Cells and Microscopy

What Cells and Microscopy covers

Cells and Microscopy is examined in all three written papers — the specification states that Components 01, 02 and 03 can each assess content from any of the five modules, so nothing is confined to one paper. It covers microscopy and the cell theory, blood smears, staining and microscope drawings, blood cells and their structure, magnification and measuring cells, haemocytometer cell counts and dilutions, flow cytometry in blood analysis, ultrastructure of the animal cell, plant and prokaryotic cells, membrane lipids and the fluid mosaic model, movement of molecules across membranes and the roles of membranes and the secretion of proteins.

The 11 subtopics

Each one has its own page.

• Microscopy and the cell theoryRecall questions on the cell theory, resolution and magnification, the resolution limit of the light microscope, transmission and scanning electron microscopes, artefacts, the confocal scanning laser microscope, and why light microscopy is still used in clinical blood work.Open →
• Blood smears, staining and microscope drawingsRecall questions on preparing and drying a blood smear safely, differential staining with Leishman's stain, recognising erythrocytes, neutrophils, lymphocytes, monocytes and platelets in a stained smear, and the conventions for biological drawings, plan drawings and high-power drawings.Open →
• Blood cells and their structureRecall questions on the biconcave shape of erythrocytes and their lack of a nucleus and mitochondria, platelets and megakaryocytes, the functions of neutrophils, lymphocytes and monocytes, and what a differential white cell count shows.Open →
• Magnification and measuring cellsRecall questions on the magnification formula and unit conversions, calculating magnification and actual size from micrographs, typical cell sizes, calibrating an eyepiece graticule with a stage micrometer, field of view calculations and sources of measurement error.Open →
• Haemocytometer cell counts and dilutionsRecall questions on the ruling and 0.1 mm depth of the haemocytometer, volumes over its squares, loading it until Newton's rings appear, diluting blood and the boundary-line rule, calculating dilution factors and erythrocyte and leucocyte counts, recognising anaemia, and sources of counting error.Open →
• Flow cytometry in blood analysisRecall questions on how cells are made to pass a laser singly, what forward- and side-scattered light reveal, fluorescent antibody labelling, reading a scatter plot, and the technique's limitations.Open →
• Ultrastructure of the animal cellRecall questions on the ultrastructure of the nucleus, nuclear pores and nucleolus, rough and smooth endoplasmic reticulum, ribosomes, the Golgi apparatus, lysosomes and vesicles, mitochondria and their cristae, the cytoskeleton and centrioles.Open →
• Plant and prokaryotic cellsRecall questions on the structure and function of chloroplasts, palisade mesophyll cells, the vacuole, cell sap and tonoplast, the cellulose cell wall, and prokaryotic cells with their nucleoid, plasmids, mesosomes, pili and flagella, and how they differ from eukaryotic cells.Open →
• Membrane lipids and the fluid mosaic modelRecall questions on triglycerides and ester bonds, saturated and unsaturated fatty acids, phospholipids and the bilayer, the fluid mosaic model with intrinsic and extrinsic proteins, cholesterol, glycolipids and glycoproteins, and why membranes leak above about 40 °C.Open →
• Movement of molecules across membranesRecall questions on simple and facilitated diffusion, channel and carrier proteins, active transport and respiratory inhibitors, endocytosis, phagocytosis, pinocytosis and exocytosis, surface area to volume ratio in agar cubes, and investigating membrane permeability with beetroot and a colorimeter.Open →
• The roles of membranes and the secretion of proteinsRecall questions on the roles of the plasma membrane, compartmentalisation, membranes that hold enzymes and store energy as ion gradients, cell signalling, and the secretory pathway from nucleus and rough endoplasmic reticulum through the Golgi apparatus, transport vesicles and motor proteins to exocytosis.Open →

What you need to know

Answer each one before you reveal it.

Take Cells and Microscopy further

The same content, four other ways.

Commonly confused

Pairs that lose marks when they are blurred together.

• Magnification vs Resolution

  Magnification: how many times larger an image appears than the real object it was made from. Resolution: the shortest distance between two points at which they can still be seen as separate, set by the wavelength of the radiation used.

• Rough endoplasmic reticulum vs Smooth endoplasmic reticulum

  Rough endoplasmic reticulum: flattened sacs studded with ribosomes, where newly made proteins are folded and packaged for transport. Smooth endoplasmic reticulum: a network of tubules bearing no ribosomes, where lipids and steroids are synthesised.

• Intrinsic membrane protein vs Extrinsic membrane protein

  Intrinsic membrane protein: one that spans the whole width of the bilayer, with hydrophobic amino acids on its outside, and acts as a channel, carrier or pump. Extrinsic membrane protein: one attached to a single surface of the bilayer only, which does not cross it and acts as an enzyme, a receptor or an anchorage point.

Questions from this topic

Each one with the model answer underneath.

1. 1

   What does the cell theory state?

   Model answer

   It states that all living organisms are composed of one or more cells, that the cell is the basic unit of structure and function in living things, and that all cells arise from pre-existing cells.

2. 2

   Why could the cell theory not have been proposed before the microscope was developed?

   Model answer

   Cells are far too small to be seen with the unaided eye, so it was only when lenses of sufficient magnification and resolution allowed cells to be observed directly in many different tissues that the generalisation could be made and tested.

3. 3

   Define the resolution of a microscope.

   Model answer

   Resolution is the shortest distance between two points that can still be seen as two separate points rather than merging into one.

4. 4

   Why does increasing magnification beyond a certain point reveal no extra detail?

   Model answer

   Once the limit of resolution has been reached the image is simply enlarged and becomes progressively more blurred, because no additional detail can be separated by the instrument.

5. 5

   What sets the limit of resolution of a light microscope at roughly 200 nm?

   Model answer

   The wavelength of visible light, since two points closer together than about half a wavelength of the light used cannot be resolved.

6. 6

   State the approximate maximum useful magnification of a light microscope.

   Model answer

   About ×1500.

What is inside Levo

Six ways to work the same material.

Cells and Microscopy revision questions

What does Cells and Microscopy cover in OCR A-Level Biology B?

11 subtopics: microscopy and the cell theory, blood smears, staining and microscope drawings, blood cells and their structure, magnification and measuring cells, haemocytometer cell counts and dilutions, flow cytometry in blood analysis, ultrastructure of the animal cell, plant and prokaryotic cells, membrane lipids and the fluid mosaic model, movement of molecules across membranes and the roles of membranes and the secretion of proteins. Each one has its own page with questions and model answers.

How is Cells and Microscopy organised?

By the OCR H422 specification, subtopic by subtopic, so it matches the order you are taught it in.