
All subunits switch from T (tense) to R (relaxed) at the same time.
Substrates/activators prefer R; inhibitors prefer T
113
wdwm by sequential model ?
One subunit changes to R when substrate binds, then helps nearby subunits also shift to R.
114
Glycolysis taking place in cytoplasm; Krebs cycle in mitochondria. is an example of wt ?
Compartmentation
115
Substrates and activators have a greater affinity
for the
R state
116
Inhibitors favour which state ?
T state
