Aqa A Level Biology Revision Study Guide Graded A+

Describe the ways in which prokaryotic cells and eukaryotic cells differ. [3] {Ans: Prokaryotic cells do not have a nucleus / have genetic material in cytoplasm; DNA in loop / ring; Not associated with proteins / do not have chromosomes /chromatin / do not divide by mitosis; Smaller ribosomes; No membrane-bound organelles; Such as mitochondria / lysosomes / endoplasmic reticulum / Golgi / chloroplasts; Prokaryotic cells may have mesosomes; Prokaryotic cells smaller; May be enclosed by capsule;}Explain how a change in the primary structure of a globular protein may result in a different three-dimensional structure. [3] {Ans: Sequence of amino acids changes; tertiary structure changes/folds in a different way; bonds form in different places (not peptide);}Name two structures present in eukaryotic cells that are not present in the cells of prokaryotes. [2] {Ans: Nucleus; mitochondria; chloroplast, Golgi, RER; SER; centrioles}Explain why specific base pairing is important in DNA replication. (4 marks) {Ans: identical/exact copies made; same base sequence as original DNA; both strands act as template/complementary base pairing occurs on both strands;}Which bonds are found in a)Primary structure [1]b)Secondary structure [1] c)Tertiary structure [2] {Ans: a)Peptide b) Hydrogen (and peptide) c)Ionic, disulphide bridges, hydrophobic interactions