Weak-7 Flashcards

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1
Q

What are the 2 types of cell communication

A

Local signalling: neighbouring cells communicate
though cell junctions, cell-to-cell recognition or local
regulators

➢ Long distance signalling: distant cells in multicellular
organisms communicate using chemical messengers
(e.g. hormones)

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2
Q

Types of local signalling and what species found in

A

Direct contact: via cell junctions (animal and plant)

Cell-cell recognition: via surface molecules (animal
cells only)

Local regulators: in paracrine/synaptic signaling
(animal cells only)

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3
Q

What is direct contact describe, and what cells use them.

A

Animal and plant cells have cell junctions that directly
connect the cytoplasm of adjacent cells • Cell junctions coordinate the function of neighbouring
cells in a tissue

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4
Q

Cell to cell recognition describe,and what cells?

A

In local signaling, animal cells communicate and recognize
each other via direct contact using surface molecules (e.g.
membrane carbohydrates)

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5
Q

Local regulators .

A
Local regulators: messenger molecules that travel only
short distances (e.g. growth factors, neurotransmitters)

Paracrine and synaptic signaling: animal cells
communicate using local regulators

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6
Q

Cell junction types ,location and what group they fall under

A

Communicating junctions———

Gap junctions: in animal cells, no cytoskeletal connection

Plasmodesmata: in plant cells, no cytoskeletal connection

Occluding junctions——-

Tight junctions: connect with actin microfilaments

Anchoring junctions——-

Desmosomes: connect with intermediate filaments
Adherens junctions: connect with actin microfilaments

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7
Q

plasmodesmata functions , and location

A

• Channels connecting neighbouring cells
• Allow cell communication and molecule exchange (e.g.
small molecules and water)

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8
Q

what are junctions found in animals

A

• Tight junctions: prevent
intercellular communication

• Desmosomes:
anchor cells through ECM

•Gap junctions:

  • channels between cells
  • allow molecule exchange between cells
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9
Q
Gap junctions------ Functions, 
what is it made up of?
What goes through it?
what does it transport?
Location?
A

• Cytoplasmic channels made by membrane proteins
(connexins) connecting adjacent cells
• Necessary for cell-to-cell communication
• Allow small molecule and ion exchange between cells (e.g.
cAMP, Ca+2)
• Located along the apical surfaces of cells of various
tissues (e.g. epithelial cells and heart muscle)
• Transport of Ca+2 between neighbouring smooth muscle
cells through gap junctions
Synchronized contraction of intestine and uterus during
birth

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10
Q

Tight junctions
Location?
function?
What are the two types?

A

• Underneath the apical surface of epithelial cells
• Inhibit cell-to-cell communication (molecule exchange)
• Create an exclusion zone around the cells
=> prevent leakage of extracellular fluid from a layer of
epithelial cells (e.g skin layer)
• Made by 2 types of transmembrane proteins:
- Claudin and occludin
• Τhe cytoplasmic part of occludin is linked to the actin
microfilaments

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11
Q

Anchoring junction types

A

• Connect neighbouring cells (Cell-to-cell connection):

  • Desmosomes
  • Adherens junctions

• Connect cells with ECM (Cell to ECM connection):

  • Focal adhesions
  • Hemidesmosomes
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12
Q

Desmosomes
Functions?(3)
What do they connect?(3)

A

• Function like rivets fastening cells together into strong
sheets
• Anchor to the cytoplasm though intermediate filaments
(e.g. keratin)
• Connect cells via transmembrane adhesion proteins
(cadherins)
• Desmosomes connect with:
- Keratin intermediate filaments in epithelial cells
- Desmin intermediate filaments in heart muscle cells and
smooth muscle cells
• Desmosomes attach muscle cells to each other in a
muscle
=> Some ‘muscle tears’ involve the rupture of desmosomes

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13
Q

Adherens junctions
Function/location?
connects what?(2)

A

• Create an adhesion zone (belt) underneath the apical
surface of epithelial cells

• Connect the plasma membranes of neighbouring cells via
transmembrane adhesion proteins (cadherins)

• Intracellular attachment proteins (catenins, vinculin, αactinin): connect cadherins with actin microfilaments

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14
Q

what are the 2 sections of anchoring junctions

A

• Connect neighbouring cells (Cell-to-cell connection):

  • Desmosomes
  • Adherens junctions

• Connect cells with ECM (Cell to ECM connection):

  • Focal adhesions
  • Hemidesmosomes
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15
Q

Cell –ECM connection types

A
  • Focal adhesions (contacts):

* Hemidesmosomes:

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16
Q

Focal adhesions (contacts):

A
  • Extracellular connection: Connect cells to the ECM through
    integrins (transmembrane proteins)
  • Intracellular connection: Integrin cytoplasmic domain connects
    with actin microfilaments through attachment proteins (talin, αactinin, vincoulin)
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17
Q

Hemidesmosomes:

A
  • Found mainly in basal surface of epithelial cells
  • Extracellular connection: Stabilise epithelial cells by anchoring
    them to the ECM through integrins (transmembrane proteins;
    integrin binds to basement membrane laminin)
  • Intracellular connection: connect with keratin intermediate
    filaments through attachment proteins (plectin)
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18
Q

page 28 week 7 diagram

A

look

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19
Q

page 31 week 7 diagram

A

look

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20
Q

What is used in Long distance signaling?

A
• In long-distance signaling, both
plants and animals use hormones
• Hormonal signaling in animals:
- also known as endocrine signaling
- specialized cells release hormone
molecules which travel via the
circulatory system to target cells in
other parts of the body
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21
Q

What are the 3 stages of cell signaling

A
  1. Reception
  2. Transduction
  3. Response
22
Q

Reception signaling process

A

• Reception: the signaling molecule binds to a receptor
protein, causing it to change shape (conformational change)

• The receptor protein conformational change initiates the process
of transduction

23
Q

1.Reception: receptor types

A

• Receptor types:

  • Plasma membrane receptors
  • Intracellular receptors

+(The binding between the signal molecule (ligand) and
receptor is highly specific)

24
Q

Intracellular receptor
types?
what uses these receptors?
examples?

A

• Intracellular receptors: cytoplasmic or nuclear proteins

• Signaling molecules that are small or hydrophobic and can
readily cross the plasma membrane use these receptors

• Example: steroid hormones bind to intracellular
receptors (e.g. estrogen receptors)

25
Q

Plasma membrane receptors types?(3)

A

– G-protein-coupled
– Tyrosine kinases
– Ion channels

26
Q
G protein-coupled receptors.
define?
Bound to what?
process/function?
involved in diseaese?
example?
A

• G protein-coupled receptors: plasma membrane receptors
linked to a G protein
• G-proteins: proteins bound to GTP/GDP
• G proteins act as an on/off switch:
– If GDP is bound to the G protein => G protein is inactive
– If GTP is bound to the G protein => G protein is active
• Involved in many human diseases, including bacterial infections
• Example: cholera toxin and botulinum toxin are bacterial
products that interfere with G protein function
• More than 60% of all medicines used today exert their effects by
influencing G protein pathways

27
Q

Receptor tyrosine kinases.
function?(2)
Domains?
examples?

A

• Protein kinases: enzymes that phosphorylates protein
substrates (adds phosphate groups to them)
• Receptor tyrosine kinases: transmembrane receptors
that attach phosphates to tyrosine residues
• 2 domains:
- Extracellular ligand binding domain
- Intracellular domain with tyrosine kinase activity
• Growth factor receptors are commonly receptor tyrosine
kinases (e.g. EGFR, PDGFR, etc)

28
Q

Receptor tyrosine kinases and clinical correlations?(4)
examples?
what blocks it?

A

• Abnormal tyrosine kinase receptors may contribute to
some kinds of cancer
- truncated receptors that function in the absence of
signaling molecules (lack the ligand-binding domain)
- overexpression/ amplification of receptors:

  • Example: EGFR (Epidermal Growth Factor Receptor)
    amplification (overexpression) in many cancers (e.g. breast
    cancer)
    • Several anti-cancer drugs block tyrosine kinase activity
    (herceptin, Gleevec)
29
Q

Ion channel receptors.
Function?
process?(3)

A

• Ligand-gated ion channel
receptors: acts as a gate
which opens when the
receptor changes shape

1. Binding of signaling
molecule (ligand) to the
receptor
2. Receptor changes shape
(the gate opens)
3. Specific ions (e.g. Na+,Ca2+) pass through a channel in the receptor
30
Q

2.Transduction

process?(2)

A

• Transduction: the signal from the receptor converted to a
form that can cause a specific cellular response
• Transduction usually requires a series of changes in a
series of different target molecules

31
Q

Signal transduction pathways:

A
  • cascades of molecular interactions that relay signals from
    receptors to target molecules in the cell
- At each step in a pathway the signal is transduced into a
different form (usually a conformational change in a
protein)
32
Q

Protein Phosphorylation and Dephosphorylation
related to signal transduction
(not sure about this week 7 pg48)

A

• Many signal pathways include phosphorylation cascades
(e.g. MAPK signaling pathway)
• In this process:
– Protein kinases: enzymes that add a phosphate to
the next protein kinase in line => activate protein
kinases
– Phosphatases: enzymes that remove the phosphates
=> deactivate the protein kinases

33
Q

Second Messengers.
What are they?
examples?

A

• Second messengers: small, non-protein, water-soluble
molecules or ions that acts in the signal transduction
pathways

• Examples:

  • cAMP
  • Ca+2
34
Q
Cyclic AMP (cAMP).
how is it produced?
(also I think memorize chart)
A

Produced from ATP through the enzyme adenylyl cyclase

35
Q

Cyclic AMP.
What triggers it?
function?

A

• Many G-proteins trigger the formation of cAMP
• cAMP then acts as a second messenger in the signal
transduction pathways

36
Q

Calcium ions
function?
importance?

A

• Calcium ions (Ca+2), when released into the cytosol of a cell,
acts as a second messenger in many different pathways

• Calcium is an important second messenger because cells are
able to regulate its concentration in the cytosol

37
Q

name 2 other second messengers:

A
  • Diacylglycerol (DAG)
  • Inositol triphosphate (IP3)

• IP3
triggers an increase in calcium concentration in
the cytosol

38
Q
  1. Response.

function?

A

• Response: the transduced signal triggers a specific cellular
response

• Cell signaling leads to regulation of cytoplasmic activities
(cytoplasmic response) or transcription (nuclear response)

39
Q

slide 59 week 7???

A

look

40
Q

nuclear response to a signal?

examples?

A

• Other pathways regulate genes by activating transcription
factors that turn gene expression on or off

• Example: steroid hormone signaling pathways, MAPK
signaling cascade

41
Q

benefits of multistep signaling pathways?(3)

A

Multistep signaling pathways have two important benefits:
– Amplification of the signal => amplification of the
response
– Contribution to the specificity of the response

 Provide more opportunities for coordination and
regulation

42
Q

Signal Amplification.

A

• Each protein in a signaling pathway amplifies the signal by
activating multiple copies of the next component in the
pathway

• At each step, the number of activated products is much
greater than in the preceding step

43
Q

The Specificity of Cell Signaling.

explain it?

A

• Different kinds of cells have different types of proteins

• Different proteins allow cells to detect and respond to
different signals
=> Even the same signal can have different effects in cells
with different proteins and pathways

• The different combinations of proteins in a cell give the cell
great specificity in both the signals it detects and the
responses it carries out

44
Q

what is cross-talk”?

A

• Pathway branching and “cross-talk” further help the cell to coordinate incoming signals
slide64week7diagram

45
Q

Scaffolding proteins.

what are they?
Function?

A
  • Large relay proteins to which other relay proteins are
    attached
  • Function: increase the signal transduction efficiency by
    grouping together different proteins involved in the same
    pathway

more efficient
activation of
signaling pathways

46
Q

how is signal response terminated?

A

• Signal response is terminated quickly
– By the reversal of ligand binding
=> Ligand released from the receptor

47
Q

(summmary) Local signalling

A

cell junctions, cell-cell recognition, local

regulators

48
Q

(summary) Distal signalling

A

hormones

49
Q

(summary) 3 stages of cell signalling

A

reception, transduction,

response

50
Q

(summary) Intracellular receptors

A

cytoplasmic or nuclear

51
Q

(summary) Plasma membrane receptors

A

G-protein coupled,

receptor tyrosine kinases, ion channels

52
Q

(summary)Second messengers

A

cAMP, Ca+2, DAG, IP3