Biology 9700 · AS & A Level · Testing for biological molecules

Testing for biological molecules — practice question

Glycogen is a highly branched polysaccharide that mammals store in the liver, kidney and muscles. Fig. 4.1 shows a small section of a glycogen molecule.
(a(i))[1]

Identify the bond at X.

(a(ii))[2]

State the benefits to a mammal of a storage molecule that has many branches.

(a(iii))[2]

State two structural differences between cellulose and glycogen.

(b(i))[2]

Calculate the percentage of the energy in animal feed that becomes energy available for human consumption. Show your working.

(b(ii))[3]

Explain why humans obtain much less energy from animal products than from the same energy supplied directly by crop plants such as cereals.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: $\alpha(1\rightarrow6)$ glycosidic bond

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