Topic 6: Extracellular Structures

Question 1

What are multicellular organisms organized into

Answer 1

Tissues

Question 2

What does the extra cellular components do

Answer 2

Help connect cells by adherence and to coordinate cellular activities

Question 3

What does the extracellular structures function

Answer 3

Allows the formation and function of tissues in our multicellular organisms (some single)

Question 4

Where do most cells ____ and ____their materials

Answer 4

Synthesize and secrete

The plasma membrane

Question 5

What does the extracellular structures include

Answer 5

• Plant cell walls
• Since animals don’t have cell walls, they have,
• The extracellular matrix instead
• Intercellular junctions (both plants and animals)

Question 6

What is the major component that distinguishes animal and plant cells

Answer 6

The cell wall

Note: prokaryotes, some protists have cell walls

Question 7

What are the functions of the cell wall

Answer 7

• Protects the cell
• Maintains the cell shape which gives the plants its structure
• Prevents excess uptake of water

Question 8

What is the structure of the plant cell wall made of

Answer 8

Cellulose fibres that are embedded in polysaccharide and proteins (in the matrix)
These cellulose are strong fibers and are substances in the matrix

Question 9

These cellulose fibers work like

Answer 9

Steel reinforced concrete (concrete is the matrix and steel is the fiber) or fiberglass

Question 10

What is the cell wall

Answer 10

An extracellular structure that is different depending on - if the organism is a animal or plant

Question 11

Plant cell wall has multiple layers

Answer 11

• Made of the primary cell wall
• Middle lamella
• Secondary cell wall

Question 12

Relatively thin and flexible?

Answer 12

• Primary cell wall (all plant cells have this)

- Thin and flexible so cell can shape and expand

Question 13

In between the 2 plant cells Thin layer between primary walls of adjacent cells?

Answer 13

Middle lamella

Question 14

Added between the plasma membrane and the primary cell (in some cells)

Answer 14

Secondary cell wall - does not occur in all cells since cells only get their second cell wall after completely growing
- Extremely tough and rigid

Question 15

What is plasmodesmata? Is it selective or nonselective

Answer 15

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)

Question 16

What do animal cells lack that plants have? What do they have instead?

Answer 16

Animal cells don’t have a cell wall but has extracellular matrix instead

Question 17

What are the functions of the ECM in animals

Answer 17

• 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

Question 18

What is the ECM of animal cells made of

Answer 18

• Glycoproteins (proteins covalently bonded to sugars) such as
• Collagen, proteoglycan, fibronectins

Question 19

All these glycoproteins of the animal ECM can bind to

Answer 19

Integrins (anchor to integrins)

Question 20

Ex. what do fibronectin proteins bind to

Answer 20

Integrins

Question 21

What is the Function of proteoglycan aggregate (bunch of proteins)

Answer 21

It hydrates tissue

Question 22

Function of collagen

Answer 22

Long fibers that provides structure support

Question 23

What percent of proteins in humans are collagen

Answer 23

40%

Question 24

How does the animal ECM regulate cell behaviour (outside to inside information)

Answer 24

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)

Question 25

the ECM influences the activity of genes in the

Answer 25

Nucleus

Question 26

How does mechanical signal occur (signal transduction of outside to inner)

Answer 26

Through the cytoskeletal changes (in the microfilaments) that trigger chemical signals in the cell

Question 27

Describe cell junctions

Answer 27

How cells adhere (in tissues, organs and organ systems) interact and communicate through physical contact

Question 28

This contact is facilitated by

Answer 28

Cellular junctions

Question 29

Animals have 3 types

Answer 29

1) Tight junctions - in animals
2) Desmosomes - in animals
3) Gap junctions - in animals

Question 30

Plant cellular junctions: the plasmodesmata does what?

Answer 30

Makes tunnels of cytoplasm through the cell wall or channels that perforate (puncture) plant cell walls

Question 31

The bridges (tunnels) are called

Answer 31

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)

Question 32

Describe Tight junctions

Answer 32

Membranes of neighbouring cells are pressed together, and bound together by proteins, prevents leakage of extracellular fluid

Question 33

How do tight junctions prevent leakage?

Answer 33

membranes of adjacent cells that are compressed together to be bound together by proteins

Question 34

Describe Desmosomes (anchoring junctions)

Answer 34

function like rivets to hold cells together into strong sheets

Question 35

Gap Junction (communicating junction)

Answer 35

provide cytoplasmic channels between adjacent cells

• similar to plasmodesmata
• non selective