BOT 200 Chapter 3
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This 5 page Class Notes was uploaded by Keely Egelhoff on Friday September 9, 2016. The Class Notes belongs to 200 at Western Illinois University taught by Dr. Meiers in Fall 2016. Since its upload, it has received 12 views. For similar materials see Introduction to Botany in Botany at Western Illinois University.
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Date Created: 09/09/16
Chapter 3 Cell structure Organelles smaller parts nuclei, mitochondria and chloroplasts Cells are also the physical framework where metabolism occurs Composed of more than one cell is multicellular organism One cell is unicellular The division of labor allows the entire organism to become more efficient Negative consequences- as each cell becomes more specialized it depends more on others Having thick walls makes other cells create photosynthesis mineral absorption and reproduction Mother cell is the first cell and after it divides it produces two daughter cells grows into protoplasm Membranes Membranes perform many important tasks Regulate passage of molecules into and out of cells and organelles Divide the cell into numerous compartments Act as surfaces that hold enzymes Made up of proteins and two layers of phospholipid molecules form a single layer called monolayer Hydrophilic phospholipids Hydrophobic fatty acids project out of the layer If agitated they will fold over and form a bilayer Can diffuse laterally but not vertically Intrinsic proteins- proteins that are even partially immersed in the lipid bilayer Extrinsic proteins/peripheral proteins are located outside the membrane and lay next to it Domains are proteins that interact with adjacent proteins Fluid mosaic membrane- heterogeneous liquid Glycoproteins are oligosaccharides bound to intrinsic proteins converted Make the membrane more distinctive and easy to recognize Properties of Membranes Vesicles- entire pieces of membrane are moved as small bubbles Membrane fusion allows for transport of material Exocytosis is a means to excrete almost anything Endocytosis is basically the opposite process: a small invagination forms in the outer membrane then pinches shut creating a new vesicle Selectively/differentially permeable- all biological membranes substances can cross the membrane more easily and rapidly Facilitated diffusion- movement of charged substances is assisted by large intrinsic proteins that span the membrane and act as hydrophilic channels Molecular pumps- actually bind to a molecule on one side of the membrane changes shape using energy and releases the molecule on the other side Active transport is the active pump Compartmentalization all life depends on it Freely permeable membrane- allows everything to pass through quickly Impermeable membrane- nothing I allowed through Constantly changing Basic cell types Prokaryotic are simpler and found in bacteria Eukaryotic are found in plants animals’ fungi and protists has a true membrane Protoplasm- is a mass of proteins lipids nucleic acids and water Plasma membrane- membrane that completely covers the surface of the protoplasm selectively permeable Nucleus serves as the archive Nuclear envelope surrounds the nucleus of a eukaryotic cell composed of and outer membrane and inner one Nuclear envelope separates nuclear material from the rest of the cell Small pores in this are nuclear pores involved in the transport of material between the nucleus and the rest of the protoplasm Central Vacuole Vacuoles have a single membrane and carry mainly water and salts Can form fast and make the cell grow fast as well Can also hold nutrient and waste products Helps protect the plant by keeping the waste Old cell and membranes are broken down here Cytoplasm/ Mitochondria Most of the material left floating around is cytoplasm Mitochondria are organelles that carry out cellular respiration Folded mitochondrial membranes are cristae Matrix is in between the cristae Around all of this is the outer mitochondrial membrane Freely permeable inner mitochondrial membrane Have their own DNA and ribosomes different from the rest of the cells Plastids Are a group of dynamic organelles able to perform many functions Carries out photosynthesis carried out by chloroplasts Are the site of synthesis of amino acids Have an inner and outer membrane Inner fluid is called stroma Grow and reproduce by pulling apart Proplastids are young rapidly dividing calls When exposed too light proplastids develop into chloroplasts which creates chlorophyll Thylakoids project into the stroma Granum is the bag like vesicles that stack together Key feature of photosynthesis is the active transport of protons into a small space to build up and electrical charge Amylopasts are proplastids that cannot photosynthesize and store starch for months or years in starchy seeds If exposed too light amyloplasts can be converted to chloroplasts Colors such as red, yellow, or orange can accumulate and are called chromoplasts Plastoglobuli are discrete droplets in a system that does not have grana but has pigments This is how the leaves change color in the fall the lipid pigments do not change like the chloroplasts so we can see the different colors Leucoplasts are unpigmented plastids that have neither chlorophyll nor lipid pigments Plant protein is called phytoferritin stored in the plastids Ribosomes Responsible for protein synthesis Polysome are ribosomes bound together by mRNA Endoplasmic Reticulum Large molecules are moved with the ER verses diffusion like a lot of smaller molecules Rough ER are ribosomes attached to the ER giving it the appearance of being rough ER that lacks ribosomes is smooth ER and is involved in lipid synthesis and membrane assembly After the ER derived vesicles reach the correct organelle the fuse with it SER is abundant only in cells that produce large amounts of fatty acids Dictyosomes Modifies material secreted by a cell Cisterna is ER vesicles accumulated on one side of the dictyosome that fused together The forming face is where all of these fuse together The maturing face are vesicles are being released after the contents have been processed Golgi bodies are cup shaped structures example is root hairs in plants Accumulating that dictyosomes also polymerize sugars into polysaccharides used in cell wall construction Endomembrane system consists of all membranes of the cell except the inner membranes of mitochondria and plastids Microbodies Cells are seen to contain numerous small spherical bodies Use stains to tell the contnts and types of reactions the bodies have Microbodies have two classes peroxisomes and glyoxysmoes Both isolate reactions that either produce or use the dangerous compound peroxide Peroxisomes are involved in detoxifying certain byproducts of photosynthesis closely associated with chloroplasts Dlyoxysomes occur only in plants are involved in converting stored fats into sugars Cytosol Cytosol is the volume of cytoplasm in a clear substance form Microtubules Are the most abundant and easily studied of the structural elements of a cell Act as a cytoskeleton holding certain regions of the cell surface back while others expand Can assemble into arrays like an antenna which can catch vesicles and guide them to specific sites or cover a region excluding vesicles from entering. Are the means of motility for both organelles and whole cells Alpha-tubulin and beta-tubulin are the types of protein in a globular tertiary structure Tubulin are further crystallizing into a straight tubule Microtubule can depolymerize back into its monomers Centriole is made up of nine sets of three short microtubules the nine triplets are held together by fine protein spokes Cilia and flagella cilia is short and occurs in groups flagella are longer and occus either singly or in sets of two or four Basal bodies appear to be identical to centrioles by electron microscopy Microfilaments Are constructed by the assembly of globular proteins usually actin Cell wall Metabolism and proving strength occurs in the cell wall Microfibril are parallel cellulose molecules that have crystallized Hemicelluloses are cellulose microfibrils thaqt are bound together by polysaccharides They deposite between the cellulose microfibrils and bind to cellulose with hydrogen bonds Middle lamella holds the walls together and is composed of pectic substances Primary cell wall is the outer wall Secondary cell wall in between the primary wall and the plasma membrane Much thick than primary wall and contains compound lignin Fungal Cells Do not contain plastids of any type Walls contain chitin not cellulose Chitin is much like cellulose but contains nitrogen and is synthesized by a different mechanism Association of Cells Plasmodesmata allow plant cells to communicate Primary pit filed is where clusters of plasmodesmata are Symplast is the protoplasm within a single plant and is all interconnected
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