collagen and tensile strength..?

[hassam]

explain it..

 

[hassam]

An oxygen molecule diffuses directly from the air in an alveolus to haemoglobin in a red blood
cell.
What is the minimum number of cell surface membranes through which this molecule must pass?
A 2 B 3 C 4 D 5

 

[OakMoon!]

Collagen is a fibrous protein whose molecule consists of three polypeptide chains with each in the shape of helix. These helix shaped chains of polypeptides wound around each other to form a three stranded 'rope'. The small size of the glycine amino acid in the chain allows the three chains to lie close together and tightly coil. Any other amino acid would be too large.
The three chains are held together by strong hydrogen bonds that give it huge relative strenghth. This triple helical strand run parallel to other such triple helical chains with cross-links between them and the ends of the parallel molecules are staggered together. This forms fibres giving collagen as a whole tremendous tensile strength.
Hope this helped

 

[beacon_of_light]

An oxygen molecule diffuses directly from the air in an alveolus to haemoglobin in a red blood
cell.
What is the minimum number of cell surface membranes through which this molecule must pass?
A 2 B 3 C 4 D 5

now between air in the alveolus and the haemoglobin there are two cell layers, one cell thick layer of alveolus and one cell thick layer of blood capillary ...

Molecule of oxygen would diffuse into the cell surrounding alveolus, crossing one membrane and when it will diffuse out it will cross the second membrane of the same alveolar cell... it will then diffuse into the cell of capillary, crossing another membrane and then diffuse out of the cell crossing 4th membrane..finally it will diffuse into the red blood cell yt crossing the 5th membrane...
You just need to count the TOTAL number of "Cell Membranes" ...
see the diagram below ...i've shown the crossing of cell membranes with different coloured arrows.