Chapter 3 Section 1
A cell is smaller than a period in the textbooks we read, yet these cells have all the necessary items to carry out life’s activities. As most cases, there are a few exceptions to the rule. You may have seen one of the largest cells in the world. A chicken egg is an individual cell. The largest cell we can see easily is the Ostrich egg.
Humans have about 200 different kinds of cells and each type is specialized to carry out a specific function (job). Example of human cells: bone cells, heart cells, blood cells, and skin cells are just a few.
Tissues: Cells Working in Teams
Cells are grouped together to make a tissue that is designed to perform a specific job in the body. A tissue is a group of cells that work together to perform a specific job in the body.
Organs: Teams Working Together
When two or more tissues work together to perform a specific job, the group of tissues is called an organ. Examples of organs: Stomach. Intestines, Heart, Lungs, and Skin.
Plants also have tissues. The bark on a tree is a tissue. The leaves on plants are tissues because they have specialized cells to capture sunlight and carry out photosynthesis.
Organ Systems: A Great Combination
Organs work together to accomplish different jobs or tasks. When we have several organs working together, we call these organ systems. Each system has a specific job to do in the body. Example: The cardiovascular system is responsible for carrying nutrients to cells and waste products away from cells. The nervous system is responsible for sending impulses to the brain and sending messages impulses or reactions away from the brain.
We have 11 organ systems: Digestive, Urinary, Cardiovascular, Integumentary, Nervous, Respiratory, Lymphatic, Endocrine, Muscular, Skeletal, and Reproductive systems.
Organisms: Independent Living
Anything that can live on its own is called an organism. If a single cell is living on its own, it is called unicellular. Most unicellular organisms require a microscope to see them.
Humans have many cells and are called a multicellular organism. This means that humans can only exist as a group of cells and the cells can remain alive as long as they are a part of your body. If you are running and fall down and scrape off some of your skin, those cells scraped off will die.
Recap of how cells make organisms:
Cells make tissues, tissues make organs, organs make up organ systems, and organ systems make up organisms.
The Big Picture
Unicellular and multicellular organisms can live by themselves many times, but they usually do not. These organisms interact with each other.
Populations
A group of organisms that are of the same kind (species) that live in the same area make up a population. Example: All of the largemouth bass living in Lake Chickamauga, all of the deer in Catoosa County.
Communities
When two or more populations are living in the same area, they make up a community. Example: All of the deer, wild turkey, and coyotes living in Catoosa County. Are we part of the community? YES.
Ecosystems
All of the community and the non-living things that have an affect on the community make up an ecosystem.
Example: Living Non-living
Humans Rocks
Deer Air
Turtles Light
Birds Temperature
Hopefully, you get the picture of some of the interactions going on in an ecosystem. Ecosystems that are on land are called terrestrial ecosystems and those in water are called aquatic.
Terrestrial Examples Aquatic Examples
Forest Lake
Desert Stream
Prairies Ocean
Even small fish tanks in your home are aquatic ecosystems.
Chapter 2 Section 2
The Discovery of Cell
Remember, the majority of cells are so small that we cannot see them without a microscope.
Who saw the first cells?
In 1665, Robert Hooke was looking for something to show other scientists. He made a microscope and looked at cork with the microscope. H noticed the cork had small “block like” structures. Hooke was seeing the first cells. Hooke named these “boxes” cells which means “little rooms” in Latin.
Cells in Other Living Things
Anton van Leeuwenhoek also made a microscope and was looking at pond scum and discovered other living things were made of cells. He named the small organisms animalcules meaning small animals. He also began looking at other objects under the microscope and was the first to view bacteria.
Cell Theory
Two centuries after Hooke had viewed the first cell, Matthias Schleiden determined that all living things were made of cells. Shortly after this, Theordor Schwann wrote the first two parts to the cell theory.
1) All organisms are composed of one or more cells.
2) The cell is the basic unit of life in all living things.
About 20 years after Schwann made his declaration, Rudolph Virchow
3) All cells come from existing cells.
Cells come in many different shapes and many have specialized functions, but they do have some things in common.
Cell Membrane
All cells are surrounded by a double layer of phospholipids called a cell membrane. The cell membrane regulates what goes into and out of the cell. The cell will need food products in order to survive and it must remove waste products in order to survive.
Hereditary Information
Inside each cell there is a copy of the hereditary (genetic) information. This information is in the form of DNA. This DNA is “housed” in the nucleus of the cell. This DNA has all of the information for cells to produce all of the needed proteins and it controls other activities. This information also has the needed information to produce new cells.
Cytoplasm and Organelles
All cells have the necessary structures and materials to live and grow, as well as reproduce. These structures are called organelles. These structures and materials are surrounded by a fluid called cytoplasm.
Cells are very small. Your body will have 80-100 trillion cells in it and it would take over 100 to cover up the period at the end of this sentence.
Surface to Volume Ratio
In order for cells to have the capability to transport the needed material into and out of the cell, they must have a large surface to volume ratio. As a cells volume increases, the surface must grow. The volume of a cells will grow faster than the surface and this limits the size of the cell. If the surface area is not large enough, the cell membrane will not have enough “openings” to allow the proper materials into and out of the cell.
Benefits for Multicellular Organisms
If you were a single cell, the surface area would not be large enough to supply the volume of nutrients and removal of wastes your body would need in order to survive. Since we are multicellular, all of the tiny cells actually increase the surface area and this allows all of the cells to be able to transport the needed materials into and out of the cell for survival.
Also, another benefit is the fact that we have specialized cells that carry out specific functions. This is more effective than a unicellular organism. These specialized cells can form specialized tissues that will can make specialized organs (heart, kidney, and pancreas to mention a few) that have the special abilities to carry out unique functions.
Two Types of Cells
There are two types of cells: 1) prokaryotic and 2) eukaryotic.
Prokaryotic Cells – these cells do not have a nucleus and are also called bacteria. These cells are the worlds smallest cells. Bacteria do not have membrane covered organelles, but they do have round organelles called ribosomes. These ribosomes make proteins. Most bacteria are covered by a hard cell wall outside of the cell membrane.
Eukaryotic Cells
These are more complex than prokaryotic cells. They are about ten times larger than prokaryotic cells and have a high surface to volume ratio. Eukaryotic cells have a nucleus and other organelles that are enclosed by membranes.
There is more DNA in eukaryotic cells than prokaryotic, and the DNA is stored in the nucleus and is linear in shape. The DNA in prokaryotic cells is circular. All eukaryotic cells have a cell membrane, and some of them have a cell wall (plants, fungi, and some unicellular organisms).
Chapter 3 Section 3
What Is Inside Eukaryotic Cells
All the structures of eukaryotic cells have specific functions.
Cell Membrane
All cells are covered by a cell membrane that keeps the cytoplasm in and allows nutrients into the cell and wastes to be transported outside of the cell. The cell membrane also prevents the organelles from having direct contact with things outside of the cell.
Cell Wall
Some eukaryotic cells also have a cell wall that is outside of the cell membrane. This is what provides structural support for the cell. This is why plants are able to stand erect. The cell wall is made of cellulose.
Nucleus
The largest organelle in the eukaryotic cell is the nucleus. It is often called the “control center” of the cell because all of the information (DNA) to regulate what is occurring in the cell is housed in the nucleus.
Nucleolus
Within the nucleus you can find a darkened area called the nucleolus. The function of the nucleolus is to store the materials to produce ribosome’s that will be used later to make proteins.
Ribosome
The ribosome is responsible for connecting amino acids together to make the proper proteins that the cell needs. Remember that the “building blocks” of proteins are amino acids and ribosomes are responsible for the assembly of the amino acids to make proteins.
Endoplasmic Reticulum
The endoplasmic reticulum (ER) is a membrane covered tunnel structure. It provides transportation of materials within the cell and it packages proteins to be taken out of the cell. The ER also breaks down drugs and other chemicals that can damage the cell.
The ER that is covered with ribosomes looks “rough” and the proteins made at these ribosomes pass into the ER in order to be released and used elsewhere. This ER is called rough endoplasmic reticulum.There is also smooth ER, “without ribosomes”.
Mitochondria
Once food gets inside the cells it is broken down and made into the type of energy the cell can use. We already know this energy is called ATP (adenosine triphosphate). The mitochondria are bean shaped structures that have an inner and outer membrane. The inner membrane has many folds and these folds are where most of the ATP is made. Cells that contain many mitochondria are those that require a lot of energy (heart cells, and liver cells are highly active and require a lot of energy). Cells that do not require a lot of energy only have a few mitochondria.
Chloroplast
These are found in cells that carry out photosynthesis (plants and algae). These are oval structures which if cut in half have stacks of structures that resemble coins in a stack. The “stacks of coins” are the location of chlorophyll that captures sunlight and utilizes it to produce ATP. This process occurs when these plants and algae are carrying out photosynthesis.
History of Mitochondria and Chloroplasts
Many scientists think it was possible these structures were bacteria that were consumed by other organisms and they adapted to carry out the functions they have today. Their argument is that these structures are about the same size as bacteria and the structures are covered by two membranes. Scientists think the outer membrane was formed when the bacteria were engulfed by an organism and the inner membrane is actually the membrane from the bacteria.
Golgi Complex
This organelle is also referred to as the Golgi Apparatus and Golgi Body. The function of the organelle is to package materials up that will be taken out of the cell or to other parts of the cell.
The Storage Areas of Cells
Vesicles – all eukaryotic cells have membrane covered compartments called vesicles. These vesicles could be formed when a portion of the Golgi complex packages up material and pinches itself off.
Vacuoles – You find vacuoles in most plant cells and they store water and other liquids. Some unicellular organisms have contractile vacuoles and they are used to regulate the amount of water in the cell. Contractile vacuoles actually constrict and pump the excess water out of the organism (paramecia have contractile vacuoles).
Lysosomes
These organelles contain special enzymes that destroy the cell. Some scientists refer to these as suicide sacs. If these cells rupture, they will break down the cell. (This is how the tail of a tadpole disappears). Lysosomes are also responsible for destroying old and worn out cells or cells that have become damaged.
Plant Cells vs. Animal Cells
Plant and Animal Cells Only Plant Cells
Organelles Organelles
Nucleus Large Vacuole
Golgi Complex Chloroplasts
Mitochondria Cell Wall
Lysosome
Endoplasmic Reticulum
Cell Membrane
Ribosome
STUDENTS: You should learn these notes in order to be thoroughly prepared for any question about the cells that I could ask or that may show up on the state test (CRCT) that you will be taking later.