Anatomy and Physiology IWeek 3:The Cellular Level of Organization
Chapter Objectives•The purpose of thechapter is to:1.Introduce the parts of acell2.Discuss the importanceof the plasma membrane3.Discuss the componentsof the cytoplasm4.Compare and contrastmitosis and meiosis5.Understand the effectsaging has on the cell
Cytology and Cell Diversity•Cytology: the scientific study of cells•Cell Theory:•All organisms are composed of cells.•Cells are the basic units of structureand function in organisms.•Cells come from preexisting cellsbecause cells are self-reproducing.•Cells will differ in size and shape in orderto best fulfill necessary life functions inhumans.
Basic Components of a Cell
Cellular Structure: Plasma Membrane•The plasma membrane issemi-permeablemeaning that it allowsonly certain things into the cell whilekeeping others out.•Composition of the plasmamembrane:•Phospholipids– forms a bilayer that ishydrophilic on either side of themembrane but hydrophobic in thecenter of the membrane.•Cholesterol-prevents the plasmamembrane from becoming too fluid athigh temps and too solid at lowertemps.•Proteins-•Trans-membrane(Integral) proteinspermeates through the plasma membrane tointeract with each side.•Peripheral proteinsdo not protrude throughphospholipids but bind to either side of thecell.•Glycoproteins– cellular markers that actas identification tags.
Cilia and Flagella-Extensions of thePlasma Membrane
•Filtrationis theprocess of themovement of fluidinto or out of amembrane viapressure differences.•Utilized via bloodcapillaries in order totransport water,salts, nutrients intotissues and removalof waste products.Membrane Transport -Filtration
•Simple diffusionis themovement particles from anarea of high concentration toan area of low concentration.•Diffusion is influenced by:1.Steepness of the concentrationgradient2.Temperature3.Mass of diffusion substance•Diffusion decreases as massincreases4.Surface area5.Diffusion distance•Diffusion decreases as distanceincreasesSimpleDiffusion
Osmosis•Osmosis: the diffusion ofwater across a selectivelypermeable membranefrom an area of low soluteconcentration to an area ofhigh solute concentration.•As water cannot penetratethe membrane directly andwill require specializedprotein channels known asaquaporins.
Osmosis andTonicity•Tonicity: refers to the strength ofthe solution.•E.g. A 0.9% solution of NaCl (saline) isknown to be isotonic to red blood cells.