Cells are the Starting Point - http://www.biology4kids.com/files/cell_main.html_
Cells are the Starting Point
All living organisms on Earth are divided into cells. The main concept of cell theory is that cells are the basic structural unit for all organisms. Cells are small compartments that hold the biological equipment necessary to keep an organism alive and successful. Living things may be single-celled or they may be very complex such as a human being.
There are smaller pieces that make up cells such asmacromolecules and organelles. A protein is an example of a macromolecule while a mitochondrion is an example of an organelle. Cells can also connect to form larger structures. They might group together to form the tissues of the stomach and eventually the entire digestive system. However, in the same way that atoms are the basic unit when you study matter, cells are the basic unit for biology and organisms.
In larger organisms, the main purpose of a cell is to organize. Cells hold a variety of pieces and each cell type has a different purpose. By dividing responsibilities among different groups of cells, it is easier for an organism to survive and grow.
If you were only made of one cell, you would be very limited. You don't find single cells that are as large as a cow. Cells have problems functioning when they get too big. Also, if you were only one cell you couldn't have a nervous system, no muscles for movement, and using the internet would be out of the question. The trillions of cells in your body make your way of life possible.
One Name, Many Types
There are many types of cells. In biology class, you will usually work with plant-like cells and animal-like cells. We say "animal-like" because an animal type of cell could be anything from a tiny microorganism to a nerve cell in your brain. Biology classes often take out a microscope and look at single-celled microbes from pond water. You might see hydra, amoebas, or euglena.
Plant cells are easier to identify because they have a protective structure called a cell wall made of cellulose. Plants have the wall; animals do not. Plants also have organelles such as the green chloroplast or large, water-filledvacuoles. Chloroplasts are the key structure in the process of photosynthesis.
Cells are unique to each type of organism. If you look at very simple organisms, you will discover cells that have no defined nucleus (prokaryotes) and other cells that have hundreds of nuclei (multinucleated).
Humans have hundreds of different cell types. You have red blood cells that are used to carry oxygen (O2) through the body and other cells specific to your heart muscle. Even though cells can be very different, they are basically compartments surrounded by some type of membrane.
All living organisms on Earth are divided into cells. The main concept of cell theory is that cells are the basic structural unit for all organisms. Cells are small compartments that hold the biological equipment necessary to keep an organism alive and successful. Living things may be single-celled or they may be very complex such as a human being.
There are smaller pieces that make up cells such asmacromolecules and organelles. A protein is an example of a macromolecule while a mitochondrion is an example of an organelle. Cells can also connect to form larger structures. They might group together to form the tissues of the stomach and eventually the entire digestive system. However, in the same way that atoms are the basic unit when you study matter, cells are the basic unit for biology and organisms.
In larger organisms, the main purpose of a cell is to organize. Cells hold a variety of pieces and each cell type has a different purpose. By dividing responsibilities among different groups of cells, it is easier for an organism to survive and grow.
If you were only made of one cell, you would be very limited. You don't find single cells that are as large as a cow. Cells have problems functioning when they get too big. Also, if you were only one cell you couldn't have a nervous system, no muscles for movement, and using the internet would be out of the question. The trillions of cells in your body make your way of life possible.
One Name, Many Types
There are many types of cells. In biology class, you will usually work with plant-like cells and animal-like cells. We say "animal-like" because an animal type of cell could be anything from a tiny microorganism to a nerve cell in your brain. Biology classes often take out a microscope and look at single-celled microbes from pond water. You might see hydra, amoebas, or euglena.
Plant cells are easier to identify because they have a protective structure called a cell wall made of cellulose. Plants have the wall; animals do not. Plants also have organelles such as the green chloroplast or large, water-filledvacuoles. Chloroplasts are the key structure in the process of photosynthesis.
Cells are unique to each type of organism. If you look at very simple organisms, you will discover cells that have no defined nucleus (prokaryotes) and other cells that have hundreds of nuclei (multinucleated).
Humans have hundreds of different cell types. You have red blood cells that are used to carry oxygen (O2) through the body and other cells specific to your heart muscle. Even though cells can be very different, they are basically compartments surrounded by some type of membrane.
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The Plant Cell
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Local Pond Water
Protozoa
Protozoa are a diverse group of unicellular eukaryotic organisms.Historically, protozoa were defined as single-celled organisms with animal-like behaviors, such as motility and predation.
Paramecium
Paramecium is a genus of unicellular ciliated protozoan, commonly studied as a representative of the ciliate group. Paramecia are widespread in freshwater, brackish, and marine environments and are often very abundant in stagnant basins and ponds.
Microscope Experiments
Half the fun of a compound microscope lies in the slide preparation. This is particularly true with younger children where slide preparation and viewing provides a wonderful opportunity for cross-generational bonding. Moreover, slide preparation is engaging without being overly taxing - a good combination for younger children. For students and hobbyists, these basic processes can be applied to any number of different experiments - limited only by your imagination!
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CORK CELLS
In the late 17th century an Englishman, Robert Hooke, discovered the honeycomb structure or ‘Cells” of a cork when viewing them under his microscope. It was Hooke who coined the term ‘cells’. You can easily recreate Hooke’s experience by following these instructions:
Materials
- Plain glass microscope slide
- Slide cover slip
- Microtome, sharp knife or razor blade
- Pipette • Water
- Tweezers
- Paper Towel
- Petroleum jelly (optional)
- Toothpick (optional)
Slide Preparation (Wet Mount)
- Using great care, cut as thin a slice of cork as possible from the end of the cork.
- Using the pipette, place one drop of water on the slide. After making sure that the water drop is larger than the slice of cork, use the tweezers to place the slice of cork on the water.
- Hold the cover slip at an angle to the slide so that one edge of it touches the water drop.
- Carefully lower the cover slip and ensure no air bubbles are trapped beneath it.
- The water will seal the cover slip but use the corner of a paper towel to gently absorb any excess water.
- If you want to retain the slide longer, smear a little petroleum around the cover slip with a toothpick.
- This will keep it from drying out.
- Then mount the slide on your microscope and view it using the lowest objective lens, first.
CHEEK CELLS
A scientist's favorite! Viewing your own body tissue and a cheek cell is a good way to start. Cheek cells are called Squamous Epithelium cells and they are also a good first use of a microscope stain, in this case Methylene Blue.
Materials Needed
- Plain glass microscope slide
- Slide cover slip
- Methylene blue stain
- Q tip or flat toothpick
Instructions
- Scrape the inside of your cheek with the Q-tip and wipe it on to the center of the slide.
- Hold the coverslip or another slide with one end flush on the slide and gently wipe the edge of the coverslip over the scrapings.
- This is called a smear and it makes a specimen layer thin enough to view clearly.
- Leave the cells to dry.
- When dry, add a drop of Methylene Blue stain.
- This helps add contrast to the nuclei of animal cells, making them easier to view.
- Lower the cover slip, mount on your microscope and view starting with the lowest power objective.
ONION CELLS
This is another good experiment that illustrates the plant cell.
Materials
- Onion
- Plain glass microscope slide
- Slide cover slip
- Microtome, sharp knife or razor blade
- Tweezers
Instructions
- Peel the onion and cut a small section from the inside layers of the onion.
- Use a pair of tweezers to peel away the transparent membrane that you will find on the inside layers.
- Create a wet mount and add a drop of Eosin Y stain. Eosin Y helps highlight vegetable proteins.
- Mount on your microscope and view starting with the lowest power objective lens.
How to use Basic Stains
Stains are used in microscopy to help view bacteria, which are normally colorless and hard to see in their natural state even with a microscope.
Methylene BlueMethylene Blue is a popular alkaline stain used to view microscopic life in brilliant color. It helps make cells show up against their background, where their shape can help you determine what they are (their morphology).
It's attraction to acid makes it particularly useful for viewing animal cells since these cell nuclei contain deoxyribonucleic acid (DNA). It’s also used in aquariums to guard against fungal infections in fish.
Eosin Y
Eosin Y Stain is a reversible, fluorescent red, acidic dye, commonly used in hospital histology labs. Eosin's most important medical uses are in blood and bone-marrow testing, including the PAP smear. It can also test for protein in plant, animal and blood specimens. This stain is a valid substitute for Congo Red or Neutral Red and is frequently used as a counter-stain to Haematoxylin in H&E staining.
Both employ the same process, as follows:
ProcessFor best results, follow the sequence below:
Stains are used in microscopy to help view bacteria, which are normally colorless and hard to see in their natural state even with a microscope.
Methylene BlueMethylene Blue is a popular alkaline stain used to view microscopic life in brilliant color. It helps make cells show up against their background, where their shape can help you determine what they are (their morphology).
It's attraction to acid makes it particularly useful for viewing animal cells since these cell nuclei contain deoxyribonucleic acid (DNA). It’s also used in aquariums to guard against fungal infections in fish.
Eosin Y
Eosin Y Stain is a reversible, fluorescent red, acidic dye, commonly used in hospital histology labs. Eosin's most important medical uses are in blood and bone-marrow testing, including the PAP smear. It can also test for protein in plant, animal and blood specimens. This stain is a valid substitute for Congo Red or Neutral Red and is frequently used as a counter-stain to Haematoxylin in H&E staining.
Both employ the same process, as follows:
ProcessFor best results, follow the sequence below:
- Prepare a wet mount slide with a specimen.
- Place a single drop of stain on one outer edge of the cover slip on top of your slide.
- Place some paper towel against the opposite edge of the cover slip - as close to the edge as possible.
- The paper towel will draw the stain underneath the cover slip.
- Wait until all of the stain has been pulled in between the cover slip and the slide.
- The stain should completely cover the specimen on the slide.
- If it does not, add another drop of stain to the edge of the cover slip.
- Remove the piece of paper towel and place the slide on the microscope stage and you should see cell nuclei show up as the darkest blue portion of the imagery.
