Section 1: Cell Size, Microscopes, and The Cell Theory
The cell is the basic structural and functional unit of all known living functional unit of all known living organisms. The cell is the smallest organisms. The cell is the smallest unit of life that is classified as a unit of life that is classified as a living thing, and is often called the living thing, and is often called the building block of life. building block of life. Most cells are much smaller than a grain of sand. than a grain of sand. Cells and cell structures are measured in incredibly small metric units called ‘ micro ’ and ‘ nano ’ meters. Cells are only visible with either light microscopes or electron microscopes.
Surface area to volume ratios must be small so substances can move in, move out, and move throughout the cell easily and rapidly. This limits the largest of cells in your body to about 20 micrometers, or about 1/3 the width of a human hair.
A compound light microscope uses two lenses to focus light and magnify an image on a transparent slide. A compound light microscope magnifies images up to 2,000 times. 4X Scanning Objective Lens 10X Low Power Objective Lens 40X High Power Diaphragm (Ocular lens)
A transmission electron microscope operates in a vacuum and uses a stream of electrons to bombard a metal stained specimen, creating a fluorescent computer image. It allows all but the smallest cell structures to be viewed (magnifies up to 200,000 times).
Scanning tunneling microscopes utilize a needle-like probe to tract voltage differences caused by electrons which ‘ leak ’ or ‘ tunnel ’ from the object being viewed.
The STM (scanning tunneling microscope) the image
The cell theory was developed in the mid- 1800s, and was the work of several scientists over many years. The major scientists that contributed to the cell theory were: 1665 – Robert Hooke – first used the name ‘cell’ after observing structures in cork 1674 – Anton van Leeuwenhoek – improved the microscope and observed living cells
1838 – Matthias Schleiden – discovered that plants were composed of cells 1839 – Theodor Schwann – discovered that animals were composed of cells 1855 – Rudolph Virchow – proposed a theory that every cell comes from another living cell The observations of scientists such as Schleiden, Schwann, and Virchow led to the development of The Cell Theory.
The cell theory states: 1.All living things are composed of one or more cells. 2.Cells are the basic units of structure and function in all organisms. 3.New cells are produced only from existing cells (cells divide, or replicate).
Section 2: Types of Cells, Cytoskeleton, Cell Membranes, and Membrane Proteins
Cells are classified based on their structure and the way they obtain energy. Cells are classified as either prokaryotes or eukaryotes.
Prokaryotes are a group of organisms that lack a cell nucleus, or any other membrane-bound organelles. Most prokaryotes are unicellular, but a few types have multicellular stages in their life cycles. Characteristics: Prokaryotes have no nuclear membrane -- the genetic material is dispersed throughout the cytoplasm. They have no membrane-bound organelles. Most prokaryotes have a cell membrane, cytoplasm, and cell wall. They do not have a nucleus, mitochondria, or chloroplasts. Examples: staph, E. coli, strep, bacteria
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes are generally more complex and larger than prokaryotes. Characteristics: They have a distinct nucleus and nuclear membrane surrounding genetic material. They have numerous membrane-bound organelles. Eukaryotes have a larger, more complex internal structure than prokaryotes. Examples: plants, animals, protists, and fungi All cells in multi-cellular organisms are eukaryotic.
Animals, plants, protists, and fungi are all eukaryotes and have a cell membrane, nucleus that contains DNA, cytoplasm, and mitochondria. Plants and fungi also have a cell wall, but eukaryotes do not. Only plants have chloroplasts. Flagella and cilia (short, hair-like structures used for movement) are a common features among single-celled eukaryotes.
There are some key differences between plant cells and animal cells. In addition to a cell membrane, plant cells have a rigid cell wall composed of cellulose which provides structure and protection.
Plant cells also contain unique organelles called chloroplasts which use sunlight, carbon dioxide, and water to make carbohydrates (sugars) in a process called photosynthesis.
Plant cells contain a large membrane bound central vacuole which takes up the vast majority of the cell volume. The central vacuole is used for storage in plant cells, and contains mostly water and other minerals. Turgor pressure is the pressure caused when a full central vacuole presses the cytoplasm against the cell wall, creating rigidity that allows plants to stand upright.
nerve cell muscle cells with nerve cell attached red and white blood cells
All Cells have several common structures: 1. Cell membrane the protective layer around all cells that give the cell shape and support Animal Cell Plant Cell
2. Cytoplasm the watery gel-like fluid that fills the inside of the cell Animal Cell Plant Cell
3. DNA or genetic material controls cell functions and carries hereditary information Animal Cell Plant Cell
4. Ribosomes the site where proteins are made Animal Cell Plant Cell
The cytoskeleton provides the interior framework of an animal cell and is composed of an intricate network of protein fibers anchored to the inside of the plasma membrane.
There are three kinds of cytoskeleton fibers: (1.) Actin fibers – form a network just beneath the cell surface that is anchored to the membrane proteins embedded within the cell membrane. Actin fibers help determine the shape of an animal cell by pulling on the plasma membrane.
(2.) Microtubules – are within the cytoskeleton and act as a transportation system for information from the nucleus to different parts of the cell. RNA is also transported along microtubules. (3.) Intermediate fibers – provide a frame on which ribosomes and enzymes can be confined to a particular region of the cell. The cell can organize complex metabolic activities efficiently by anchoring particular enzymes near one another.
http://learn.genetics.utah.edu/ Click on Amazing Cells, and then Directing Traffic: How Vesicles Transport Cargo. Scroll down to Vesicles Travel Cellular Highways to learn more about travel along the microfilaments.
The cell membrane is the outer boundary of the cell which is selectively permeable to certain substances. This selective permeability is caused mainly by the way phospholipids interact with water. A phospholipid is a lipid made of a phosphate group and two fatty acids.
In a cell membrane, the phospholipids are arranged in a double layer called a lipid bilayer. Polar water molecules, both inside and outside the cell, repel the nonpolar fatty acid tails, forcing them to the inside of the lipid bilayer.
Ions and most polar molecules, including sugars and some proteins, are repelled by the nonpolar interior of the lipid layer. The lipid bilayer allows lipids and substances that dissolve in lipids to pass through.
Polar molecules have a slightly negative charge at one end, and a slightly positive charge at the other end.
Because of the unequal pull of electrons exhibited by polar molecules, they have a tendency to attract one another. Non-polar molecules do not attract one another as much, and therefore exhibit different properties.
The nonpolar part of a membrane protein is attracted to the interior of the lipid bilayer, but is repelled by the water on either side of the lipid bilayer. In contrast, the polar parts of the protein are attracted to the water on either side of the lipid bilayer. This attraction helps to hold the protein in the lipid bilayer.
44 Three Forms of Transport Across the Membrane
Receptor proteins, marker proteins, channel proteins, transport proteins, carrier proteins, and enzymes are all part of the cell membrane. receptor protein transport protein
Receptor proteins recognize and bind to substances outside the cell. Marker proteins attached to a cell’s surface advertise cell type. Transport proteins (channel proteins, carrier proteins) help substances move across the cell membrane. Enzymes are a type of protein that assist in the chemical reactions inside the cell.
Parts of the Animal Cell Cell Membrane The cell membrane, or plasma membrane, is the outer layer that surrounds a cell. It allows food, water and gases into the cell while allowing waste to leave the cell. The cell membrane is found in both plant and animals cells.
Parts of the Animal Cell Cell Membrane The cell membrane is made up of a lipid bilayer (two layers). A lipid bilayer is a thin membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around the cell.
The Lipid Bilayer The lipid bilayer is the barrier that keeps ions, proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be.
53 The polar heads are hydrophilic -- “water loving.” The nonpolar tails are hydrophobic -- “water fearing.” This makes the membrane “selective” in what crosses into and out of the cell. Cell Membrane
Parts of the Animal Cell Cytoplasm Cytoplasm is the thick, clear, gel- like fluid that holds all the other organelles in place. Cytoplasm is between the cell membrane and the nucleus.
Parts of the Animal Cell The Nucleus The nucleus is the “control center,” or nerve center of the cell that contains the cell's hereditary information and controls the cell's growth and reproduction. The nucleus is the largest cellular organelle in animals.
Parts of the Animal Cell The Nucleus The nucleus has three major parts: The nuclear pores are protein complexes that allow the transport of water-soluble molecules across the nuclear envelope. The nucleolus is the home of the transcription of ribosomal RNA. The nuclear membrane is a double lipid bilayer that encloses the genetic material in eukaryotic cells.
Mitochondria Mitochondria are the cell’s power sources that function in the conversion of the potential energy of food molecules into ATP. Mitochondria are membrane-enclosed organelles distributed through the cytosol of most eukaryotic cells. Mitochondria are found in cells that use a lot of energy, such as muscle cells. cristae – folded membranes which are the sites of chemical reactions that convert food molecules into ATP
Golgi Apparatus The Golgi apparatus is a system of membranes that modifies and refines proteins built in the endoplasmic reticulum and prepares them for export outside of the cell, or for transport to other locations in the cell. Proteins are modified according to where in the cell they will be sent and their role in the cell. The Golgi apparatus is often considered the “distribution and shipping department” for the cell's chemical products.
Parts of the Animal Cell Lysosomes Lysosomes are organelles that contain digestive enzymes (acid hydrolases). They are the cell’s “recycling bin.” Lysosomes digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria Lysosomes digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria.
Parts of the Animal Cell Centrioles Centrioles are a pair of cylindrically-shaped organelles that organize the mitotic spindle and help regulate cell division. Centrioles are found in most eukaryotic cells, and are usually absent in plants and most fungi. A centriole is made of 9 sets of centrosome triplets.
The rough endoplasmic reticulum is the transport system that consists of a series of tubes and membranes that moves materials, (water, protein, oxygen and food) throughout the cell. The rough endoplasmic reticulum is covered in ribosomes, which are organelles that produce proteins needed to perform tasks. Rough Endoplasmic Reticulum
Smooth Endoplasmic Reticulum The smooth endoplasmic reticulum does not have ribosomes attached to its surface, and functions in the regulation of several metabolic processes. For example, the smooth endoplasmic reticulum aids in the synthesis of lipids and steroids, metabolism of carbohydrates, regulation of calcium concentration, drug detoxification, attachment of receptors on cell membrane proteins, and steroid metabolism.
Ribosomes Ribosomes are the places where cells make new proteins. Most ribosomes are scattered throughout the cytoplasm, and others are attached to the surface of the rough endoplasmic reticulum. Unlike most organelles, ribosomes are not surrounded by membranes. Ribosomes are made up of proteins and RNA that are bound together.
http://www.youtube.com/watch?v=JnlULOjUhSQ white blood cell chases bacteria on You Tube
http://www.youtube.com/watch?v=Ow0jH2Eg8v4&feature=related http://www.youtube.com/watch?v=LKN5sq5dtW4&feature=related FLUID MOSAIC CELL MEMBRANE VIDEO http://www.youtube.com/watch?v=cqzGWgAr4Ww&feature=related PODCAST OF CELL ORGANELLES http://www.youtube.com/watch?v=36Duq-v8Ysk&feature=related BILL NYE CELLULAR HAZE http://www.youtube.com/watch?v=jqUhWDp73bM&feature=related SCIENCE TEACHER RAPS ABOUT CELL ORGANELLES INTRODUCTION TO CELLS IN 3-D
http://www.youtube.com/watch?v=-zafJKbMPA8 CELLS, CELLS…THEY’RE MADE OF ORGANELLES http://www.bing.com/videos/search?q=cell++rap&mid=465289358E 4E70FA7353465289358E4E70FA7353&view=detail&FORM=VIRE5 THREE GIRLS SING CELL RAP REALLY WELL http://www.youtube.com/watch?v=gfzVWG2DnQ4&feature=related PROKARYOTE/EUKARYOTE SONG
Additional Parts of the Plant Cell …so which parts of a PLANT CELL make it so different?
Cell Organelles Found Only in Certain Eukaryotic Cells Cell Wall The cell wall is the rigid outer wall that gives plants additional shape and support. The cell wall has tiny pores that allow materials to enter and exit. The cell wall is found in plant cells, bacteria, some protists, and fungi.
Cell Organelles Found Only in Certain Eukaryotic Cells Chloroplasts Chloroplasts are the organelles where photosynthesis occurs. Chloroplasts contain the green pigment chlorophyll that traps the energy of sunlight and makes plants green. Plants and some protists such as algae contain chloroplasts.
Cell Organelles Found Only in Certain Eukaryotic Cells Vacuoles Vacuoles are sacs that store water and dissolved materials. In plants, there is one large central vacuole. In animal cells, smaller vacuoles are spread out in the cell. The turgor pressure from the liquid-filled vacuole allows plants to support heavy structures such as leaves and flowers.
Plasmodesmata in Plant Cells Plasmodesmata are narrow channels that act as intercellular cytoplasmic bridges that are found in the cell walls of plants. Plasmodesmata function to facilitate communication and transport of materials between plant cells. Plasmodesmata
Flagella Flagella are long, thread-like appendages which provide some live single cells with the ability to move. Bacteria which have flagella are either rod or spiral-shaped. Cocci, or round bacteria, are almost all nonmotile. Animal sperm cells also have flagella. The flagella in prokaryotic cells such as bacteria are made of a different proteins than those of eukaryotic cells. Special Structures for Movement Special Structures for Movement
Cilia Cilia are tiny tubes on single- cell organisms that use wave- like hairs to move the cell around, or can be used to move something around in the cell of a multicellular organism. Cilia are responsible for such things as protecting us from germs in our lungs and pushing an ovum down the fallopian tube. Single-celled organisms use cilia to move through liquid. Special Structures for Movement
Prokaryotic cells lack organelles bound by membranes. Mitochondria and chloroplasts have their own DNA. The DNA in the nucleus does not instruct the cell to make mitochondria or chloroplasts. The endosymbiosis theory proposes that some early prokaryotes evolved internal cell membranes which eventually led to the development of primitive eukaryotic cells.
The theory goes on to say that other prokaryotic organisms then entered the primitive eukaryotic cell and lived inside. The eukaryotic cell formed a mutualistic relationship with the prokaryotes, one in which each organism benefits from the other.
Over time, those prokaryotes evolved into the cell organelles of the modern eukaryotic cell. It is believed to be the means by which such organelles as mitochondria and chloroplasts arose within eukaryotic cells.
Endosymbiosis is a type of symbiosis in which one organism lives inside the other, and the two typically behave as a single organism. It is believed to be the means by which such organelles as mitochondria and chloroplasts arose within eukaryotic cells.
Organelles in Both Plant and Animal Cells PLASMA MEMBRANE - phospholipid bilayer barrier between outside and inside of cell - semi-permeable – made of phospholipids and proteins NUCLEUS - control center of cell - contains instructions for making proteins - houses chromatin (blue prints) or strands of DNA NUCLEOLUS - assembles ribosomes from subunits - found inside the nucleus NUCLEAR ENVELOPE (MEMBRANE) - protects the DNA from the rest of the cell’s contents - made of a phospholipid bilayer with nuclear pores instead of proteins ROUGH ENDOPLASMIC RETICULUM (RER) - covered in ribosomes (appears rough) - the ribosomes are the location where proteins are made - folded membrane that continues off of nuclear envelope SMOOTH ENDOPLASMIC RETICULUM (SER) - no ribosomes present (appears smooth) - produces and store lipids and carbohydrates CYTOPLASM - clear jelly-like fluid that suspends the organelles and is made mostly of water
Organelles in Both Plant and Animal Cells RIBOSOMES - organelles that makes proteins according to the directions of the DNA - ribosomes are not bound by a membrane - can be found on the rough endoplasmic reticulum, or loose in the cytoplasm GOLGI APPARATUS (or GOLGI BODY) - modify and sorts proteins from the rough endoplasmic reticulum, loads them into vesicles, and sends them to destinations VESICLES - sacs that form around and transport substances such as proteins (enzymes), lipids (steroids) and carbohydrates to specific locations CYTOSKELETON (MICROTUBULES, MICROFILIMENTS) - the framework or backbone of the cell – supports the cell shape, anchors the organelles, provides highway system for cellular materials MITOCHONDRIA - provides energy to the cell by breaking down glucose - Mitochondria take in oxygen and release ATP, and are numerous in muscle cells. VACUOLES - compartment that serve as temporary storage of materials PLANTS – one big vacuole ANIMALS – many small vacuoles
CILIA / FLAGELLA Cilia – short hairs that work like oars on a row boat Flagella – one or two long tails, whips back and forth both provide movement (protista and sperm cells) CENTRIOLE play an important role in cell division (guide the chromosomes to the proper places) Organelles of the Animal Cell ONLY Organelles of the Plant Cell ONLY CELL WALL LARGE CENTRAL VACUOLE rigid structure outside the cell membrane provides structure/support for plants, fungi & bacteria – made of cellulose, porous, not selective are sacs that store water and dissolved materials. Plants have one large central vacuole, animals have several smaller vacuoles. PLASTIDS (CHLOROPLAST, CHROMOPLAST, AMYLOPLAST) Chloroplast – location of photosynthesis, contain chlorophyll Chromoplast – contain carotenoids, yellow to red color Amyloplasts – no pigments, clear, store starch grains