Enzyme regulation Flashcards
1
Q
2 ways to regulate the amount of activity at a given time
A
- increase or decrease the number of
enzyme molecules - increase or decrease the activity of
each enzyme molecule.
2
Q
approximate the prevailing
in vivo concentration of their S
A
Km values
3
Q
slows down as P accumulates and eqbm is
approached
A
enzymatic rate v= d[P]/dt
4
Q
: no further rxn
A
[P]/[S] = Keq
5
Q
the amount of E synthesized by a cell
is determined by?
A
transcription regulation
6
Q
- E synthesis through transcriptional
activation
A
induction
7
Q
- shutdown of E synthesis
induction & repression - important mechanisms for the
regulation of metabolism
A
repression
8
Q
- activation/inhibition of enzymatic
activity through noncovalent
interaction of the E w/ small
molecules (metabolites) other than
the S
A
Allosteric regulation
9
Q
allo means?
A
other than
10
Q
- different sterically from the S
- results from reversible binding of
regulatory ligands to the E - cellular response time can be virtually
instantaneous
A
allosteric regulators/effector molecules
11
Q
- reversible covalent attachment of a
chemical group
A
covalent modification
12
Q
- can be reversibly converted between 2
forms - a fully active E can be converted into
an inactive form by the covalent
attachment of a functional group
A
interconvertible enzymes
13
Q
- a class of converter E
- act in covalent modification by
attaching a phosphoryl moiety to
target proteins
A
protein kinases
14
Q
- occur very quickly
- response times of seconds or even
less for significant changes in
metabolic activity
A
covalent modification events
15
Q
- acquire full activity only upon specific
proteolytic cleavage of one or several
of their peptide bonds
A
zymogens or proenzymes
15
Q
- an irreversible process
- a strategy frequently exploited by
biological systems to switch on
processes at the appropriate time and
place
A
zymogen activation
16
Q
- an 86-residue precursor
to insulin - proteolytic removal of
residues 31 to 65 yields
A
Proinsulin
17
Q
- residues 1-30 (the B
chain) remain linked to
residues 66-87 (the A
chain) by a pair of
interchain disulfide
bridges
A
insulin
18
Q
E of the digestive tract that serve to
hydrolyze dietary proteins are
synthesized in the stomach and
pancreas as Blank
A
zymogens
19
Q
- the formation of blood clots is the
result of a series of zymogen
activations
A
Blood Clotting
20
Q
2 routes to blood clot formation
A
- Intrinsic pathway
- extrinsic pathway
21
Q
7 of the clotting factors in their
active form are serine proteases
A
- kallikrein
- XIIa
- Xia
- Ixa
- VIIa
- Xa
- thrombin
22
Q
thrombin excises peptides rich in
negative charge from fibrinogen,
converting it to Blank
A
fibrin
23
Q
specifically cleaves Arg-Gly peptide bonds and is homologous to trypsin
A
thrombin
24
* exists in 2 prominent oligomeric forms,
M and H
mammalian lactate dehydrogenase (LDH)
25
* an A4 homotetramer (the A subunit is
encoded by the LDH A gene)
LDH M
26
* a B4 homotetramer (the B subunit is
encoded by the LDH B gene)
LDH H
27
* can also form, depending on the
relative expression of the LDH A and
LDH B genes in different tissues
heterotetrameric isozymes
28
What are the 3 heterotetrameric iaozymes
* A3B
* A2B2
* AB3
29
* acts to modulate E situated at key
steps in metabolic pathways
Allosteric Regulation
30
A =
precursor
31
F =
end product (AA or nucleotide)
32
* F, the essential end product, inhibits
enzyme 1, the first step in the pathway
* when sufficient F is synthesized, it
blocks further synthesis of itself
feedback inhibition or feedback regulation
33
F acts at a binding site distinct from
the S-binding site →
allosteric inhibition
34
* composed of more than one
polypeptide chain (subunit)
* have more than one S-binding site and
more than one effector-binding site per
E molecule
allosteric enzymes have an oligomeric
organization
35
the regulatory effects exerted on the
E’s activity are achieved by Blank occurring in the protein when effector metabolites bind
conformational changes
36
* regulated both by allosteric controls and by covalent modification
* catalyzes the cleavage of glucose units from the nonreducing ends
of glycogen molecules
glycogen phosphorylase
37
1. HOW DID INSULIN BECOME ACTIVE OR INACTIVE?
- Insulin is produced as an inactive precursor called proinsulin and becomes active through a series of modifications. Proinsulin is a single chain of amino acids that includes an A chain, a B chain, and a connecting C-peptide. To activate insulin, specific enzymes cleave proinsulin, removing the C-peptide. This process leaves the A and B chains linked by disulfide bonds, creating the active form of insulin. Insulin becomes inactive when it’s no longer needed or after it has been broken down in the liver, which regulates the amount of insulin available in the body.
38
HOW MANY DISULFIDE BOND ARE THERE
Active insulin contains three disulfide bonds:
* Two disulfide bonds connect the A chain to the B chain.
* One disulfide bond is internal, within the A chain itself.
39
HOW MANY INTRAMOLECULAR BOND? HOW MANY INTERMOLECULAR BOND?
- In active insulin:
* Intramolecular bond: There is one intramolecular disulfide bond within the A chain itself.
* Intermolecular bonds: There are two intermolecular disulfide bonds that link the A chain to the B chain.
40
WHEN IS INSULIN NEEDED? WHAT IS THE NORMAL BLOOD SUGAR LEVEL?
- Insulin is needed when blood sugar (glucose) levels rise, typically after eating. Its role is to help cells absorb glucose from the blood for energy or storage, thus lowering blood sugar levels back to normal.
The normal blood sugar range is approximately:
* Fasting (before meals): 70-99 mg/dL (3.9-5.5 mmol/L)
* Two hours after eating: less than 140 mg/dL (7.8 mmol/L)
If blood sugar levels go higher than this range, insulin is released from the pancreas to help bring it down, maintaining stable and healthy glucose levels.
41
SCIENTIFIC EXPLANATION WHY COLD COMPRESS IS BEING APPLIED IF THE BRUISE IS FRESH AND WHY HOT COMPRESS IF IT IS ALMOST HEALED?
- According to the rate of reaction theory, the higher the energy the higher the reaction, it is not advisable to apply a hot compress because the bruising will get worse. Applying a cold compress reduces the temperature in the affected area, which lowers molecular kinetic energy. According to the rate of reaction theory, this slows down chemical reactions, reducing blood flow, swelling, and inflammation, and also helps numb pain. When the injury reaches the healing phase, a hot compress can be applied to raise the temperature. According to the rate of reaction theory, this increases in temperature boosts molecular kinetic energy, speed up biochemical reactions that enhance blood flow and cellular repair.
41
WHAT CONCLUSION COULD YOU CONCLUDE OF ISOMERS OF LACTASE DEHYDROGENASE?
The isomers of lactase dehydrogenase reveal important aspects of enzyme functionality and tissue-specific metabolism. LDH exists in five main isomeric forms LDH-1 through LDH-5, each composed of different combinations of the enzymes Heart and Muscle subunits. These isomers are distributed across various tissues, where they support tissue-specific energy needs by catalyzing the interconversion of lactate and pyruvate, an essential step in anaerobic and aerobic respiration.
