Mr kousen is… Water Man

What are you made of ?

You could say atoms or elements.  That would be right, but rocks & student desks &  pizza boxes are made of atoms and elements too. What makes you different from those things ?

You could say organic compounds.  That would be a better response I guess.  Organic compounds come from living things.  That answer would distinguish us from rocks & desks & pizza boxes.  But other things are composed of organic compounds too; things like sugar and cow poop.

So I guess a better question is : what are you made of that makes you alive ?

A pretty big question, kind of philosophical.  Since I'm a science teacher and not a philosopher, we'll just focus on the scientific units that make up each & every living thing on this planet : CELLS.

In just a second we'll review some of the dudes who were among the first to study cells.  In order for any of these guys to make any observations or discoveries, there had to have been certain technological tools available to them. The biggest of these tools was certainly the compound light microscope.  An understanding of the microscope is "a must" in any biology course.
I have dedicated a page to the microscope in my "LAB REVIEW" Pages.  To look at that now, click here.

For now, here is a quick exercise to review some important tools & techniques related to cell study. Match the tool or technique with its description. 
 
 

Tools & Techniques For Cell Study

compound microscope electron microscope microdissection apparatus phase-contrast microscope simple microscope staining stereomicroscope ultracentrifuge

1. microscope composed of one lens
2. microscope that creates an image using two lenses
3. adding a chemical that makes certain cell structures easier to see, usually kills the cells
4. a high resolution microscope used to study living cells
5. microscope that provides images of the greatest magnification & resolution
6. microscope with two oculars, usually used during dissections to observe relatively large structures in more detail
7. small tools used to remove or transplant cell organelles
8. machine that can be used to separate cell organelles according to their densities

OK, let's continue our review/study of the cell by reviewing the guys who first studied the cell.  Number from 1-7 on a piece of paper & match each dude with his claim to fame. 

1) first to use the term "protoplasm"
2) while studying cork, he was the first to use the term "cell"
3) stated that all new cells come from other living cells
4) studied many microscopic organisms using a strong simple microscope
5) stated that all plants are composed of cells
6) stated that all animals are composed of cells
7) "discovered" the nucleus

• the exact wording of the cell theory may vary depending on what textbook you use, but it's always composed of those 3 ideas
• the "life functions" referred to in statement #2 are the same ones covered on my life functions page
• if you peek back to the scientists review, you may notice that statements #1 & 2 are primarily a combo of Schleiden & Schwann's research, & statement #3 is Virchow's big idea
• keep in mind that The Cell Theory is based on over 300 years of scientific investigations, beginning with Hooke in 1665 and continuing through today
• some notable questions or "exceptions" to the Cell Theory do exist

1. Viruses - are they alive ?
According to the Cell Theory we have to say "no" because a virus is not a cell.  Viruses are made of two chemicals, protein & nucleic acid, but have no membranes, nucleus, or protoplasm. They appear to be alive when they reproduce after infecting a host cell.
2. Mitochondria & chloroplasts.
These cell organelles (small structures inside the cell) have their own genetic material & reproduce independently from the rest of the cell.
3. Where did the first cell come from ?
According to statement #3 of the cell theory, all cells come from other living cells.  So how did the first cell ever appear ?  It's the old "chicken & egg" dilemma.  We will investigate this question (& its possible answer) in more detail during the Evolution Unit.

ORGANELLE \or-ga-'nel\ n : 1. smaller structures within a cell, each organelle has a certain function.

PROTOPLASM \pro-to-paz-'um\ n : 1. general term for the living material in a cell

YOU HAVE TWO  MISSIONS RELATED TO THIS SECTION :
Mission #1 : be able to identify all cell organelles in a diagram or picture
Mission #2 : be able to describe the function of each cell organelle

In this course we concern ourselves mostly with the differences between prokaryotic cells & eukaryotic cells, and between animal cells & plant cells.

The prokaryotic-eukaryotic difference is easy; prokaryotic cells do not have a nucleus & eukaryotic cells do. Remember that all prokaryotic organisms are classified in the Moneran Kingdom. The organisms in the other four Kingdoms have eukaryotic cells.
(If you want to review the 5 Kingdoms, check out my "5 Kingdoms Page".)

The animal-plant cell differences aren't too bad either.  Basically, some organelles are found in plant cells and not animal cells & vice versa.  More on that in a minute.

First ......

A little note : cell diagrams tend to be either overly complicated (fancy 3-D graphics) or too simplified (bare minimum "know this" stuff).  Diagrams like the ones  here have been seen in Regents Review Books & tests so I figure they are the most practical for us to use.

Take a look at the answers.
 
 
 

If you can label diagrams of a plant or animal cell, then you pretty much know what the differences are between them.

This table summarizes the differences :

Now that you know what each organelle looks like, it's time to get the functions of each organelle to stick to your brain somewhere.  Choose an organelle from the word bank for each description in #1-15.
 
 

WORD BANK

cell membrane cell wall chloroplast centrioles centrosome cytoplasm endoplasmic reticulum golgi apparatus lysosome mitochondria nuclear membrane nucleolus nucleus ribosomes vacuole

1. liquid inside the cell, mostly water
2. made of lipids & proteins, it is the boundary of the cell; it controls what substances enter or leave the cell
3. "control center of the cell" where genetic material (DNA) is found
4. nonliving border that surrounds plant cells, made of cellulose
5. very small organelles that are the sites of protein synthesis
6. system of tubes through the cytoplasm involved in transporting materials
7. a flat stack of tubes involved in "packaging" materials that will exit the cell
8. site of cellular respiration (where energy is released from nutrients)
9. storage sac for water or other materials
10. controls what enters or exits the nucleus
11. dark round structure within the nucleus that produces ribosomes
12. specialized vacuole that stores digestive enzymes
13. structure in animal cells involved in cell division
14. spherical structure that contains the centrioles
15. site of photosynthesis in plant cells
 

OK, let's have even more fun & check your answers !

Um, some last minute thoughts on organelles :

• Some organelles have two names : golgi apparatus = golgi bodies; cell membrane = plasma membrane.
• The organelles that you, an average biology student, would see in lab using a compound light microscope would be : the cell membrane, cell wall, nucleus, nucleolus, chloroplasts, large vacuoles.  Other organelles require higher magnification and better resolution microscopes that typical high schools don't have on hand.
• You should know a few more details about the plasma (cell) membrane.  It is composed of lipids (fat molecules) & protein in what is described as the "Fluid Mosaic Model".

The Fluid Mosaic Model of the cell membrane looks like so :

All of the molecules (lipids & proteins) "float" around, exchanging positions. This gives the membrane flexibility. The microscopic spaces between the molecules allow certain materials to enter or leave the cell.  This is the primary function of the plasma membrane.  The membrane is described as "selectively permeable", meaning it selects what substances enter or leave.  In other words, not all substances are allowed to pass through the membrane.

StuDyiNG the CeLL - ANSWER PAGES
 

Answers to "Cell Scientists Matching" :
1) J. Purkinje
2) R. Hooke
3) R. Virchow
4) A. von Leeuwenhoek
5) M. Schleiden
6) M. Schwann (has an "a" in last name - animal cells)
7) R. Brown
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Answers to "Animal Cell Diagram" :

 

1. lysosome
2. endoplasmic reticulum
3. chromosome (DNA)
4. golgi body (apparatus)
5. vacuole
6. mitochondria
7. ribosome
8. nucleolus
9. nucleus (nuclear membrane would also be OK)
10. centrioles
11. plasma membrane
12. cytoplasm

NOTES & TIPS :
#1 - generally, lysosomes are illustrated as "shaded-in" circles or ovals.
#2 - channels running through the cytoplasm
#3 - the genetic material of the cell.  humans have 46 chromosomes in each body cell (except eggs & sperm).  this cell is eukaryotic because its genetic material is inside a nucleus.
#4 - stacks of membranes (like pancakes)
#5 - an "empty" oval or circle
#6 - you can recognize the mitochondria by the zig-zag line that is usually drawn in them.  these represent internal membranes where respiration reactions occur.
#7 - very small dots, sometimes on the endoplasmic reticulum, sometimes out floating in cytoplasm
#8 - drawn as a dark circle inside the nucleus
#9 - generally depicted as the largest "shaded-in" circle inside the cell
#10 - drawn in pairs, two cylinder-like structures at right angles to each other
#11 - the outer boundary
#12 - the watery fluid that everything else floats in

1. nucleus
2. nucleolus
3. plasma membrane
4. cytoplasm
5. cell wall
6. vacuole
7. chloroplast
 
 
 
 
 

NOTES & TIPS :
#1 - looks like an animal cell nucleus --- usually the largest "shaded-in" circle
#2 - same as an animal cell --- dark circle inside the nucleus
#3 - the plasma membrane in a plant cell is just inside the cell wall
#4 - cytoplasm is cytoplasm, everything else floats around in it
#5 - outermost boundary in a plant cell, looks like a picture frame.  it is nonliving, not very flexible, and made of a polysaccharide called cellulose
#6 - drawn as "empty" areas in the cell, usually very large in plant cells
#7 - small dark ovals.  sometimes get confused with mitochondria --- remember that mitochondria have the zig-zag, chloroplats are usually shaded "solid"

ANSWERS to "Organelle Functions" Matching :
1. cytoplasm
2. cell membrane
3. nucleus
4. cell wall
5. ribosomes
6. endoplasmic reticulum
7. golgi apparatus
8. mitochondria
9. vacuole
10. nuclear membrane
11. nucleolus
12. lysosome
13. centrioles
14. centrosome
15. chloroplast
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