Notes on this presentation

Transcription

1 Notes on this presentation This talk is designed for year olds, to complement a module in the Year 7 curriculum on cells. It also touches on ph indicators, another Year 7 topic. It incorporates quiz questions that are designed to work with specific software and clicker handsets to display the answers on the screen (like Who wants to be a millionaire ). If used without this facility, the answers to the quiz are: 3-B, 4-D, 5-A, 6-A. For the Phenol Red indicator dye demo, DMEM tissue culture medium, lemon juice and diluted bleach are required. Resources: Imperial College London: health.yahoo.com Textbook diagrams: Molecular Biology of the Cell, Fourth Edition, ISBN Fluorescence images: Alexandra Anderson, Michael Delves, Jane Saffell, Imperial College London.

2 Breaking free the importance of cell crawling Dr Jane Saffell, Imperial College London

3 Different types of animal cell The importance of cell crawling Finding out how cells crawl Growing cells in the laboratory Watching cells but first, clicker practice..

4 Switch on your clicker by pressing the black button once. A green light will come on. If you change your mind, the last answer is the one counted, but you can only do this twice. When the question comes up you will have 30 seconds or 1 minute to answer using your clicker. First decide whether you think A, B, C or D is correct When you are ready to answer, point the clicker at the receiver and press 1A, 2B, 3C, or 4D. Each clicker has a number on the back. You can tell if your answer has been registered by checking if the square on the screen corresponding to the last two digits of your number lights up.

5 Qu 1: The best football team in England is: A B C D Manchester United Arsenal Chelsea Charlton

6 Qu 2: The best band that has ever existed is: A B C D Led Zeppelin My Chemical Romance Take That Nirvana

7 Qu 3: If a liquid has a ph of 3 it is: A B C D water acidic alkaline neutral

8 Different types of animal cells Animal cells come in many shapes and sizes, depending on their job in the body

9 Red blood cell White blood cell Nerve cells Skin cell These are just four of the hundreds of different cell types in our bodies.

10 A nerve cell can be up to 1 m long! E.g. stretching from the spine to the muscles of the big toe. Nerve cells control everything - all our thoughts and movements, and even keep out heart beating

11 Red and white blood cells in a blood clot of a wound An electron microscope is required to see this much detail

12 Qu 4: Which of these is true? Whatever their shape, all animal cells have: A B C D Cell wall, nucleus, cytoplasm Cell membrane, cell wall, nucleus Cell wall, chloroplast, nucleus Cell membrane, nucleus, cytoplasm

13 Cytoplasm Nucleus Cell membrane Nucleus: Contains the DNA, the instructions for making the proteins which do the work in cells. Cytoplasm: Contains water, salts and sugars and chemicals the cell needs to live, and cell organelles. Cell membrane: Holds the cell contents in and only allows certain things in and out. It is flexible, allowing the cell to change shape and move.

14 Breaking free cell crawling Why is cell crawling important? Development before birth Fighting infection Cancer

15 DEVELOPMENT A baby s development before birth involves cell division but also cell crawling. In this baby and the mouse, the white patches are areas where the coloured skin cells didn t manage to crawl to the right place when the body was developing.

16 Wall of blood vessel White blood cell Blood FIGHTING INFECTION The job of white blood cells in the blood is to fight infections. They have to crawl out of the blood vessel and towards the site of the infection. White blood cells have crawled to the wound site

17 Boil Health.yahoo.com At the site of infection white blood cells eat bacteria and infected cells or kill them with toxic chemicals. Pus contains all the dead bacteria and cells resulting from a white blood cell battle against infection.

18 Dividing cancer cells in a tumour Cancer cells crawling away Crawling into a blood vessel CANCER Blood vessel Blood can carry cancer cells.. to a new place in the body.. where they crawl out of the blood vessel. The cancer cells divide and form a tumour in this new place Cancer cells that cannot crawl are much easier to treat. Most cancer cells cannot crawl.

19 Finding out how cells crawl Why? To help fight infection To find out why our bodies sometimes don t form properly To fight cancer How? One way is to grow cells out of the body in the laboratory and watch them crawling.

20 Growing cells in the laboratory What are the things you think cells might need to be able to grow outside the body?

21 Correct temperature e.g. Warmth (37 C) for mammalian cells Room temperature for insect cells Sugars and salts for energy and the correct cell growth environment Protein building blocks to make the proteins that do the work in cells Sterile environment to prevent bacteria and fungi from growing Neutral ph

22 Demo: Monitoring the ph of cell growth solution using Phenol Red indicator dye. The solution I use to grow cells contains all the sugars, salts and protein building blocks cells require. It also contains a ph indicator dye called Phenol Red to help us check that the solution is not too acidic or too alkaline. It is red at neutral ph 7. (This is different from universal indicator)

23 QU 5 Guess: When lemon juice is added the solution will go: A B C D Yellow Purple Green Blue

24 QU 6 Guess: When bleach is added the solution will go: A B C D Pink Green Blue Colourless

25 Let s check

26 My lab is at

27 My research group is trying to find out more about how cells crawl

28 As well as leading a cell biology research group, I lecture the university students.

29 Cells need to stick down to be able to crawl. The cell membrane at the front of the cell stretches outwards. The rear catches up. What makes the cell membrane stretch out at the

30 To investigate, we need to watch crawling cells Cells are transparent so they are very difficult to see, even using a microscope. These are nerve cells which should look like this But we can t see them very well.

31 You used iodine to help you see onion skin cells using the microscope. In my laboratory we use special fluorescent dyes that only stick to particular proteins in cells. These allow us to see the cell shape very clearly.

32 Using a green fluorescent dye we can clearly see the nerve cells in green. A blue fluorescent dye that sticks to DNA allows us to clearly see the nucleus of each cell as a blue circle.

33 Here we are looking at two different types of cell in a cross-section of the centre of the spine using red and green fluorescent dyes. The nucleus of all the cells is shown in blue.

34 All of these pictures are of the same bit of spine, but photos of each fluorescence can be taken separately. Blue sticks to DNA Red sticks to one type of cell Green sticks to another type of cell Here all three are shown together

35 The protein is called acetylcholinesterase (ACE) Using fluorescent dyes like these, we discovered that a protein we are interested in is found in patches and rings (red) at the front of a crawling skin cell on the cell membrane. Alexandra Anderson & Jane Saffell

36 The green fluorescent dye, which sticks to a different protein in the cytoplasm, shows us the shape of the cell.

37 Here a red fluorescent dye, which sticks to fibres in the cytoplasm, shows us the shape of some cells that have just started crawling. The ACE protein (green this time) is on fingers of cell membrane being pushed out at the front. This tells us that this protein is probably important for cell crawling.

38 This is very interesting as up until now the ACE protein was thought to be only important in nerve cells. Perhaps in the future you could help find out the many things we still need to know about cells ACE is VERY important for nerve cells. Nerve gas inactivates it, leading to death. If we can find out more about HOW ACE at the front of cells helps them crawl, it will help the design of drugs to help fight infection and cancer. The most important quality in a scientist is curiosity, so never stop asking questions.

39 The End Thank you all for listening, and I hope you find the Imperial College bags useful.