A Tour of the Cell

Page
12

The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water

Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein

Slide 97

Plant cell walls may have multiple layers:

Primary cell wall: relatively thin and flexible

Middle lamella: thin layer between primary walls of adjacent cells

Secondary cell wall (in some cells): added between the plasma membrane and the primary cell wall

Plasmodesmata are channels between adjacent plant cells

Slide 98

Fig. 6-28

Secondary cell wall

Primary cell wall

Middle lamella

Central vacuole

Cytosol

Plasma membrane

Plant cell walls

Plasmodesmata

1 µm

Slide 99

Fig. 6-29

10 µm

Distribution of cellulose synthase over time

Distribution of microtubules over time

RESULTS

Slide 100

The Extracellular Matrix (ECM) of Animal Cells

Animal cells lack cell walls but are covered by an elaborate extracellular matrix (ECM)

The ECM is made up of glycoproteins such as collagen, proteoglycans, and fibronectin

ECM proteins bind to receptor proteins in the plasma membrane called integrins

Slide 101

Fig. 6-30

EXTRACELLULAR FLUID

Collagen

Fibronectin

Plasma

membrane

Micro-

filaments

CYTOPLASM

Integrins

Proteoglycan

complex

Polysaccharide

molecule

Carbo-

hydrates

Core

protein

Proteoglycan

molecule

Proteoglycan complex

Slide 102

Fig. 6-30a

Collagen

Fibronectin

Plasma membrane

Proteoglycan complex

Integrins

CYTOPLASM

Micro-filaments

EXTRACELLULAR FLUID

Slide 103

Fig. 6-30b

Polysaccharide molecule

Carbo-hydrates

Core protein

Proteoglycan molecule

Proteoglycan complex

Slide 104

Functions of the ECM:

Support

Adhesion

Movement

Regulation

Slide 105

Intercellular Junctions

Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact

Intercellular junctions facilitate this contact

There are several types of intercellular junctions