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LS 2 Midterm 2 > Midterm 2: Cell Communication Slides > Flashcards

Midterm 2: Cell Communication Slides Flashcards

(55 cards)

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1
Q

Hormones (general def. and 2 examples)

A

Long-range chemical messengers secreted into the bloodstream by endocrine glands in response to a signal, and carried in the blood to other sites where they affect target cells
-e.g., insulin and adrenaline

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2
Q

Paracrine signals/local mediators (def. and 2 examples)

A

Released by cells into the extracellular medium in their neighborhood and act locally
-e.g., histamine, epidermal growth factor (EGF)

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3
Q

Neurotransmitters (def. and example)

A

Chemical messengers that diffuse across synapses (small distance) to target cell
-e.g., acetylcholine

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4
Q

Key characteristic of target cells

A

Must have appropriate receptors to bind hormone and induce physiological response

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5
Q

Describe the endocrine system.

A

Composed of endocrine glands located throughout the body, and generally regulates activities that require duration rather than speed

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6
Q

What secretes hormones into the blood?

A

Endocrine glands

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7
Q

What are the types of hormones?

A

Peptides, amines, steroids

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8
Q

Describe peptides.

A

They comprise most hormones, including those secreted by the hypothalamus, anterior and posterior pituitary, pancreas, and parathyroid

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9
Q

Describe amines.

A

Derived from tyrosine (amino acid); includes hormones secreted by thyroid gland and adrenal medulla (catecholamines)

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10
Q

What are catecholamines?

A

Adrenomedullary hormones

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11
Q

Describe steroids.

A

Neutral lipids derived from cholesterol; includes hormones secreted by adrenal cortex, ovaries, and testes. They are lipid soluble (lipophilic).

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12
Q

How are water-soluble hormones transported and where are their receptors?

A

Dissolved in the plasma; receptors on the cell surface

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13
Q

How are lipophilic hormones transported and where are their receptors?

A

Bound to plasma proteins; receptors in the cytoplasm

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14
Q

Which types of hormones are water-soluble and which ones are lipophilic?

A

Water-soluble: peptides, proteins, catecholamines

Lipophilic: steroids

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15
Q

How do hormones produce their effects?

A

By altering intracellular protein activity

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16
Q

What happens when hormones bind with specific target cell receptors?

A

Starts chain of events in target cell which produces effects characteristic of that hormone

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17
Q

Classification of hormones based on receptors location

A
  • Hydrophilic peptides and catecholamines are not soluble in lipids, so cannot cross lipid bilayer: bind to plasma membrane receptors
  • Lipophilic steroids and thyroid hormones cross lipid bilayer and bind to intracellular receptors (inside cell)
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18
Q

Possible effects of epinephrine/adrenaline (4)

A
  • Contraction of vascular smooth muscle
  • Relaxation of respiratory airway smooth muscle
  • Breakdown of liver glycogen
  • Increased rate and force of contraction of heart
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19
Q

How hydrophilic hormones affect target cells (2)

A
  • Most bind to cell surface receptor and produce second messenger molecule in target cell (hormone is 1st)
  • Some bind to cell surface receptors and alter cell permeability by opening/closing ion channels
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20
Q

How lipophilic hormones affect target cells

A

Bind to intracellular receptors, activate specific genes (through transcriptional regulation in nucleus), causing new intracellular proteins to form and produce a characteristic physiological effect

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21
Q

Cortisol: what kind of hormone, produced where, made from what

A

Steroid hormone, cortex of adrenal gland, made from cholesterol

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22
Q

Types of cell surface receptors (3)

A
  • Ligand-gated ion channels (e.g., acetylcholine receptor)
  • G-protein-linked receptors
  • Enzyme-linked receptors (e.g., insulin receptor)
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23
Q

What is the general idea behind G-protein-linked receptors?

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A

Guanyl nucleotide binding proteins (G proteins) act as molecular switches that are active when GTP is bound and inactive with GDP due to action of intrinsic GTPase

24
Q

How are G proteins classified with regards to subunits? What are the subunits?

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A

Heterotrimeric: alpha, beta, and gamma subunits

25
How is cyclic AMP (cAMP) formed?
Formed from ATP by adenylyl cyclase, an enzyme that's activated by a G protein
26
What do most effects of cAMP involve?
Binding to and activating cAMP dependent protein kinase (PKA), which phosphorylates specific proteins on serine or threonine residues, leading to physiological change
27
What do kinases and phosphatases do?
- Kinases phosphorylate molecules | - Phosphatases dephosphorylate molecules
28
What are the steps of the glycogenolytic cascade?
- Liver cells respond to epinephrine by activating G proteins - G proteins activate cAMP synthesis - cAMP activates a kinase cascade which releases glucose from glycogen - Glycogen synthesis inhibited - Kinase cascade amplifies epinephrine signal
29
What is the important of releasing glucose in the glycogenolytic cascade?
Key part of "fight or flight" response
30
Why are there so many steps in the glycogenolytic cascade?
Amplification: each epinephrine binding to a receptor on liver plasma membrane can release 10,000 molecules of glucose into bloodstream
31
Overview of inositol lipid signaling pathway
Phosphatidylinosital 4,5-bisphosphate cleaved by phospholipase C after receptor activation of a G protein to form 2 intracellular messengers
32
What are the two intracellular messengers formed in the inositol lipid signaling pathway and what do they do?
- Diacylyclycerol: activates protein kinase C | - Inositol trisphosphate (IP3): releases calcium from ER; is polar molecule
33
How is calcium concentration in the cytoplasm intentionally kept low?
Active transport, both out of the cell and into the ER
34
What happens once a signal triggers Ca2+ channels to open?
Ca2+ concentration quickly rises to 100x the resting concentration
35
Where do calcium ions bind?
To a specific calcium-binding protein called calmodulin, which can activate Ca2+-dependent protein kinases
36
Basic elements of cell signaling process (4)
Signaling cell, signaling molecule (wide variety), receptor (cell surface or intracellular), target cell response (cell-dependent)
37
Cell communication (def.)
How cells send and receive signals and how a cell responds after it receives a signal
38
4 examples of signal transduction pathways
- Nitric oxide pathway (more detail elsewhere) - Growth factors: signal to nucleus and affect cell division via small G protein (ras) - Sense of smell: odorant molecules activate G protein and cause cAMP to open ion channel - Apoptosis: programmed cell death
39
General overview of nitric oxide signal transduction pathway
Nitric oxide (NO, gas) is intracellular messenger that links affects of acetylcholine to relaxation of smooth muscles of blood vessels
40
Steps in NO signal transduction pathway
- Acetylcholine acts on endothelial cells, stimulates IP3 pathway to produce Ca2+ influx - Stimulates NO synthase to produce NO from arginine - NO diffuses to underlying smooth muscle cell - Stimulates guanylyl cyclase, produces cGMP (another intracellular messenger) - cGMP stimulates kinase cascade leading to lowering of intracellular Ca2+, and muscle relaxation
41
What is nitric oxide in smooth muscle relaxation?
Second messenger
42
Why is the NO signaling pathway important?
NO formation from L-arginine by vascular endothelium important in blood pressure regulation and hypotensive actions of acetylcholine; by keeping small blood vessels dilated, blood pressure decreases
43
What is a Ras protein and how does it behave?
Monomeric G protein; behaves similarly to alpha subunit of heterotrimeric G proteins
44
What is Ras involved in and why are Ras mutations significant?
Involved in signaling cascade of growth factors that promote cell division; Ras mutations occur in many human tumors (esp. in pancreas, colon, bladder)
45
What is the function of intrinsic GTPase and what does it normally do to Ras?
Function is to hydrolyze bound GTP to GDP; it normally turns off Ras
46
What is the effects of mutations that impair GTPase?
Keep Ras active and over-stimulate cell division, leading to cancer
47
What are terms for mutated ras and normal ras?
- Mutated ras: oncogene (tumor-promoting gene) | - Normal ras: proto-oncogene
48
Steps in the "sense of smell" pathway
- Odorant molecules activate G protein, which activates cAMP synthesis - cAMP synthesis causes ion channels to open - Change in ion concentrations generates action potential that travels along olfactory nerve to brain - Brain perceives signal as a scent
49
What is apoptosis?
Programmed cell death, where cell dies neatly without damaging its neighbors
50
What is the importance of apoptosis?
Normal part of development and aging, and it's a homeostatic mechanism to maintain cell populations in tissues
51
Steps (general) of apoptosis mechanism
- Cysteine proteases (caspases) are activated | - Triggers complex cascade of events (proteolysis) leading to cell death
52
What is an important cell surface death receptor?
Fas
53
What molecules can trigger apoptosis (and how)?
Tumor necrosis factor (TNF) and other ligands can trigger it by binding to their receptors
54
Why would drugs want to target cell signaling pathways? Give example of drug that does so.
Almost all known diseases involve dysfunctional signaling pathways. Example is Viagra
55
How does Viagra generally work?
Inhibits cyclic GMP phosphodiesterase (an enzyme)

LS 2 Midterm 2 (5 decks)

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