Grade: Grade 5 Subject: Science Unit: Cells SAT: ProblemSolving+DataAnalysis ACT: Science

Investigation Lab: Observing Cells

Learn

Becoming a Cell Scientist

Scientists use microscopes to observe cells because cells are too small to see with our eyes alone. In this lab, you'll learn how to use a microscope properly and observe real plant and animal cells!

When scientists make observations, they carefully record what they see, draw detailed diagrams, and compare their findings. Today, you'll practice these important scientific skills.

Safety First!

  • Always carry microscopes with two hands (one on the arm, one under the base)
  • Never touch the lens with your fingers
  • Start with the lowest magnification and work your way up
  • If using glass slides, handle them carefully to avoid cuts
  • Wash your hands after handling specimens

Parts of a Microscope

Before we start observing, let's review the important parts of a microscope:

  • Eyepiece (Ocular lens) - Where you look through
  • Objective lenses - Different magnifications (usually 4x, 10x, 40x)
  • Stage - Where the slide sits
  • Light source - Illuminates the specimen
  • Coarse focus knob - Makes big adjustments
  • Fine focus knob - Makes small, precise adjustments

Lab Materials

🔬 Compound microscope
🧅 Onion (for plant cells)
💧 Cheek cells (for animal cells)
📋 Glass slides & coverslips
💜 Iodine stain (for plant cells)
💙 Methylene blue (for cheek cells)
💧 Water dropper
📝 Lab notebook

Lab Procedure

Part A: Observing Plant Cells (Onion)

  1. Prepare the slide: Peel a thin, transparent layer from the inside of an onion scale (the curved piece).
  2. Place the specimen: Lay the onion skin flat on a glass slide. Add one drop of water.
  3. Add stain: Add one drop of iodine stain to make the cells easier to see.
  4. Cover: Carefully place a coverslip at an angle and lower it slowly to avoid air bubbles.
  5. Focus: Start with the lowest objective (4x). Look from the side while lowering the lens close to the slide.
  6. Observe: Look through the eyepiece and slowly raise the lens using the coarse focus until the cells come into view.
  7. Increase magnification: Switch to 10x, then 40x. Use only the fine focus at higher magnifications.
  8. Record: Draw what you see and label the parts you can identify.

Part B: Observing Animal Cells (Cheek Cells)

  1. Collect cells: Gently scrape the inside of your cheek with a clean toothpick.
  2. Transfer: Smear the toothpick onto the center of a clean glass slide.
  3. Add stain: Add one drop of methylene blue to make the cells visible.
  4. Cover: Carefully place a coverslip over the specimen.
  5. Focus: Start with 4x magnification and use the same focusing technique as before.
  6. Observe: Look for flat, rounded cells with a dark spot (nucleus) in the center.
  7. Compare: Note how these cells look different from the plant cells.
  8. Record: Draw what you see and label the parts you can identify.

Recording Your Observations

Feature Plant Cell (Onion) Animal Cell (Cheek)
Shape
Cell wall visible?
Nucleus visible?
Cell membrane visible?
Arrangement of cells
Magnification used

Draw Your Cells

Plant Cell Drawing

[Draw your plant cell here on paper or in your lab notebook]

Label these parts if you can see them:

Animal Cell Drawing

[Draw your animal cell here on paper or in your lab notebook]

Label these parts if you can see them:

Drawing Tip: Scientific drawings should be large, clear, and neat. Use pencil so you can erase mistakes. Draw what you actually see, not what you think cells should look like!

Practice

Answer these questions based on your lab observations and what you've learned.

Question 1: Why do we add stain to cell samples?

A) To kill the cells
B) To make cell structures easier to see
C) To make the cells grow larger
D) To change the cell's shape

Question 2: When observing cells with a microscope, why should you start with the lowest magnification?

A) Low magnification shows more detail
B) It's easier to find and focus on your specimen first
C) High magnification can damage the microscope
D) The cells look better at low magnification

Question 3: A student observes rectangular cells arranged in neat rows with visible cell walls. What type of cells are they most likely observing?

A) Plant cells
B) Animal cells
C) Bacteria
D) Cannot determine from this information

Question 4: Why is it important to lower the coverslip slowly at an angle?

A) To crush the cells so they're flat
B) To add more stain to the sample
C) To prevent air bubbles from forming
D) To make the slide stick to the stage

Question 5: What is the total magnification if you use a 10x eyepiece with a 40x objective lens?

A) 50x
B) 100x
C) 400x
D) 4000x

Question 6: Which part of the microscope should you use ONLY for small adjustments at high magnification?

A) Coarse focus knob
B) Fine focus knob
C) Stage clips
D) Light adjustment

Question 7: During your observation, you notice the cheek cells look rounder and less organized than the onion cells. What explains this difference?

A) The cheek cells are damaged
B) Animal cells lack a rigid cell wall
C) The stain wasn't applied correctly
D) The microscope magnification was too low

Question 8: Which of the following is NOT a proper microscope safety rule?

A) Carry with two hands
B) Start with lowest magnification
C) Touch the lens to clean smudges with your finger
D) Handle glass slides carefully

Check Your Understanding

Lab Reflection Questions

  1. What was the most challenging part of using the microscope?
  2. How did the plant cells and animal cells look different under the microscope?
  3. Why is it important for scientists to make detailed drawings and observations?
  4. If you could observe any other type of cell, what would you choose and why?
Real Scientists: The observations you made today are similar to what Robert Hooke did in 1665 when he first discovered cells by looking at cork under a microscope. You're following in the footsteps of great scientists!

Summary

🔬

Microscope Skills

Focus from low to high magnification

💜

Staining

Makes cell structures visible

📝

Recording

Draw and label observations

🔍

Comparing

Plant vs animal cell differences

Next Steps

  • Complete your lab drawings with detailed labels
  • Write a conclusion paragraph summarizing what you observed
  • Move on to learn about organizing and graphing cell data