BIOL 201 Chapter 4 notes PART 1
BIOL 201 Chapter 4 notes PART 1 BIOL 201-015
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This 4 page Class Notes was uploaded by Kayla Wisotzkey on Thursday September 29, 2016. The Class Notes belongs to BIOL 201-015 at Towson University taught by Cheryl D. Warren in Fall 2016. Since its upload, it has received 19 views. For similar materials see Intro to Cell Biol & Genetics in Biology at Towson University.
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Date Created: 09/29/16
Kayla Wisotzkey Chapter 4 Part 1 Cells: differ in size and complexity Cells were discovered in 1665 by Robert Hooke Schleiden and Schwann proposed the cell theory Modern cell theory: 1) All organisms are composed of one or more cells, and the life processes of metabolism and heredity occur in these cells 2) Cells are the smallest living things 3) Cells arise only from preexisting cells No additional cells are spontaneously originating at present… life represents a continuous line of descent from early cells Cell size is limited most cells are small because of the necessity of diffusion of substances in and out of them diffusion: movement of molecules or particles from a concentrated region to a less concentrated region Rate of diffusion is affected by: 1) Surface area available for diffusion 2) Temperature 3) Concentration gradient of diffusion substance 4) Distance over which diffusion must occur surfacetovolumeratio: as a cell’s size increases, its volume increases more quickly than its surface area… it’s beneficial for a cell to be small Microscopes other than egg cells, not many cells are visible to the naked eye Resolution: the minimum distance two points can be apart and still be distinguished as two separate points… there is limited resolution in the human eye Lightmicroscopes: operate with visible light, use two magnifying lenses to achieve high clarity and magnification… not powerful enough to resolve many structures within cells, can resolve structures that are 200 nm apart Electron microscope: has 1000 times the resolving power of a light microscope, employs electron beams, resolves structures that are 0.2 nm apart Transmission electron microscope: the electrons used to visualize the specimens are transmitted through the material Scanning electron microscope: beams electrons onto the surface of the specimen (3D image) Chemical stains: stains are absorbed differently by the different structures of the cell, makes it easier to see the different structures Structural features of cells 4 major features all cells have in common: 1) nucleoid or nucleus: where DNA is located 2) Cytoplasm 3) ribosomes: used in protein synthesis 4) plasma membrane: phospholipid bilayer, proteins embedded in it In prokaryotes, most of the genetic material lies in a single circular molecule of DNA located in the nucleoid In eukaryotes, the DNA is stored in the nucleus, which is surrounded by the double membrane nuclear envelope Cytoplasm: the semifluid matrix that fills the interior of the cell; aqueous medium Organelles: any macromolecular structure in the cytoplasm that has a job Cytosol: the fluid portion of the cytoplasm; contains dissolved organic molecules and ions Plasma membrane: encloses a cell, separates its contents from its surroundings; phospholipid bilayer Prokaryotes consist of cytoplasm surrounded by a plasma membrane singlecelled, encased within a rigid cell wall: the whole prokaryote operates as one unit chromosomes are circular some harvest light by photosynthesis, and some break down organisms and recycle their components contain organelles like ribosomes that carry out protein synthesis, but lack membrane bound organelles… so DNA, enzymes, and other cytoplasmic constituents have access to the whole cell Two main domains: Archaea and Bacteria Bacteria: encased by a cell wall that is composed of peptidoglycan (carbohydrate matrix crosslinked by polypeptide units) Bacterial cell walls protect the cell, maintain its shape, and prevents excessive uptake or loss of water Archaea: their cell walls are composed of various compounds including polysaccharides and proteins, but lack peptidoglycan Archaea can’t adapt to changing temperatures because they aren’t able to alter the degree of saturation of their hydrocarbons Prokaryotic flagellum: protein fibers that extend out from the cell. Their rotary motor, which is powered by a protein gradient, powers the flagellum Eukaryotes central vacuole: a large membranebound sac that is inside a plant cell stores proteins, pigments, and waste materials involved in plant cell growth tonoplast: the membrane surrounding the central vacuole contains channels for water that are used to maintain the cell’s osmotic balance vesicles: small sacs found in both plants and animals that store and transport a variety of materials the DNA is found in the nucleus and is wound around proteins and packaged into chromosomes cytoskeleton: a network a protein microfilaments and microtubules in the cytoplasm that maintains the shape of the cell and anchors the organelles nucleus: the largest organelle that is usually found in the center of the cell membrane bound, stores DNA and enables the synthesis of all proteins nucleolus: dark middle of the nucleus, intensive synthesis of rRNA happens here nuclear envelope: the bounding structure of the nucleus made of two phospholipid bilayers with the outer one connected to the endoplasmic reticulum nuclear pores: shallow openings in the nuclear envelope that allow some proteins and nucleic acids in and out of the nucleus nuclear lamina: network of fibers on the inner surface of the nucleus made of nuclear lamins, gives nucleus shape chromatin: the complex of DNA and proteins of which chromosomes are composed can cause changes in gene expression ribosomes: make proteins; there are to forms: bound: attached to the Endoplasmic Reticulum, synthesizing a protein free: floating in the cytoplasm, synthesize proteins in cytoplasm, nucleus, mitochondria, and other organelles The Endomembrane System endoplasmic reticulum: largest of the internal membranes, composed of a phospholipid bilayer embedded with proteins, forms channels in the cytoplasm. Two types of endoplasmic reticulum: 1. Rough E.R.: has a pebbly surface because there are proteins synthesized on the surface. glycoprotein: newly synthesized proteins attached to carbohydrates cells that synthesize proteins have more R.E.R. (antibodies) 2. Smooth E.R.: contains a variety of structures ranging from a network of tubules to flattened sacs and tubular arrays; more tubular than R.E.R. enzymes anchored within the S.E.R. are involved in the synthesis of carbohydrates and lipids S.E.R. stores intracellular Ca to keep the cytoplasmic level low so Ca can be used as a signaling molecule S.E.R. modifies foreign substances to make them less toxic cells that carry out lipid synthesis have more S.E.R. (brain, testes, intestine) Golgi bodies: collections of flattened stacks of membranes in the cytoplasm functions in collection, packing, and distribution proteins and lipids manufactured in the E.R. are transported and modified in the Golgi apparatus (the Golgi bodies add and modify sugar chains) Polysaccharides secreted by plants are synthesized by the Golgi bodies lysosome: membranebound enzyme that is produced by the Golgi bodies help catalyze macromolecules microbodies: membraneenclosed vesicles that contain enzymes peroxisome: a microbody that contains enzymes involved in the oxidation of fatty acids; contains the enzyme catalase which breaks down hydrogen peroxide into water and oxygen
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