Different types of microscopes Lesson Element OCR 2017

Different types of microscopes Lesson Element © OCR 2017

Objectives Learners should be able to: • explain how an electron microscope is different to a light microscope • define the terms magnification and resolution • convert units of measurement used in microscopy • state with examples, when different microscopes are used. © OCR 2017

3 • What is the smallest thing you can see with your eyes? • What is the smallest thing you can see with a light microscope? © OCR 2017

Light Microscopes Eyepiece lens Objective lenses Stage Light rays are focussed using glass lenses to magnify objects up to x 1500 Coarse and fine Focusing Stage clips Diaphragm Mirror © OCR 2017

Cheek cell plasma membrane cytoplasm © OCR 2017 nucleus

Onion cells © OCR 2017

To see more detail an electron microscope can be used • Electron microscopes use an electron beam instead of light, which is focussed using electromagnets. • The specimen has to be specially prepared and held inside a vacuum chamber from which the air has been pumped out (because electrons do not travel very far in air). • The image is formed as a photograph (called an electron micrograph) or as an image on a TV screen. © OCR 2017

Electron microscope electron gun high voltage anode condenser lens objective aperture lens Intermediate lens specimen projector lens fluorescent screen © OCR 2017 • Specimen is dead and dehydrated. • Black and white image [or false colour]. • Objects can be magnified up to x 500 000!

Which parts of this cell would be visible using a light microscope? • • © OCR 2017 Nucleus Cytoplasm Cell membrane Possibly mitochondria

Which parts of the cell would be visible using an transmission electron microscope (TEM) • • © OCR 2017 Nucleus Cytoplasm Cell membrane Possibly mitochondria

What can be seen with an electron Microscope? © OCR 2017

Scanning electron microscope Work in a similar way but are designed to make images of the surfaces of objects. © OCR 2017

Resolution • Resolution means how close together 2 objects can be, and still be seen as separate objects. • Resolution of a light microscope 0. 250 µm • Resolution of an electron microscope 0. 25 nm • Do you know how small µm and nm are? © OCR 2017

Magnification • Magnification is how many times bigger an object is in an image, than in real life. • Magnification using light microscope – up to x 1500 • Magnification using an electron microscope – up to x 500 000 © OCR 2017

Comparing light and electron microscopes Light microscope Magnification Resolution Type of radiation used Focussed by Type of material that can be viewed Size Preparation and cost of material © OCR 2017 Electron microscope

Comparing light and electron microscopes Light microscope Electron microscope Magnification x 1500 X 500, 000 Resolution 250 nm 0. 25 nm Type of radiation used Light Electrons Focussed by Glass lenses Electromagnets Type of material that can be viewed Living/moving/dead/abiotic Dead/abiotic Size Small and portable Large and static Preparation and cost of material Cheap and easy Difficult and expensive © OCR 2017

How big are cells? Units for measurements • mm • Micrometers - µm • Nanometers – nm • 1 mm = 1000µm • 1µm = 1000 nm © OCR 2017

Cheek cell • Approximately 60µm in diameter. © OCR 2017

Onion cell • Approximately 200µm in length. © OCR 2017

Mitochondrion • Approximately 2µm in diameter. © OCR 2017

HIV Virus • Approximately 2µm in diameter. © OCR 2017

Put these in size order starting with the biggest • • • © OCR 2017 Cilia 10µm Mitochondrion 2µm Sperm cell 55µm Ribosome 20 nm Human kidney 13 cm Nerve cell from a giraffes neck 3 m Red blood cell 9µm HIV virus 100 nm Human egg 100µm

Put these in size order starting with the biggest - answers • • • © OCR 2017 Nerve cell from a giraffes neck 3 m Human kidney 13 cm Human egg 100µm Sperm cell 55µm Cilia 10µm Red blood cell 9µm Mitochondrion 2µm HIV virus 100 nm Ribosome 20 nm

Convert these measurements 1. 2. 3. 4. 5. 6. © OCR 2017 10 mm = µm 3 mm = µm 670 µm = mm 0. 75 mm = µm 24 µm = nm 186 nm = µm

Convert these measurements - answers 1. 2. 3. 4. 5. 6. © OCR 2017 10 mm = 3 mm = 670 µm = 0. 75 mm = 24 µm = 186 nm = 10 000µm 3 000µm 0. 67 mm 750µm 24 000 nm 0. 186µm

Quick quiz © OCR 2017

What sort of microscope would you use to… • study the internal structure of a mitochondria? © OCR 2017

What sort of microscope would you use to… • view sperm cells to see if they are moving? © OCR 2017

What sort of microscope would you use to… • look at organisms, cells or tissues that are alive? © OCR 2017

What sort of microscope would you use to… • view the surface of a bacterial cell? © OCR 2017

What sort of microscope would you use to… • observe the double membrane around a chloroplast? © OCR 2017

What sort of microscope would you use to… • look at a cross-section of a sample at high resolution? • What do you think this is a picture of? © OCR 2017

What sort of microscope would you use to… • look at a viral cell? © OCR 2017

What sort of microscope would you use to… • look at the shape and surface of red blood cells in detail? © OCR 2017

What have we learnt using electron microscopes? • Cells contain organelles to carry out different functions. • The internal structure of organelles and how they function. • Structure of bacteria and viruses. • Causes of medical conditions e. g. MS, HIV. © OCR 2017

Objectives Can you: • explain how an electron microscope is different to a light microscope • define the terms magnification and resolution • convert units of measurement used in microscopy • state with examples, when different microscopes are used. © OCR 2017

37 We’d like to know your view on the resources we produce. By clicking on ‘ Like’ or ‘Dislike’ you can help us to ensure that our resources work for you. When the email template pops up please additional comments if you wish and then just click ‘Send’. Thank you. Whether you already offer OCR qualifications, are new to OCR, or are considering switching from your current provider/awarding organisation, you can request more information by completing the Expression of Interest form which can be found here: www. ocr. org. uk/expression-of-interest Looking for a resource? There is now a quick and easy search tool to help find free resources for your qualification: www. ocr. org. uk/i-want-to/find-resources/ OCR Resources: the small print OCR’s resources are provided to support the delivery of OCR qualifications, but in no way constitute an endorsed teaching method that is required by the Board, and the decision to use them lies with the individual teacher. Whilst every effort is made to ensure the accuracy of the content, OCR cannot be held responsible for any errors or omissions within these resources. © OCR 2017 - This resource may be freely copied and distributed, as long as the OCR logo and this message remain intact and OCR is acknowledged as the originator of this work. OCR acknowledges the use of the following content michaeljung/shutterstock. com, PASIEKA/Britannica. com, Eye of Science/Britannica. com, Encyclopaedia Britannica, Inc. /Britannica. com, sciencepics/shutterstock. com, Media for Medical/Britannica. com, Media for Medical/UIG/Britannica. com, The Natural History Museum/Britannica. com, Phototake/Britannica. com, POWER AND SYRED/Britannica. com, STEVE GSCHMEISSNER/Britannica. com, NIBSC/Britannica. com, Warren Rosenberg/Britannica. com, Michael Abbey/Britannica. com, Superstock/Britannica. com, DR KARI LOUNATMAA/Britannica. com, THOMAS DEERINCK/Britannica. com, MOREDUN ANIMAL HEALTH LTD/Britannica. com, ASTRID & HANNS-FRIEDER MICHLER/Britannica. com, Kenneth Eward/Britannica. com Please get in touch if you want to discuss the accessibility of resources we offer to support delivery of our qualifications: resources. feedback@ocr. org. uk © OCR 2017