A-LevelBiologyBiological molecules9700/21 · May/June 2019 · Q111 Marks

Antibody molecules are proteins that show primary structure, secondary structure, tertiary structure and quaternary structure. [Figure 1.1] shows a ribbon diagram of an antibody molecule.

(a)Describe how Fig. 1.1 shows the secondary structure and tertiary structure of the antibody molecule. secondary structure tertiary structure[3]
(b)(i)The hybridoma cell in Fig. 1.2 synthesises and secretes molecules of a monoclonal antibody. State the roles of the structures labelled X and Y in the production of antibody molecules in the hybridoma cell. X Y[2]
(b)(ii)The hybridoma method for the production of monoclonal antibodies involves a number of stages. One of these stages is the formation of hybridoma cells. Outline the stage in which hybridoma cells are formed.[3]
(b)(iii)Outline the use of monoclonal antibodies in the treatment of disease.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

any three from:
secondary structure
1 (many) ẞ-pleated / beta-pleated, sheets ; R 'B'
2 random structure / irregular structures / loops / beta turns / AW ;
tertiary structure
3 folding/coiling, of, (each) polypeptide chain(s) / secondary structure;
R idea of polypeptide chains interacting (quaternary structure)
4 ref. to globular A description, e.g. spherical I circular / round or ref. to 3D, shape / structure; A 3D arrangement
X - site of synthesis of, (light and heavy) polypeptides ; A protein(s)
A transport / modification, of, polypeptides / proteins
A assembly of polypeptides / translation
R answers that name the Golgi body
Y - production of ATP ;
R 'produce / create / AW, energy'
A release of energy / provide energy
cell/membrane, fusion / AW; I 'mix'
(named) fusogen / hybridogen used; e.g. polyethylene glycol / electrofusion / electric current A PEG for polyethylene glycol
(between) plasma cell / (activated) B-lymphocyte / (activated) B-cell / splenocyte, and, tumour / cancer/myeloma, cell ; R ẞ cells
any three from:
1 some mAbs act directly on target cells / some mAbs work indirectly to kill cells / mAbs do not damage other (non-target) cells;
2 by binding to, specific / complementary, antigens/cell surface receptors;
3 (named), drugs / radioactive isotopes, can be attached to mAbs; A 'tagged' I labelled
4 enzymes can be attached to mAbs ;
5 so drug can be activated at site of action (linked to mp4);
6 bispecific mAbs attach two cells together ;
7 ref. to interrupting cell signalling;
8 use of mAbs for passive immunity; A described in context of therapeutic antibody for treatment of disease
9 stimulating / AW, immune system / phagocytes / macrophages / T-lymhocytes, to kill, cancer cells ;
10 name of a cancer or autoimmune disease that is treated with mAbs ;