1. Lesson starter
Give one similarity and one difference between diffusion and osmosis
Explain why water is described as a polar molecule.

2. Answers
Both are involved in movement from an area of high concentration to an area of low concentration / are passive / do not require ATP
Osmosis refers to water molecules only, but diffusion refers to many different molecules and ions.
2. It has different areas of positive and negative charges.

3. Learning question: How do cells communicate?
Title: Communication between cells December 2018
Learning question: How do cells communicate?
Homework: Homework due Wednesday 15th October LP9

4. Key words Pathogens Cell signalling Cytokines Receptor Antigen
Complementary
Lymphocyte
Chemotaxis
Antigen-presenting cell

5. Aims from specification
(i) outline the mode of action of antibodies, with reference to the neutralisation and agglutination of pathogens;
(j) describe the structure and mode of action of T lymphocytes and B lymphocytes, including the significance of cell signalling and the role of memory cells;

6. Task 1 - Measuring blood glucose concentrations
Read the section “Cell Signalling” on page 170
Summarise what cell signalling is
Tell the person next to you what you have summarised
Write down key words that you think are important

7. Cell signalling
“foreign” proteins are recognised by cell – coordinated response initiated so cells can work together, effectively
Chemicals called cytokines released and detected by other cells that bring about the immune response
Some cells in the body have surface receptor proteins that are complementary to foreign antigens
Once detected, lymphocyte is activated

8. What sort of information is communicated?
Identification
Sending distress signals
Antigen presentation
Instructions

9. Identification Pathogens initiate the signalling (a bit silly)
Antigens on cell surface act as flags to your own body’s cells, telling them that they are foreign / not part of you
Signals are detected by body cells…

10. Sending distress signals
Pathogens can be damaged by lysosomes to try and fight invader
Results in pathogen damage and parts of pathogen end attached to PM
Results in:
Distress signals sent out which are detected by the immune system
Act as markers to indicate damage to host cell – Killer T cells recognise infection and destroy infected cell

11. Antigen Presentation
Lymph nodes may start to swell – accumulation of macrophages
Macrophages are phagocytes – they partially digest foreign cells
Antigens are separated out from the partially digested mix of pathogen and the macrophage presents these on its own cell surface
Macrophage becomes an antigen presenting cell
Macrophage goes off to find lymphocytes that can neutralise that particular antigen

13. Instructions
Cytokines – chemical signals that act as instructions to their target cells
Cytokines travel over short distances and in low concentration
They act by binding to specific membrane-bound receptors on the target cell
Causes the release of second messengers inside the cell to alter the cell’s gene expression (therefore behaviour)

14. Instructions Cytokine communication includes the following:
Macrophages release monokines (chemicals that attract neutrophils)
Monokines stimulate B cells to differentiate and produce antibodies
(Chemotaxis – movement of cells towards a chemical)

15. Instructions
T and B cells and macrophages release interleukins, which can stimulate proliferation (growth) and differentiation (specificity) of B and T cells
Cells release interferon, inhibits viral replication and stimulates activity of T killer cells

16. Antigen presenting cell
Macrophages present fragments of foreign cell protein on cell surface
Antigen presenting cell
Macrophages release monokines that attract neutophils.
B cells stimulated to release antibodies
Chemotaxis
Proliferation and differentiation of B and T cells
Many cells release inferon – inhibit viral replication and stimulate activity of killer T cell
Interleukins release

17. Questions to think about
I wonder why cell surface receptors have to be specific
I wonder why the immune system does not attack its own cells

18. Task 2
Have a go at some questions on immunity and see what you’ve learned so far!

19. Title: The specific immune response 26 December 2018
Learning question: what is a specific immune response and how does it work?
Homework: Be fabulous

20. Key words Immunological memory Clonal selection Plasma cells B cells
T helper cells
T killer cells
T memory cells

21. Aims from specification
(j) describe the structure and mode of action of T lymphocytes and B lymphocytes, including the significance of cell signalling and the role of memory cells;

22. The Immune Response

23. The Immune Response Specific response to the detection of pathogens
Specialised WBCs have receptors on plasma membrane surface
Antibodies produced to fight foreign antigens
Immunological memory – memory cells – long term protection (remain in body for years)

24. Starting the response
Invading pathogens have foreign antigens – detected by specific B and T lymphocytes in immune response
Receptor molecules (cell surface proteins) are complementary to antigen
Once the correct B/T cell detects the antigens, immune response begins

25. Starting the response
Initial immune response can be slow (few B/T cells to find antigens)
Presentation of foreign antigens increases chance of correct B/T cells finding antigen
Cells that are attacked by pathogen will display pathogenic antigens on cell surface
Macrophages in lymphatic system can become antigen presenting cells – many copies displayed for B/T cells to see

26. Antigen presenting cell
Macrophages present fragments of foreign cell protein on cell surface
Antigen presenting cell
Macrophages release monokines that attract neutophils.
B cells stimulated to release antibodies
Chemotaxis
Proliferation and differentiation of B and T cells
Many cells release inferon – inhibit viral replication and stimulate activity of killer T cell
Interleukins release

27. Starting the response
Selecting the correct B and T lymphocytes = clonal selection
Lymphocytes increase their numbers before attacking the foreign antigen – clonal expansion
Division occurs by mitosis! Why not meiosis??

28. Lymphocytes
T lymphocytes
B lymphocytes

29. Lymphocytes T lymphocytes B lymphocytes
T helper cells
Release cytokines – stimulate B cells to stimulate phagocytes
T killer cells
Attack and kill infected body cells
T memory cells
Immunological memory
B lymphocytes
Plasma cells
Flow in body
Manufacture and release antibodies
B memory cells
Remain in body for several years – immunological memory

31. Questions to think about
I wonder what the difference is between T helper cells and T killer cells.
I wonder what the role of memory cells are.