Chapter 5 Biology
Cell Theory 1. All organisms are made up of cells. 2. Cells are the smallest units of life 3. Cells are the primary structural and functional units of all organisms. 4. Cells are capable of self-reproduction.
Spontaneous Generation Louis PasteurCh. 26 life could arise spontaneously in organic materials
Cells Are Small How big is a FOOT? Cells range in size from a frog's egg (one millimeter) down to one micrometer or less.
Why are Cells small? • 1. Cells need surface area of plasma membrane large enough to adequately exchange materials. • 2. Surface-area-to-volume ratio requires that cells be small.
How do we see Cells? • 1. Light microscope uses light rays focused by glass lenses. • 2. Electron microscope uses electrons focused by magnets.
Revolution in Optics • New glass-making techniques were introduced by Italians in the 1590s • Antony van Leeuwenhoek (1632-1723) • Robert Hooke (1635-1703) • Galileo Galilei (1564-1642)
Microscopy of Today • Magnification is the increase in apparent size of an object • Resolution is minimum distance between two objects before they are seen as one larger object.
Prokaryotic Cells are relatively simple • 1. Bacteria are prokaryotic cells • 2. 1-10 um in diameter, just visible with light microscopes. • 3. Metabolically diverse. • 4. No True Nucleus
Procaryotic Structure - Plasma membrane is the outermost membrane; regulates the entrance and exit of molecules. - Cell wall is for structural support. - Bacteria may be surrounded by a capsule and/or gelatinous sheath called a slime layer. - Motile bacteria usually have flagella, which rotate like propellers to move through fluid medium. - Fimbriae are short appendages that help them attach to an appropriate surface.
Procaryotic Structure • Cytoplasm consists of cytosol, a semifluid medium. • Ribosomes are granular inclusions that coordinate synthesis of proteins. • Nucleoid contains most genes in a circular DNA molecule. • Plasmids are small accessory rings of DNA aside from the nucleoid. • Thylakoids are flattened discs with light-sensitive pigment molecules
Compartmentalization • Why are there organelles? • Optimization of process. • Protection of processes. • Specificity of processes.
Eukaryotic Cells Components Cell Wall • contains cellulose • support and protection Cell membrane / Plasma membrane • Phospholipid bilayer with embedded proteins • boundary layer and transport Nucleus • nuclear envelope, nucleoplasm, chromatin, nucleoli • storage and synthesis of genetic material. Nucleolus • chromatin, RNA and proteins • Ribosome formation
d. Nucleoplasm is semifluid medium of nucleus; has a different pH from cytosol. • e. Nucleoli are dark-staining spherical bodies in nucleus; sites where rRNA joins proteins to form ribosomes. • f. Nuclear envelope is a double membrane that separates nucleoplasm from cytoplasm. • g. Nuclear pores (100 nm) permit passage of proteins into nucleus and ribosomal subunits.
Eukaryotic Cells Components • Ribosomes • protein and RNA in 2 subunits • protein synthesis • Endoplasmic Reticulum (ER) • membranous flattened channels and tubular canals • site of protein synthesis and other substances • transport products in vessicles
The Endomembrane System • a. Endoplasmic Reticulum (ER) is system of membranous channels continuous with outer membrane of the nuclear envelope. • b. Rough ER is studded with ribosomes; is site where proteins are synthesized and enter the ER interior for processing and modification. • c. Smooth ER is continuous with rough ER, but lacks ribosomes; site of various synthetic processes, detoxification, and storage; smooth ER forms transport vesicles.