1.1 introduction to cells understanding: -according to the cell theory, living organisms are...
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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
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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
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Cell theory principles
1. All organisms are made of one or more cells2. Cells are the smallest units of life3. One cell can perform all functions of life
Cells vary in shape and size but have some common features…
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Cell common features
1. Every living cell is surrounded by a membrane, separating the cell contents from everything else
2. Cells contain genetic material – storing all instructions for cell activities
3. Enzymes inside cell catalyze reactions
4. Cells create their own energy
Nothing smaller than a cell can survive on it’s own
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Misfits
Do not fit cell theory
- Striated muscle- Fungi hyphae- Giant algae
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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
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Unicellular organisms
How do they carry out some of the functions of life?
ParameciumChlorella
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Function of life Paramecium Chlorella
Reproduction Divides transversely Divides transversely
Metabolism Metabolic pathways happen in cytoplasm
Metabolic pathways happen in cytoplasm
Homeostasis Manages water content using vacuole
Manages water content using vacuole
Growth Ingests food, grows and divides Ingests food, grows and divides
Response Cilia moves in waves = movement
Cilia moves in waves = movement
Nutrition Cilia sweep food into cell ‘mouth’
Photosynthesis in cytoplasm provides foodAlso ingests
Excretion Expel water containing metabolic waste controlled by
membrane
Oxygen waste controlled by plasma membrane
Also metabolic waste
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Draw a picture of an animal cell
Draw a simple animal cell
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Rules when drawing cells
Correct or annotate onto your diagram:
1. Sharp pencil2. Draw single lines not sketches3. No shading4. Label each structure with a straight line 5. Include a title6. Include the magnification or scale
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Light microscope
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Resolution
Low MagnificationGood Resolution
High MagnificationPoor Resolution
Microscope’s ability to separate objects that are close together so more detail can be seen
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MagnificationMagnification 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
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Microscopes
Create a table to describe the key differences between the three types of microscopes:
1. Light microscope2. Transmission electron microscope3. Scanning electron microscope
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Light Microscopes
Thin specimens
Requires staining
Limited magnification
Most commonly used
Living or dead specimens
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Light Microscopes
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Transmission Electron Microscopes
Thin specimens
Beam of electrons
Far greater range of magnification with much improved resolution
Expensive, used mostly in research
Dead specimens
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Transmission Electron Microscopes
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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
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Scanning Electron Microscopes
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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
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Calculating magnification & actual size
um
um x
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Calculating actual size:
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Calculating magnification:
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Calculating magnification & actual size:
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Magnification
Magnification = Apparent size of image Real size of image
Green blobs always measure 0.01 mm
Remember to convert into um
first1mm = 1000 um
30mm
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Magnification
0.01 mm x 1000 = 10 um30 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
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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!
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Magnification Practical
1. Collect microscope2. Follow instructions – find pre-prepared cells3. Follow instructions – create onion slide4. Follow instructions – find onion cells 5. Draw onion cell using drawing rules 6. Label diagram and include magnification