Onion Peel Cell Lab Quiz: Observing Mitochondria

Study Notes

Microscopy and Temporary Mounts

Use a thin camel hair paintbrush to transfer onion peel for observation.
Safranin solution is applied to the peel before adding a coverslip; prevent air bubbles.
Temporary mounts allow for observation under low and high power of a compound microscope.
Similar structures in onion bulbs of different sizes indicate that cells are uniform regardless of onion size.

Cells and Their Characteristics

Cells are the basic building units of all organisms, including onions.
The cell membrane acts as a selectively permeable barrier, regulating substance movement.
Diffusion facilitates the movement of substances from high to low concentration areas.
CO2 diffuses out of cells when its concentration is higher inside than outside, while O2 enters when its concentration decreases inside the cell.

Diffusion and Osmosis

Diffusion is vital for gas exchange between cells and their external environment.
Osmosis describes the diffusion of water across a selectively permeable membrane towards higher solute concentration.
The effect of surrounding solutions on cells:
- Hypotonic Solution: Cell gains water, causing swelling.
- Isotonic Solution: No net water movement; cell remains the same size.
- Hypertonic Solution: Cell loses water, potentially leading to shrinkage.

Prokaryotic vs. Eukaryotic Cells

Prokaryotic cells are generally small (1-10 µm); eukaryotic cells are larger (5-100 µm).
Prokaryotic nuclear regions lack a defined membrane; eukaryotic nuclear regions are well-defined and membrane-bound.
Prokaryotic cells typically have a single chromosome; eukaryotic cells contain multiple chromosomes.
Membrane-bound organelles are absent in prokaryotic cells but present in eukaryotic cells.

Endoplasmic Reticulum (ER)

The ER is a network of membranes, comprising two types: rough (RER) and smooth (SER).
RER appears rough due to ribosomes attached, which are essential for protein synthesis.
Proteins synthesized in RER are distributed throughout the cell as needed.
SER is involved in lipid production, vital for cell function and membrane biogenesis, along with synthesis of enzymes and hormones.

Description

Test your knowledge on using a compound microscope to observe an onion peel temporary mount. Learn about the steps involved in preparing the mount and observing the slide under different magnifications.