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Biochem Exam 3 > Bartling Study Guide > Flashcards

Bartling Study Guide Flashcards

1
Q

What do cellular signal transduction cascades do?

A

detect, amplify and integrate external signals

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2
Q

What are cellular signal transduction cascades comprised of?

A

specific cell surface membrane receptors, effector signaling elements, regulatory proteins

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3
Q

What are the 6 steps of signaling?

A
  1. synthesis of a signaling molecule (ligand)
  2. release of the signaling molecule (ligand)
  3. Transport to signaling molecule to target cell
  4. Binding of the ligand by a specific receptor protein and change in conformation
  5. Change in cellular metabolism, function or development = cellular response
  6. Removal of ligand, termination of cell response and degradation of ligand
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4
Q

What are hormones?

A

Chemical messengers made by endocrine cells and secreted into the bloodstream.

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5
Q

What do hormones affect?

A

gene expression and protein synthesis

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6
Q

What hormone acts on the same cell that secreted them?

A

autocrine

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7
Q

Which type of hormone acts on other cells?

A

paracrine

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8
Q

What are types of hormones?

A

steroids, amine (AA derived and secreted from the thyroid and adrenal medulla), peptide, polypeptide

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9
Q

What are some examples of cholesterol precursors of steroid hormones?

A

corticosteroids (cortisol), androgens (testosterone), estrogens

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10
Q

Which type of hormones immediate diffuse out of endocrine cells into the bloodstream?

A

Steroid hormones

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11
Q

Are steroid hormones lipid soluble?

A

Yes, can cross cell membrane

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12
Q

Where are cytoplasmic receptors located for steroid hormones?

A

intracellularly, inside target cells

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13
Q

Are steroid hormones for peptide hormones longer acting?

A

steroid hormones

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14
Q

How do hormones lead to signal cascades?

A
  1. hormones diffuse through phospholipid bilayer
  2. Bind to receptor Turing on/off specific genes
  3. mRNA directs synthesis of new protein
  4. Proteins alters activity
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15
Q

What are amine hormones derived from?

A

Tyrosine or tryptophan

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16
Q

Where are amine hormones stored?

A

endocrine cells until secreted

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17
Q

Where can the receptor for amine hormones be located?

A

cell surface or intracellular

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18
Q

Which hormones do not immediately enter bloodstream?

A

polypeptide (can be stored in endocrine cell vesicles)

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19
Q

Which hormones are water soluble?

A

polypeptide hormones, do not readily pass through cell membrane

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20
Q

Why are polypeptide hormones termed first messengers?

A

bind to external receptors

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21
Q

What mediates intracellular effects?

A

second messengers- low molecular weight signaling molecules (cAMP or calcium)

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22
Q

What is the structure of G-protein coupled receptors?

A

integral membrane protein (extracellular N-terminus), 7 transmembrane spanning alpha helices, 3 extracellular and intracellular loops, Intracellular C-terminal tail membrane

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23
Q

T/F G-protein coupled receptors have intrinsic catalytic domains

A

F

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24
Q

What does G-protein activate?

A

adenylyl cyclase (converts ATP to cAMP) which activates protein kinases in the cytosol (signal cascade)

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25
Q

What inactivates cAMP?

A

Phosphodiesterase

26
Q

What subunit contains the GTP-binding site and helps activate adenylyl cyclase?

A

Alpha subunit also contains intrinsic GTPase activity

27
Q

How many bound molecules of adenylyl cyclase can stimulate Gs alpha subunits?

A

one molecule can stimulate many Gs alpha subunits that amplify the original hormone signal

28
Q

What are some bacterial toxins that target G-proteins?

A

cholera toxin and Pertussis toxin (whooping cough)

29
Q

What occurs when cholera toxin is present?

A

increase in cAMP within intestinal epithelial cells leads to phosphorylation of Cl- channels and efflux of electrolytes and water (severe diarrhea)

30
Q

What happens when pertussis toxin is present?

A

enhances cAMP levels that inhibits neutrophil functions

31
Q

Do tyrosine kinase linked receptors have intrinsic enzymatic activity?

A

No

32
Q

What activates tyrosine kinases?

A

Ligand binding forms dimers activating tyrosine kinases that phosphorylate downstream targets (signal cascade)

33
Q

What are intrinsic enzymatic activity receptors?

A

ligand-triggered protein kinases, similar to tyrosine linked receptors (form dimers upon ligand binding)

34
Q

What does the ligand/receptor complex of intrinsic enzymatic activity receptors act as?

A

tyrosine kinase (phosphorylates other kinases) activating other protein kinases

35
Q

What happens when ligand binding to ion-channel receptors occurs?

A

confirmation change of receptor allowing specific ions (Na+, K+) to flow through

36
Q

What bacterial toxins indirecting affect ion channels?

A

botulinum toxin: prevents release of AcH NT and cleaves proteins involved in docking of NT vesicles

37
Q

What is the steep intracellular/extracellular calciumconcentration gradient of cells?

A

100nM/1mM enables radical changees in Ca concentration via hormone ligation

38
Q

What does calcium bind to inducing a formation change?

A

calmodulin, two globular domains joined by a long alpha helix

39
Q

What does the calcium/calmodulin complex bind to and modify?

A

target proteins (kinases) that initiate signal cascades

40
Q

What is the second messenger responsible for calcium mobilization?

A

phosphatidylinositol 4,5-bisphosphate (PIP2)

41
Q

What hydrolyzes PIP2?

A

PLC to generate two second messengers: inositol triphosphate (IP3) and diacylglycerol (DAG)

42
Q

T/F IP3 is water insoluble and can mobilize calcium

A

F; IP3 is water soluble and mobilizes calcium

43
Q

How is DAG anchored in the plasma membrane?

A

due to hydrophobic fatty acid side chains

44
Q

What can DAG activate?

A

key protein kinase C family

45
Q

What can phosphatylcholine produce when hydrolyzed by other phospholipase?

A

lipid second messengers: DAG species generated by PLC, Phosphatidic acid generated by PLD and arachidonic acid generated by PLA2

46
Q

What are key inflammatory and pain mediators?

A

arachidonic acid

47
Q

What are arachidonic acid precursors of?

A

eicosanoids: prostaglandins, prostacyclins, thromboxjnes, and leukotriene (all act like hormones and signal via G-protein coupled receptors

48
Q

What modulates smooth m contraction, platelet aggregation, gastric acid secretion and salt and water balance?

A

arachidonic acid

49
Q

What is involved in arachidonic acid conversion to prostaglandins?

A

cyclooxyrgenase isoforms

- COX-1 and COX-2 (made only in response to inflammatory mediators)

50
Q

What do prostaglandins do?

A

stimulate inflammation, regulate blood flow to organs such as the kidney, control ion transport across membranes, modulate synaptic transmission and induce sleep

51
Q

What inhibits cyclooxygenase?

A

non steroidal anti-inflammatory drugs (NSAIDs) - aspirin and Ibuprofen

52
Q

How do aspirin and ibuprofen inhibit cyclooxygenase?

A

block conversion to prostaglandins, aspirin irreversibly inactivates both forms

53
Q

What are effective treatments for inflammatory conditions? (rheumatoid arthritis)

A

inhibitors of COX-2

54
Q

What is arachidonic acid converted into leukotrienes by?

A

lipoxygenase

55
Q

How does receptor-independent signaling work?

A

low molecular weight signaling molecules (NO) cross plasma membrane and directly modulate activity of catalytic domains of transmembrane receptors or cytoplasmic signal transfusing enzymes

56
Q

What stimulate guanylate cyclase which generates cGMP (relaxes blood vessels)?

A

NO, angina symptoms treated with glyceryl trinitrate which is converted to NO

57
Q

Does endocytosis require ATP?

A

YES

58
Q

What is pinocytosis?

A

“drinking”, nonspecific absorption of ECF

59
Q

Phagocytosis

A

“eating” activated any attachment of PAMPS

60
Q

Receptor-mediated endocytosis

A

selective, form vesicles containing receptors at surface of membrane (clathrin coated vesicles form polyhedral lattice)

61
Q

Movement of receptors to different membrane from the one in which it was endocytosed

A

transcytosis

Biochem Exam 3 (4 decks)

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