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

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.

Learning question: How do cells communicate? Title: Communication between cells 26 December 2018 Learning question: How do cells communicate? Homework: Homework due Wednesday 15th October LP9

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

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;

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

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

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

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…

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

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

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)

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)

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

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

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

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

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

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

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;

The Immune Response

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)

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 http://www.nobelprize.org/educational/medicine/immunity/immune-detail.html

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

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

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??

Lymphocytes T lymphocytes B lymphocytes

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

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.