Level 6-Guiding Question: How different are the organelles between cells & why does it matter?
Structurally, plant and animal cells are very similar because they are both eukaryotic cells. They both contain membrane-bound organelles such as the nucleus, mitochondria, endoplasmic reticulum, golgi apparatus, lysosomes, and peroxisomes. Both also contain similar membranes, cytosol, and cytoskeletal elements. The functions of these organelles are extremely similar between the two classes of cells (peroxisomes perform additional complex functions in plant cells having to do with cellular respiration). However, the few differences that exist between plant and animals are very significant and reflect a difference in the functions of each cell.
Chloroplasts
In animal cells, the mitochondria produces the majority of the cells energy from food. It does not have the same function in plant cells. Plant cells use sunlight as their energy source; the sunlight must be converted into energy inside the cell in a process called photosynthesis. Chloroplasts are the structures that perform this function. They are rather large, double membrane-bound structures (about 5 micrometers across) that contain the substance chlorophyll, which absorbs sunlight. Additional membranes within the chloroplast contain the structures that actually carry out photosynthesis. Chloroplasts carry out energy |
conversion through a complex set of reactions similar to those performed by mitochondria in animals. The double membrane structure of chloroplasts is also reminiscent of mitochondria. The inner membrane encloses an area called the stoma, which is analogous to the matrix in mitochondria and houses DNA, RNA, ribosomes, and different enzymes. Chloroplasts, however, contain a third membrane and are generally larger than mitochondria.
The Cell Wall
Another structural difference between in plant cells is the presence of a rigid cell wall surrounding the cell membrane. This wall can range from 0.1 to 10 micrometers thick and is composed of fats and sugars. The tough wall gives added stability and protection to the plant cell. Cell walls are made from cellulose and hemi-cellulose that are structural carbohydrates that provide the rigidity that acts similar to an animal's skeleton. Cellulose is one of the main reasons that plant material are difficult to digest. |
Vacuoles
Are large, liquid-filled organelles found only in plant cells. Vacuoles can occupy up to 90% of a cell's volume and have a single membrane. Their main function is as a space-filler in the cell, but they can also fill digestive functions similar to lysosomes (which are also present in plant cells). Vacuoles contain a number of enzymes that perform diverse functions, and their interiors can be used as storage for nutrients or, as mentioned, provide place to degrade unwanted substances. |
Level 6-Investigation: What are the differences between the two?
Read the chapter on Animal & Plant cells and answer the question on the Google form below.
Level 6-Videos: Plant & Animal cell VDOs
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Level 6-ElaboratE: Comparing Animal and Plant Cells
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After you watch the animation on the Cells- Alive website build a models of Animal and Plant cells using Play-dough or other materials and label at least 8 organelles, or create a short video trailer using iMovie make sure you have the organelles featured as your main characters.
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Assignment product: Student project "Comparing Animal & Plant Cells"
Level 6-Review: Why do their differences matter?
Start by visiting the online textbook above or reading the presentation about animal and plants (click on the link entitled "sciencegeek.net". Use an iPad and open the app "Cell and Cells Structure" to compare plant and animal cells. Watch the VDO: "Prokaryotic and Eukaryotic cells" (see above in the VDO section).
Level 6-summary: Unit Test
Study for the unit test by review the terms and take the practice test by clicking on the button "Start Game"!