The Microscopic World of Cells. The Microscopic World of Cells. The Microscopic World of Cells 9/21/2012

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1 Organisms are either: Single-celled, such as most prokaryotes and protists or Multicelled, such as plants, animals, and most fungi How do we study cells? Light microscopes can be used to explore the structures and functions of cells. Electron Microscope 10 m Human height 1 m Length of some nerve and muscle cells 10 cm Chicken egg 1 cm Unaided eye 1 mm Frog eggs 100 mm Plant and animal cells 10 mm Nucleus Most bacteria Mitochondrion 1 mm Smallest bacteria 100 nm Viruses 10 nm Lipids 1 nm Small molecules Light microsc cope Electron microscope 0.1 nm Atoms Figure 4.3 1

2 TYPES OF MICROGRAPHS Light Micrograph (LM) (for viewing living cells) Scanning Electron Micrograph (SEM) (for viewing surface features) Transmission Electron Micrograph (TEM) (for viewing internal structures) LM Colorized SEM Colorized TEM Light micrograph of a protist, Paramecium Scanning electron micrograph of Paramecium Transmission electron micrograph of Paramecium The Two Major Categories of Cells The countless cells on earth fall into two categories: Prokaryotic cells Bacteria and Archaea Eukaryotic cells Eukarya protists, plants, fungi, and animals All cells have several basic features. 1. They are all bound by a thin plasma. 2. All cells have DNA. 3. All cells have ribosomes. Cytoplasm-the entire contents of a cell Prokaryotic Cells Prokaryotes Are smaller than eukaryotic cells Lack internal structures surrounded by s Lack a nucleus Have a rigid cell wall Plasma (encloses cytoplasm) Cell wall (provides Rigidity) Capsule (sticky coating) Prokaryotic flagellum (for propulsion) (synthesize s) Nucleoid (contains DNA) Colorized TEM Pili (attachment structures) 2

3 Eukaryotic Cells Eukaryotic cells are fundamentally similar. *Generalized plant cell *Generalized animal cell The plasma separates the living cell from its nonliving surroundings. region of bilayer (a) bilayer of regions of (b) Fluid mosaic model of structure s are amphipathic molecules 3

4 The plasma separates the living cell from its nonliving surroundings. region of bilayer (a) bilayer of regions of (b) Fluid mosaic model of Some functions of s Cytoplasm Fibers of extracellular matrix c Enzymatic activity b Cell signaling a Attachment to cytoskeleton and extracellular matrix Cytoskeleton d Transport e Intercellular joining f Cell-cell recognition Cytoplasm Cell surface Extracellular Matrix Nucleus The nucleus is an organelle that houses the genetic Nuclear material of the cell. Chromatin envelope Nucleolus Pore Chromatin Nuclear envelope Nucleolus TEM TEM Nuclear Pore Surface of nuclear envelope Nuclear pores 4

5 Chromatin DNA molecule Chromatin fiber Chromosome Figure 4.9 build all the cell s s ( synthesis) Composed of s and Ribosomal RNA Free: s for cytosol Membrane-bound: s for cell s and export How DNA Directs Protein Synthesis DNA controls the cell by transferring its coded information into RNA The information in the RNA is used to make s 1 Synthesis of mrna in the nucleus Nucleus 2 Movement of mrna into cytoplasm via nuclear pore DNA mrna Cytoplasm mrna Ribosome 3 Synthesis of in the cytoplasm Protein 5

6 The Endo System Many of the membranous organelles in the cell belong to the endo system The Endo System Golgi apparatus Rough ER Transport vesicle from ER Secretory vesicle from Golgi Secretory Vacuole Lysosome Plasma The Endoplasmic Reticulum Produces an enormous variety of molecules Is composed of smooth and rough ER Nuclear envelope Rough ER Smooth ER 6

7 The Endoplasmic Reticulum After the rough ER synthesizes a molecule it packages the molecule into transport vesicles Transport vesicle buds off 4 Ribosome 3 Secretory inside transport vesicle 1 2 Protein Rough ER Polypeptide 7