Unit 2 Chapter 8: Cell-Cell Interactions

Question 1

What is the primary cell wall

Answer 1

• forms when plant cells first form
• defines shape
• initial fibre composite
• fibrous component = long strands of cellulose, crosslinked by other filaments and bundled into cable-like microfibrils
• space between microfibrils is filled with gelatinous pectins, which attract and store lots of H2O to make cell wall moist

Question 2

What is turgor pressure

Answer 2

pressure exerted by the inflated plasma membrane caused by an inward flow of water due to osmosis, leads to cell growth

Question 3

What is the secondary cell wall

Answer 3

• made when cells stop growing
• inside primary cell wall
• structure varies, could be lignin, cellulose,etc.

Question 4

What is the extracellular matrix

Answer 4

• found in animal cells
• fibre composite
• contains much more protein than a cell wall
• dominated by collagen
• matrix that surrounds collagen is made of gel forming polysaccharides with a protein core
• most components synthesized in ER-golgie-secreted

Question 5

What is collagen

Answer 5

3 polypeptide chains that wind around eachother

Question 6

Why is the link between the cytoskeleton and extracellular matrix critical

Answer 6

• keeps cells in place, helps adjacent cells adhere via their common connection
• if the link is broken cancer can form

Question 7

What are focal adhesions

Answer 7

adhesion sites between actin filaments in the cell and the extracellular matrix

Question 8

What are integrins

Answer 8

transmembrane proteins that bind to actin filaments in the cytoskeleton which also bind to proteins in ECM called fibronectins which bind to collagen

Question 9

What is a tight junction

Answer 9

cell-cell attachment made of special proteins in the plasma membranes of adjacent cells

• looks like quilting where proteins act as stitches
• form a water tight seal
• found in epithelial cells in stomach and intestines
• open and close in response to environmental conditions

Question 10

What are desmosomes

Answer 10

• particularly common in epithelial and muscle cells
• bind the cytoskeletons of adjacent cells
• contain proteins that bind to eachother and to larger proteins that anchor inter.filaments in the cytoskeletons of the 2 cells

Question 11

What is cell recognition

Answer 11

one cell specifically binds to another cell of a certain type

Question 12

What is cell-cell adhesion

Answer 12

cells stably bind to eachother

Question 13

What is selective adhesion

Answer 13

cells adhere to other cells of the same tissue type (only one species and one cell type)

Question 14

What are caherins

Answer 14

the attachment molecules in desmosomes

Question 15

What does the presence of holes or gaps do

Answer 15

allows adjacent plant cells to retain their own organelles, proteins, nucleic acids but communicate by sharing ions and small molecules in their cytoplasm

Question 16

What are plasmodesmata

Answer 16

direct connections between the cytoplasm of adjacent cells in PLANTS

Question 17

What are gap junctions

Answer 17

• in animal cells
• connect adjacent cells
• key feature=specialized proteins that create channels between cells
• channels allow water, ions and small molecs to move between adjacent cells

Question 18

What are adherens

Answer 18

joins actin bundles in neighbouring cells

Question 19

What are focal adhesions

Answer 19

anchor actin filaments to the basal lamina