Weak-7 Flashcards
What are the 2 types of cell communication
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)
Types of local signalling and what species found in
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)
What is direct contact describe, and what cells use them.
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
Cell to cell recognition describe,and what cells?
In local signaling, animal cells communicate and recognize
each other via direct contact using surface molecules (e.g.
membrane carbohydrates)
Local regulators .
Local regulators: messenger molecules that travel only short distances (e.g. growth factors, neurotransmitters)
Paracrine and synaptic signaling: animal cells
communicate using local regulators
Cell junction types ,location and what group they fall under
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
plasmodesmata functions , and location
• Channels connecting neighbouring cells
• Allow cell communication and molecule exchange (e.g.
small molecules and water)
what are junctions found in animals
• Tight junctions: prevent
intercellular communication
• Desmosomes:
anchor cells through ECM
•Gap junctions:
- channels between cells
- allow molecule exchange between cells
Gap junctions------ Functions, what is it made up of? What goes through it? what does it transport? Location?
• 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
Tight junctions
Location?
function?
What are the two types?
• 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
Anchoring junction types
• Connect neighbouring cells (Cell-to-cell connection):
- Desmosomes
- Adherens junctions
• Connect cells with ECM (Cell to ECM connection):
- Focal adhesions
- Hemidesmosomes
Desmosomes
Functions?(3)
What do they connect?(3)
• 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
Adherens junctions
Function/location?
connects what?(2)
• 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
what are the 2 sections of anchoring junctions
• Connect neighbouring cells (Cell-to-cell connection):
- Desmosomes
- Adherens junctions
• Connect cells with ECM (Cell to ECM connection):
- Focal adhesions
- Hemidesmosomes
Cell –ECM connection types
- Focal adhesions (contacts):
* Hemidesmosomes:
Focal adhesions (contacts):
- 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)
Hemidesmosomes:
- 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)
page 28 week 7 diagram
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page 31 week 7 diagram
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What is used in Long distance signaling?
• 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