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Transcript
1 THE DISCOVERY OF THE CELL • It was not until the mid-1600’s that scientists began to use microscopes to observe cells. • In 1665, Englishman Robert Hooke used an early compound microscope to look at a slice of cork, plant material. 2 3 CORK CELLS 4 • Hooke saw thousands of empty chambers in which he called cells. • They reminded him of a monastery’s tiny rooms, which were called cells. 5 • In Holland around the same time, Anton van Leeuwenhoek used a single-lens microscope to observe pond water and other things. • He discovered that living things seemed to be everywhere, even in the water he was drinking. 6 DUST MITE EUGLENA FLAGELLA 7 THE CELL THEORY • In 1838, German botanist Matthias Schleiden concluded that all plants were made of cells. • In 1839, German biologist Theodor Schwann stated that all animals were made of cells. 8 9 • In 1855, German physician Rudolf Virchow concluded that new cells could be produced only from the division of existing cells. • These discoveries, confirmed by other biologist, are summarized in the cell theory. 10 11 • CELL THEORY STATES… 1. All living things are composed of cells. 2. Cells are the basic units of structure and function in living things. 3. New cells are produced from existing cells. 12 13 THE CHANGE OF THE MICROSCOPE • Hooke, Virchow, and others used crude microscopes to study the cells. • Today scientist can use… 1. Fluorescent Labels (to mark moving cell parts) 14 2. Confocal light ( scans cells with a laser beam to build threedimensional images ) 3. High resolution video to make movies of cells as they grow. 4. Transmission electron microscope ( electrons pass through thin slices of cell parts) 15 5. Scanning electron microscope ( produces three-dimensional images of cells without having to cut cell parts into small slices) 6. In the 1990’s, researchers developed the scanning probe microscope ( produce images that trace objects with a probe…DNA ) 16 STEM CELLS 17 CONFOCAL LIGHT TEM TEM 18 CHLOROPLAST MARINE DIATOM SEM SCANNIING ELECTRON MICROSCOPE pea weevil egg 19 White pine sheath mite on eastern white pine Scanning electron microscope image of white pine sheath mite 20 SCANNING PROBE 21 PROKARYOTES and EUKARYOTES • Cells fall into two categories, depending on whether they contain a nucleus. 1. Eukaryotes (YOUkaryotes)- have a nucleus. (means “true nut”) 2. Prokaryotes (Pro=Before)- no nucleus. (means “before nut”) 22 PROKARYOTIC CHACTERISTICS • Smaller than eukaryotic cells • Genetic information is not contained by a nucleus. • Some have a few internal membranes • Less complicated compared to eukaryotic cells • They grow, reproduce, and respond to their environment. 23 • Some glide and swim through liquids. • Forms of locomotion are: 1. Cilia – hair like structures 2. Flagella – whip like structure. (sperm) • Examples: Bacteria 24 25 EUKARYOTIC CHARACTERISTICS • Larger than prokaryotes • They usually contain dozens of structures and internal membranes. • Genetic information is carried by a nucleus. • Some live solitary lives while others form large multicellular organisms. • Examples: plants, animals, fungi, and protists. 26 27 28 A typical animal cell ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER Nuclear envelope Nucleolus NUCLEUS Chromatin Flagelium Plasma membrane Centrosome CYTOSKELETON Microfilaments Intermediate filaments Ribosomes Microtubules Microvilli Golgi apparatus Peroxisome Figure 6.9 Mitochondrion Lysosome In animal cells but not plant cells: Lysosomes Centrioles Flagella (in some plant sperm) 29 PARTS OF THE CELL • Cell biologists divide eukaryotic cell into two parts: the nucleus and the cytoplasm. • The cytoplasm is the portion of the cell that is outside the nucleus. 30 NUCLEUS Nucleus 1 µm Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Pore complex Rough ER Surface of nuclear envelope. Ribosome 1 µm 0.25 µm Close-up of nuclear envelope Pore complexes (TEM). Nuclear lamina (TEM). 31 THE NUCLEUS • The nucleus is the control center of the cell. • It contains the cell’s DNA and the code for making proteins (mRNA) and other important molecules (rRNA and tRNA). • The nucleus is surrounded by a nuclear envelope composed of two membranes. 32 • The envelope is dotted with thousands of pores, which allows materials to leave the nucleus to other parts of the cell. • Inside of the nucleus is a granular material called chromatin. • Chromatin consists of DNA bound to protein. 33 • When a cell divides, the chromatin condenses to form chromosomes. • These are the distinct structures that are passed from cell to cell…generation to generation. • Deep inside the nucleus is the nucleolus which is where assembly of ribosomes begins. 34 35 ? QUESTION ? • WHAT KIND OF INFORMATION IS CONTAINED IN CHROMOSOMES ? • ANSWER: GENETIC INFORMATION KNOWN AS DNA 36 RIBOSOMES • One of the most important jobs carried out in the cell is ribosomes making proteins. • Proteins are assembled on ribosomes. 37 38 • Ribosomes are small particles of RNA and protein and are found throughout the cytoplasm. • Ribosomes produce proteins by following coded instructions that come from the nucleus. 39 ? QUESTION ? • WHAT DO RIBOSOMES PRODUCE ? • ANSWER: PROTIENS 40 PARTS OF THE CELL • Cell biologists divide eukaryotic cell into two parts: the nucleus and the cytoplasm. • The cytoplasm is the portion of the cell that is outside the nucleus. 41 Cell basics . . . Plasma membrane Nucleus Cytosol Organelles Cytoplasm 42 Cytoskeleton fibers adsorb water and crosslink to each other, giving the cytoplasm the consistency of gelatin (without the strawberry flavor) 43 ENDOPLASMIC RETICULUM • The ER membrane – Is continuous with the nuclear envelope Smooth ER Rough ER ER lumen Cisternae Ribosomes Transport vesicle Smooth ER Nuclear envelope Transitional ER Rough ER 200 µm 44 ENDOPLASMIC RETICULUM • The endoplasmic reticulum is also known as ER. • It is the site where lipid components of the cell membrane are assembled along with proteins and other materials. 45 • The portion of the ER involved in synthesis of plasma membrane, lysosomal, and secretory proteins is called Rough ER. • Rough ER = ribosomes found on the surface of endoplasmic reticulum. • Newly made proteins leave ribosomes and are inserted into the Rough ER, where they can be chemically modified. 46 • There are other portions of the ER called Smooth ER because no ribosomes are embedded. • Smooth ER contains enzymes that synthesize lipids and are involved in the detoxification of drugs. (liver cells contain Smooth ER) 47 48 ? QUESTION ? • WHAT IS THE ROLE OF THE ROUGH ER ? • ANSWER: TO SYNTHESIZE PLASMA MEMBRANE, LYSOSOMAL AND SECRETORY PROTEINS 49 GOLGI APPARATUS • The Golgi Apparatus receives proteins from the Rough ER. • The job of the Golgi Apparatus is to modify, sort, and package proteins for storage or secretion outside the cell. 50 • Functions of the Golgi apparatus Golgi apparatus cis face (“receiving” side of Golgi apparatus) 1 Vesicles move 2 Vesicles coalesce to 6 Vesicles also form new cis Golgi cisternae from ER to Golgi transport certain Cisternae proteins back to ER 3 Cisternal maturation: Golgi cisternae move in a cisto-trans direction 5 Vesicles transport specific proteins backward to newer Golgi cisternae 0.1 0 µm 4 Vesicles form and leave Golgi, carrying specific proteins to other locations or to the plasma membrane for secretion trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus 51 • The Golgi Apparatus is like a customizing shop that puts on the final touches before proteins are shipped out. 52 53 54 ? QUESTION ? • WHAT IS THE ROLE OF THE GOLGI APPARATUS ? • ANSWER: IT MODIFIES, SORTS, AND PACKAGES PROTEINS. 55 56 LYSOSOMES • Lysosomes are the clean up crew of the cell. • They are small organelles filled with enzymes that break down and digest lipids, carbohydrates, and proteins. 57 Lysosomes carry out intracellular digestion by Phagocytosis Nucleus - Autophagy 1 µm Lysosome containing two damaged organelles 1µm Mitochondrio n fragment Peroxisome fragment Lysosome Lysosome contains active hydrolytic enzymes Food vacuole fuses with lysosome Hydrolytic enzymes digest food particles Lysosome fuses with vesicle containing damaged organelle Hydrolytic enzymes digest organelle components Digestive enzymes Lysosome Plasma membrane Lysosome Digestion Food vacuole Vesicle containing damaged mitochondrion (a) Phagocytosis: lysosome digesting food Digestion (b) Autophagy: lysosome breaking down damaged organelle 58 ? QUESTION ? • WHAT IS THE ROLE OF THE LYSOSOME ? • ANSWER: CLEAN UP THE CELL AND GET RID OF WASTE MATERIALS. 59 60 VACUOLES • Vacuoles are saclike structures that store materials such as water, salts, proteins, and carbohydrates. • Plant cells have vacuoles. They help each cell maintain water pressure to hold up heavy structures such as leaves and flowers. 61 • Some single-celled organisms have contractile vacuoles which regulates the water inside the cell. • Contractile vacuoles help cells maintain Homeostasis (“internal balance”) 62 • Central vacuoles – Are found in plant cells – Hold reserves of important organic compounds and water Central vacuole Cytosol Tonoplast Nucleus Central vacuole Cell wall Chloroplast 5 µm 63 • Central vacuoles – Are found in plant cells – Hold reserves of important organic compounds and water Central vacuole Cytosol Tonoplast Nucleus Central vacuole Cell wall Chloroplast Figure 6.15 5 µm 64 65 ? QUESTION ? • WHAT IS THE ROLE OF A VACUOLE ? • ANSWER: THEY STORE MATERIALS AND HELP PLANTS MAINTAIN THEIR STRUCTURE. 66 67 CELLS AND THEIR POWER • Nearly all eukaryotic cells, including plants contain Mitochondria. • Mitochondria are organelles that convert the chemical energy stored in food into compounds that are more convenient. 68 • In humans, all or nearly all our mitochondria come from the cytoplasm of the ovum, or egg cell. 69 • In plants chloroplasts are the organelles that capture the energy from the sunlight and convert it into chemical energy in a process called photosynthesis. 70 • Both mitochondria and chloroplasts are the only organelles that have small DNA molecules. • Scientists believe that these two organelles may have been descendants of ancient prokaryotes at one time. 71 72 73 CYTOSKELETON • The cytoskeleton is a network of protein filaments that help the cell maintain its shape. • Microfilaments and Microtubules make up the cytoskeleton. • Microfilaments are threadlike and made of a protein called actin. 74 • Microtubules are hollow structures that are made up of proteins called tubulins. • In animal cells, tubulin helps in the development of centrioles. • Centrioles are located near the nucleus and help in cell division. 75 76 77 CELL MEMBRANE • The cell membrane regulates what enters and also leaves the cell and also provides protection and support. • The cell membrane is made up of two layers called a phospholipid bilayer. • Scientists refer to it as a “mosaic model” that contains different molecules. 78 79 80 CELL WALL • Many cells also produce a strong supporting layer around the membrane known as the cell wall. • Cell walls are present in plants, algae, fungi, and many prokaryotes. • The main function of the cell wall is to provide support and protection for the cell. 81 A typical plant cell Nuclear envelope Nucleolus Chromatin NUCLEUS Centrosome Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes (small brwon dots) Central vacuole Tonoplast Golgi apparatus Microfilaments Intermediate filaments CYTOSKELETON Microtubules Mitochondrion Peroxisome Plasma membrane Chloroplast Cell wall Plasmodesmata Wall of adjacent cell In plant cells but not animal cells: Chloroplasts Central vacuole and tonoplast Cell wall Plasmodesmata 82 CELL WALL 83 DIFFUSION THROUGH CELL BOUNDARIES • In a solution, particles move constantly. They will collide into one another and tend to spread out randomly. • Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. • This process will continue until equilibrium is reached. • No energy is required by the cell. 84 85 86 • • Osmosis is the diffusion of water through a selectively permeable membrane. Selectively permeable membrane means that some substances can pass and some cannot. 87 88 • There are 3 effects of Osmosis on the cell: 1.Isotonic: The concentration is the same on both sides of the cell. (Normal Cell) 2.Hypertonic: The solution, in which the cell is in, is of higher solute concentration than the cell. (Skinny Cell) 3.Hypotonic: The solution, in which the cell is in, is of lower solute concentration than the cell. (Swollen Cell) 89 90 91 92 93 94 95 FACILITATED DIFFUSION • Sometimes in a cell there are certain molecules that cross the selective permeable membrane that are to large for it to happen by osmosis. • The process that helps large molecules pass the membrane in a cell is called facilitated diffusion. • This happens when protein molecules act as channels for large molecules to pass from one side of the membrane to the other side. • No energy is required by the cell. 96 97 ACTIVE TRANSPORT • This a process in which the cell does require energy to transport materials across the cell membrane. • This is the movement of molecules against the concentration differences. • Types of active transport consist of: • 1. Endocytosis= this occurs by infoldings, or pockets, of the cell membrane. 98 99 100 2. Phagocytosis= “cell eating” extensions of the cytoplasm surround a particle and package it within a cell a food vacuole. 3. Pinocytosis= tiny pockets form along the cell membrane, fill with liquid and then pinch off to form vacuoles within the cell. 4. Exocytosis= this is the removal of contents from the cell. Contractile vacuoles are examples of exocytosis. 101 102 103 104 105 106 THE DIVERSITY OF CELLULAR LIFE • Single cell organisms are called unicellular. • Organisms made of many cells are called multicellular organisms. • Cells through out organisms can develop in different ways to perform different tasks. This process is called cell specialization. 107 LEVELS OF ORGANIZATION • In multicellular organisms, cells are the first level of organization. • Similar cells are grouped into units called tissues. • Many groups of tissues working together form an organ. • A group of organs that work together to perform a particular function is called an organ system. 108 109