Download The Cell: Structure and Function

Name ___________________
Date ________________
Block _______
The Cell: Structure and Function
Diagram
/16
Lab Report
/30
Background Information: One of the first scientists to look at cells under a microscope was an English scientist
by the name of Robert Hooke. He viewed and described the appearance of cork under the microscope and decided
to name the tiny box-like structures that he observed “cells” because they looked like the small chambers where
monks lived.
By the early part of the 19th century, it was accepted that all living things are composed of cells. Cells
come in a variety of shapes and sizes, and cells perform different functions. Although cells may appear outwardly
different, they resemble each other because they share common structures. In this lab you will look at two types of
cells, a human cheek cell and an onion cell and see how they are similar and how they are different.
Objectives:
1.
Understand the differences between prokaryotes and eukaryotes and identify structures
characteristics of each.
2.
Prepare a wet mount to view cells with a compound light microscope.
3.
Understand the function of organelles visible with a light microscope.
4.
Examine a cell’s structure and determine whether it is from a plant or animal.
1. List the 3 tenets of the Cell Theory (3pts)
a. _____________________________________________________________
b. _____________________________________________________________
c. _____________________________________________________________
2. Write a short description of each of the following (5pts):
--cell membrane __________________________________________________________
--cytoplasm _____________________________________________________________
--nucleus ________________________________________________________________
--organelle ______________________________________________________________
---nuclear membrane ______________________________________________________
Procedure: Onion Cell
1. Get a clean slide. Place a drop of water on the slide. Take a piece of onion from the beaker on the teacher’s
demo table. Fold the onion so that it doesn’t completely break. Peel back one half of the onion so that you are able
to obtain one layer of epidermal tissue.
2. Place the layer of tissue on a slide and then add a small drop of iodine to the slide. Place a coverslip on the slide,
slowly lowering it over the sample to avoid creating air bubbles.
3. Place the slide on the stage and view the slide under the low objective. Once you have found an area with
several good cells, switch to a higher objective. Remember to only use the fine adjustment to focus at higher
powers.
4. Draw one or two onion cells in detail. Label the following: cell membrane, cytoplasm, cell wall, vacuole,
nuclear membrane, and nucleus. When making a drawing of objects as seen under a microscope, it is important
to
*draw on unlined paper only
*draw clearly; make distinct lines
*only use pencil
*provide the name of the object and the power under which it was observed.
---Sketch. Draw your cells to scale (6 pts)
Low ____X
Med ____X
High ____X
5. Clean the slide and return.
6. On a blank piece of paper, complete a sketch of an onion cell under high power. Use all the rules for drawing
biological diagrams. See rubric attached.
Discussion Questions: (16pts)
Answer the following questions in complete sentences unless instructed to do otherwise.
1. Why do we need to use iodine instead of just water in this lab?
2. List 2 organelles that were NOT visible but should have been in the cheek cell.
3. How does the shape of the onion cells differ from that of animal cells?
4. Which of the organelles you observed are only found in plant cells?
5. What structures were you able to see that are found in animal and plant cells?
6. Both plant cells and animal cells contain mitochondrion and yet there were not visible in the cells you viewed in
this lab. Does this mean that these organelles are not found in onion cells? Why or why not? Explain your
reasoning.
7. In class and in your reading you learned that one difference between plant and animal cells is that plant cells
contain chloroplasts. Were any chloroplasts visible in the onion cells? Why or why not? Explain your reasoning.
8. In plant cells, each of the small regularly shaped units are cells surrounded by cell walls made primarily of
cellulose. Iodine is a stain specific for starch. Why do you think we used iodine instead of food colouring to stain
the onion cells?