Picornaviruses are small viruses that are 30 nm in diameter. Picornaviruses are able to enter the cells of mammals and birds and can replicate within these cells. Fig. 1.1 shows the entry of a picornavirus into its host cell.

Mark scheme

Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.

1. [2] any two from protein coat/capsid; A capsomeres nucleic acid core / DNA or RNA ; acellular/AW;
2. [3] any three from no, because resolution of light microscope, too low / not high enough ; only able to distinguish points 200nm or more apart or size of virus / 30 nm, too small for resolution of (light microscope) of 200 nm ; A range 100-300 nm wavelength of light too long; idea that virus too small to interfere with light waves ;
3. [3] any three from virus binds to receptors (on host cell surface membrane); ref. to specificity / complementary shapes / complementary binding; endocytosis; description; e.g. membrane infolds / pinches in vesicle formed; A vacuole