Question
a.i. Distinguish between the structure of amylose and the structure of amylopectin. [1]
a.ii. Suggest the reason for cellulose passing undigested through the human gut. [1]
b. Draw an annotated diagram to show how a peptide bond is formed. [3]
c. State two structural features that differ between RNA and DNA. [2]
▶️Answer/Explanation
Markscheme
amylose unbranched/helical while amylopectin branched / vice versa
enzymes required to digest cellulose not present in the human gut
OR
undigested cellulose provides bulk/fibre
a. correct structure of two amino acids
b. H2O lost
c. C from COOH of one links to N of NH2/NH3+ from the other
d. correct labelling of the peptide bond
e.g.
a. number of strands
OR
(usually) only one strand in RNA/two strands in DNA
b. base composition
OR
uracil only in RNA / thymine only in DNA
c. type of pentose
OR
ribose only in RNA / deoxyribose only in DNA
Question
a. Sketch the complementary strand to complete the section of a DNA diagram.
[3]
b.i. Define mutation. [1]
b.ii. Explain how evolution by natural selection depends on mutations. [4]
▶️Answer/Explanation
Markscheme
a. correct base sequence: T, G, A;
b. strand drawn anti-parallel;
c. correct shapes used;
change in genetic makeup/DNA/nucleotide/base sequence
a. mutations cause variation among organisms of same species/population;
b. some variations/mutations make individual more suited to its environment/way of life;
c. individuals that are better adapted survive and produce offspring;
d. individuals pass on genetic characteristics/mutation/variation to offspring;
e. natural selection increases frequency of characteristics/alleles that make individuals better adapted;