Fig. 1.1 is a diagram showing part of a cell surface membrane of an animal cell. [Figure 1.1] Fig. 1.2 is a drawing of a transmission electron micrograph (TEM) of a cell from the palisade mesophyll of a leaf. The drawing does not show all of the organelles visible in a transmission electron micrograph. [Figure 1.2]

Mark scheme

Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.

1. [1] 7 nm; A a suitable range
2. [1] A within the range 5 to 10 nm
3. [1] unit must be shown
4. [4] one mark per row – name and letter must agree in row 3 – glycolipid and glycoprotein
5. [4] If no rows are correct or one row is correct, mark by column to give max 2 if one or two columns are correct
6. [4] component: channel protein, function: facilitated diffusion or transport of, water / ions / water soluble substances / polar molecules / charged substances / hydrophilic substances I named examples of each category, letter on Fig.1.1: A ;
7. [4] component: phospholipid, function: forms a bilayer or a role within bilayer e.g. barrier to, water soluble / polar substances / ions allows diffusion of, fat soluble / non-polar, substances allows fluidity / provides stability / forms a hydrophobic core / AW, letter on Fig.1.1: E ;
8. [4] component: glycoprotein A glycolipid, function: receptor for cell signalling, letter on Fig.1.1: B D ;
9. [4] component: cholesterol, function: gives (mechanical) stability / maintains fluidity / regulates fluidity / barrier to water soluble substances or at low temperatures, maintains or increases fluidity / prevents close packing A prevents hydrophobic 'tails' interacting at low temperatures or at high temperatures, stabilises the membrane / decreases fluidity, letter on Fig.1.1: F ;
10. [3] each organelle must be drawn in the cytoplasm and labelled for a mark
11. [3] max 2 if organelles are drawn correctly but not labelled or are not labelled correctly
12. [3] labels must clearly identify the organelles
13. [3] R any 3D drawings
14. [3] mitochondrion with two membranes and at least one crista ;
15. [3] rough endoplasmic reticulum with at least one cisterna (two lines close together) and ribosomes attached on the outside; R if any ribosomes completely inside the organelle
16. [3] smooth endoplasmic reticulum with at least one tube with no ribosomes ;
17. [3] A RER and SER as labels
18. [3] A if RER or SER attached to nuclear envelope
19. [2] Golgi body / dictyosome; A Golgi, apparatus / complex
20. [2] plus any one from:
21. [2] modifies / processes, protein(s) / polypeptide(s) / lipid(s) ; A any suitable type of modification or a description e.g. glycosylation / addition of sugars forming tertiary or quaternary structures
22. [2] packaging of proteins into (Golgi) vesicles ; I transports
23. [2] AVP; e.g. forming lysosomes / cell wall enzymes assembled