Cell Structure and Function Chapter 4 Principles of Modern Cell Theory Every living organism is made up of one or more cells. The smallest living organisms are single cells. Cells are the functional units of multicellular organisms. All cells arise from preexisting cells. The Microscope: Viewing Cells Relative Sizes in Biology Most cells are 1-100 µm. Larger cells would be too slow at exchanging nutrients. Light Microscope Uses lenses of glass to focus visible light rays on the specimen. Cells first described by Robert Hooke and refined by Anton van Leeuwenhoek in the late 1600s.
The Microscope: Viewing Cells Electron Microscope Uses beams of electrons focused by magnetic fields. Transmission Electron Microscopy (TEM) Visualize internal features of a cell. Scanning Electron Microscopy (SEM) Visualize surface structures of a cell. Cells Share Common Features Plasma Membrane Encloses the cell. Mediates interactions between the cell and its environment. Cytoplasm The materials and structures within the plasma membrane. DNA and RNA DNA used as a hereditary blueprint RNA used to copy the blueprint and implement its construction. Obtain energy and nutrients from the environment. The Plasma Membrane Composed of phospholipids and proteins. Isolates the cells contents from the external environment. Regulates the flow of materials into and out fo the cell. Allows for interaction with other cells and the extracellular environment. The Cytoplasm Includes all of the material between the plasma membrane, outside the region of DNA. The fluid that makes up the cytoplasm is called the cytosol. It consists of water, salts, and organic molecules. Location of most metabolic activity in the cell. The cytoplasm is a very crowded place.
Two Types of Cells Prokaryotic Cells Prokaryotic: before the nucleus Bacteria and Archaea Simpler life forms Eukaryotic: true nucleus Bodies of animals, plants, fungi, and protists. Possess many more organelles which contribute to complexity membrane bound structures that perform specific functions. The Prokaryotic Cell Unique Properties of Prokaryotes Nucleoid Regional location of non-membrane bound circular chromosomal DNA. Plasmids Small rings of DNA that are located outside the nucleoid. Novel Propulsion and Attachment Prokaryotic flagella (movement) Pili (attachment and sharing)
Prokaryotic Flagella Assembly Prokaryotic Flagella Assembly The Prokaryotic flagella is a long helical filament made of many protein subunits. - The motor is assembled inside the cell in concentric rings that use H + for power to rotate at 20,000rpm. - The filament pushes through the membrane and assembles 20-30,000 protein subunits folding on the outside of the cell. Animated video from Dr. Keiichi Namba. http://www.nanonet.go.jp/english/mailmag/2004/011a.html http://www.nanonet.go.jp/english/mailmag/2004/011a.html Thiocapsa sp. The Eukaryotic Animal Cell Helicobacter pylori Prochlorococcus Nitrosococcus Anabaena Prokaryotic Diversity Planctomyces Desulfovibrio desulfuricans Beggiatoa Leptospira Agrobacterium
The Eukaryotic Plant Cell Cytoskeleton Made up of thin microfilaments, medium-sized intermediate filaments, and thick microtubules. Cytoskeleton Functions of the Cytoskeleton Intermediate filaments determine cell shape. Microtubules and microfilaments assemble and disassemble, causing cell movement. Microtubules and microfilaments move organelles within the cell. Microfilaments form centrioles, the spindle that apportions the genetic material during cell division.
Movement in Eukaryotes Cilia are shorter and more numerous. Rowing motion. Flagella are longer and fewer in number. Provide force perpendicular to the cell membrane. Both are composed of microtubules. The Nucleus Nuclear pores keep nuclear material in, while allowing water, ions, and small molecules to pass. Organelle that houses genomic DNA. The nuclear envelope is a double membrane dotted with nuclear pores. Chromatin The interior of the nucleus is filled with chromatin, DNA associated with proteins, which form chromosomes for cell division. Chromosomes are long strands of DNA and its associated proteins that become condensed (thicker and shorter) for cell division.
Nucleolus Ribosomes Little Nuclei Site of ribosome synthesis. Consists of ribosomal RNA (rrna), proteins, ribosomes in stages of synthesis, and DNA. DNA contains the genes for rrna. Two subunit complex of RNA and proteins. Synthesize proteins from messenger RNA (mrna). Located freely throughout the cytoplasm or associated with the nuclear envelope and endoplasmic reticulum. Protein structures from the RCSB Protein Databank The Cytoplasm Contains a System of Membranes A set of membrane bound organelles that connect the nucleus with the outside. Three major components: The endoplasmic reticulum Contacts the nucleus directly. Vesicles Membrane bound sacs that act as shuttles between to an from the organelles. The golgi apparatus Final modifications to the exported product. The Endoplasmic Reticulum (ER) Network within the cytoplasm Interconnected membrane-enclosed tubes and channels through the cytoplasm. Composed of two parts: Smooth ER Without ribosomes. Rough ER With ribosomes.
Smooth Endoplasmic Reticulum: Without ribosomes. Manufacture of lipids. Detoxification in the liver. Creates vesicles through budding. Rough Endoplasmic Reticulum: With ribosomes. Site of protein synthesis. Manufacture of membrane proteins, digestive enzymes and protein hormones Synthesis of new ER membrane. Aide in tertiary structure folding. The Golgi Apparatus Set of membranes derived from the ER. Modify, sort, and package proteins: Modifies some molecules Example: adding carbohydrates make glycoproteins. Synthesizes polysaccharides Example: Cellulose and pectin. Sorts proteins and lipids from the ER to their destination. Packages molecules into vesicles for transport. 5 4 3 2 1 Protein Synthesis and Export 1. The protein is synthesized on ribosomes and transported into channels of the rough ER. 2. Protein is packaged into vesicles. 3. Vesicles fuse with Golgi and carbohydrates (or other modification) are added. 4. Completed protein is packaged in vesicles. 5. Vesicles merge with the plasma membrane to release the protein. Lysosomes The cell s digestive system. Enclosed vesicles housing digestive enzymes (to break apart food subunits) Merge with food vacuoles to digest food into amino acids, fatty acids, and monosaccharides. Recycle by breaking down defective organelles and membrane sections. Food Vesicles Recycling
4 2 3 Formation of Lysosomes and Food Vacuoles 1. Enzymes synthesized in ER. 2. Golgi modifies enzymes. 3. Lysosome buds from Golgi. Vacuoles Sacs of cellular membrane filled with fluid containing various molecules. Temporary vacuoles include food and recycling vacuoles visited by lysosomes. Permanent vacuoles help maintain cell integrity by regulating water. 1 4. Lysosome fuses with food vacuole and enzymes digest food. Contractile vacuoles of freshwater protists. Central vacuoles of plant cells. Contractile vacuoles of freshwater protists Contains a pore to release excess liquid and salts acquired through osmosis. Central vacuoles of plant cells Regulator of water balance. Dump site for toxins. Storage for sugars and amino acids. Provides rigidity for cell shape.
Energy Generation in Cells Through two organelles: Mitochondria Convert sugar to ATP. Chloropasts Capture energy from sunlight. Both thought to be evolved from bacterial endosymbionts. Organisms living within another organism for the mutual benefit of both species. Ribosomal RNA of both organelles matches that of bacteria, not eukaryotes. Mitochondria Powerhouse of the cell Allow eukaryotic cells to use oxygen in the otherwise anaerobic digestion of food, obtaining 16x more ATP. Mitochondria Found in higher numbers in very active cells. Example: Muscles Less abundant in less active cells. Example: Bone and cartilage. Chloroplast Organelle where photosynthesis occurs. Found in all plant cells and some protists. Contain chlorophyll which directly captures energy from the sun.
Bioflix Animations of Animal and Plant Cells Bioflix can be found in the Study Area of Mastering Biology. Homework Read the article by Keiichi Namba on the Prokaryotic flagella, and the section in your book titled "Cilia and Flagella " with Figure 4-6 and 4-7 on the Eukaryotic flagella. Compare and contrast how the Prokaryotic and Eukaryotic flagella are made and organized, and how they move a cell. Be sure to discuss one thing unique about each structure.