BIO 100 Chapter 4 Notes
BIO 100 Chapter 4 Notes BIO 100
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This 5 page Class Notes was uploaded by Lauren Tebbe on Wednesday September 28, 2016. The Class Notes belongs to BIO 100 at Eastern Kentucky University taught by Kenneth Blank in Fall 2016. Since its upload, it has received 6 views.
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Date Created: 09/28/16
Chapter 4 BIO notes 1 Cells Under the Microscope o A cell is the fundamental unit of life. o Structure of each cell is specialized to perform its particular function. o The light microscope allows us to see cells but not much of their complexity because properties of light limit the amount of detail revealed. (can see chloroplasts, human eggs, plant cells, most bacteria) o Electron microscopes overcome this limit by using beams of electrons instead of beams of lights. This enables us to see the surface features and fine details of cells plus larger molecules in them. o Atomic force microscope is able to distinguish objects around a nanometer in size o Cells are so small because they need to rapidly exchange materials with the external environment (nutrients in waster out). o The higher the ratio of surface to internal volume, the faster the exchange of materials with the environment. o Scanning electron microscope uses a beam of electrons to view 3D surface features 2 Plasma Membrane o All cells have an outer membrane called the plasma membrane which acts as a boundary between the outside and inside of a cell. Regulates the passage of molecules and ions in and out of cell. o Plasma membrane is a phospholipid bilayer with embedded proteins. The polar (hydrophilic) heads are in 2 different directions. The nonpolar (hydrophobic) tails face inward towards each other where there is no water. o The fluid components is the phospholipid molecules. o Plasma membrane structure is called the fluid-mosaic model since the protein molecules embedded in the membrane have a pattern with the fluid phospholipid bilayer. o Short chains of sugars are attached to the outer surface of proteins forming glycoproteins, often involved in the identity of the cell. 3 Functions of Membrane Proteins: o Channel Proteins - form a tunnel across the entire membrane allowing only one or a few types of specific molecules to simply move across the membrane o Transport Proteins - involved in the passage of molecules and ions through the membrane with an input of energy. o Cell Recognition Proteins - glycoproteins that enable our bodies to distinguish between our own cells and the cells of other organisms. o Receptor Proteins - has a shape that allows specific molecules called a signal molecule to bind to it causing the receptor protein to change shape and being about cellular response o Enzymatic Proteins - directly participate in metabolic reactions, without these, the cell would never be able to perform degradative and synthetic reactions. o Junction Proteins - junctions assist cell-to-cell adhesion and communication. 4 The 2 Main Types of Cells o The idea that all organisms are composed of cells and that cells come only from preexisting cells are the two central tenets of the cell theory. o Common characteristics in all cells: - plasma membrane - semifluid interior called cytoplasm where chemical reactions occur - genetic material (DNA) provides info needed for cellular activities like growth and reproduction o Divided into 2 main types bases on the way their genetic material is organized: Prokaryotic (lack membrane bounded nucleus and DNA is located in the region of the cytoplasm called the nucleoid) Eukaryotic (has nucleus that houses its DNA) 1 Prokaryotic Cells o Contains organisms from the domains Archaea and Bacteria o Generally much smaller in size and simpler in structure which allows them to reproduce very quickly and effectively o Many bacteria decompose dead remains and contribute to ecological cycles o E coli is a bacterium that lives in humans intestines o In bacteria, the cytoplasm is surrounded by a plasma membrane and the cytoplasm contains enzymes that are organic catalysts that speed up the many types of chemical reactions that are required to maintain an organism. o Cell wall maintains shape o The capsule is a protective layer of polysaccharides lying outside the cell wall. o DNA of bacterium is located in a single circular coiled chromosome that resides in a region of the celled called the nucleoid. o The many proteins specified by bacterial DNA are synthesized on tiny structures called ribosomes. o Flagella are tail-like appendages that allow bacteria to propel themselves (rotary). 2 Eukaryotic Cells o Membranes create internal spaces divide the labor necessary to conduct life functions, eukaryotic are very compartmentalized. o Organelles are the compartments that carry out specialized functions that together allow the cell to be more efficient and successful and are surrounded by a membrane with embedded proteins called enzymes. o Nucleus contains genetic and heredity info and communicates with ribosomes in the cytoplasm and the organelles of the endomembrane system o Products are transported around the cell by transport vesicles (membranous sacs that enclose the molecules and keep them separate from the cytoplasm). o Vesicles move around by means of an extensive network of protein fibers called the cytoskeleton which also maintains cell shape and assists with cell movement. o Chloroplasts and mitochondria are responsible for majority of energy in plants. 3 Nucleus and Ribosomes o Nucleus contains chromatin (network of DNA and protein, composed of DNA, protein and RNA) within in semifluid nucleoplasm o Chromatin condense and form rodlike structure called chromosomes before division o Info is transferred from the nucleus to the ribosome, the info in the RNA is translated into a polypeptide chain o rRNA is produced in the nucleolus. o Nuclear envelope (double membrane of phospholipids) separates nucleus from cytoplasm o Nuclear pores allows communication and passage of RNA molecules out of nucleus and into cytoplasm o Ribosomes are in prokaryotes and eukaryotes with subunits of rRNA and proteins o Ribosomes bind to endoplasmic reticulum where polypeptide being synthesized enters the lumen where it can further be modified and assume final shape. o Ribosome sites are important for protein synthesis. 4 Endomembrane System o Consists of the nuclear envelope, the membranes endoplasmic reticulum, golgi apparatus, and numerous vesicles. o Endoplasmic reticulum consists of a complicated system of membranous channels and saccules. 1. Rough ER is studded with ribosomes on the side of the membrane that faces the cytoplasm meaning its able to synthesize polypeptides. Transports vesicles taking proteins to other parts of cell 2. Smooth ER is continuous with rough ER but does not have attached ribosomes. Synthesizes lipids like phospholipids and steroids. Also transports vesicles that carry molecules to other parts of the cell o The Golgi Apparatus consists of stacks of slightly curved, flattened saccules resembling pancakes. Transfer station: receives transport vesicles from rough and smooth ER, modified between the 2 saccules, and sorts modified molecules and packages them into new transport vesicles according to their new destinations. o Lysosomes are vesicles produced by the Golgi apparatus that digest molecules and even portions of the cell itself. o Vacuoles, like vesicles, are membranous sacs but are larger than vesicles. Contractile rid of excess water and digestive break down nutrients. 5 Energy-Related Organelles o Chloroplasts and mitochondria are two eukaryotic membranous organelles that specialize in energy conversion. o Chloroplasts use solar energy to synthesize carbs. o Mitochondria break down carbs to produce adenosine triphosphate (ATP) molecules. o ATP serves as a carrier of energy in cells and is used whenever a cell synthesize molecules, transport molecules, or carries out a special function such as muscle contraction or nerve conduction. o Carbon dioxide gas, water, energy from the sun are used to produce carbs during photosynthesis in the chloroplasts. o Inner membrane is called the stoma containing a concentrated mix of enzymes and disclike sacs called thylakoids called granum. o Pigments that capture solar energy are in the membranes of the thylakoids and enzymes that synthesize carbs are in the stroma. o Mitochondria are much smaller than chloroplasts and like chloroplasts they are bounded by a double membrane. Inner is called the cristae which increase surface area. o Mitochondria are often called the powerhouses of cells because they produce most of the ATP the cell utilizes. o Inner membrane encloses the matrix which breaks down carbs and other nutrient molecules. Cellular Respiration is also used because oxygen is needed and carbon dioxide is given off. o The matrix also contains mitochondrial DNA and ribosomes. o All eukaryotic cells have mitochondria but only chloroplast organisms have chloroplasts. o Chloroplasts and Mitochondria contain their own DNA o Chloroplasts are double smooth membranes surrounding a highly folded third membrane and a fluid called the stoma. 6 The Cytoskeleton and Motor Proteins o The cytoskeleton is a network of interconnected protein filaments and tubules that extends from the nucleus to the plasma membrane in eukaryotic cells. They maintain shape and with motor proteins, allow the cell and its organelles to move. o Cytoskeleton includes microtubules, intermediate filaments, and actin filaments. o Motor proteins associated with the cytoskeleton are instrumental in allowing cellular movements, major ones being myosin, kinesin, and dynein o Myosin interacts with actin when movement occurs, when a cell contracts, myosin pulls actin filaments towards the middle of the cell. o Kinesin and dynein move along microtubules much as a car travels along a highway moving organelles from one place to another acting similarly when transport vesicles take materials from the Golgi apparatus to their final destinations. o Microtubules are small, hollow cylinders composed of 13 long chains of tubulin dimers, they are dynamic easily changing length by removing tubulin dimers through a process controlled by centrosome (microtubule organizing center) o Microtubules that radiate from the centrosome near the nucleus maintain shape so materials can move through. o Intermediate filaments are medium size between actin and microtubules, ropelike assembly of proteins that typically run between nuclear envelope and plasma membrane. o Each actin consists of 2 chains of globular actin monomers twisted about one another in a helical manner to form a long filament. They support the cell and microvilli. 7 Centrioles o Centrioles are located in centrosomes and are short, barrel-shaped organelles composed of microtubules. 8 Cilia and Flagella o Whiplike projections of cells. Cilia move swiftly and flagella move in an undulating snakelike fashion. Cilia are short and flagella are longer 9 Plant Cell Walls o All plants have cell walls. Primary cell walls contain cellulose fibrils and noncellulose substances allowing the wall to stretch when the cell is growing. Middle lamella is the layer that holds two plants cells together. o Secondary cell walls form inside the primary cell wall and have greater quantity of cellulose fibrils, contains lignin for added strength. o Living cells are connected by plasmodesmata which is numerous, membrane-lined channels that pass thought the cell wall. Only allows water and small solutes to pass freely from cell to cell. 10 Exterior Cell Surfaces in Animals o Animal cells do not have a cell wall but they do have 2 other exterior surface features of interest: An extracellular matrix existing outside the cell and various junctions occur between some cell types. o The extracellular matrix is a meshwork of fibrous proteins and polysaccharides in close association with the cell that produced them . (Collagen and elastin are proteins in it) o Polysaccharides direct migration of cells along collagen fibers during development o 3 types of junctions are found between certain cells: adhesion, tight, and gap. o The types of junction depends on whether or not the cells needs to be able to exchange materials and if the cells need to be joined together very tight. o Adhesion junctions, internal cytoplasmic plaques are firmly attached to cytoskeleton within each cell and are joined by intercellular filaments. Firm but allows stretching. o Tight Junctions in plasma membrane, proteins actually attach to each other, producing zipper like fasting. o Gap junctions allow cells to communicate, formed by 2 identical plasma membrane channel joining. Allows molecules and ions to pass between them. Six membrane proteins allow the joined channel to open and close.
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