Topic 6: Extracellular Structures Flashcards
What are multicellular organisms organized into
Tissues
What does the extra cellular components do
Help connect cells by adherence and to coordinate cellular activities
What does the extracellular structures function
Allows the formation and function of tissues in our multicellular organisms (some single)
Where do most cells ____ and ____their materials
Synthesize and secrete
The plasma membrane
What does the extracellular structures include
- Plant cell walls
- Since animals don’t have cell walls, they have,
- The extracellular matrix instead
- Intercellular junctions (both plants and animals)
What is the major component that distinguishes animal and plant cells
The cell wall
Note: prokaryotes, some protists have cell walls
What are the functions of the cell wall
- Protects the cell
- Maintains the cell shape which gives the plants its structure
- Prevents excess uptake of water
What is the structure of the plant cell wall made of
Cellulose fibres that are embedded in polysaccharide and proteins (in the matrix)
These cellulose are strong fibers and are substances in the matrix
These cellulose fibers work like
Steel reinforced concrete (concrete is the matrix and steel is the fiber) or fiberglass
What is the cell wall
An extracellular structure that is different depending on - if the organism is a animal or plant
Plant cell wall has multiple layers
- Made of the primary cell wall
- Middle lamella
- Secondary cell wall
Relatively thin and flexible?
- Primary cell wall (all plant cells have this)
- Thin and flexible so cell can shape and expand
In between the 2 plant cells Thin layer between primary walls of adjacent cells?
Middle lamella
Added between the plasma membrane and the primary cell (in some cells)
Secondary cell wall - does not occur in all cells since cells only get their second cell wall after completely growing
- Extremely tough and rigid
What is plasmodesmata? Is it selective or nonselective
They are channels (tunnels) between the plant cells to pass nutrients to cytoplasm of other plant cell
They are non selective (any molecule they get passes)
What do animal cells lack that plants have? What do they have instead?
Animal cells don’t have a cell wall but has extracellular matrix instead
What are the functions of the ECM in animals
- Adhere tissue cells together (Maintains adhesion across tissues)
- Support and protect tissues (provides tissue integrity by bringing cells together as a unit)
- Allows communication across tissues → coordination of the cells activity which is done through
What is the ECM of animal cells made of
- Glycoproteins (proteins covalently bonded to sugars) such as
- Collagen, proteoglycan, fibronectins
All these glycoproteins of the animal ECM can bind to
Integrins (anchor to integrins)
Ex. what do fibronectin proteins bind to
Integrins
What is the Function of proteoglycan aggregate (bunch of proteins)
It hydrates tissue
Function of collagen
Long fibers that provides structure support
What percent of proteins in humans are collagen
40%
How does the animal ECM regulate cell behaviour (outside to inside information)
communicate with integrin how?
signal transduction - which transfers information from the outer matrix to the inside of the cell
(inside of the cell information from outer information is transferred through the cytoskeleton (microfilaments)(involved through anchoring glycoproteins)
the ECM influences the activity of genes in the
Nucleus
How does mechanical signal occur (signal transduction of outside to inner)
Through the cytoskeletal changes (in the microfilaments) that trigger chemical signals in the cell
Describe cell junctions
How cells adhere (in tissues, organs and organ systems) interact and communicate through physical contact
This contact is facilitated by
Cellular junctions
Animals have 3 types
1) Tight junctions - in animals
2) Desmosomes - in animals
3) Gap junctions - in animals
Plant cellular junctions: the plasmodesmata does what?
Makes tunnels of cytoplasm through the cell wall or channels that perforate (puncture) plant cell walls
The bridges (tunnels) are called
plasmodesmata bridges
Note: this means that the cytoplasm is semi continuous across plant tissues (can move back and forth water, solutes, RNA amongst the tissues)
Describe Tight junctions
Membranes of neighbouring cells are pressed together, and bound together by proteins, prevents leakage of extracellular fluid
How do tight junctions prevent leakage?
membranes of adjacent cells that are compressed together to be bound together by proteins
Describe Desmosomes (anchoring junctions)
function like rivets to hold cells together into strong sheets
Gap Junction (communicating junction)
provide cytoplasmic channels between adjacent cells
- similar to plasmodesmata
- non selective
