StuDocu is not sponsored or endorsed by any college or universityChapter 3 Cellular LevelHuman Anatomy and Physiology (Athabasca University)Downloaded by Yury Elena Ezhov ([email protected])lOMoARcPSD|1516709
Chapter 3: The Cellular Level of Organizaion CellsLiving structural and funcional units enclosed by a membrane. Cell Division All cells arise from cell division; one cell divides into two idenical cells.Cell Biology (cytology) Study of cellular structure and funcion.3.1 Parts of a Cell1.Plasma MembraneFlexible outer surface separaing the external and internal environments.Selecive barrier that regulates low of materials for normal cellular aciviies. Plays a role in communicaion between cells.2.CytoplasmArea between the membrane and nucleusi.Cytosol (intracellular luid): contains water, dissolved solutes, and paricles.ii.Organelles: characterisic shapes and funcions.3.NucleusContains the DNAChromosomes: a single molecule of DNA, contains thousands of genes.Genes: controls the aspect of cellular structure and funcion. Downloaded by Yury Elena Ezhov ([email protected])lOMoARcPSD|1516709
3.2 The Plasma Membrane Plasma Membrane Funcions: Sturdy lipid (amphipathic) barrier that surrounds the cytoplasm of the cell. Allows passage of several lipid-soluble molecules, but prevents polar substances to come in or out. oIon Channels (integral proteins) are pores or holes that lets speciic ions, such as K+, lowthrough. They are selecive. oCarriersselecively move polar substances or ions across the membrane. Proteins in the layer can act as signal receptors or links the plasma membranes to intra/extracellular proteins.oReceptors (integral proteins) recognizes and binds to speciic molecules. Speciic molecules that bind to the receptor is called a Ligand.oEnzymes catalyze chemical reacions in and outside the cell. oLinkersconnect proteins of plasma membrane to other cells. SoIdenity Markers (glycoprotein and glycolipids) enable a cell to recognize other similar cells during issue formaion, and recognize and respond to dangerous foreign cells. Plasma Membrane Structure: The Lipid Bilayertwo back-to-back layers of 3 types of lipid molecules.1.Phospholipids (75%): Phosphate (polar, hydrophilic) head, and faty acid (non-polar,hydrophobic) tail. They orientate themselves with the head outward – cytosol and extracellular luid – and tails point inward, hydrophobic membrane interior. 2.Cholesterol (20%): hydroxyl head (polar) forms hydrogen bonds with the phosphate of phospholipids. Sif, steroid rings (non-polar tails) it with the faty acids of the membrane. 3.Glycolipids (5%): carbohydrate (polar) head faces the extracellular luid (outside of cell), while the faty acid (non-polar) tails are in the membrane layer.