Cell-Cell Interactions 1

describe the molecular organization of cell walls in plants

The primary cell wall in plant cells is a fibrous composite

• components of primary cell wall

 cellulose fibers

 strong cable-like microfibrils

 cross-linking polysaccharides

 pectins

 a gelatinous polysaccharide

 fills the extracellular space between cellulose fibers

• cell walls are strong to withstand the intracellular turgor pressure

•secondary cell walls between cell membrane and primary cell wall vary among plant cell types

describe the molecular organization of the extracellular matrix

-proteoglycans and collagen proteins are arranged in layers

-laminin are ECM crosslinking proteins between integrins and ECM proteins

-integrins bind to bind to laminins (extracellular) and cytoskeleton (intracellular)

-components are synthesized in rough endoplasmic reticulum (rER), processed in the Golgi complex and secreted by endocytosis

distinguish between gap junctions, tight junctions and desmosomes

gap junctions facilitate direct electrical and chemical signaling, tight junctions prevent leakage between cells, and desmosomes anchor intermediate filaments for structural integrity. 

describe the function of plasmodesmata

Plasmodesmata are channels that link adjacent plant cells, enabling direct cytoplasmic communication and the transport of molecules between them. Their primary functions include the movement of small molecules like sugars and amino acids, the transport of larger signaling molecules such as hormones and RNA, and the regulation of plant growth, development, and responses to the environment. They are crucial for coordinating plant-wide processes and defense mechanisms

explain the difference between apoplast and symplast

• in plants plasmodesmata form

a symplast (continuous network of cytoplasm)

• apoplasts

 region outside of a plasma membrane

;  consists of cell walls, middle lamella, and air spac

gap junctions

• gap junctions are direct molecular connections between cells that form channels

• ions and small chemical compounds (such as amino acids, nucleotides, and second messenger molecules) can pass through gap junction

s • gap junction proteins

 connexins; are pore proteins that are integrated into cellular membranes

 connexins of adjacent cells connect to each other forming a direct cellto-cell channe

tight junctions

• tight junctions

 hold adjacent cells together

 form weak intercellular connections

• proteins in tight junctions

 stitch cell membranes of adjacent cells together  generate a water impermeable seal between cells • connections between adjacent cells can be modified

desmosomes

• desmosomes

 form strong connections between adjacent cells; rivet-like

• proteins in desmosomes

 anchoring proteins are located inside cells

 membrane proteins are located outside cells; integral membrane proteins that form molecular bridges between cells

 intermediate filaments of the cytoskeleton attach to internal surface of desmosomes; reinforce connections