OCR Biology A Level Module 2: Foundations in Biology Exam -Study Guide-With 100%
verified answers
Light microscope - simple - (answer)Poor resolution due to the long wavelength of light
Living samples can be examined and a colour image is obtained
Transmission electron microscopes - simple - (answer)High magnification and resolution
Electrons pass through the specimen to create an image
Scanning Electron microscope - simple - (answer)High magnification and resolution
Electrons bounce off the surface of the specimen to create an image
Laser scanning Confocal Microscopes - simple - (answer)High resolution and 3D imaging
Uses laser light to produce an image
Resolution - (answer)The minimum distance between two objects in which they can still be viewed as
separate
Optical microscope - resolution - (answer)Determined by the wavelength of light
Electron microscope - Determined by the wavelength - (answer)Determined by the wavelength of the
beam of electrons
Magnification - (answer)How many times larger the image is compared to the object.
The 4 types of slide preparations for light microscopes - (answer)Dry mount
Wet mount
Squash slide
Smear slide
,OCR Biology A Level Module 2: Foundations in Biology Exam -Study Guide-With 100%
verified answers
Dry mounts - (answer)When thin slices or whole specimens are viewed, with just the coverslip placed on
top. E.g. plant tissue or hair
Wet mounts - (answer)When water is added to the specimens before lowering the coverslip a mounted
needle to prevent air bubbles from forming. Aquatic organisms could be viewed this way
Squash slides - (answer)Wet mounts which you push down on the coverslip to squash the sample to
ensure you have a thin layer to enable light to pass through. This is used when creating a rot tip squash
sample to view the chromosomes in mitosis.
Smear slides - (answer)Created by placing a drop of the sample at one end of the slid and using the edge
of another slide (held at an angle) to smear the sample across the first slide to create a smooth, thin,
even coated sample. A cover slip is placed on top after smearing. This is used when examining blood
cells in a blood sample
Eye piece Graticule - (answer)Used to measure the size of objects you are viewing under the
microscope. Each time you change the objective lens and the magnification you have to calibrate the
eyepiece.
How to calibrate the eye piece graticule - (answer)-Line up the stage micrometer and eyepiece graticule
whilst looking through the eyepiece
Count how many divisions on the eyepiece graticule fit into one division on the micrometer scale
Each division on the micrometer in 10 um so this can be used to calculate what one division on the
eyepiece graticule that is at that current magnification.
Magnification calculation - (answer)Size of the image/ size of the real objects
Differential staining - (answer)Involves many chemical stains being used to stain different parts of a cell
in different colours.
, OCR Biology A Level Module 2: Foundations in Biology Exam -Study Guide-With 100%
verified answers
Crystal violet and methylene blue staining - (answer)Positively charged, and therefore are attracted to
and stain negatively charged materials
Nigrosin and Congo red staining - (answer)Negatively charged and therefore cannot enter the cells as
cytosol repels them. This creates a stained background and the unstained cells then stand out.
Electron microscopes - explained - (answer)A beam of electrons has a very short wavelength - a high-
resolution. Small organelles and internal structures can be visualised. Image is created using an
electromagnet to focus the beam of negatively charged electron. Electrons are absorbed by air = EM
must be in a vacuum Therefore only non-living specimens ca be examined. The image is also black and
white as the samples must be stained
Transmission Electron Microscope - explained - (answer)Extremely thin specimens are stained and
placed in a vacuum. Electron gun produces a beam of electrons that passes through the specimen. Some
parts of the specimen absorb the electrons and make them appear darker. The image is 2D and shows
detailed images of the internal structures of cells.
Scanning Electron microscope - explanation - (answer)Specimen does not need to be thin, as the
electron are not transmitting through. Electrons are beamed onto the surface and the electrons are
scattered in different ways depending on the contours. This produces a 3D image of the surface of the
specimen
Nucleus structure - (answer)Nuclear Envelope- Double membrane (protects from damage in the
cytoplasm)
Nuclear pore (allows molecules to move into and out of the nucleus)
Nucleoplasm- granular, jelly-like material
Chromosomes - protein-bound, linear DNA
Nucleolus
Nucleolus - (answer)Smaller where inside when nucleus which is responsible for producing ribosomes. It
is composed of proteins and RNA.
verified answers
Light microscope - simple - (answer)Poor resolution due to the long wavelength of light
Living samples can be examined and a colour image is obtained
Transmission electron microscopes - simple - (answer)High magnification and resolution
Electrons pass through the specimen to create an image
Scanning Electron microscope - simple - (answer)High magnification and resolution
Electrons bounce off the surface of the specimen to create an image
Laser scanning Confocal Microscopes - simple - (answer)High resolution and 3D imaging
Uses laser light to produce an image
Resolution - (answer)The minimum distance between two objects in which they can still be viewed as
separate
Optical microscope - resolution - (answer)Determined by the wavelength of light
Electron microscope - Determined by the wavelength - (answer)Determined by the wavelength of the
beam of electrons
Magnification - (answer)How many times larger the image is compared to the object.
The 4 types of slide preparations for light microscopes - (answer)Dry mount
Wet mount
Squash slide
Smear slide
,OCR Biology A Level Module 2: Foundations in Biology Exam -Study Guide-With 100%
verified answers
Dry mounts - (answer)When thin slices or whole specimens are viewed, with just the coverslip placed on
top. E.g. plant tissue or hair
Wet mounts - (answer)When water is added to the specimens before lowering the coverslip a mounted
needle to prevent air bubbles from forming. Aquatic organisms could be viewed this way
Squash slides - (answer)Wet mounts which you push down on the coverslip to squash the sample to
ensure you have a thin layer to enable light to pass through. This is used when creating a rot tip squash
sample to view the chromosomes in mitosis.
Smear slides - (answer)Created by placing a drop of the sample at one end of the slid and using the edge
of another slide (held at an angle) to smear the sample across the first slide to create a smooth, thin,
even coated sample. A cover slip is placed on top after smearing. This is used when examining blood
cells in a blood sample
Eye piece Graticule - (answer)Used to measure the size of objects you are viewing under the
microscope. Each time you change the objective lens and the magnification you have to calibrate the
eyepiece.
How to calibrate the eye piece graticule - (answer)-Line up the stage micrometer and eyepiece graticule
whilst looking through the eyepiece
Count how many divisions on the eyepiece graticule fit into one division on the micrometer scale
Each division on the micrometer in 10 um so this can be used to calculate what one division on the
eyepiece graticule that is at that current magnification.
Magnification calculation - (answer)Size of the image/ size of the real objects
Differential staining - (answer)Involves many chemical stains being used to stain different parts of a cell
in different colours.
, OCR Biology A Level Module 2: Foundations in Biology Exam -Study Guide-With 100%
verified answers
Crystal violet and methylene blue staining - (answer)Positively charged, and therefore are attracted to
and stain negatively charged materials
Nigrosin and Congo red staining - (answer)Negatively charged and therefore cannot enter the cells as
cytosol repels them. This creates a stained background and the unstained cells then stand out.
Electron microscopes - explained - (answer)A beam of electrons has a very short wavelength - a high-
resolution. Small organelles and internal structures can be visualised. Image is created using an
electromagnet to focus the beam of negatively charged electron. Electrons are absorbed by air = EM
must be in a vacuum Therefore only non-living specimens ca be examined. The image is also black and
white as the samples must be stained
Transmission Electron Microscope - explained - (answer)Extremely thin specimens are stained and
placed in a vacuum. Electron gun produces a beam of electrons that passes through the specimen. Some
parts of the specimen absorb the electrons and make them appear darker. The image is 2D and shows
detailed images of the internal structures of cells.
Scanning Electron microscope - explanation - (answer)Specimen does not need to be thin, as the
electron are not transmitting through. Electrons are beamed onto the surface and the electrons are
scattered in different ways depending on the contours. This produces a 3D image of the surface of the
specimen
Nucleus structure - (answer)Nuclear Envelope- Double membrane (protects from damage in the
cytoplasm)
Nuclear pore (allows molecules to move into and out of the nucleus)
Nucleoplasm- granular, jelly-like material
Chromosomes - protein-bound, linear DNA
Nucleolus
Nucleolus - (answer)Smaller where inside when nucleus which is responsible for producing ribosomes. It
is composed of proteins and RNA.
