Essay About Cell Structure And Food Molecules

Bio Chapter 3 Cell Structure and Function
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Unit 3 Cell Structure and Function3.1 Cell Theory                           All organisms are made of cells[pic 1]Principles of cell theory     All existing cells are produced by other living cells                            The cell is the most basic unit of lifeProkaryotic cells and eukaryotic cellsProkaryotic cellEukaryotic cellDoesn’t have a nucleusHas a nucleusDoesn’t have membrane-bound organellesHas membrane-bound organellesUsually unicellularUsually multicellular-Shared characteristics: enclosed by a membrane, filled with cytoplasm, have DNA and ribosomes.3.2 Cell OrganellesNameStructure and componentsFunctionOthersCytoskeletonMicrotubules Shape the cell, position and transport organelles, assist in cell division—Intermediate filamentsGive the cell its strengthMicrofilamentsEnable cells to move and divideNucleusDNA enclosed in the nuclear envelopeNucleolus (where ribosomes assemble)Stores genetic information—Endoplasmic reticulumAn interconnected network of thin, folded membranesSmooth ER (without ribosomes)Rough ER (studded with ribosomes)Accommodate the process of producing proteins and lipids—Ribosomes—Use the information from DNA to link amino acids and form proteinsStudded on the ER or suspended in the cytoplasmGolgi apparatusClosely layered stacks of membrane-enclosed spacesProcess, sort, package and deliver proteins—VesiclesSmall membrane-bound sacsTransport proteins to the Golgi apparatusPinched off from the ERMitochondriaTwo membranesHave their own ribosomes and DNASupply energyVacuoleFluid-filled sacsStore materials needed by a cell (e.g. water, food molecules, inorganic ions, enzymes)Plant cells contain central vacuolesLysosomesContain enzymesHydrolyze (break down) proteins, fats, polysaccharides and nuclear acidsLysosomal enzymes work best in acidic environment inside lysosomesCentrosomesContain two centrioles perpendicular to each otherHelp in cell divisionForm cilia and flagella (hair-like structures that enable the cell to “swim”)Cell wallsA rigid layer surrounding the cellGives protection, support and shape to the cellDoes NOT exist in animal cellsChloroplasts Two membranesHave their own ribosomes and DNACarry out photosynthesisDoes NOT exist in animal cells3.3 Cell MembraneBasic structure                     Charged phosphate group[pic 2][pic 3][pic 4]Phospholipids   Glycerol                     Fatty acid chains      —— Nonpolar “tail-Phospholipids form double layers because the polar heads bond to water molecules in the fluid inside and outside the cell, while the nonpolar tails are attracted to each other and repelled by water.        2. Embedded substances: cholesterol, protein, carbohydrate chain, proteins, protein channels…Selective permeability (allowing some materials, but not all, to pass)PassDon’t passSmall Large Nonpolar Polar Not chargedCharged -Function: enables a cell to maintain homeostasis in spite of the changing conditions outside the cellTransmission of chemical signals1. Ligand: signal molecules that bind to the receptors2. Receptors: proteins that detect a signal molecule and perform an action in response-Intracellular receptors: bind to certain small signal molecules that cross the membrane-Membrane receptors: bind to signal molecules outside the cell      change shape      cause molecules inside the cell to respond[pic 5][pic 6]