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Antigen
Antigen
Activate
B-cell
Clone
Memory
Cell
Activate
Helper
T-cell
Immunity:
Summary
Plasma Cell
phagocyte
Antibodies
What is an antigen? (2 marks)
Part of an organism or substance that stimulates
an immune response
Scores 1 out of 2 marks. Why?
What is an antigen? (2 marks)
Part of an organism or substance that stimulates
an immune response
Scores 1 out of 2 marks. Why?
Mark scheme:
molecule / part of molecule / protein / glycoprotein / named molecule;
that stimulates an immune response / eq;
Describe the role of
phagocytes/macrophages in
stimulating B lymphocytes. (1 mark)
These bind to B cells and stimulate the production of B cells
Scores 0 out of 1 mark. Why?
Explain why B lymphocytes increase the number of
mitochondria, and the amount of RER and Golgi apparatus
within their cytoplasm after stimulation (4 marks).
There are more
mitochondria to provide
more energy. There are
more Gologi body to modify
protein. Their is more RER
to synthesise proteins.
Scores 3 out of 4 marks. Why?
Describe the role of
phagocytes/macrophages in
stimulating B lymphocytes. (1 mark)
These bind to B cells and stimulate the production of B cells
Scores 0 out of 1 mark. Why?
Markscheme:
antigen in membrane presented to lymphocytes
Explain why B lymphocytes increase the number of
mitochondria, and the amount of RER and Golgi apparatus
within their cytoplasm after stimulation (4 marks).
There are more
mitochondria to provide
more energy. There are
more Gologi body to modify
protein. Their is more RER
to synthesise proteins.
Scores 3 out of 4 marks. Why?
Markscheme:
mitochondria provide (more) ATP / energy;
(more) RER / ribosomes synthesise proteins;
(more) Golgi body secretes / modifies or packages proteins /
produces glycoproteins;
(B lymphocytes) produces antibodies;
Describe how a B lymphocyte
responds when they are stimulated by
antigens (3 marks)
They divide to form clones. They make
antibodies that then produce memory cells.
Scores 1 out of 3 marks. Why?
Describe how a B lymphocyte
responds when they are stimulated by
antigens (3 marks)
They divide to form clones. They make
antibodies that then produce memory cells.
Scores 1 out of 3 marks. Why?
Markscheme:
divide by mitosis / form clones;
produce plasma cells;
(plasma cells)
make antibodies;
(plasma cells) produce memory cells;
Changes to the protein coat of the influenza
virus cause antigenic variability. Explain how
antigenic variability has caused some people to
become infected more than once with influenza
viruses. (2 marks)
The B cells for the old influenza virus do not
recognise the new antigens.
Scores 1 out of 2 marks. Why?
Changes to the protein coat of the influenza
virus cause antigenic variability. Explain how
antigenic variability has caused some people to
become infected more than once with influenza
viruses. (2 marks)
The B cells for the old influenza virus do not
recognise the new antigens.
Scores 1 out of 2 marks. Why?
Markscheme:
memory B / T cells do not recognise (new antigens);
antibodies previously produced are not effective
as shape not complementary to new antigen;
Extension:
Explain how antibodies were produced when
the mice were injected with sheep red blood
cells.(3 marks)
Markscheme:
Sheep red blood cells have antigens (on their surface);
Antigens are proteins foreign to mice / are non-self;
Stimulate B cells to produce antibodies;