Cells: The basic unit of living things
Section 1: Discovery and Diversity of Cells • All living things are made of cells. • Cells are membrane-covered structures that contain all the materials necessary for life. • Cells weren’t discovered until the mid-1600’s once the microscope was invented.
The Discovery of Cells • Robert Hooke first described cells while looking at a thin slice of cork. • Hooke saw the cork under the microscope as “little boxes” • He named them cells which means “little rooms” in Latin. http://askabiologist.asu.edu/research/buildingblocks/images/hookecork.jpg
The Discovery of Cells Continued • Hooked looked at many different types of organisms. • He spent most of his time looking at plants and fungi, because they have cell walls and are easy to see. • Because he could not see the outline of animal cells easily, Hooke thought that animals were not made of cells. http://www.cerebromente.org.br/n17/history/sm101-h1.jpg
Finding Cells in Other Organisms • Anton van Leeuwenhoek, a Dutch merchant, made his own microscopes • He looked at pond scum and saw small organisms he called animalcules (we now call them protists) • Also looked at animal blood. He noticed differences between frog and human blood cells. • First person to see bacteria and he discovered yeast is a single-celled organism. http://www.glyphs.com/art/vermeer/geograph.jpg
The Cell Theory • It took 200 years before scientists realized that all living things had cells. • Matthias Schleiden concluded that all plant parts were made of cells (in 1938). • Theodor Schwann concluded that all animal tissues were made of cells (in 1939) • Rudolf Virchow saw that cells formed only from other cells - nineteen years later. • Together, German scientists formed what we now call the cell theory. http://home.tiscalinet.ch/biografien/images/schwann.jpg
The Cell Theory States: • 1. All organisms are made of one or more cells. • 2. The cell is the basic unit of all living things. • 3. All cells come from existing cells. http://fig.cox.miami.edu/~cmallery/150/unity/cell.text.htm
Cells Are Small • Why are cells so small? The physical reason for cells being so small is because of how much food and waste must cross their cell membranes. If a cell was to grow larger, then the volume inside of the cell would grow faster than the surface area (where the cell membrane is). The cell could not get enough food or remove enough waste to keep it alive. So the surface area to volume ratio limit’s the cell’s size. http://www.udel.edu/biology/Wags/wagart/anaglyphpage/red%20cells%20.gif
A few cells are big • There are a few exceptions to the cell’s size. • A single cell can become large if it does not take in nutrients like the chicken egg. http://www.rain.org/~mkummel/stumpers/26sep03a.jpg
Parts of the Cell • All cells have some things in common – no matter what type: • 1. Cell membrane surrounds the cell and acts like a barrier to allow only certain things into and out of the cell. • 2. Cytoplasm is the fluid in the cell. • 3. Organelles are structures that enable cells to live and reproduce. • 4. Genetic Material or DNA is the information needed to make new cells and control the activities of the cell.
Three Types of Cells • 3 basic types of cells on Earth: • 1. Eubacteria • 2. Archaebacteria • 3. Eukaryotes • These cells have some things in common, but they differ in important ways. http://www.palaeos.com/Kingdoms/Prokaryotes/Images/EubacteriaStructure.gif http://sps.k12.ar.us/massengale/bacter2.gif http://www.williamsclass.com/SeventhScienceWork/ImagesCells/EukaryoticCell.jpg
To have a nucleus, or not to have a nucleus… • A major difference between the cells is whether it has a nucleus or not: • Eukaryotes are organisms with a nucleus. Many are multi-cellular • Prokaryotes are organisms without a nucleus. Also called bacteria and single-celled organisms. Prokaryotic eukaryotic cell cell http://www.rpi.edu/dept/chem-eng/Biotech-Environ/FUNDAMNT/streem/cells.jpg
The Prokaryotes • Eubacteria: • Most common type of bacteria. • Live almost everywhere on Earth from soil to water or in or on other organisms. • Smaller than eukaryotic cells. • No nucleus, no membrane-bound organelles. • Have a cell wall to help it retain its shape. • Come in different shapes. • Can cause disease or be helpful. http://library.thinkquest.org/C004535/media/prokaryote.gif http://images.google.com/images?svnum=10&um=1&hl=en&rls=GGLD%2CGGLD%3A2004-47%2CGGLD%3Aen&q=eubacteria
Prokaryotes Continued • Archaebacteria • Not as common as eubacteria. • Has circular DNA like eubacteria • Lacks nucleus and membrane-bound organelles • Cell wall is made of different materials • Live where other bacteria could not survive like a hot-spring or very salty water • 3 types of archaebacteria: • “Heat-loving” • “Salt-loving” • “Methane-making” http://universe-review.ca/I11-29-archaea1.jpg
Eukaryotes • Eukaryotic cells • Largest cells • About 10 times larger than most bacterial cells • Have a nucleus and other membrane-bound organelles. • Many are multi-cellular like animals and humans.
Section 2: Eukaryotic Cells • Eukaryotic cells are larger than prokaryotic cells. • Still so small that you can only see them in detail with a microscope. • It took a long time before scientists were able to tell what cells were made of. • In this section, we look at these organelles that help keep eukaryotic cells alive.
Cell Wall • Provides strength and support to a cell membrane. • Outermost structure of a cell. • Some eukaryotes have cell walls. • Plants and algae have cell walls made of cellulose. • Cell wall allows it to stand upright and in some plants need to have water to inflate the cell wall. • Fungi (yeasts and mushrooms) have cell walls made of chitin.
Cell Membrane • All cells have a cell membrane. • Cell membrane is a barrier between the contents of the cell and the outside environment. • Controls what moves into and out of the cell. • Has two layers made of lipids, a kind of fat.
The Cell’s Scaffold • Cytoskeleton is a web of proteins located in the cytoplasm which helps the cell keep its shape and well as help it move. • Made of many proteins.
The Cell’s Library • Nucleus • Large organelle covered by two membranes • Often has a dark spot in the nucleus called the nucleolus which contains materials that will be used to make ribosomes. • Contains the genetic material called DNA or deoxyribonucleic acid. • Contains the information on how to make the cell’s proteins, which in turn control the chemical reactions in a cell and provide structural support for cells and tissues.
Protein Factories • Ribosomes are organelles that make proteins. • Join amino acids together which are the building blocks of proteins. • All cells have ribosomes because all cells need proteins to live. • Smallest organelles and the most abundant organelles in the cell. • Some free floating and others are attached to organelles. • Ribosomes are not covered by a membrane.
The Cell’s Delivery System • Endoplasmic Reticulum (ER) • Many chemical reactions occur on or in the ER • Makes lipid and other materials. • Breaks down chemicals that damage the cell. • Folded membrane that contains tubes and passageways. • Is the internal delivery system in which substances can move through to different places within the cell. • Can be either rough (covered with ribosomes) or smooth (not covered with ribosomes)
The Cell’s Power Plants • Mitochondria • Powerhouses of a cell • “burn” food molecules to release energy, called ATP. • Uses this energy to do work • Most energy is produced in the inner membrane of mitochondria. • Most eukaryotic cells have mitochondria. • Are the size of some bacteria and divide within the cell • Like bacteria, mitochondria have their own DNA • Covered by two membranes
Food Factories • Chloroplasts • make food for cells • Plants and algae have chloroplasts • Surrounded by two membranes and have their own DNA • Green because they contain chlorophyll, a green pigment. • Chlorophyll traps energy of sunlight and uses this energy to make sugar, which stores chemical energy in a process called photosynthesis.
The Cell’s Packaging Center • Golgi complex • Ships proteins out of a eukaryotic cell • Lipids and proteins from the ER are delivered to the Golgi complex where they are modified for different functions. • The modified products are pinched off in a small bubble made of the golgi complex’s membrane which transports the contents to other parts of the cell or outside of the cell.
Cell Compartments Vesicles - membrane-covered compartment which forms from part of the membrane of the ER or golgi complex that pinches off or when part of the cell membrane surrounds an object outside the cell.
Packages of Destruction • Lysosome • Vesicles that contain enzymes which destroy worn-out or damaged organelles as well as get rid of waste materials and protect the cell from foreign invaders. • Found in animal and fungal cells.
Water Storage and Hydraulic Support • Vacuoles • Large vesicles found in plant cells which store water and other liquids. • Vacuoles full of water help support the cell
Eukaryotic Cells and Their Organelles • You can see which organelles are found in animal, plant, fungal and protist cells.
The Organization of Living Things • Organisms are similar to machines because they both have many parts. • Each part has a job (or function) • The cell is the smallest part of an organism, yet it has everything needed to carry out life’s activities.
The Benefits of Being Multicellular • Multicellular Organism means that the organism is made of many cells. • Why be multicellular? • Many cells performing specific jobs can do more (perform more functions) than a single cell working alone.
These are some of the specialized cells in the human body that work with other cells of the same kind to allow you to be who you are. http://www.dannynicholson.co.uk/learningzone/body/organs/Cells.jpg
We’ve talked about cells • Cells alone can’t do as much as many cells. • Cells of the same kind will group together in a multicellular organism to perform more functions, they form . . .
Tissues • Tissue is a group of cells that work together to perform a specific job. • This includes material around and between the cells • Animals have 4 types of tissues: • Nerve • Muscle • Connective • Protective • Plants have 3 types of tissues: • Transport • Protective • ground
Tissues Working Together • When two or more tissues work together to perform a specific job, we call them organs.
Organs working together • Organs working together form an organ system. • Each system has a specific job to do in the body.
Together the organ systems form • An organism like yourself. • Organism is anything that can live on its own. • Can be a single cell or unicellular or it can be many cells or multicellular.
Structure Vs. Function • Structure determines function • Structure is the shape of a part and the material the part is made of. • Function is the job the part does.
How Cells Make More Cells • Cells divide in a process called mitosis. • One cell (the original cells) splits into two identical cells (called daughter cells)
INTERPHASE • Longest period in the cell cycle • Cells grow • DNA makes a copy of itself • Centrioles (the centrosome) divides into two
PROPHASE • Nucleolus fades • DNA condenses and becomes visible as chromosomes (both pairs have the same information) • Spindles (like strings) grow from the centrioles
METAPHASE • Nucleus disappears • Spindles become longer and attach to the chromosomes. • The chromosomes line up in the center of the cell.
ANAPHASE • Spindles become shorter. • Chromosomes separate • Each piece move to separate sides of the cell.
TELOPHASE • Chromosomes are on each side of the cell. • Spindles start to disappear. • Nucleus reappears.
CYTOKINESIS • One cell now becomes two • The spindles are completely gone. • The cytoplasm finishes separating.
Quiz: Using your notes, Label the steps of mitosis (cell division) 2. 3. 1. centriole centromere chromosomes microfibers 4. 5.