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AnaPhy ni Ma'am E > Membrane junctions > Flashcards

Membrane junctions Flashcards

1
Q
  • large, automatic, bidirectional
     connexon (functional unit), connexins (protein
    subunits)
     Allows the movement of 2nd messengers to
    trigger a cellular response on the next cell
A

gap junctions

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2
Q

this is the functional units of gap junctions

A

connexon

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3
Q

this is the protein subunits of gap junctions

A

connexins

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4
Q

 small, voltage-sensitive
 Allows ions (most esp cations), water, and other small molecules to pass through the apical layer of the cell membrane

A

tight junctions

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5
Q

 Links the cytoskeleton of adjacent cells
 Functions more as a structural component, than as a membrane junction
 Non-discriminatory (allows substances smaller than proteins to pass through)

A

desmosomes

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6
Q

what are the membrane junctions?

A

gap junctions, tight junctions, desmosomes

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7
Q

 Cells communicate by releasing extracellular
signaling molecules that bind to receptor
proteins located in the plasma membrane,
cytoplasm, or nucleus.
 This signal may activate or inactivate
intracellular messengers by interacting with
receptors.

A

signal transduction

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8
Q

ability to coordinate cellular
activities and function

A

cell signaling

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9
Q

what are the cellular responses?

A

 Movement
 Apoptosis
 Synthesis
 Differentiation
 Metabolism
 Secretion
 Multiplication
 No response (also a response)

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10
Q

TYPES OF INTRACELLULAR SIGNALLING

A

 Electrical
 Cell-cell communication
 Chemical

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11
Q

 direct phone call”
 Direct communication via gap junction which
changes a cell’s membrane potential
 2 connexons = 12 connexins (6 connexins each) = intercellular channel
 E.g. cardiac muscle

A

electrical signaling

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12
Q

 Direct contact between adjacent cells.
 Can also compared to a “face to face”
communication
 Once the signal is present on the membrane of the cell it will make a physical contact on the
protein found on the target cell.
 Important during development and in immune responses.
 i.e. Interleukins of T cell

A

cell-cell communication

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13
Q

what are the goals of cell-cell signaling

A
  1. Reaching only the correct recipient(s)
  2. Imparting the correct information
  3. Timeliness
  4. Cause the desired effect
  5. Effective termination of information
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14
Q

 Signals are released in extracellular
compartments (interstitial fluid & vascular
compartment).
 Once the signal is in the target cell, it will be
received by a receptor protein.
→ Intracellular receptor
→ Receptors in plasma membrane
 Examples: hormones, neurotransmitters, growth factors, and products of cellular metabolism.

A

chemical signaling

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15
Q

what are the 3 types of chemical signaling?

A

autocrine
paracrine
endocrine

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16
Q

→ Released signal affects cell of origin or the neighboring cells of the same type.
→ Released to the interstitial fluid
→ i.e. Insulin-like growth factor which is secreted by chondrocytes

A

autocrine

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17
Q

→ Signal is released by one cell and act on an adjacent cell.
→ The chemical mediators are rapidly metabolized after release thus can only affect cells close to the source.
→ Released to the interstitial fluid like the autocrine.
→ i.e. β cell of the islet of Langerhans
→ Insulin travels to the islet of Langerhans and affect glucagon and somatostatin secretion

A

paracrine

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18
Q

→ Signal would travel in the bloodstream before it could reach its target cell
→ Similar to radio broadcast
→ i.e. Insulin travels to different organs.

A

endocrine

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19
Q

what are the cellular receptors?

A

intracellular receptors and plasma membrane receptors

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20
Q
  • For lipid-soluble (hydrophobic) messengers
  • Act as transcription factors to alter the rate of transcription of particular genes
     For gene transcription and initiation of protein
    synthesis
     Has longer effects
     Inactive receptors are bound by proteins that are dissociated in the presence of its specific ligand
A

intracellular receptors

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21
Q
  • For lipid-insoluble (hydrophilic) messengers
  • Purposes/Act as:
    → Ion channels
    → Enzymes
    → Activates Cytoplasmic JAK kinases
    → Activates G protein
    → Act upon effector proteins (either ion
    channels or enzymes) in the plasma membrane
A

plasma membrane receptors

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22
Q

what are the steroid receptors?

A

cortisol
sex hormones
vitamin D
cytoplasmic/ gated receptor
nuclear receptor

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23
Q

→ Released by adrenal cortex
→ For gluconeogenesis

A

cortisol

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24
Q

→ Released by gonads
→ For primary and secondary sexual
development

A

sex hormones

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25
Q

→ Released by kidneys
→ Ca binding proteins
→ For Ca reabsorption in intestine

A

Vitamin D

26
Q

 Receives signals in the cytoplasm which
goes inside the nucleus to elicit a
response

A

cytoplasmic/ gated receptor

27
Q

 Receptor found inside nucleus
 Signal goes directly inside the nucleus
and then attaches to receptor

A

nuclear receptor

28
Q

Lipophobic, lipid insoluble ligands
→ Release secondary messengers
→ Secondary messengers are needed to elicit a response

A

plasma membrane receptors

29
Q

 Also known as ligand-gated ion channels or
ionotropic receptors.
 Controls influx and efflux of ions that leads to a change in membrane potential causing
depolarization and hyperpolarization.

A

ion channels

30
Q

 Involves transducing a chemical signal into an
electrical signal, which elicits a response
 e.g. ryanodine receptors (located in the
sarcoplasmic reticulum of skeletal muscle), gets activated by Ca2+ (or by caffeine, ATP, or
metabolites of arachidonic acid) to release Ca2+ from SR → facilitates muscle contraction

A

ligand-gated channel linked signal

31
Q
  • Function: Bind guanine nucleotides GDP (inactive) and GTP (active)
  • regulate activity of other proteins
A

G protein coupled receptor

32
Q

what are the two types of GPCR?

A

monomeric and heterotrimeric

33
Q

Play a central role in many enzyme linked receptor pathways [Berne, et al, 2018]
▪ Also functions in the regulation of gene expression and cell proliferation, differentiation, and survival [Berne, et
al, 2018]

A

monomeric

34
Q
  • Consists of α,β,ɣ subunits
    Regulates the activity of other protein (enzymes & ion channels).
    ● The interaction between receptor and target protein is mediated by heterotrimeric G protein (composed of 𝛼,𝛽,𝛾 subunits)
A

heterotrimeric

35
Q

this is the site of ligand binding

A

extracellular domain

36
Q

Attached heterotrimeric
complexes

A

intracellular domain

37
Q

without ligand the G protein is __________

A

inactive

38
Q

with ligand, G protein is______________

A

activated

39
Q

What are the GPCRs target effectors?

A

→ Ion channels
→ Cyclic Adenosine Monophosphate (cAMP)
→ Phospholipase C (PLC)
→ Cyclic Guanosine Monophosphate (cGMP)

40
Q

→ α goes to adenylyl cyclase
→ cAMP signal pathway
→ cAMP and cGMP

A

adenylyl cyclase

41
Q

→ Phospatidyl-inositol signal pathway

A

phospholipase c

41
Q

releaser of Ca2+ on the ER

A

IP3

42
Q

activates protein kinase C (for cellular growth and proliferation)

A

Diacylglycerol (DAG)

43
Q

what are the enzyme-linked/ catalytic receptor?

A

guanylyl cyclase
threonine/ serine kinase
tyrosine kinase
tyrosine kinase- associated

44
Q

what are the cytokines and ligands of guanylate cyclase?

A

atrial natriuretic peptide (ANP) and Nitric Oxide

45
Q

What are the cytokines and ligands of tyrosine kinase

A

EGF, platelet-derived
growth factor (PDGF), and
insulin

46
Q

→ ANP or NO + GC receptor > metabolizes GTP to cGMP > cGMP activates protein kinase G > PKG phosphorylates protein on specific serine and threonine residues

A

guanylate cyclase receptor

47
Q

what are the two types of guanylate cyclase receptor?

A

transmembrane guanylate cyclase receptor and soluble guanylate cyclase receptor

48
Q

− Activated by atrial natriuretic peptide
− Present in the cell membrane
− Result: Inhibits sodium and water reabsorption in kidney.

A

transmembrane guanylate cyclase receptor

49
Q

− Activated by nitric oxide (vasodilator).
− Present inside the cell
− Result: smooth muscle relaxation

A

Soluble guanylate cyclase receptor

50
Q

 Involved in the activation of inositol-1,4,5-
triphosphate (IP3) pathway.
 Signal binds to GPCR > GDP is displaced by GTP > 𝛼 subunit dissociate and attach to PLC >
hydrolysis of PIP2 producing Diacylglycerol
(DAG) and IP3.
- Physiological significance: Ca 2+ promotes
muscle contraction.

A

Phospholipase C

51
Q
  • is structurally composed of two regulatory
    and two catalytic subunits. When the produced cAMP bind to the two regulatory subunit, the two catalytic subunit will dissociate and will now function as the active protein kinase.
  • as a member of the transferase family of
    enzymes catalyzes the transfer of phosphate
    groups or phosphorylation reaction
A

Phosphokinase A (PKA)

52
Q

Stimulus involved is light (phototransduction).

A

cyclic GMP

53
Q
  • absorbs light in the rods of eyes.
A

rhodopsin

54
Q

Once rhodopsin absorbs light it activates G
protein ____________ via alpha T which then
activates cGMP phosphodiesterase

A

transducin

55
Q

 cell differentiation, proliferation & survival;
induces cell division/mitosis;
prevents/encourages cell growth in cell cycle
 Ligand-dependent ; commonly triggered by
hormones (e.g. estradiol) and growth factors

A

mitogen-activated protein kinase (MAPK) pathway

56
Q

produces lymphokines modifying host
organism to improve immunity

A

T cells

57
Q

producing immunoglobulins/antibodies

A

B cells

58
Q
  • activates AKT/Protein Kinase B
  • Associated with the Go phase of mitosis (when the pathway is less active) and long term potentiation among neural stem cells
  • Overactivity of this pathway reduces apoptotic activity of cells which allow proliferation
A

P13K (Phosphoinositide-3-Kinase)

59
Q

 Tyrosine-associated Kinase receptor
 Involved in immunity, cell division and death as well as tumor formation

A

JAK/ STAT pathway

AnaPhy ni Ma'am E (5 decks)

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