Cell adhesion 1

What is a simple way to define tissues

as a cooperative assembly of cells and extracellular matrix woven together to form a multicellular fabric with a distinctive function

what is a simple way to define the extracellular matrix

the non cellular network of molecules found outside of cells, providing structural support and biochemical cues to the surrounding cells

what structure give supportive tissues their strength

the extracellular matrix

what are the two strategies that multicellular organisms have to transmit physical stress

using the extracellular matrix and using the cytoskeletons and cell to cell adhesion

do plants mostly use the extracellular matrix or cytoskeletons to transmit physical stress

they use the extracellular matrix

what is the supportive matrix in plants

the cell wall

describe the two key features of the plant primary cell wall

relatively thin and flexible, can expand as cells grow

when is a secondary plant cell wall often made

once cell growth stops

what are the tree key features of the secondary plant cell wall

it is thicker and more rigid, no longer needs to expand, most common is lignin

what is the most common macromolecule on earth

cellulose

what is the basic structure of cellulose

long unbranched chains of linked glucose subunits

how many cellulose molecules assemble to form a microfibril

16

what material is the tensile strength of cellulose comparable with

steel

what type of plant cell wall does cellulose predominate in

secondary cell walls

what does pectin provide resistance to

compression

what is the basic structure of pectin

long complex polysaccharides rich in galacturonic acid, highly hydrated and binds cations

what is the space filling effect of pectin similar to

similar to glycosaminoglycans in animal ECM

what does pectin form crosslinks with

cellulose

what type of plant cell wall is pectin abundant

in primary plant cell walls

give a basic overview of the structure of primary plant cell walls

cellulose microfibrils in the middle layer provide tensile strength, other polysaccharides crosslink the cellulose microfibrils, pectin in the middle provides resistance to compression

give a basic structure of lignin

a complex polymer of cross-linked phenolic compounds and is rigid when wet

do animal or plant cell (walls) contain more proteins

animal

how high can the turgor pressure be in plant cells

10 atmospheres

what does the orientation of cellulose microfibrils influence

the direction in which the cell elongates

why might microtubules help direct the deposition of cellulose

beneath the plasma membrane, microtubules are aligned exactly with cellulose microfibrils

what is the function of microtubules in cellulose synthesis

they serve as tracks that guide enzyme complexes

what type of animal tissues have much less than normal ECM

epithelial tissues

what carries the mechanical load from cell to cell in epithelial tissues

the cytoskeleton

what are some examples of connective tissues

tendons, ligaments, cartilage, bone, skin, vitreous humour

what is the name given to bone forming cells

osteoblasts

what do osteoblasts secrete

a collagen matrix

what are some properties of bone

mineralised, cell sparse, contain osteons

what is the structure of an osteon

composed of concentric rings of mineralised matrix deposited around a central canal containing blood vessels and nerves

what cell types are capable of making collagen

osteoblasts and mesenchymal skin cells

which cell type makes collagen in bone

osteoblasts

what proteins are abundant in cartilage

collagen and proteoglycan

where is vitreous humour found

between the lens and retina

what are the basic properties of vitreous humour

clear viscous gel, made of water, collagen, and hyaluronic acid, virtually acellular, amorphous appearance on tissue sections

what is the major protein of the ECM

collagens

how many collagen genes are there in animals

more than 40

how much of the protein mass in animals is made up by collagen

about 25%

what type of cell produces most of the collagen

fibroblasts

what is the order of collagen assembly

monomer, trimer, fibril, fibre

what type of pattern are collagen fibrils in the skin arranged in

a plywood like pattern

what does the plywood like pattern of collagen in animals allow skin to do

resist tensile stress in multiple directions

what do tendons do

attach muscles to bone

how are tendons aligned

they are in parallel along the axis of extension

why are collagen molecules secreted in a precursor form

they have an additional peptide extension that obstructs premature fibril assembly

what are the simple steps of collagen formation

procollagen is found in a secretory vesicle, it is secreted, procollagen proteinase cleaves terminal procollagen extensions, these collagen molecules then self assemble into fibrils

what can incorrect assembly of collagen cause

skin to become hyperextensible

what is Ehlers-Danlos syndrome caused by

mutations in genes encoding collagens and proteins that affect collagen assembly