The Fundamental Units of Life Pt.1
The Fundamental Units of Life Pt.1 Biology 105
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This 0 page Bundle was uploaded by Ashley-Maria Farnen on Tuesday November 10, 2015. The Bundle belongs to Biology 105 at Indiana University of Pennsylvania taught by in Summer 2015. Since its upload, it has received 39 views. For similar materials see Cell Biology in Biology at Indiana University of Pennsylvania.
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Date Created: 11/10/15
Bio Notes Chapter 6 part 1 1 Overview The Fundamental Units of Life a b c d All Organism are made of cells The cells is the simplest collection of matter that can be alive Cell Structure is correlated to cellular function All cells are related by their descent from earlier cells 2 The Cell A living unit grater than the sum of its parts a b Cells rely on the integration of structure and organelles in order to function For example a macrophage s ability to destroy bacteria involves the whole cell coordinating component such as cytoskeleton ysosomes and plasma membrane 3 Biologists use microscopes and the tools of biochemistry to study cells a b D k l 4 Cell F Various techniques enhance contrast and Though usually too small to be seen by the unaided eye cells can be complex Scientists use microscopes to visualize cells too small to see with the naked eye In a light microscope LM visible light is passed through a specimen and then through glass lenses Lenses refract bend the light so that the image is magni ed Three important parameters of microscopy i Magni cation the ratio of an object s image size to its real size Resolution the measure of the clarity of the image or the minimum distance of two distinguishable points Contrast visible differences in parts of the sample LMs can magnify effectively to about 1000 times the size of the actual specimen 6 enable cell components to be stained or labeled Most subcellular structures including organelles membrane enclosed compartments are too small to be resolved by an LM Two basic types of electron microscopes EMs are used to study subcellular structures Scanning electron microscopes SEMs focus a beam of electrons onto the surface of a specimen providing images that look 3D Transmission electron microscopes TEMs focus a beam of electrons through a specimen TEMs are used mainly to study the internal structure of cells ractionation Cell fractionation takes cells apart and separates the major organelles from one another Centrifuges fractionate cells into their component parts Cell fractionation enables scientists to determine the functions of organelles d Biochemistry and cytology help correlate cell function with structure e 5 Eukaryotic cells have internal membranes that compartmentalize their functions a The functional unit of every organism is one of two types of cells prokaryotic or eukaryotic b Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells c Protists fungi animals and plants all consist eukaryotic cells 6 Comparing Prokaryotic and Eukaryotic Cells a Basic i ii iii features of all cells Plasma membrane Semi uid substance called cytosol Chromosomes carry genes Ribosomes make proteins b Prokaryotic cells are characterized by having i ii iii iv 211 Pearsm Educal l 0 No nucleus 1 DNA in an unbound region called the nucleoid No membranebound organelles Cytoplasm bound by the plasma membrane c Eukaryotic cells are characterized by having vi vii viii ix x d A Pan DNA in a nucleus that is bounded by a membranous nuclear envelope Membranebound organelles Cytoplasm is the region between the plasma membrane and nucleus Eukaryotic cells are generally much larger than prokaryotic cells The plasma membrane is a selective barrier that allows sufficient passage of oxygen nutrients and waste to service the volume of every cell The general structure of a biological membrane is a double layer of phospholipids Metabolic requirements set upper limits on the size of cells The surface area to volume ratio of a cell is critical As the surface area increases by a factor of n2 the volume increases by a factor of n3 Small cells have a greater surface area relative to volume oramic View of the Eukaryotic Cell A eukaryotic cell has internal membranes that partition the cell into organelles Plant and animal cells have most of the same organelles e The eukaryotic cell s genetic instructions are housed in the nucleus and carried out by the ribosomes iv V vi vii The nucleus contains most of the DNA in a eukaryotic cell Ribosomes use the information from the DNA to make proteins 1 The nucleus contains most of the cell s genes and is usually the most conspicuous organelle 2 The nuclear envelope encloses the nucleus separating it from the cytoplasm 3 The nuclear membrane is a double membrane each membrane consists of a lipid biayer In the nucleus DNA is organized into discrete units called chromosomes Each chromosome is composed of a single DNA molecule associated with proteins The DNA and proteins of chromosomes are together called chromatin Chromatin condenses to form discrete chromosomes as a cell prepares to divide The nucleolus is located within the nucleus and is the site of ribosomal RNA rRNA synthesis f Ribosomes Protein Factories Ribosomes are particles made of ribosomal RNA and protein Ribosomes carry out protein synthesis in two locations 1 In the cytosol free ribosomes 2 On the outside of the endoplasmic reticulum or the nuclear envelope bound ribosomes g The endomembrane system regulates protein traffic performs metabolic functions Components of the endomembrane system 1 Nuclear envelope 2 Endoplasmic reticulum 3 Golgi apparatus 4 Lysosomes 5 Vacuoles 6 Plasma membrane These components are either continuous or connected via transfer by vesicles h The endoplasmic Reticulum Biosynthetic Factory The endoplasmic reticulum ER accounts for more than half of the total membrane in many eukaryotic cells The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER 1 Smooth ER which lacks ribosomes 2 Rough ER surface is studded with ribosomes i Functions of Smooth ER The smooth ER 1 Synthesizes lipids 2 Metabolizes carbohydrates 3 Detoxi es drugs and poison 4 Stores calcium ions 5 The rough ER a Has bound ribosomes which secrete glycoproteins proteins covalently bonded to carbohydrates b Distributes transport vesicles proteins surrounded by membranes C Is a membrane factory for the cell j The Golgi Apparatus Shipping and Receiving Center The Golgi apparatus consists of attened membranous sacs called cisternae Functions of the Golgi apparatus 1 Modi es products of the ER 2 Manufactures certain macromolecules 3 Sorts and packages materials into transport vesicles k Lysosomes Digestive Compartments vi A ysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes can hydrolyze proteins fats polysaccharides and nucleic acids Lysosomal enzymes work best in the acidic environment inside the ysosome Some types of cell can engulf another cell by phagocytosis this forms a food vacuole A ysosome fuses with the food vacuole and digests the molecules Lysosomes also use enzymes to recycle the cell s own organelles and macromolecules a process called autophagy Vacuoles Diverse Maintenance Compartments A plant cell or fungal cell may have one or several vacuoles derived from endoplasmic reticulum and Golgi apparatus Food vacuoles are 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 m Mitochondria and chloroplasts change energy from one form to another i Mitochondria are the sites of cellular respiration a metabolic process that uses oxygen to generate ATP ii Chloroplasts found in plants and algae are the sites of photosynthesis iii Peroxisomes are oxidative organelles n The Evolutionary Origins of Mitochondria and Chloroplasts i Mitochondria and chloroplasts have similarities with bacteria ii Enveloped by a double membrane iii Contain free ribosomes and circular DNA molecules iv Grow and reproduce somewhat independently in cells
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