A Level Biology CAIE
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44 topics in 19 modules
☑️ Cell Structure 2 topics
- The microscope in cell studies
- Cells as the basic units of living organisms
☑️ Biological Molecules 4 topics
- Testing for biological molecules
- Carbohydrates and lipids
- Proteins
- Water
☑️ Enzymes 2 topics
- Mode of action of enzymes
- Factors that affect enzyme action
☑️ Cell Membranes and Transport 2 topics
- Fluid mosaic membranes
- Movement into and out of cells
☑️ The Mitotic Cell Cycle 2 topics
- Replication and division of nuclei and cells
- Chromosome behaviour in mitosis
☑️ Nucleic Acids and Protein Synthesis 2 topics
- Structure of nucleic acids and replication of DNA
- Protein synthesis
☑️ Transport in Plants 2 topics
- Structure of transport tissues
- Transport mechanisms
☑️ Transport in Mammals 3 topics
- The circulatory system
- Transport of oxygen and carbon dioxide
- The heart
☑️ Gas Exchange 1 topic
- The gas exchange system
☑️ Infectious Diseases 2 topics
- Infectious diseases
- Antibiotics
☑️ Immunity 2 topics
- The immune system
- Antibodies and vaccination
☑️ Energy and Respiration 2 topics
- Energy
- Respiration
☑️ Photosynthesis 2 topics
- Photosynthesis as an energy transfer process
- Investigation of limiting factors
☑️ Homeostasis 2 topics
- Homeostasis in mammals
- Homeostasis in plants
☑️ Control and Coordination 2 topics
- Control and coordination in mammals
- Control and coordination in plants
☑️ Inheritance 3 topics
- Passage of information from parents to offspring
- The roles of genes in determining the phenotype
- Gene control
☑️ Selection and Evolution 3 topics
- Variation
- Natural and artificial selection
- Evolution
☑️ Classification, Biodiversity and Conservation 3 topics
- Classification
- Biodiversity
- Conservation
☑️ Genetic Technology 3 topics
- Principles of genetic technology
- Genetic technology applied to medicine
- Genetically modified organisms in agriculture
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A Level Biology CAIE Revision Content
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A Level Biology CAIE - Cell Structure - The microscope in cell studies Content Preview
Cell Structure
The microscope in cell studies
The Microscope in Cell Analysis
- Microscopes allow us to visualise minute biological structures, aiding us in understanding the complexity of cells.
- There are three main types of microscopes used in cell biology: the light microscope, the transmission electron microscope (TEM) and the scanning electron microscope (SEM).
Light Microscope
- The light microscope uses light to illuminate the sample, generating a magnified image on a screen or photographic film.
- It has a relatively low resolution, so it can't resolve smaller structures like individual ribosomes.
- However, it allows for the viewing of living samples and processes over time, like mitosis.
Transmission Electron Microscope (TEM)
- The TEM works by transmitting a beam of electrons through a very thinly sliced specimen.
- TEMs have a high resolution and can magnify up to two million times, revealing minute cellular structures.
- However, they can't be used to image living cells or tissues, as samples have to be fixed, dehydrated, and embedded in resin.
Scanning Electron Microscope (SEM)
- The SEM emits a beam of electrons onto the surface of a specimen causing secondary electrons to bounce off and form a 3D image.
- SEM provides a three-dimensional view of the specimen surface, but with lower resolution compared to TEM.
- Similar to TEM, SEM requires extensive sample preparation rendering the samples unusable for studying live processes.
Electron Microscopy vs Light Microscopy
- Both electron microscopes (TEM & SEM) allow for much higher resolution and magnification than light microscopes, revealing far more cellular detail.
- However, they require more extensive sample preparation and cannot be used to study living specimens.
- Understanding the strengths and weaknesses of each type of microscope allows for their effective use in cell biology.
Question: What type of microscope would a cell biologist likely use to study the detailed internal structures of a cell, and why?
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