7. Which of the following correctly describes exocytosis?
increases in size
(Total 1 mark)
1. (a) I: is the plasma membrane / cell (surface) membrane / phospholipid bilayer;II:is the mesosome; 2
(b) size of drawing divided by magnification / figures using this equation; (units not required) Award  for working even if length measurement is incorrect. 1.41 (0.02) m; (units required) 2
Accept answers given in m, cm, mm and nm.
(d) bacterium / bacteria / prokaryote;reason: [1 max]as no nuclear membrane / no nucleus;
as no mitochondria / membrane bound organelles;as mesosomes / small size / circular DNA;
(Do not accept naked DNA or no histone.)2 maxReject reasons if cell type is incorrectly identified.
2.b 3. (a) 2
Award  for each correct column.
(ii) enzyme binds to substrate;lowers activation energy;by weakening bonds;making substrate more likely to react; 3 max
(c) one hexose sugar / glucose is converted to two 3-carbon compounds / pyruvate;at start 2 ATP are used / phosphorylation of glucose;net gain of 2 ATP / 4 ATP produced in total;production of 2NADH + H+ / reduced NAD; 3 max
4. (a) small cells have larger ratio (than larger cells) / ratio decreases as size increases;
surface area / membrane must be large enough to absorb nutrients / oxygen / substances needed;
surface area / membrane must be large enough to excrete / pass out waste products;
need for materials is determined by (cell) volume;
cell size is limited (by SA / vol ratio) / cells divide when they reach a certin size;
reference to diffusion across / through membrane / surface area; 3 max
(b) Award [1 max] for each organelle. Mark first answer only. (i) translation / produces polypeptides / proteins / protein synthesis;(ii) support of ribosomes / site of protein synthesis / synthesis of proteins for secretion / folding of polypeptides;(iii) produces glycoproteins / processing of proteins / forms lysosomes / formation of vesicles (for exocytosis); 3 max
(c) Award for each of the following pairs. Mark first answer only in boxes 1, 2 and 3.prokaryotic cellseukaryotic cells
nucleoid / no nucleus / nuclear membrane vs. nucleus / nuclear membrane;
naked DNA / no histones vs. NA associated with protein / histone;
no mitochondria vs. mitochondria present;
no Golgi / no ER vs. Golgi / ER present;
circular DNA vs. linear DNA;
no / very few membrane-bound organelles vs. membrane-bound organelles;
ribosomes smaller / 70S vs. ribosomes larger / 80S; dbb