Using everything you've learned, tell me what you would look for to tell whether a cell was prokaryotic or eukaryotic. Be specific. HERE IS THE LESSON JUST IN CASE YOU NEED IT.

(1.1) As mentioned last lesson there are two types of cells, prokaryotic cells (prokaryotes) and eukaryotic cells (eukaryotes). Prokaryotic cells are the earliest cell types we've discovered, and are virtually unchanged from way back then to now. The only prokaryotic cells you'll find today are bacteria and archaea.

Escherichia coli: Scanning electron micrograph of Escherichia coli, grown in culture and adhered to a cover slip. This image was taken at Rocky Mountain Laboratories, NIAID, NIH. As a work of the U. S. federal government, this image is in the public domain.

(1.2) Eukaryotic cells, on the other hand, are much more varied and complex, and make up most living things. They will be different dependent upon what kind of cells they are: plant cells will be different from human blood cells; muscle cells will be different from bone cells. Eukaryotes contain a nucleus and other membrane-bound organelles.

(1.3) The study of cells is called cytology. Let's take a moment to learn a little more about the parts that make up the insides of cells--particularly eukaryotic cells. There will be a lot of unfamiliar terms in this lesson, take your time in reading each section--some parts of cells will only be mentioned now, and will be discussed in more detail later.

2. Parts of Cells: Structure and Protection
(2.1) Starting from the outside in, the first part of the cell is the cell wall. Not every type of cell will have a cell wall--it is a special cell component usually found in plants, fungi, and bacteria. Cell walls in plants are made chiefly of cellulose; fungi use chitin to make their cells walls; while bacterium use a substance called peptidoglycan. The cell wall is located outside the cell membrane.

(2.2) Since we learned a lot about the cell membrane last lesson, the next cell-part we'll talk about is the cytoskeleton. This is the framework of the cell, containing small microfilaments and larger microtubules which help in both the anchoring and the movement of the organelles. Microtubules are also important for cell division.

3. Vacuoles and Vesicles
(3.1) Finally we're getting to some of the organelles we keep mentioning! Vacuoles are single-membrane organelles, sacs that help in food digestion or helping the cell maintain its water balance. In plant cells they are known as tonoplasts. Many organisms will use vacuoles as storage areas. Vesicles are smaller serve as transport sections both inside and to the outside of the cell.

4. Endoplasmic Reticulum and Golgi Apparatus
(4.1) In the last lesson we learned a little about ribosomes and the endoplasmic reticulum (occasionally shortened to ER). There is both smooth and rough endoplasmic reticulum. Rough ER is rough because of all the ribosomes it contains. This type of ER releases newly made proteins into the cell. The smooth ER is ribosome free, and functions in poison detoxification.

(4.2) The golgi apparatus works with what the ribosomes and endoplasmic reticulum pump out: It is a series of flattened sacs that modifies, packages, stores, and transports materials out of the cell.

5. Lysosomes
(5.1) The golgi form vesicles called lysosomes. The lysosome is a membrane bound organelle containing a variety of enzymes. They help digest food particles inside or out side the cell, helping the cell to create energy needed to live. They are also instrumental in recycling cellular debris.
6. DNA
(6.1) The center of cellular activity is the nucleus. The nucleus occurs only in eukaryotic cells and controls the shape and features of the cell. The nucleus is bordered by a porous membrane, and contains thin fibers of DNA and protein called chromatin. It also contains the nucleolus, which is the area where ribosomes are constructed.

(6.2) Mitochondria contain their own DNA (termed mDNA) and may have come from bacteria-like organisms incorporated into eukaryotic cells over 700 million years ago. They create the high-energy compound ATP. Mitochondria are bounded by two membranes. The inner membrane folds into a series of cristae, which are the surfaces on which ATP is generated.

(6.3) Plastids are also membrane-bound organelles that only occur in plants and photosynthetic eukaryotes. (Chloroplasts, leukoplasts, and chromoplasts are some types of plastids.) Like mitochonria, chloroplasts have their own DNA, termed cpDNA, and contains a double membrane. The center section of chloraplasts contain stacks of coin-like grana, which make up the thylakoid. The thylakoid contains the light sensitive chemicals that allow photosynthesis to take place. The grana is surrounded by a gel-like material called the stroma.

A three-dimensional cross-section of an animal cell. This image is from a web publication of the NIH. As a work of the U. S. federal government, this image is in the public domain.