A-LevelBiologyCell structure9700/22 · Oct/Nov 2020 · Q415 Marks
In the immune system, a plasma cell develops from an activated B-lymphocyte. Mature plasma cells synthesise and secrete antibody molecules. (a) Fig. 4.1 is a diagram of a transmission electron micrograph of a plasma cell. [Figure 4.1] The plasma cell can be seen in greater detail using an electron microscope compared with using a light microscope.
- (a)(i)Describe the extra detail of the nucleus that can be seen using an electron microscope.[3]
- (a)(ii)Explain why cell structures, such as ribosomes and the rough and smooth endoplasmic reticulum, cannot be seen using a light microscope.[2]
- (b)The transition from the activated B-lymphocyte to the fully mature plasma cell requires a number of mitotic cell cycles to occur. This process, which is known as clonal expansion, results in a large number of genetically identical plasma cells. Fig. 4.2 describes events, A to F, that occur during the mitotic cell cycle of the B-lymphocyte. [Figure 4.2] Table 4.1 lists the stages occurring during one cell cycle of the B-lymphocyte. These stages are not in the correct order. [Table 4.1] Complete Table 4.1 by writing the letter of the event described in Fig. 4.2 that correctly matches the stage of the cell cycle listed. Leave a blank space if there is no matching description for the stage in the list. Use each letter once only. One of the letters in Table 4.1 has already been added for you.[5]
- (c)Clonal expansion also results in the production of memory B-lymphocytes. Explain the importance of clonal expansion and the production of memory B-lymphocytes in providing protection for a person against an infectious disease.[3]
- (d)Myasthenia gravis is an example of a disease where the immune system fails to distinguish between self and non-self. Explain what is meant by this statement.[2]
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 (Oct/Nov 2020). The mark or mark type is shown in brackets.
- [3] any three from:
- I heterochromatin / euchromatin
- envelope / two membranes / double membrane / inner and outer membrane ;
- nuclear pores ; A pores in nuclear envelope for two marks
- (outer surface of) outer membrane with ribosomes ;
- ref. to (outer nuclear) membrane continuous with RER; R inner membrane
- AVP; e.g. perinuclear space A intermembranous space
- pore complexes
- [2] any two from:
- resolution / resolving power, is, low / lower / poor / AW / 200 nm / 0.2 µm ;
- (A range 100–300 nm)
- A electron microscope has a higher resolution
- further detail; e.g. ribosomes / ER, smaller than 200 nm
- can only see cell structures greater than (limit of) resolution
- cannot see structures smaller than 200 nm
- cell structures too small for the resolution (needs ref. to resolution)
- cell structures, too small to / do not, interfere with light waves; AW
- [5] if letter used in more than one row, R these rows
- correct interphase knowledge G2 = A, S = B, G1= blank ;
- cytokinesis blank ;
- prophase C ;
- anaphase E;
- telophase D;
- [3] any three from:
- large numbers of B-lymphocytes/plasma cells (in primary immune response)
- 1 large quantity of (specific) antibody, produced / released
- or
- (large quantity of) antibody to form antibody-antigen complexes / to bind antigen (for phagocytosis) / AW ;
- large numbers of memory B-lymphocytes so
- 2 provide long term immunity / memory cells long-lived / provides immunological memory ;
- A remain in, circulation (for a long time) AW
- 3 able to produce fast(er), secondary (immune) response ;
- A second response will be fast(er)
- A immune response faster on second encounter (with antigen / pathogen) / AW
- 4 higher concentration / faster production, of antibodies (than primary response); I 'more' alone
- 5 person does not have, symptoms / become ill (of /from, same disease);
- A presence of same, pathogen / antigen, does not cause disease
- 6 AVP; e.g. memory cells can (divide to) produce plasma cells
- more plasma cells present than primary response
- able to form more memory cells
- [2] any two from:
- immune response / antibodies produced, against, self antigens ;
- I immune system attacks self
- A autoimmunity / autoimmune disease
- idea that faulty B-lymphocytes not destroyed;
- A ref. to T-lymphocytes if in correct context
- (specific) antibody, binds to / acts on / AW, self-antigen / receptor, on the (cell surface membranes of) muscle cells / at neuromuscular junction ;
- A antibody binds to acetylcholine receptors
- ref. to consequence to muscle cells ; e.g.(nerve) impulse conduction impaired
- action of transmitter substance hindered
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