BIO LECTURE 1710 CH4
BIO LECTURE 1710 CH4 BIOL 1710
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This 6 page Class Notes was uploaded by Anoosha Mardani on Tuesday September 20, 2016. The Class Notes belongs to BIOL 1710 at University of North Texas taught by Mark Burleson in Fall 2016. Since its upload, it has received 6 views. For similar materials see BIOL SCI MAJORS 1 in Biochemistry at University of North Texas.
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Date Created: 09/20/16
Bio Lecture September 14th, 2016 Chapter 4 Cells: The Fundamental Units of Life • Cell Theory - All organisms are made of cells • simplest collection of matter that can live • structure is correlated to function Comparing Prokaryotic and Eukaryotic Cells • Basic features of all cells: – Plasma membrane – Semifluid substance called cytosol – Chromosomes (carry genes) – Ribosomes (make proteins) • Prokaryotic cells are characterized by having • No nucleus, • No membrane-bound organelles – Cytoplasm bound by the plasma membrane • Eukaryotic cells – DNA in a membrane-bound nucleus – Membrane-bound organelles – Cytoplasm in the region between the plasma membrane and nucleus • plasma membrane - selective barrier that allows passage of oxygen, nutrients, and waste • a double layer of phospholipids • The logistics of carrying out cellular metabolism sets limits on the size of cells • The surface area to volume ratio is critical • Small cells have a greater surface area relative to volume What physical process limits the size of cells? A.Surface area B.Size C.Surface area/volume D.Volume E.Diffusion Answer: E. Diffusion The Nucleus: Information Central • The nucleus contains most of the cell’s genes and usually the most conspicuous organelle • double membrane; each membrane consists of a lipid bilayer • DNA and proteins form chromatin • Chromatin condenses to form discrete chromosomes • The nucleolus is site of ribosomal RNA (rRNA) synthesis • Ribosomes - particles made of ribosomal RNA and protein • carry out protein synthesis in two locations: – In the cytosol (free ribosomes) – On the endoplasmic reticulum or the nuclear envelope (bound ribosomes) Endomembrane system regulates protein traffic and performs metabolic functions in the cell • Components of the endomembrane system: – Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane • These components are either continuous or connected via transfer by vesicles Endoplasmic Reticulum: Biosynthetic Factory • ER accounts for more than half of the total membrane in eukaryotic cells • continuous with the nuclear envelope • two distinct regions: – Smooth ER - lacks ribosomes – Rough ER - with ribosomes studding its surface Functions of ER • The smooth ER – Synthesizes lipids – Metabolizes carbohydrates – Detoxifies poison – Stores calcium • The rough ER – secrete glycoproteins (proteins covalently bonded to carbohydrates that function in cell recognition) – Distributes transport vesicles, proteins surrounded by membranes – Is a membrane factory for the cell Lysosomes: Digestive Compartments • membranous sac of hydrolytic enzymes • enzymes hydrolyze (digest) proteins, fats, polysaccharides, and nucleic acids • Phagocytosis – eating another cell • lysosome fuses with the food vacuole and digests the molecules • also in recycling old organelles • Mitochondria and chloroplasts – Are not part of the endomembrane system – Have a double membrane – Have proteins made by free ribosomes – Contain their own DNA Chloroplasts: Capture of Light Energy • member of a family of organelles called plastids • contain chlorophyll, Cytoskeleton organizes structures and activities in the cell • cytoskeleton is a network of fibers extending throughout the cytoplasm • three types of molecular structures: – Microtubules – Microfilaments – Intermediate filaments Roles of the Cytoskeleton • supports the cell and maintain its shape • It interacts with motor proteins to produce motility • vesicles travel along “monorails” provided by the cytoskeleton Centrosomes and Centrioles • “microtubule-organizing center” • a pair of centrioles, each with nine triplets of microtubules arranged in a ring • not in plants Extracellular components and connections between cells • Most cells synthesize and secrete materials external to the plasma membrane – Cell walls of plants – The extracellular matrix (ECM) of animal cells – Intercellular junctions • Functions: – Support – Adhesion – Movement – Regulation Intercellular Junctions • Neighboring cells in tissues, organs, or organ systems can adhere, interact, and communicate through direct physical contact • There are several types of intercellular junctions – Plasmodesmata – Tight junctions – Desmosomes – Gap junctions Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells • tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid • Desmosomes (anchoring junctions) fasten cells together into strong sheets • Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells Microscopy • Two basic types of electron microscopes ( 1. Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3-D 2. Transmission electron microscopes (TEMs) focus a beam of electrons through a thin slice of a specimen • used to study the internal structure of cells • Food vacuoles formed by phagocytosis • Contractile vacuoles, found in many freshwater protists, pump excess water out of cells • Central vacuoles, found in many mature plant cells, hold organic compounds and water • Mitochondria - sites of cellular respiration, a metabolic process that generates ATP • Chloroplasts, found in plants and algae, are the sites of photosynthesis • Peroxisomes - oxidative organelles Peroxisomes: Oxidation • specialized metabolic compartments bounded by a single membrane • produce hydrogen peroxide and convert it to water • used to break down different types of molecules esp. fatty acids (beta oxidation) Components of the Cytoskeleton • Three main types of fibers – Microtubules are the thickest – Microfilaments, also called actin filaments, are the thinnest components – Intermediate filaments are fibers with diameters in a middle range
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