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BioChem > Lecture 12 part 1 > Flashcards

Lecture 12 part 1 Flashcards

1
Q

Transduction

A

transfer of info by converting it from one form to another. An extracellular signal becomes an intracellular signal in another form

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2
Q

Specificity

A

achieved by precise molecular complementarity between receptor and ligand and expression of receptors only on specific cell types

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3
Q

2 factors that contribute to sensitivity

A

high affinity of receptors for ligands (super low Kd), amplification of the signal by enzyme cascades

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4
Q

Densensitization

A

happens if a signal is present continuously. feedback circuit that shuts off the receptor or removes it from the surface

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5
Q

Integration

A

systems can receive multiple signals that produce a unified response. (additive or negating)

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6
Q

6 basic signaling mechanisms

A

G protein-coupled receptor, receptor tyrosine kinase, receptor guanylyl cyclase, gated ion channels, adhesion receptors, and nuclear receptors (steroid receptors)

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7
Q

Receptor guanylyl cyclase

A

ligand binding to extracellular domain stimulates formation of second messenger cGMP from GTP.

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8
Q

Adhesion receptors (integrins)

A

binds molecules in extracellular matrix, changes conformation, thus altering its interactions with cytoskeleton.

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9
Q

G-Protein coupled signaling’s two components

A

use a G-Protein coupled receptor, G protein

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10
Q

G-protein coupled receptor

A

alpha helical integral membrane proteins. 7 helices.

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11
Q

G-proteins

A

heterotrimeric (alpha, beta, gamma) proteins that bind GTP. Peripheral proteins with often a lipid and isoprene group attached.

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12
Q

Where are the phosphate groups when the GTP is bound to the G protein?

A

internally, thus driving a conformational change when bound.

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13
Q

What three primary systems use G-Protein coupled receptors?

A

oflactory (smell), gustatory (taste), and rhodopsin light-sensing system (vision)

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14
Q

What is the timer in G proteins?

A

G proteins slowly hydrolyze GTP to GDP, thereby inactivating themselves

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15
Q

Adenylyl cylcase and its mechanism

A

integral membrnae protein. takes ATP and makes cAMP. Activates the 3’ OH and via general base catalysis will attack the alpha phosphorous and kick off PPi, creating the cyclic group.

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16
Q

Cyclic nucleotide phosphodiesterase and its function

A

will hydrolyze the bond on cAMP by attacking the phosphorous bond, breaking the cyclic structure and creating AMP. Thus shutting down the signal transduction

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17
Q

G-Protein coupled receptor mechanism

A

Hormone binds to receptor (cc) binds to the GDP bound G protein (cc) causes GDP to leave and GTP to bind. This binding kicks off the receptor and beta and gamma. GTP bound G protein will bind to adenylyl cyclase, causing ATP -> cAMP.

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18
Q

Which subunit on the G protein binds to adenylyl cyclase?

A

Alpha binds to adenylyl cyclase in the presence of GTP.

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19
Q

Alpha subunit of G protein

A

responsible for binding GTP or GDP.

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20
Q

Alpha subunit when not bound to receptor

A

will bind GDP

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21
Q

Alpha subunit when bound to activated receptor

A

will exchange GDP for GTP

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22
Q

What does cAMP activate?

A

activates PKA

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23
Q

PKA can now do what?

A

Phosphorylates inactive phopshorylase b kinase, converting it to its active form.

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24
Q

Why does beta-gamma subunits not go far from the alpha subunit?

A

because it is isoprenylated and will stay as a peripheral membrane

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25
Q

Beta-gamma subunits when disscoiate

A

can activate signaling proteins such as isoforms of AC, ion channels, protein tyrosine kinases, and phospholipase C

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26
Q

What is different in inhibitory G proteins?

A

Their alpha is different but the beta-gamma could be the same. Alpha will interact with AC to inhibit cAMP production.

27
Q

Cholera

A

cant hydrolyze GTP, thus high levels of cAMP. Excess water, chloride, sodium, and bicarbonate go into the lumen of the small intestine, causing diarrhea.

28
Q

B-adrenergic receptor desensitization mechanism

A

Phosphorylation of serine residues causes desensitization. Beta-gamma (BG) will recruit Bark to phosphorylate serine residues at the c-terminus of the receptor. (cc) B-arrestin (Barr) will bind to the protein and the receptor complex will be endocytosed. Barr is removed. Receptor is dephopshorylated and eventually put back onto the membrane

29
Q

Beta adrenergic receptor kinase (Bark)

A

recruited by beta-gamma. will phopshorylate serine residues on the c-terminus of the receptor.

30
Q

B-arrestin (Barr)

A

causes the phosphorylated complex to be endocytosed into the cell and then Barr will leave.

31
Q

GTPase activating protein (GAP)

A

increases rate of GTP hydrolysis by alpha as much as 2000-fold. Thus an inhibitor

32
Q

Guanine nucleotide exchange factor (GEF)

A

induces a G protein to release GDP allowing binding of GTP to occur. Activator.. Thus dont even need a receptor to be stimulated.

33
Q

Guanine nucleotide dissociation inhibitor (GDI)

A

inhibitions dissociation of GDP. Thus an inhibitor since GTP cant bind.

34
Q

Epinephrine

A

will get glucose into the cell quickly for fight or flight. Epi reaches the B-adrenergic receptor in the liver, and this will release glucose into the blood stream

35
Q

Agonists

A

compounds that bind to a receptor and mimic the effect of the natural ligand (drugs with higher affinity)

36
Q

Antagonists

A

compounds that bind to a receptor and do not elicit a response. Often has an extremely low Kd but is still reversible.

37
Q

Inactive PKA structure

A

two catalytic subunits and two regulatory subunits

38
Q

Active PKA structure

A

binding of cAMP to the R unit dissociates R2C2 into two active catalytic subunits. .

39
Q

Phosphorylase b kinase

A

Phosphorylated by PKA using ATP. activates glycogen phosphorylase, resulting in glycogen degradation and glucose release.

40
Q

How many cAMPs are needed to make PKA active?

A
  1. 2 cAMPS on each regulatory subunit.
41
Q

Route of cAMP to glucose release

A

cAMP -> PKA + ATP -> Phosphorylase b kinase -> glycogen phosphorylase - > glucose

42
Q

Phospholipase C hydrolyzes PIP2 to what?

A

IP3 and DAG by being activated by the alpha subunit.

43
Q

IP3

A

acts as a 2nd messenger and diffuses to the ER, stimulating Ca release into the cytoplasm by opening the IP3 receptor ion channel. polar molecule and thus wants to stay in cytosol.

44
Q

DAG

A

hydrophobic and thus remains in the membrane and activates PKC, which also requires Ca.

45
Q

PKC

A

Requires Calcium to make it fully active. Integral membrane protein. phosphorylates several proteins to modulate their activities.

46
Q

Calmodulin

A

binds to Ca and will recognize Ca in cytosol (after IP3 channel opens) and cause addition transduction events to occur.

47
Q

Phospholipase A1

A

severs on the C1 of the glycerol backbone

48
Q

Phospholipase A2

A

severs on the C2 of the glycerol backbone

49
Q

Phospholipase D

A

will sever the inositol from the phosphate moiety.

50
Q

Bis phosphate vs bi phosphate

A

Bis means they occur in different positions.

Bi means they occur on the same position.

51
Q

Calcium concentrations

A

oscillate thus allowing the cell’s status to be determined by the frequency and the amplification of the stimulus.

52
Q

Tyrosine Kinase receptor structure

A

ligand binding site on the extracellular surface and an enzyme active site on the cytosolic side.

53
Q

Tyrosine Kinase receptor’s main function

A

to phosphorylate a tyrosine

54
Q

Insulin receptor’s structure

A

tyrosine kinase. two alpha chains that bind insulin and two beta chains that have the tyrosine kinase activity. Always exists as a dimer.

55
Q

Insulin receptor

A

after you eat a big meal, the goal is to store glucose. insulin binds to the alpha subunits, causing autophosphorylation on the other side of the membrane. Ultimately synthesizes GLUT4 to bring glucose into the cell through passive transport.

56
Q

How many tyrosine residues in insulin receptors?

A

3 on each beta chain, thus 6 total.

57
Q

Target protein for insulin receptors?

A

IRS-1 (insulin receptor substrate 1) is phopshorylated and serves as a nucleation site for a protein complex.

58
Q

What binds to IRS-1 in the insulin receptor mechanism?

A

Grb2, then Sos, which replaces GDP by GTP on the G protein Ras, which recruits Raf.

59
Q

IRS-1 associates with what else?

A

phosphatidylinositol 3-kinase (PI-3K).

60
Q

PI-3K

A

converts PIP2 to PIP3 by adding on the 3 position.

61
Q

Protein kinase B (PKB) in insulin regulation of metabolism

A

binds PIP3 and is then phosphorylated by phosphoinositide dependent kinase (PDK1) to become active

62
Q

Activated PKB

A

phosphorylates glycogen synthase kinase 3, inactivating it.

63
Q

Inactive glycogen synthase kinase 3 (GSK3)

A

can no longer inactivate glycogen synthase, thus glycogen synthesis occurs.

64
Q

PKB and GLUT4

A

PKB will help insert GLUT4 into the plasma membrane from internal membrane vesicles

BioChem (14 decks)

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