1 Cell structure
1.1 The microscope in cell studies ANIMAL CELL
a) Differences between plant and animal cells
PLANT CELL
Images: Cambridge International AS & A Level Biology Coursebook
b, c, e) Magnification calculations
LIGHT MICROSCOPE
ANIMAL CELL
CONVERSIONS
1 mm = 1000 or 103 µm
1 µm = 1000 or 103 nm
PLANT CELL d) Resolution and magnification
Ø magnification – how much bigger a sample appears
to be under a microscope than it is in real life
ELECTRON MICROSCOPE
Ø resolution – the ability to distinguish between 2
separate points.
- as resolution increases, image clarity and detail
also increase
Types of microscopes
LIGHT ELECTRON
SEM – 3 nm
RESOLUTION 200 nm
TEM – 0.5 nm
MAGNIFICATION x1500 x250,000 – x500,000
1 www.alevel-notes.weebly.com
, a) Light microscopes a) Electron micrographs of plant and animal
• limit of resolution: half the wavelength cells
• ribosomes (25nm) can’t be seen with a light a) Plant cells
microscope as they don’t interfere with the light
waves
Image: https://cronodon.com/BioTech/Plant_Bodies_Cells.html
Image: Cambridge International AS & A Level Biology Coursebook
• different stains are absorbed by different cell
organelles so they can be observed more clearly
b) Electron microscopes
• vacuum (electrons cannot be focused without a
vacuum as they will collide with air molecules and
scatter)
• water boils at room temperature in a vacuum, so the
sample must be dehydrated (specimen has to be
Image: https://www.tuttee.co/blog/gce-cie-biology-animal-and-plant-cell-structures-and-functions
dead)
Advantages of a light microscope over an electron
microscope b) Animal cells
1) can observe living tissue
2) more portable
3) easier to use - no technical training required
4) possible to see real/natural colours and a live
specimen
5) can stain particular types of tissue for better visibility
1.2 Cells as the basic units of
living organisms
The cell is the basic unit of all living organisms.
The interrelationships between these cell structures show Image: https://brainly.in/question/1540878
how cells function to transfer energy, produce biological
molecules including proteins and exchange substances
with their surroundings.
2 www.alevel-notes.weebly.com
1.1 The microscope in cell studies ANIMAL CELL
a) Differences between plant and animal cells
PLANT CELL
Images: Cambridge International AS & A Level Biology Coursebook
b, c, e) Magnification calculations
LIGHT MICROSCOPE
ANIMAL CELL
CONVERSIONS
1 mm = 1000 or 103 µm
1 µm = 1000 or 103 nm
PLANT CELL d) Resolution and magnification
Ø magnification – how much bigger a sample appears
to be under a microscope than it is in real life
ELECTRON MICROSCOPE
Ø resolution – the ability to distinguish between 2
separate points.
- as resolution increases, image clarity and detail
also increase
Types of microscopes
LIGHT ELECTRON
SEM – 3 nm
RESOLUTION 200 nm
TEM – 0.5 nm
MAGNIFICATION x1500 x250,000 – x500,000
1 www.alevel-notes.weebly.com
, a) Light microscopes a) Electron micrographs of plant and animal
• limit of resolution: half the wavelength cells
• ribosomes (25nm) can’t be seen with a light a) Plant cells
microscope as they don’t interfere with the light
waves
Image: https://cronodon.com/BioTech/Plant_Bodies_Cells.html
Image: Cambridge International AS & A Level Biology Coursebook
• different stains are absorbed by different cell
organelles so they can be observed more clearly
b) Electron microscopes
• vacuum (electrons cannot be focused without a
vacuum as they will collide with air molecules and
scatter)
• water boils at room temperature in a vacuum, so the
sample must be dehydrated (specimen has to be
Image: https://www.tuttee.co/blog/gce-cie-biology-animal-and-plant-cell-structures-and-functions
dead)
Advantages of a light microscope over an electron
microscope b) Animal cells
1) can observe living tissue
2) more portable
3) easier to use - no technical training required
4) possible to see real/natural colours and a live
specimen
5) can stain particular types of tissue for better visibility
1.2 Cells as the basic units of
living organisms
The cell is the basic unit of all living organisms.
The interrelationships between these cell structures show Image: https://brainly.in/question/1540878
how cells function to transfer energy, produce biological
molecules including proteins and exchange substances
with their surroundings.
2 www.alevel-notes.weebly.com
