OCR A LEVEL BIOLOGY PAPER 2 EXAM 2026
COMPLETE QUESTIONS AND VERIFIED
SOLUTIONS
◉ 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.
◉ What are the maximum resolutions of the different microscopes?
Answer: Light: 200nm; SEM: 10nm; TEM: 0.2nm.
◉ What is the maximum magnification of the different microscopes?
Answer: Light: 1,500X; SEM: 100,000X; TEM: 500,000X.
◉ What are the main structures of all eukaryotic cells? Answer:
Nucleus; nucleolus; cytoplasm; cytoskeleton; plasma
, membrane;mitochondria; Golgi apparatus; smooth endoplasmic
reticulum; rough endoplasmic reticulum; ribosomes.
◉ What is the structure and function of the nucleus? Answer:
Surrounded by a double membrane (the nuclear envelope). Contains
chromatin (DNA wound around histones). Stores the human
genome, controls the cell by providing instructions for protein
synthesis.
◉ What is the structure and function of the nucleolus? Answer:
Made of RNA, produces ribosomes.
◉ What is the structure and function of the nuclear envelope?
Answer: A double membrane embeded with channel proteins
forming pores. Separates the nucleus from the rest of the cell. Pores
allow ribosomes and mRNA to leave the nucleus.
◉ What is the structure and function of the rough endoplasmic
reticulum (RER)? Answer: A system of fluid filled membranes
studded with ribosomes. Continuous with the nuclear membrane.
Large surface area formed by folding, enables lots of protein
synthesis. Proteins pinched off in vesicles transported to the Golgi
apparatus.
◉ What is the structure and function of the smooth endoplasmic
reticulum (SER)? Answer: A system of fluid filled membranes. No
COMPLETE QUESTIONS AND VERIFIED
SOLUTIONS
◉ 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.
◉ What are the maximum resolutions of the different microscopes?
Answer: Light: 200nm; SEM: 10nm; TEM: 0.2nm.
◉ What is the maximum magnification of the different microscopes?
Answer: Light: 1,500X; SEM: 100,000X; TEM: 500,000X.
◉ What are the main structures of all eukaryotic cells? Answer:
Nucleus; nucleolus; cytoplasm; cytoskeleton; plasma
, membrane;mitochondria; Golgi apparatus; smooth endoplasmic
reticulum; rough endoplasmic reticulum; ribosomes.
◉ What is the structure and function of the nucleus? Answer:
Surrounded by a double membrane (the nuclear envelope). Contains
chromatin (DNA wound around histones). Stores the human
genome, controls the cell by providing instructions for protein
synthesis.
◉ What is the structure and function of the nucleolus? Answer:
Made of RNA, produces ribosomes.
◉ What is the structure and function of the nuclear envelope?
Answer: A double membrane embeded with channel proteins
forming pores. Separates the nucleus from the rest of the cell. Pores
allow ribosomes and mRNA to leave the nucleus.
◉ What is the structure and function of the rough endoplasmic
reticulum (RER)? Answer: A system of fluid filled membranes
studded with ribosomes. Continuous with the nuclear membrane.
Large surface area formed by folding, enables lots of protein
synthesis. Proteins pinched off in vesicles transported to the Golgi
apparatus.
◉ What is the structure and function of the smooth endoplasmic
reticulum (SER)? Answer: A system of fluid filled membranes. No
