2023 AQA AS
BIOLOGY 7401/2
Paper 2 Question
Paper & Mark
scheme (Merged)
June 2023
[VERIFIED]
,What is a light microscope used
for?✔✔✔ANSWER➖Observing living and dead
specimins
What are the pros and cons of a light
microscope?✔✔✔ANSWER➖Pros: Cheap, portable,
easy to use, can study living specimens. Cons: Limited
magnification, poor resolution.
What is a laser scanning confocal microscope used
for?✔✔✔ANSWER➖Creating a high resolution, high
contrast image, at different depths of the specimen.
What is a transmission electron microscope be used
for?✔✔✔ANSWER➖Observing the internal
ultrastructure of cells under high magnification and
resolution
What is a scanning electron microscope used
for?✔✔✔ANSWER➖Viewing the surface of objets
under high magnification and resolution
What are the pros and cons of an electron
microscope?✔✔✔ANSWER➖Pros: Very high
,magnification and excellent resolution. Cons: specimen
has to be dead, very expensive, very large, needs great
skill and training to use.
What is the difference between a transmission and an
scanning electron microscope?✔✔✔ANSWER➖TEM
sends a beam of electrons through the specimen, the SEM
bounces electrons off the surface.
What is the difference between light and electron
microscopes?✔✔✔ANSWER➖Light uses lenses to focus
a beam of light. Electron uses a beam of electrons,
focused by magnets.
What is an eye piece graticule?✔✔✔ANSWER➖A small
ruler fitted to a light microscope's eyepiece. It must be
calibrated using a stage micrometer before being used to
measure specimens.
What is a stage micrometer?✔✔✔ANSWER➖A
millimeter long ruler etched onto a slide. it has 100
divisions, each of 0.01mm or 10 micrometers. It is used to
calibrate the eyepiece graticule
Why do we stain specimens?✔✔✔ANSWER➖To
provide more contrast, and make it easier to distinguish
certain parts.
, What is differential staining?✔✔✔ANSWER➖Using a
stain to distinguish between either 2 different orgaisms, or
between organelles of a specimin due to preferential
absorbtion of stain.
What is the formula to calculate
magnification?✔✔✔ANSWER➖Magnification = Image
size / Actual size
What is the formula to calculate actual object
size?✔✔✔ANSWER➖Actual size = Image size /
Magnification
How do we work out image size?✔✔✔ANSWER➖Use a
ruler and measure the image.
What is magnification?✔✔✔ANSWER➖A measure of
how much larger the image of a specimen looks under the
microscope
What is resolution?✔✔✔ANSWER➖The ability to
distinguish between to adjacent individual points as
separate.
BIOLOGY 7401/2
Paper 2 Question
Paper & Mark
scheme (Merged)
June 2023
[VERIFIED]
,What is a light microscope used
for?✔✔✔ANSWER➖Observing living and dead
specimins
What are the pros and cons of a light
microscope?✔✔✔ANSWER➖Pros: Cheap, portable,
easy to use, can study living specimens. Cons: Limited
magnification, poor resolution.
What is a laser scanning confocal microscope used
for?✔✔✔ANSWER➖Creating a high resolution, high
contrast image, at different depths of the specimen.
What is a transmission electron microscope be used
for?✔✔✔ANSWER➖Observing the internal
ultrastructure of cells under high magnification and
resolution
What is a scanning electron microscope used
for?✔✔✔ANSWER➖Viewing the surface of objets
under high magnification and resolution
What are the pros and cons of an electron
microscope?✔✔✔ANSWER➖Pros: Very high
,magnification and excellent resolution. Cons: specimen
has to be dead, very expensive, very large, needs great
skill and training to use.
What is the difference between a transmission and an
scanning electron microscope?✔✔✔ANSWER➖TEM
sends a beam of electrons through the specimen, the SEM
bounces electrons off the surface.
What is the difference between light and electron
microscopes?✔✔✔ANSWER➖Light uses lenses to focus
a beam of light. Electron uses a beam of electrons,
focused by magnets.
What is an eye piece graticule?✔✔✔ANSWER➖A small
ruler fitted to a light microscope's eyepiece. It must be
calibrated using a stage micrometer before being used to
measure specimens.
What is a stage micrometer?✔✔✔ANSWER➖A
millimeter long ruler etched onto a slide. it has 100
divisions, each of 0.01mm or 10 micrometers. It is used to
calibrate the eyepiece graticule
Why do we stain specimens?✔✔✔ANSWER➖To
provide more contrast, and make it easier to distinguish
certain parts.
, What is differential staining?✔✔✔ANSWER➖Using a
stain to distinguish between either 2 different orgaisms, or
between organelles of a specimin due to preferential
absorbtion of stain.
What is the formula to calculate
magnification?✔✔✔ANSWER➖Magnification = Image
size / Actual size
What is the formula to calculate actual object
size?✔✔✔ANSWER➖Actual size = Image size /
Magnification
How do we work out image size?✔✔✔ANSWER➖Use a
ruler and measure the image.
What is magnification?✔✔✔ANSWER➖A measure of
how much larger the image of a specimen looks under the
microscope
What is resolution?✔✔✔ANSWER➖The ability to
distinguish between to adjacent individual points as
separate.
