Chapter 3
THE CELLULAR LEVEL OF ORGANIZATION
Chapter Synopsis
Students are presented with the structural and functional aspects of cells through analysis of a generalized animal cell. The cell is divided into three principal parts for ease of study: the plasma membrane, the cytoplasm consisting of the cytosol and organelles, and the nucleus. The anatomy and physiology of the plasma membrane is covered in extensive detail. Consideration is given to important processes of movement of materials across the plasma membrane, including diffusion, osmosis, diffusion through the lipid bilayer, diffusion through membrane channels, facilitated diffusion, active transport, and vescicular transport (endocytosis including receptor mediated endocytosis, phagocytosis and pinocytosis, and exocytosis). The form and function of the cytosol, organelles, and nucleus are similarly covered. Attention is also given to the events involved in protein synthesis following the processes of transcription of DNA to mRNA and translation of mRNA to the creation of a protein. The result, mechanisms, and importance of somatic - mitotic cell division and reprocutive cell division are examined thoroughly. The chapter concludes with a discussion of the effects of aging on cells and cellular diversity. Cancer is discussed as a homeostatic imbalance exemplified by uncontrolled division of cells. The subject of cancer is explored in several areas: growth and spread of malignant tumors, types of cancers, causes, the multistep process of carcinogenesis, and treatment. Clinical applications that are covered include the mechanism by which cholesterol modifies membrane fluidity, the mechanism by which digitalis affects the sodium pump in heart muscle, the cellular basis of cystic fibrosis, the cellular basis of Tay-Sachs disease, recombinant DNA, abnormalities in genes that help to regulate the cell cycle and the problems they cause, and Progeria and Werner’s Syndrome.
Chapter Outline and Objectives
INTRODUCTION
- Define a cell
- Describe the connection between the chemical level of organization and cellular components.
- Relate the essential importance of the cellular level of organization to all life forms.
PARTS OF A CELL
- Describe the three principal parts of a cell.
THE PLASMA MEMBRANE
- Describe how the “fluid mosaic model” concept appropriately describes the nature and structure of the plasma membrane.
The Lipid Bilayer
- Explain how the chemical nature of the distinct regions of phospholipids automatically produces a lipid bilayer in a water solution, with a range of properties.
- Describe the function of cholesterol and glycolipids in membranes.
Arrangement of Membrane Proteins
- Distinguish between integral and peripheral proteins in cell membranes.
Functions of Membrane Proteins
- Describe the chemistry and function of membrane proteins.
Membrane Fluidity
- Discuss the fluidity of membranes and the mobility of membrane lipids and proteins.
- Explain how cholesterol modifies membrane fluidity.
Membrane Permeability
- Explain the mechanisms and factors involved in the selective movement of materials across the cell membrane.
Gradients Across the Plasma Membrane
- Define a chemical and electrical gradient and the predominant ions involved on opposite sides of the plasma membrane.
- Explain how an electrical gradient leads to the membrane potential that exists in cells of the body.
TRANSPORT ACROSS THE PLASMA MEMBRANE
- Distinguish between passive and active transport, including direction of particle movement and energy requirements.
- Distinguish between nonmediated and mediated transport.
- Discuss the role of transporter proteins in mediated transport.
- Discuss the basis of vesicular transport.
Principles of Diffusion
- Explain the concept of diffusion based on the kinetic energy of random motion in terms of concentration differences, net movement, and the properties of substances and conditions.
- List and explain the factors that influence the diffusion rate of substances in solution.
Osmosis
- Explain the process of osmosis as the net movement of a solvent through a selectively permeable membrane.
- Discuss the roles of hydrostatic pressure and osmotic pressure in regulating osmosis.
- Show the relation of osmotic pressure to tonicity by the effect on red blood cells of different concentrations of solute in a surrounding solution.
Diffusion Through the Lipid Bilayer
- Describe the movement of nonpolar, hydrophobic molecules through the lipid bilayer of the plasma membrane.
Diffusion Through Membrane Channels
- Describe the process of small, inorganic ion movement across the plasma membrane.
Facilitated Diffusion
- Detail the facilitated diffusion characteristics and process where transporter proteins move glucose molecules along their concentration gradients.
Active Transport
- Define active transport and list two energy sources used to drive the process.
Primary Active Transport
- Describe the process of primary active transport and relate it to the sodium pump.
Secondary Active Transport
- Describe the process of secondary active transport and the role of symporters and antiporters.
- Discuss the effect of digitalis on the sodium pump.
TRANSPORT IN VESICLES
- Describe the two main types of vesicular transport between a cell and its extracellular fluid.
Endocytosis
- Describe the process of endocytosis.
Receptor-Mediated Endocytosis
- Define ligand and discuss its role in receptor mediated endocytosis.
- List and explain the steps involved in receptor-mediated endocytosis.
- Describe how some viruses can use receptor-mediated endocytosis to infect body cells.
Phagocytosis
- Define phagocytosis and explain its importance.
Pinocytosis
- Define pinocytosis and explain its importance.
Exocytosis
- Describe the process of exocytosis.
CYTOPLASM
- List the two components of the cytoplasm.
Cytosol
- Describe the elements of the cytosol and how it is different from the plasma membrane.
Organelles
- Describe the basic structural features and functions of organelles.
- Distinguish between membranous and nonmembranous organelles.
The Cytoskeleton
- Distinguish the characteristics and functions of microfilaments, microtubules, and intermediate filaments.
Centrosome
- Show the relationship of cytoskeletal elements to centrioles and the centrosome and note their purpose in dividing and nondividing cells.
Cilia and Flagella
- Describe the arrangement of microtubules in flagella and cilia that allow these projections to perform the different types of transport movements.
Ribosomes
- Indicate the origin and components of ribosomes that allow them to produce proteins, and their association with other organelles in this process.
Endoplasmic Reticulum
- Specify how the interconnected form of the ER membranous labyrinth is related to its various synthetic purposes and molecular distribution within the cell.
Golgi Complex
- Describe how the Golgi apparatus conducts the processing and directing of newly synthesized molecules.
- Convey how the faulty operation of the Golgi complex is related to cystic fibrosis.
Lysosomes
- Delineate the role of lysosomal enzymes in protection, digestion, and recycling of external and internal substances.
- Describe how faulty lysosomes are related to Tay-Sachs disease.
Peroxisomes
- Describe the enzymes and reactants peroxisomes use to deactivate potentially toxic molecules.
Mitochondria
- Indicate how the two membrane layers of the mitochondrion are associated with the enzymes that produce the energy-storage molecule ATP.
- Describe the role of DNA in mitochondrial replication.
NUCLEUS
- Discuss the morphology and function of the nuclear envelope, nucleoli, and hierarchical levels of chromatin.
- Define genomics and discuss some practical applications of the science.
PROTEIN SYNTHESIS
- Accentuate that DNA acts by coding for structural and functional (enzyme) proteins,and those proteins form all the structures and perform almost all the metabolic reactions to generate and maintain an organism.
Transcription
- Describe the steps of transcription and nucleotides of the DNA sequence that are used to synthesize complementary sequences of RNA nucleotides of three types.
- Define the process and functions of the gene splicing of mRNA.
Translation
- Provide the identity and function of all the molecules involved in the translation process.
- Illustrate the relation between the codes of the DNA nucleotide triplet, the mRNA codon, and the rRNA anticodon that specifies an amino acid in the protein sequence.
- Go through the steps in which the molecular components of this process interact to translate the mRNA sequence into a successive coupling of amino acids in a protein.
- Discuss the techniques of genetic engineering and recombinant DNA.
NORMAL CELL DIVISION
- Define cell division
- Distinguish between somatic and reproductive cell division.
The Cell Cycle in Somatic Cells
- Describe the chromosome number in terms of homologous pairs and stress the importance of chromosome replication prior to cell division.
Interphase
- Indicate the objectives and activities of the DNA and cell components in each phase of the interphase cell cycle.
Mitotic Phase
- List the events of each phase of mitosis.
Cytoplasmic Division: Cytokinesis
- Explain what is happening to the cytoplasm, organelles, and plasma membrane during cytokinesis, and why.
Control of Cell Destiny
- List and describe the three possible destinies of a cell.
- Describe the role of tumor-suppressor genes in the cell cycle.
The Cell Cycle in Reproductive Cells
- Explain the importance of reducing chromosome number from diploid to haploid prior to sexual reproduction
- List the event of meiosis I and meiosis II.
CELLS AND AGING
- . Explain how the three main theories of aging (genetic programming, free radical reactions, and excess immune response) lead to the signs of aging.
CELLULAR DIVERSITY
- Discuss the concept of cellular diversity.
DISORDERS: HOMEOSTATIC IMBALANCES
- . Describe cancer (CA) as a homeostatic imbalance of cells with different characteristics for benign versus malignant tumors.
Types of Cancer
- Distinguish the origins and properties of the different types of tumors.
Growth and Spread of Cancer
- Describe the effects of hyperplasia, metastasis, and secondary site development on normal tissue.
Causes of Cancer
- Explain the nature of the numerous carcinogens and viruses and with which cell growth control genes they may interact.
Carcinogenesis: A Multistep Process
- Describe the features and progression of steps that lead a normal cell to develop into a malignancy.
Treatment of Cancer
- Discuss how it is that the multiple personalities of the cells within a tumor make the differing drug therapies difficult or ineffective.
MEDICAL TERMINOLOGY
- Define medical terminology associated with cells.
