2018 Bio H2 MCQ Explanations

1. N18Q1 B 2. N18Q2 A Envelope made of phospholipid bilayer which may contain embedded protein which contains nitrogen. Capsid is made of protein (which has nitrogen) and nucleic acids have nitrogen containing nitrogenous bases. 3. N18Q3 C A: wrong, as amylose being linear does not promote rapid digestion and amylopectin being branched does allow hydrolysis and NOT CONDENSATION. B: wrong, the part about gaps in amylose is wrong D: wrong, the close association does not promote rapid digestion. 4. N18Q4 A Glutamine has side-chains that are hydrophilic, hence hydrophobic interactions cannot occur between 2 glutamine amino acids. Since the bonds were formed between amino acids are in the same polypeptide chain, this implies that the polypeptide had folded back on itself and as a result, these bonds are likely to be within the inner core. 5. N18Q5 C A – incorrect. Not all ions are moved against the concentration gradient and the reason why they cannot pass through the phospholipid bilayer is not because they are too large but because they are charged. B – Incorrect. Glucose moves into cells via facilitated diffusion not active transport C – Correct. Oxygen is small enough to diffuse between the phospholipid molecules D – Incorrect. Water can also pass through the membrane by simple diffusion (in between the phospholipid molecules). Even though they are polar, they are small enough. GCE A Level H2 Biology 9648 Biology November 2018

6. N18Q6 B enzyme added to a solution of substrate J product Pt where enzyme acts E2 K J → K E2 and E3 M E2: J → K E3: K → L E1 and E2 K E2: J → K E1: M → N E1, E2 and E3 N E2: J→ K L → M E3: K → L E1: M → N Why not option A? If option A, when only E2 is added, the product obtained would be L not K. 7. N18Q7 C At low substrate concentration, rate of reaction is lower in the presence of the inhibitor. However, at high substrate concentration (200 mg cm -3), rate of reaction is almost the same in the presence or absence of inhibitor. This means that the effect of inhibition is overcome at higher substrate concentration and is characteristic of competitive inhibition. Also, it has to be reversible as the inhibitor must detach to allow the substrate to bind at higher concentrations. 8. N18Q8 D Statement 2 is true but does not explain why long non-coding RNAs are more likely to cause cancer in a bone marrow stem cell than mutations of p53. Inactivating tumour suppressor genes is a similarity in the effects of a p53 mutation and the presence of long non -coding RNAs. Inactivating tumour suppressor genes cannot therefore be used to account for differences in the consequences of p53 mutations and the presence of long non- coding RNAs. Statement 3 is true. Since it is mentioned in the question: the long non -coding RNAs i nactivate tumour suppressor genes and activate proto -oncogenes compared to p53 mutation which is only the tumour suppressor g