Lesson starter 1 Give one similarity and one

Lesson starter 1. Give one similarity and one difference between diffusion and osmosis 2. Explain why water is described as a polar molecule.

Answers 1. 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.

Title: Communication between cells December 2021 Learning question: How do cells communicate? Homework: Homework due Wednesday 15 th October LP 9

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

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

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 December 2021 Learning question: what is a specific immune response and how does it work? Homework: Be fabulous

Key words • • mory Immunological me 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/me dicine/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 Chemotaxis • Macrophages present fragments of foreign cell protein on cell surface • Macrophages release monokines that attract neutophils. • B cells stimulated to release antibodies Interleukins release • Proliferation and differentiation of B and T cells • Many cells release inferon – inhibit viral replication and stimulate activity of killer T cell

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? ?

T lymphocytes Lymphocytes B lymphocytes

T helper cells Release cytokines – stimulate B cells to stimulate phagocytes T lymphocytes T killer cells Attack and kill infected body cells T memory cells Immunological memory Lymphocytes Plasma cells B lymphocytes 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.