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AS LEVEL BIOLOGY NOTES 2015
INTRODUCTION
Hello, this is the summary of AS level Biology (CIE) for 2015 Exam.
As references, I am using the books:
Cambridge International A/AS-level Biology Revision Guide by Mary Jones
Cambridge International A/AS-level Biology course book third edition by Mary Jones
and other resources from Internet.
Credits to authors of pictures and video used for illustration purpose on this blog.
Happy revising and good luck!
E.L.
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CHAPTER 01- CELL STRUCTURE
#01. Microscopy
Most cells are very small, and their structures can only be seen by using a microscope.
1. Light microscopes
light rays pass through the specimen on
a slide
focused by an objective lens and
an eyepiece lens.
---> magnified image of the specimen on
the retina of your eye/screen/camera.
2. Electron microscopes
uses beams of electrons
specimen very thin, placed in a vacuum to allow electrons to pass through it.
electrons are focused onto a screen/photographic film ---> magnified image of
the specimen.
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3. Magnification and Resolution
Amount of magnification depends on the resolution of the microscope (ability to
distinguish 2 objects as separate).
The smaller the objects that can be distinguished --> the higher the resolution.
wavelength: beam of electrons <<< light
resolution: electron microscope >>> light microscope
with electron microscope, we can see much more fine detail of a cell.
Units: millimetre, micrometre, nanometre
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4. Magnification calculations
Work out the real size of an object knowing the magnification:
a. This drawing of a mitochondrion has been magnified 100 000 times.
• Use ruler to measure its length in mm (50 mm).
• Convert this measurement to µm by multiplying by 1 000.
50 x 1 000 = 50 000 µg
• Substitute into the equation:
b. This is a the drawing of a chloroplast:
- The magnification for this drawing:
- The length of the chloroplast:
• Measure the length of the image in mm (80 mm) and convert to µm ---> 80 000 µm.
• Calculate its real length:
AS LEVEL BIOLOGY NOTES 2015
INTRODUCTION
Hello, this is the summary of AS level Biology (CIE) for 2015 Exam.
As references, I am using the books:
Cambridge International A/AS-level Biology Revision Guide by Mary Jones
Cambridge International A/AS-level Biology course book third edition by Mary Jones
and other resources from Internet.
Credits to authors of pictures and video used for illustration purpose on this blog.
Happy revising and good luck!
E.L.
, 2
CHAPTER 01- CELL STRUCTURE
#01. Microscopy
Most cells are very small, and their structures can only be seen by using a microscope.
1. Light microscopes
light rays pass through the specimen on
a slide
focused by an objective lens and
an eyepiece lens.
---> magnified image of the specimen on
the retina of your eye/screen/camera.
2. Electron microscopes
uses beams of electrons
specimen very thin, placed in a vacuum to allow electrons to pass through it.
electrons are focused onto a screen/photographic film ---> magnified image of
the specimen.
, 3
3. Magnification and Resolution
Amount of magnification depends on the resolution of the microscope (ability to
distinguish 2 objects as separate).
The smaller the objects that can be distinguished --> the higher the resolution.
wavelength: beam of electrons <<< light
resolution: electron microscope >>> light microscope
with electron microscope, we can see much more fine detail of a cell.
Units: millimetre, micrometre, nanometre
, 4
4. Magnification calculations
Work out the real size of an object knowing the magnification:
a. This drawing of a mitochondrion has been magnified 100 000 times.
• Use ruler to measure its length in mm (50 mm).
• Convert this measurement to µm by multiplying by 1 000.
50 x 1 000 = 50 000 µg
• Substitute into the equation:
b. This is a the drawing of a chloroplast:
- The magnification for this drawing:
- The length of the chloroplast:
• Measure the length of the image in mm (80 mm) and convert to µm ---> 80 000 µm.
• Calculate its real length:
