Chapter 3: the cellular level organization
Chapter 3: the cellular level organization BIOL 2457 - 001
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This 11 page Study Guide was uploaded by Raina McFarlin on Wednesday January 27, 2016. The Study Guide belongs to BIOL 2457 - 001 at University of Texas at Arlington taught by Timothy L Henry in Spring 2016. Since its upload, it has received 53 views. For similar materials see HUMAN ANATOMY & PHYSIOLOGY I in Biological Sciences at University of Texas at Arlington.
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Date Created: 01/27/16
Chapter 3: The cellular Level of Organization 1. Cell theory: a. The 3 tenets to cell theory i. ALL organisms are made up of 1 or more cells ii. The most basic unit of structure, function, & organization in all organisms. iii. Arise from pre-existing (living) cells b. Big ideas i. Genetic information stored in 1D chemical sequences in DNA (occasionally in RNA) is duplicated & passed on to daughter cells. ii. 1D chemical sequences stored in DNA code for both liner & 3D structure of RNA & proteins & ultimately the architecture of cells & tissues. iii. Macromolecular structures assemble from subunits iv. Membranes; 1. separate cells from their external environment, 2. Form biochemically distinct compartments in eukaryotic cells 3. Grow by expansion of preexisting membranes. v. Signal-receptor interaction target cellular constituents to their correct locations vi. Many cellular constituent move by diffusion, but energy-consuming pumps motors move some s=constituents & whole cells. vii. Receptors & signaling mechanisms allow cells to adapt to environmental conditions. viii. Molecular feedback mechanisms control molecular composition, growth, & differentiation. 2. A generalized cell a. Plasma Membrane i. Forms the cell’s outer boundary ii. Separates the cell’s internal environment form the outside environment iii. A selective barrier (only allows certain things to enter & exit) iv. Plays a role in cellular communication. b. Cytoplasm: All the cellular contents between the plasma membrane & nucleus i. Cytosol 1. The fluid portion, mostly water 2. Surrounds the organelles a. The site of many chemical reactions b. Energy is usually released by these reactions c. Reactions provide the building blocks for cell maintenance, structure, function & growth ii. Organelles 1. Subcellular structures having characteristic shapes & specific functions 2. Specialized structures within the cell 3. Centrosome: located near the nucleus, consists of 2 centrioles & pericentriolar material 4. Cilia: short, hair-like projections from the cell surface, move fluids along a cell surface. 5. Flagella: longer than cilia, move an entire cell; only example is the sperm cell’s tail 6. Ribosomes: sites of protein sysntesis 7. Endoplasmic reticulum: network of membranes in the shape of flattened sacs/tubules a. Rough ER: connected to the nuclear envelope, a series of flattened sacs, surface is studded with ribosomes, produces various proteins b. Smooth ER: a network of membrane tubules, does not have ribosomes, sysnthesizes fatty acids & steroids, detoxifies certain drugs. c. Golgi complex: consists of 3-20 (cisternae: flattened membranous sacs) i. Modify, sort, & package proteins for transport to different destinations. ii. Proteins are transported by various vesicles. d. Lysosomes: vesicles that form from the Golgi complex, contain powerful digestive enzymes. e. Peroxisomes: i. Smaller than lysosomes ii. Detoxify several toxic substances such as alcohol iii. Abundant in the liver f. Proteasomes i. Continuously destroy unneeded, damaged,/ faulty proteins ii. Found in the cytosol & the nucleus . g. Mitochondria: “powerhouses” of the cell i. Generate ATP ii. More prevalent in physiologically active cells: muscles, liver, & kidneys iii. Inner & outer mitochondrial membranes similar in structure to the plasma membrane iv. Cristae: the series of folds of the INNER membrane v. Matrix: the large central fluid-filled cavity vi. Self-replicate during times of increased cellular demand/before cell division vii. Contain own DNA 1. Inherited only from your MOTHER c. Nucleus: large organelle that contains DNA Contains: a. Chromosomes: consists of a single molecule of DNA & associated proteins. a. Genes: thousands of hereditary units b. Spherical/oval shaped structure c. Usually most prominent feature of a cell d. Nuclear envelope: a double membrane that separates the nucleus from the cytoplasm e. Nucleus pores: numerous openings in the nuclear envelope, control movement of substances between nucleus & cytoplasm f. Nucleolus: spherical body that produces ribosomes g. Genes: the cell’s hereditary units, control activities & structure of the cell h. Chromosomes: long molecules of DNA combined with protein molecules 3. Plasma membrane a. Flexible but has a sturdy barrier b. Fluid mosaic model: the arrangement of molecules within the membrane resembles a sea of lipids containing many types of proteins c. Lipids act as a barrier to certain substances i. “gatekeepers”- what the proteins act as to certain molecules & ions. 1. Structure of a membrane: a. Lipid bilayer: made up of i. Phospholipids ii. Cholesterol iii. Glycoplipids b. Integral proteins: extend into/through the lipid bilayer i. Function: anchors filaments inside & outside the plasma membrane, providing structural stability & shape for the cell. May also participate in movement of the cell/link two cells together. c. Transmembrane proteins: most integral proteins, span the entire lipid bilayer d. Peripheral proteins: attached to the inner/outer surface of the membrane, do not extend through it. i. Function: anchors filaments inside & outside the plasma membrane, providing structural stability & shape for the cell. May also participate in movement of the cell/link two cells together. e. Glycoproteins: membrane proteins with a carbohydrate group attached that protrudes into the extracellular fluid f. Glycocalyx: “sugar coating” surrounding the membrane & made up of the carbohydrate portions of the glycolipids & glycoproteins 2. Functions of membrane proteins a. Some are ion channels i. Allow specific ion to move through water filled pore. Most plasma membranes include specific channels for several common ions. b. Transporters: selectively move substances through the membrane i. Transports specific substances across membrane by changing shape. c. Receptors: for cellular recognition i. Ligand: a molecule that binds with a receptor ii. Recognizes specific ligand alters cell’s function in some. d. Enzymes: catalyze chemical reactions i. Catalyze reaction inside/outside cell, depending on which direction the active site faces. e. (others) cell-identity markers (glycoprotein) i. Distinguishes your cells from anyone else’s (unless you are an identical twin). An important class of such markers are the major histocompatibility (MHC) proteins. 3. Permeability a. The cell is either permeable/impermeable to certain substances b. Lipid bilayer is permeable to oxygen, carbon dioxide, water & steroids but impermeable to glucose c. Transmembrane proteins act as channels & transporters to assist the entrance of certain substances (ex: glucose & ions). 4. Passive vs. active processes a. Passive processes: substances move across cell membranes without the input of any energy; use the kinetic energy of individual molecules/ions b. Active processes: a cell uses energy, primarily from the breakdown of ATP, to move a substance across the membrane, (i.e: against a concentration gradient). 5. Diffusion a. Steepness of concentration gradient b. Temperature c. Mass of diffusion substance d. Surface area e. Diffusion distance 6. Osmosis: net movement of water through a selectively permeable membrane from an area of high concentration of water (lower concentration of solutes) to one of lower concentration of water a. Water can pass through plasma membrane in two ways: i. Through lipid bilayer by simple diffusion ii. Through aquaporin’s, integral membrane proteins 7. Active transport: solutes are transported across plasm membranes with the use of energy, from an area of lower concentration to an area of higher concentration (ex: sodium- potassium pump) a. Secondary active transport mechanisms i. Antiporters: carry two substances across the membrane in opposite directions. ii. Symporters: carry two substances across the membrane in the same direction. b. Transport in vesicles i. Vesicle: a small spherical sac formed by budding off form a membrane ii. Endocytosis: materials move into a cell in a vesicle formed from the plasma membrane membrane 1. Three types a. Receptor-mediated endocytosis b. Phagocytosis c. Bulk-phase endocytosis (pinocytosis) iii. Exocytosis: vesicles fuse with the plasma membrane, releasing their contents into the extracellular fluid iv. Transcytosis: a combination of endocytosis & exocytosis. 8. The cytoskeleton a. Network of protein filaments throughout the cytosol b. Provides structural support for the cell c. Types: i. Microfilaments ii. Intermediate filaments iii. Microtubules 9. Somatic cell division a. Mitosis i. The cell cycle is a sequence of events in which a body cell duplicates its contents & divides in 2. ii. Human somatic cells contain 23 pairs of chromosomes (total-46) iii. Homologous chromosomes: the 2 chromosomes that make up each PAIR (homologs) iv. Diploid cells: 2 SETS of chromosomes in somatic cells 10. Cell division a. Interphase: cell isn’t dividing i. The cell replicates its DNA ii. Consists of 3 phases G1, S & G2, replication of DNA occurs in the S phase b. Mitotic phase: consists of nuclear division (mitosis) &a cytoplasmic division (cytokinesis) to form 2 identical cells c. Prophase: the chromatin fibers change into chromosomes d. Metaphase: microtubules align the centromeres of the chromatid pairs at the metaphase plate e. Anaphase: the chromatid pairs split at the centromere & move to opposite poles of the cell; chromatids are now chromosomes f. Telophase: 2 identical nuclei are formed around the identical sets of chromosomes now in their chromatin form 11. Cytoplasmic division: Cytokinesis a. Division of a cell’s cytoplasm to form 2 identical cells b. Usually begins in late anaphase c. The plasma membrane constricts at its middle forming a cleavage furrow d. The cell eventually splits into 2 daughter cells e. Interphase begins when cytokinesis is complete 12. Reproductive cell division a. Each new organism is the result of the union of 2 gametes (fertilization) 1 from each parent. b. Meiosis: reproductive cell division that occurs in the gonads (ovaries & testes) that produces gametes with half the number of chromosomes. i. Occurs in 2 successive stages: Meiosis 1 & 2 1. Each stage has 4 phases: a. Prophase b. Metaphase c. Anaphase d. Telophase 2. Summary: begins with 1 diploid cell & ends with 2 cells having the haploid number of chromosomes; meiosis2: each of the 2 haploid cells divides, the net result is 4 haploid gametes that are genetically different form the original diploid starting cell c. Haploid cell: gametes contain a single set of 23 chromosomes d. Fertilization restores the diploid number of chromosomes (46). 13. Cellular diversity a. The average adult has nearly 100 trillion cells b. Are about 200 different types of cells c. Cells come in a variety of shapes & sizes d. Cellular diversity permits organization of cells into more complex tissues & organs
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