1.1 Introduction to Cells Understanding: -According to the cell theory, living organisms are composed of cells -Organisms consisting of only one cell carry out all functions of life in that cell -Surface area to volume ratio is important in the limitation of size -Multicellular organisms have properties that emerge from the interaction of their cellular components -Specialised tissues can develop by cell differentiation in multicellular organisms -Differentiation involves the expression of some genes and not others in a cells genome -The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development. It also makes stem cells suitable for therapeutic uses Applications: -Questioning the cell theory using atypical examples -Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism -Use of stem cells to treat Stargardt’s disease and one other named condition -Ethics of the therapeutic use of stem cells Skills: -Use of a light microscope to investigate the structure of cells and tissues -Drawing cell structures as seen with the light microscope -Calculation of the magnification of drawings and the actual size of structures shown in drawings and micrographs Nature of science: -Looking for trends and discrepancies: although most organisms conform to cell theory, there are exceptions -Ethical implication of research: research

Robert Hooke Create a Facebook page for Robert Hooke Include: -Profile picture -Cover photo -Date of birth -What he did -What happened to him -Relevant status updates

Cell theory principles 1.All organisms are made of one or more cells 2.Cells are the smallest units of life 3.One cell can perform all functions of life Cells vary in shape and size but have some common features…

Cell common features 1.Every living cell is surrounded by a membrane, separating the cell contents from everything else 1.Cells contain genetic material – storing all instructions for cell activities 2.Enzymes inside cell catalyze reactions 3.Cells create their own energy Nothing smaller than a cell can survive on it’s own

Misfits Do not fit cell theory -Striated muscle -Fungi hyphae -Giant algae

Misfits Describe the 7 functions of life - what do cells need to do to be classed as ‘living’? How do giant algae, fungi and striated muscle not fit into the cell theory? MISFITS

Unicellular organisms How do they carry out some of the functions of life? ParameciumChlorella

Function of lifeParameciumChlorella ReproductionDivides transversely MetabolismMetabolic pathways happen in cytoplasm HomeostasisManages water content using vacuole GrowthIngests food, grows and divides ResponseCilia moves in waves = movement NutritionCilia sweep food into cell ‘mouth’ Photosynthesis in cytoplasm provides food Also ingests ExcretionExpel water containing metabolic waste controlled by membrane Oxygen waste controlled by plasma membrane Also metabolic waste

Draw a picture of an animal cell Draw a simple animal cell

Rules when drawing cells Correct or annotate onto your diagram: 1.Sharp pencil 2.Draw single lines not sketches 3.No shading 4.Label each structure with a straight line 5.Include a title 6.Include the magnification or scale

Light microscope

Resolution Low Magnification Good Resolution High Magnification Poor Resolution Microscope’s ability to separate objects that are close together so more detail can be seen

Magnification Magnification is the process of enlarging something only in appearance, not in physical size. Quantified by a calculated number The ratio of the size of an image to the size of the object

Microscopes Create a table to describe the key differences between the three types of microscopes: 1.Light microscope 2.Transmission electron microscope 3.Scanning electron microscope

Light Microscopes Thin specimens Requires staining Limited magnification Most commonly used Living or dead specimens

Light Microscopes

Transmission Electron Microscopes Thin specimens Beam of electrons Far greater range of magnification with much improved resolution Expensive, used mostly in research Dead specimens

Transmission Electron Microscopes

Scanning Electron Microscope Beam of electrons 3D image Crystal clear resolution at high magnifications Specimens coated in heavy gold ions Expensive, used mainly in research and specialist labs Dead specimens

Scanning Electron Microscopes

Working out Magnification Either: Magnification = Apparent size of image Real size of image Or: Calculated by multiplying the viewing lens magnification by that of the objective lens E.g. you have a x10 eyepiece and x40 objective, the total magnification is x400 Measurements are expressed in micrometers (um) 1mm = 1000 um

Calculating magnification & actual size um x

Calculating actual size :

Calculating magnification :

Calculating magnification & actual size :

Magnification Magnification = Apparent size of image Real size of image Green blobs always measure 0.01 mm Remember to convert into um first 1mm = 1000 um 30mm

Magnification 0.01 mm x 1000 = 10 um 30 mm x 1000 = 30,000 um Magnification = 30,000/10 Magnification = x3000 Green blobs always measure 0.01 mm 30mm Now work your way through the calculation sheet

Cell drawings Look at the drawing of an onion cell Use the tick list on the page – do you think the cell is well drawn? Use this to help you draw your own later!

Magnification Practical 1.Collect microscope 2.Follow instructions – find pre-prepared cells 3.Follow instructions – create onion slide 4.Follow instructions – find onion cells 5.Draw onion cell using drawing rules 6.Label diagram and include magnification