Enzyme regulation

Question 1

2 ways to regulate the amount of activity at a given time

Answer 1

• increase or decrease the number of
  enzyme molecules
• increase or decrease the activity of
  each enzyme molecule.

Question 2

approximate the prevailing
in vivo concentration of their S

Answer 2

Km values

Question 3

slows down as P accumulates and eqbm is
approached

Answer 3

enzymatic rate v= d[P]/dt

Question 4

: no further rxn

Answer 4

[P]/[S] = Keq

Question 5

the amount of E synthesized by a cell
is determined by?

Answer 5

transcription regulation

Question 6

• E synthesis through transcriptional
  activation

Answer 6

induction

Question 7

• shutdown of E synthesis
  induction & repression
• important mechanisms for the
  regulation of metabolism

Answer 7

repression

Question 8

• activation/inhibition of enzymatic
  activity through noncovalent
  interaction of the E w/ small
  molecules (metabolites) other than
  the S

Answer 8

Allosteric regulation

Question 9

allo means?

Answer 9

other than

Question 10

• different sterically from the S
• results from reversible binding of
  regulatory ligands to the E
• cellular response time can be virtually
  instantaneous

Answer 10

allosteric regulators/effector molecules

Question 11

• reversible covalent attachment of a
  chemical group

Answer 11

covalent modification

Question 12

• 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

Answer 12

interconvertible enzymes

Question 13

• a class of converter E
• act in covalent modification by
  attaching a phosphoryl moiety to
  target proteins

Answer 13

protein kinases

Question 14

• occur very quickly
• response times of seconds or even
  less for significant changes in
  metabolic activity

Answer 14

covalent modification events

Question 15

• acquire full activity only upon specific
  proteolytic cleavage of one or several
  of their peptide bonds

Answer 15

zymogens or proenzymes

Question 15

• an irreversible process
• a strategy frequently exploited by
  biological systems to switch on
  processes at the appropriate time and
  place

Answer 15

zymogen activation

Question 16

• an 86-residue precursor
  to insulin
• proteolytic removal of
  residues 31 to 65 yields

Answer 16

Proinsulin

Question 17

• residues 1-30 (the B
  chain) remain linked to
  residues 66-87 (the A
  chain) by a pair of
  interchain disulfide
  bridges

Answer 17

insulin

Question 18

E of the digestive tract that serve to
hydrolyze dietary proteins are
synthesized in the stomach and
pancreas as Blank

Answer 18

zymogens

Question 19

• the formation of blood clots is the
  result of a series of zymogen
  activations

Answer 19

Blood Clotting

Question 20

2 routes to blood clot formation

Answer 20

• Intrinsic pathway
• extrinsic pathway

Question 21

7 of the clotting factors in their
active form are serine proteases

Answer 21

• kallikrein
• XIIa
• Xia
• Ixa
• VIIa
• Xa
• thrombin

Question 22

thrombin excises peptides rich in
negative charge from fibrinogen,
converting it to Blank

Answer 22

fibrin

Question 23

specifically cleaves Arg-Gly peptide bonds and is homologous to trypsin

Answer 23

thrombin

Question 24

• exists in 2 prominent oligomeric forms,
  M and H

Answer 24

mammalian lactate dehydrogenase (LDH)

Question 25

• an A4 homotetramer (the A subunit is
  encoded by the LDH A gene)

Answer 25

LDH M

Question 26

• a B4 homotetramer (the B subunit is
  encoded by the LDH B gene)

Answer 26

LDH H

Question 27

• can also form, depending on the
  relative expression of the LDH A and
  LDH B genes in different tissues

Answer 27

heterotetrameric isozymes

Question 28

What are the 3 heterotetrameric iaozymes

Answer 28

• A3B
• A2B2
• AB3

Question 29

• acts to modulate E situated at key
  steps in metabolic pathways

Answer 29

Allosteric Regulation

Question 30

A =

Answer 30

precursor

Question 31

F =

Answer 31

end product (AA or nucleotide)

Question 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

Answer 32

feedback inhibition or feedback regulation

Question 33

F acts at a binding site distinct from
the S-binding site →

Answer 33

allosteric inhibition

Question 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

Answer 34

allosteric enzymes have an oligomeric
organization

Question 35

the regulatory effects exerted on the
E’s activity are achieved by Blank occurring in the protein when effector metabolites bind

Answer 35

conformational changes

Question 36

• regulated both by allosteric controls and by covalent modification
• catalyzes the cleavage of glucose units from the nonreducing ends
  of glycogen molecules

Answer 36

glycogen phosphorylase

Question 37

1. HOW DID INSULIN BECOME ACTIVE OR INACTIVE?

Answer 37

• 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.

Question 38

HOW MANY DISULFIDE BOND ARE THERE

Answer 38

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.

Question 39

HOW MANY INTRAMOLECULAR BOND? HOW MANY INTERMOLECULAR BOND?

Answer 39

• 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.

Question 40

WHEN IS INSULIN NEEDED? WHAT IS THE NORMAL BLOOD SUGAR LEVEL?

Answer 40

• 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.

Question 41

SCIENTIFIC EXPLANATION WHY COLD COMPRESS IS BEING APPLIED IF THE BRUISE IS FRESH AND WHY HOT COMPRESS IF IT IS ALMOST HEALED?

Answer 41

• 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.

Question 41

WHAT CONCLUSION COULD YOU CONCLUDE OF ISOMERS OF LACTASE DEHYDROGENASE?

Answer 41

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.