Cell Structure and Function: Topics to be discussed ❖Where are the “Molecules of Life” located in the cells? ❖What are common between different types of cells? ❖Are there differences between cells of different organisms? ❖Why is cell size so small? ❖What are the experimental techniques that help us to understand the cell structure and organization? ❖What are the different cellular organelles? E. Coli O157:H7 strain is harmful to humans oIntestinal bacteria that live in cattle, deer, goats, sheep and humans oSeverely damage the lining of human intestine http://everything-pr.com/ecoli-germany-spain/228647/ oComplications: Bloody diarrhea, kidney failure, blindness, paralysis and death oWhat makes bacteria sticky? oWhy do people but not cows get sick with E. coli O157:H7? oWe need to learn about cells and how they work? Cell is the smallest unit that shows properties of life oCells vary dramatically in shape and function oHowever, all cells share certain organizational and functional features Examples of cells Traits common to all cells 1665: Antoni van Leeuwenhoek first observed tiny moving organisms in rainwater, insects, fabric, sperm and other samples Robert Hooke coined the term cell Robert Brown first identified a cell nucleus in 1820s Matthias Schleiden first hypothesized that a plant cell is an independent living unit even when it is part of a plant Theodor Schwann together with Schleiden concluded that tissues of animals and plants are composed of cells and their products Rudolf Virchow realized that all cells descended from another living cell Cell Theory • 1. All living things are made of cells. • 2. New cells are produced from existing cells • 3. Cells are the basic unit of structure and function in living things. Surface-to-volume limits also affect the body plan of multicelled species http://voer.edu.vn/c/comparing-prokaryotic-and-eukaryotic-cells/a64457a4/6b98166e A sense of scale https://www.jic.ac.uk/microscopy/scale.html Prokaryotes vs. Eukaryotes • Prokaryotes (bacteria) have no nucleus and very few organelles. DNA is not contained • Eukaryotes (protists, fungi, plants and animals) larger,more complex,DNA is inside the nucleus Eukaryotic Cell : Animal Cell Plant Cell Vacuole Smooth endoplasmic reticulum Ribosome (free) Chloroplast Cell Membrane Ribosome (attached) Nuclear envelope Cell wall Nucleolus Golgi apparatus Mitochondrion Nucleus Rough endoplasmic reticulum Compare and Contrast Animal Cells Centrioles Plant Cells Cell membrane Ribosomes Nucleus Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Mitochondria Cytoskeleton Cell Wall Chloroplasts Internal Organization • Cells contain ORGANELLES. • Cell Components that PERFORMS SPECIFIC FUNCTIONS FOR THE CELL. Cellular Organelles • The Plasma membrane – The boundary of the cell. – Composed of three distinct layers. – Two layers of fat and one layer of protein. The Nucleus • Brain of Cell • Bordered by a porous membrane - nuclear envelope. • Contains thin fibers of DNA and protein called Chromatin. • Rod Shaped Chromosomes • Contains a small round nucleolus – produces ribosomal RNA which makes ribosomes. The nucleus controls access to DNA and permits easier packing of DNA during cell division. Ribosomes • Small non-membrane bound organelles. • Contain two sub units • Site of protein synthesis. • Protein factory of the cell • Either free floating or attached to the Endoplasmic Reticulum. Cells also contain non-membranous structures: Ribosomes, "free" or attached to membranes, participate in assembly of polypeptide chains. Endoplasmic Reticulum • Complex network of transport channels. • Two types: 1. Smooth- ribosome free and functions in poison detoxification. 2. Rough - contains ribosomes and releases newly made protein from the cell. The endoplasmic reticulum (ER) modifies newly formed polypeptide chains and is also involved with lipid synthesis. Golgi Apparatus • A series of flattened sacs that modifies, packages, stores, and transports materials out of the cell. • Works with the ribosomes and Endoplasmic Reticulum. The Golgi body modifies, sorts, and ships proteins; they also play a role in the synthesis of lipids for secretion or internal use. Lysosomes • Recycling Center – Recycle cellular debris • Membrane bound organelle containing a variety of enzymes. • Internal pH is 5. • Help digest food particles inside or out side the cell. Centrioles • Found only in animal cells • Paired organelles found together near the nucleus, at right angles to each other. • Role in building cilia and flagella • Play a role in cellular reproduction Cell membrane Cytoskeleton Endoplasmic reticulum Microtubule Microfilament Ribosomes Mitochondrion Main Components 1. The cytoskeleton is an interconnected system of fibers, threads, and lattices that extends between the nucleus and the plasma membrane. 2. It gives cells their internal organization, overall shape, and capacity to move. 3. The main components are microtubules, microfilaments, and intermediate filaments: all assembled from protein subunits. 4. Some portions are transient, such as the "spindle" microtubules used in chromosome movement during cell division; others are permanent, such as filaments operational in muscle contraction. Cytoskeleton B. The Structural Basis of Cell Movements 1. Through the controlled assembly and disassembly of their subunits, microtubules and microfilaments grow or shrink in length (example: movement of chromosomes). 2. Microfilaments or microtubules actively slide past one another (example: muscle movement). 3. Microtubules or microfilaments shunt organelles from one location to another (example: cytoplasmic streaming). Cytoskeleton C. Flagella and Cilia 1. Flagella are quite long, are usually not numerous, and are found on one-celled protistans and animal sperm cells. 2. Cilia are shorter and more numerous and can provide locomotion for free-living cells or may move surrounding water and particles if the ciliated cell is anchored. 3. Both of these extensions of the plasma membrane have a 9 + 2 cross-sectional array (arising from centrioles) and are useful in propulsion. Mitochondrion A. Mitochondria are the primary organelles for transferring the energy in carbohydrates to ATP under oxygen-plentiful conditions. B. Hundreds of thousands of mitochondria occur in cells. 1. It has two membranes, an inner folded membrane (cristae) surrounded by a smooth outer membrane. 2. Inner and outer compartments formed by the membranes are important in energy transformations. 3. Mitochondria have their own DNA and some ribosomes, a fact which points to the possibility that they were once independent entities. Mitochondria are efficient factories of ATP production. The Chloroplast • Double membrane • Center section contains grana • Thylakoid (coins) make up the grana. • Stroma - gel-like material surrounding grana • Found in plants and algae. A. Chloroplasts and Other Plastids 1. Chloroplasts are oval or disk shaped, bounded by a double membrane, and critical to the process of photosynthesis. a. In the stacked disks (grana), pigments and enzymes trap sunlight energy to form ATP. b. Sugars are formed in the fluid substance (stroma) surrounding the stacks. c. Pigments such as chlorophyll (green) confer distinctive colors to chloroplasts. the 2. Chromoplasts have carotenoids, which impart red-to-yellow colors to plant parts, but no chlorophyll. 3. Amyloplasts have no pigments; they store starch grains in plant parts such as potato tubers. Mitochondria vs. Chloroplasts • Mitochondria make energy from chemicals (food molecules) • Chloroplasts make energy from light through photosynthesis The Vacuole • Sacs that help in food digestion or helping the cell maintain its water balance. • Found mostly in plants and protists. 1. In the mature plant, the central vacuole may occupy 50 to 90% of the cell interior! a. stores amino acids, sugars, ions, and wastes. b. enlarges during growth and greatly increases the cell’s outer surface area. 2. The cytoplasm is forced into a very narrow zone between the central vacuole and the plasma membrane. Cell Wall • Extra structure surrounding its plasma membrane in plants, algae, fungi, and bacteria. • Cellulose – Plants • Chitin – Fungi • Peptidoglycan - Bacteria Smooth ER vs. Rough ER • Rough ER - ribosomes on the ER make proteins, the ER modifies the proteins • Smooth ER - makes lipids Cytoskeleton • Network of protein filaments • Maintains shape • Involved in cell movement Prokaryotes DNA is free floating Cell membrane Contain DNA Eukaryotes Nucleus Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Mitochondria Cytoskeleton Cell Wall • Provides support and protection for plant walls • Made of porous cellulose so it does not regulate what enters and leaves cell Eukaryotic Cell Walls 1. Many single-celled eukaryotes have a cell wall, a supportive and protective structure outside the plasma membrane 2. Microscopic pores allow water and solute passage to and from underlying plasma membrane. 3. In plants, bundles of cellulose strands form the primary cell wall, which is more pliable than the more rigid secondary wall that is laid down inside it later. Cell Membrane • Regulates what enters and leaves the cell and provides support and protection • Structure – lipid bilayer with embedded proteins Diffusion through Cell Boundaries • Particles move from an area of high concentration to an area of lower concentration • No energy is required Osmosis • Diffusion of water through a selectively permeable membrane Isotonic "ISO" means the same • Concentration of solutes (salts) is the same inside and outside of cell. • Water flows in and out in equal amounts • No effect on cell Hypertonic “Hyper” means more • Concentration of solutes is more outside the cell than inside • Water flows out of cell • The cell shrivels and may die. • This is why it is dangerous to drink sea water • This is also why "salting fields" was a common tactic during war, it would kill the crops in the field, thus causing food shortages. Hypotonic "HYPO" means less • Concentration of solutes is less outside the cell than in. • Water flows in • The cell swell with water and becomes “turgid” Active Transport • Carried our by protein pumps found in the membrane • Energy is required Facilitated Diffusion • Molecules move through protein channels. • No energy required Endocytosis • Cell takes material into cell by infolding of the cell membrane • Phagocytosis – eating – cell engulfs large particles • Pinocytosis – drinking – cell takes in liquid • www.endocyte.com/ animation/animation.htm Exocytosis • Cell releases large amounts of material Cell Specialization • The cells in multicellular organisms can develop in different ways to perform different tasks. Levels of Biological Organization • • • • • • • • Organism Organ system Organ Tissue Cell Organelle DNA Atoms
