Indicate whether each of the following descriptions better applies to cellulose microfibrils (C) or pectins (P) in plant cell walls. Your answer would be a five-letter string composed of letters C and P only, e.g. CPPPP.
( ) It is made into a network by cross-linking glycans.
( ) It is particularly abundant in the middle lamella.
( ) Divalent ions such as calcium can cross-link it to form gels.
( ) It forms more homogeneous polymers.
( ) It contains many negatively charged galacturonic acid units.