Cells and Microscopes Demonstrations

See also: Microbiology

Cells are the fundamental units of life, and microscopes are the tools that make them visible. This category focuses on cell structures, how they can be studied, and the diversity of cell types. Exploring cells with microscopes provides insight into how living organisms are built and function at the microscopic level.

Demonstration	Materials	Difficulty	Safety	Summary
Agar Cubes Diffusion	★★☆	★★☆	★★☆	Agar cubes infused with a pH indicator model how diffusion occurs in cells. When the cubes are placed in vinegar, hydrogen ions diffuse inward, changing the cube’s color. By comparing cubes of different sizes, students see how surface area-to-volume ratio impacts diffusion efficiency and why larger cells face transport challenges.
DNA Extraction From Kiwi Fruit	★★☆	★★☆	★☆☆	This experiment demonstrates how DNA can be extracted from fruit cells, such as from kiwi fruit. The DNA becomes visible as strands at the boundary between the fruit extract and chilled ethanol.
Exploring Pond Water with a Microscope	★★☆	★☆☆	★★☆	Students collect pond water samples and prepare microscope slides to observe microorganisms such as algae, protozoa, rotifers, and tiny crustaceans. The activity demonstrates biodiversity and introduces microscopy techniques for studying aquatic ecosystems.
Gram Staining	★★☆	★☆☆	★★☆	Gram staining is a widely used technique in microbiology to distinguish between Gram-positive and Gram-negative bacteria. By applying a series of stains and washes, students observe differences in bacterial cell walls that cause some cells to appear purple (Gram-positive) and others pink (Gram-negative) under the microscope.
Human Cheek Cells Under Microscope	★★☆	★☆☆	★★☆	Students collect a sample of their own cheek cells, prepare a wet mount slide, stain the cells with methylene blue or iodine, and observe cell structures such as the nucleus, membrane, and cytoplasm under a microscope.
Laser Microscope	★★☆	★★☆	★★☆	A laser is focused through a water droplet at the tip of a syringe, which acts as a convex lens. The light is projected onto a screen, allowing small aquatic organisms and impurities in the water to be observed.
Mitosis in Onion Root Cells	★★☆	★☆☆	★☆☆	Students use digitized images of onion root tips to identify different stages of the cell cycle. By counting the number of cells in each stage, they estimate how much time cells spend in interphase, prophase, metaphase, anaphase, and telophase.
Observing Yogurt Bacteria	★★☆	★☆☆	★★☆	Students prepare microscope slides of live yogurt cultures to observe probiotic bacteria such as Lactobacillus and Streptococcus.
Onion Root Tip Mitosis	★★☆	★★☆	★☆☆	This experiment demonstrates mitosis by preparing and observing stained onion root tip cells under a compound microscope. Students identify the stages of mitosis while understanding why onion root tips are suitable for studying active cell division.
Osmosis and Diffusion with Dialysis Tubing	★★☆	★★☆	★★☆	Dialysis tubing is filled with a starch-glucose solution and placed in iodine solution. The starch remains inside, glucose diffuses out, and iodine diffuses in, showing that small molecules can cross the semi-permeable membrane while larger molecules cannot.
Strawberry DNA Extraction	★★☆	★★☆	★★☆	By crushing strawberries and treating them with detergent, salt, and alcohol, students can extract visible strands of DNA. The detergent breaks open the cells, salt keeps proteins separate, and alcohol causes DNA to clump so it can be seen with the naked eye.
Using a Microscope	★★☆	★☆☆	★☆☆	Students learn how to properly use a microscope to observe prepared slides of plant and animal cells. They practice focusing under low and high power and record biological diagrams of what they see.
Viewing Onion Cells	★★☆	★☆☆	★☆☆	Students prepare a microscope slide using a thin layer of onion epidermis, stain it with food coloring or iodine, and observe the cell structures such as the cell wall, nucleus, and cytoplasm under different magnifications.
Wet Mount Microscope Slide	★★☆	★☆☆	★☆☆	A wet mount slide allows you to observe living cells or microorganisms in a drop of liquid under a microscope. It is a simple and quick method, but requires careful handling to avoid air bubbles and excess liquid.
Build a Cell	★☆☆	★☆☆	★☆☆	Students create models of plant and animal cells by cutting out and labeling cell parts, gluing them together, and learning about their functions. The activity reinforces understanding of cell structures, their roles, and differences between plant and animal cells.
Egg Yolk Cell Membrane	★☆☆	★☆☆	★☆☆	Water, oil, and egg yolk to model how cell membranes form and function. The interaction shows how membranes act as barriers, keeping environments separate while allowing cells to exist and replicate.
Hair Sample Analysis	★☆☆	★☆☆	★☆☆	Students act as forensic scientists by examining hair samples collected from suspects and a crime scene. Using magnifying tools, they compare features such as color, thickness, and curliness to identify the most likely suspect.
Limp Celery	★☆☆	★☆☆	★☆☆	Celery pieces are soaked in salt water and fresh water to show how water moves in or out of plant cells by osmosis, changing texture from rigid to limp.
Naked Egg Osmosis	★☆☆	★★☆	★☆☆	An egg with its shell dissolved in vinegar (a “naked egg”) demonstrates osmosis. In water, the egg swells as water enters through the semi-permeable membrane. In corn syrup, the egg shrinks as water leaves the egg.
Shrink a Potato with Osmosis	★☆☆	★☆☆	★☆☆	Potato strips are soaked in salt solutions of different concentrations to observe size and flexibility changes caused by osmosis across cell membranes. Measurements before and after soaking reveal whether water moved into or out of the potato cells.
Smelly Balloons	★☆☆	★☆☆	★☆☆	Students place small amounts of scented liquids inside latex balloons, inflate them, and identify the scent over time. The activity models diffusion across a barrier and introduces terms like concentration gradient, semi-permeable membrane, and equilibrium.

Materials
★☆☆ Easy to get from supermarket or hardware store
★★☆ Available in most school laboratories or specialist stores
★★★ Requires materials not commonly found in school laboratories

Difficulty
★☆☆ Can be easily done by most teenagers
★★☆ Available in most school laboratories or specialist stores
★★★ Requires a more experienced teacher

Safety
★☆☆ Minimal safety procedures required
★★☆ Some safety precautions required to perform safely
★★★ Only to be attempted with adequate safety procedures and trained staff