Overview of Cell Biology Bio 411 PDF

TOPIC 1 OVERVIEW OF CELL BIOLOGY BIO 411 Immunofluorescence image of the eukaryotic cytockeleton. Actin filaments are shown in red, microtubules in green, and the nuclei in blue ATTENDANCE nhi/bio411_Topic1  LE...

TOPIC 1 OVERVIEW OF CELL BIOLOGY BIO 411 Immunofluorescence image of the eukaryotic cytockeleton. Actin filaments are shown in red, microtubules in green, and the nuclei in blue ATTENDANCE nhi/bio411_Topic1  LEARNING OUTCOMES At the end of this topic, YOU should be able to: State the classical and modern principles of the cell theory State the historical background in cell biology Specify characteristics of cells nhi/bio411_Topic1  OVERVIEW Cells are fundamental units of life smallest unit of life organizational principle for biology capable of functioning independently originate from pre-existing cells contain hereditary information i.e. DNA, RNA chemical reactions take place within cells nhi/bio411_Topic1/2015  HISTORICAL BACKGROUND.. I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular.... these pores, or CELLS,... were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this...(Robert Hooke,1665) nhi/bio411_Topic1/2015  CELL THEORY The CELL THEORY proposes that: 1. All living things are composed of at least one cell 2. the cell is the fundamental unit of structure and function in all organisms. 3. The chemical composition of all cells is fundamentally alike 4. all cells arise from pre-existing cells through cell division. MATTHIAS SCHLEIDEN & THEODOR SCHWANN (1838) nhi/bio411_Topic1/2015  TENETS OF CELL THEORY Classical cell theory ▪ Classical cell theory, as developed through the observations of Hooke, Leeuwenhoek, Schleiden, Schwann, Virchow, and others, holds that: ▪ All organisms are made up of one or more cells. ▪ Cells are the fundamental functional and structural unit of life. ▪ All cells come from pre-existing cells. Modern cell theory ▪ The generally accepted parts of modern cell theory include: ▪ The cell is the fundamental unit of structure and function in living things. ▪ All cells come from pre-existing cells by division. ▪ Energy flow (metabolism and biochemistry) occurs within cells. ▪ Cells contain hereditary information (DNA) which is passed from cell to cell during cell division ▪ All cells are basically the same in chemical composition. ▪ All known living things are made up of cells. ▪ Some organisms are unicellular, made up of only one cell. ▪ Other organisms are multicellular, composed of countless number of cells. ▪ The activity of an organism depends on the total activity of independent cells. Exceptions to the theory ▪ Viruses are considered by some to be alive, yet they are not made up of cells. ▪ The first cell did not originate from a pre-existing cell. nhi/bio411_Topic1/2015  MAJOR EVENTS IN CELL BIOLOGY Koch,TB & Robert Hooke, Chlolera cells of cork layer bacteria Kolliker, Leewenhoek, mitochondria Cloned in muscle Ruska, Bacteria TEM 1665 1683 1857 1882 1898 1938 1965 1674 1838 1997 Anton Van Schwan & Golgi, Golgi Leewenhoek, Schleiden Cell apparatus Protozoa Theory SEM nhi/bio411_Topic1/2015  DEVELOPMENT OF CELL THEORY Year Description 1590 Hans and Hans and Zacharias Janssen were the inventors of the first compound microscope. Zacharias Janssen 1665 Robert Hooke English physicist Robert Hooke looked at a sliver of cork through a microscope lens and noticed some "pores" or "cells" in it. Robert Hooke believed the cells had served as containers for the "noble juices" or "fibrous threads" of the once-living cork tree. Hooke was the first person to use the word "cell" to identify microscopic structures when he was describing cork. 1668 Francesco Redi Francesco Redi, an Italian physician, did an experiment to determine if rotting meat turned into flies. He found that meat cannot turn into flies and only flies could make more flies. This was an important experiment because it helped to disprove the theory of spontaneous generation. It did this by showing that the rotten meat did not turn into flies and only flies could make more flies. 1674 Anton Van Anton Van Leeuwenhoek was the first to see and describe bacteria. Leeuwenhoek 1745 John Needham From 1745 to 1748 John Needham, a Scottish clergyman and naturalist, showed that soup that had been exposed to the air contained many micro organisms. He claimed that there was a "life force" present in the molecules of all inorganic matter, including air and the oxygen in it, that could cause spontaneous generation to occur. nhi/bio411_Topic1/2015  DEVELOPMENT OF CELL THEORY Year Description 765 Lazzaro From 1765 to 1767 Lazzaro Spallanzani, an Italian abbot and biologist, tried variations on Spallanzani John Needham’s soup experiments. He determined that soup in a sealed container was sterile and that micro organisms that caused the soup to spoil had entered from the air. 1831 Robert Brown Robert Brown discovered the cell nucleus. 1839 Matthias Theodor Schwann and Matthias Jakob Schleiden created what is called the cell theory. Schleiden The cell theory states that all living things are made up of one or more cells. 1839 Theodor Schwann proposed that all organisms are composed of cells. Together with Matthias Schwann Schleiden he formulated the cell theory of life. Schwann also discovered the cells, now known as Schwann cells, that form a sheath surrounding nerve axons and conducted experiments that helped disprove the theory of spontaneous generation. 1855 Rudolf Virchow Rudolf Virchow published his now-famous aphorism omnis cellula e cellula ("every cell stems from another cell"). He also stated that all diseases involve changes in normal cells. 1864 Louis Pasteur Louis Pasteur did an experiment that determined that soup exposed to air only spoiled if the air was not filtered or if the flask containing the soup had an opening that allowed micro organisms to get to the soup. If he used flasks with long S-shaped necks the micro organisms that spoiled the soup settled in the neck and did not spoil the soup. nhi/bio411_Topic1/2015 DEVELOPMENT OF CELL THEORY Year Description 1626 Redi postulated that living things do not arise from spontaneous generation. 1655 Hooke described 'cells' in cork. 1674 Leeuwenhoek discovered protozoa. He saw bacteria some 9 years later. 1833 Brown described the cell nucleus in cells of the orchid. 1838 Schleiden and Schwann proposed cell theory. 1855 Virchow postulated that new cells come from preexisting cells. 1857 Kolliker described mitochondria 1869 Miescher isolated DNA for the first time. 1879 Flemming described chromosome behavior during mitosis 1883 Germ cells are haploid, chromosome theory of heredity. 1898 Golgi described the golgi apparatus 1926 nhi/bio411_Topic1/2015 Svedberg developed the first analytical ultracentrifuge. DEVELOPMENT OF CELL THEORY Year Description 1938 Behrens used differential centrifugation to separate nuclei from cytoplasm. 1939 Siemens produced the first commercial transmission electron microscope 1941 Coons used fluorescent labeled antibodies to detect cellular antigens. 1952 Gey and coworkers established a continuous human cell line. 1953 Crick, Wilkins and Watson proposed structure of DNA double-helix. 1955 Eagle systematically defined the nutritional needs of animal cells in culture. Meselson, Stahl and Vinograd developed density gradient centrifugation in cesium chloride solutions for 1957 separating nucleic acids. Ham introduced a defined serum-free medium. Cambridge Instruments produced the first commercial 1965 scanning electron microscope Sato and colleagues publish papers showing that different cell lines require different mixtures of hormones 1976 and growth factors in serum-free media. 1981 Transgenic mice and fruit flies are produced. Mouse embryonic stem cell line established. 1987 First knockout mouse created. 1998 Mice are cloned from somatic cells. 2000 Human genome DNA sequence draft. nhi/bio411_Topic1/2015 METHODS IN CELL BIOLOGY MICROSCOPY; CELL STAINING; DIFFERENTIAL CENTRIFUGATION MICROSCOPY & CELL TECHNIQUES Learning outcomes: Identify structural and operational aspects of microscopes Explain the techniques in microscopy and cell biology nhi/bio411_Topic1/2015 nhi/bio411_Topic1/2015 COMPOUND LIGHT MICROSCOPE 4X, 10X, 40X, 100X nhi/bio411_Topic1/2015  COMPOUND LIGHT MICROSCOPE Modern compound microscopes operate using a dual stage magnifying design that incorporates a primary imaging lens, the objective, coupled to a secondary visualizing lens system known as the eyepiece or ocular mounted at the opposite ends of a body tube. The objective is responsible for primary image formation at varying magnifications, while the eyepiece is used to observe the image created by the objective. nhi/bio411_Topic1/2015  FUNDAMENTALS OF MICROSCOPY Image forming light rays passed through the specimen are captured by the microscope objective and directed either into the eyepieces and/or to one of the several camera ports. Throughout the optical train of the microscope, illumination is directed and focused through a series of diaphragms and lenses as it travels from the light source to illuminate the specimen and then into the eyepieces or camera attachment. Closing or opening the condenser diaphragm controls the angle of the light rays emerging from the condenser and reaching the specimen nhi/bio411_Topic1/2015  UNDERSTANDING VISIBLE LIGHT The visible spectrum runs between 390 – 760nm. 390 nm = violets 550 nm = greens 750 nm = reds As wavelength decreases, energy increases nhi/bio411_Topic1/2015 MAGNIFICATION & RESOLUTION 🞂 magnification – ability to enlarge objects 🞂 resolving power – ability to show detail nhi/bio411_Topic1/2015 ENHANCING POWER OF RESOLUTION Achieved by increasing the value of numerical aperture : increasing the angle of light incidence by altering the sub-stage condenser Allowing more light to pass through lens by widening the cone of light increasing the refractive index (RI) by using specially manufactured lenses or using immersion oil for higher objectives RI defined as the light-bending ability of a medium. (Water=1.0, Oil=1.5) nhi/bio411_Topic1/2015 REFRACTIVE INDEX: PATH OF LIGHT THROUGH DIFFERENT MEDIUMS bigger angle of refraction nhi/bio411_Topic1/2015 REFRACTIVE INDEX: PATH OF LIGHT THROUGH DIFFERING MEDIUMS Through Air Through Oil ▪ Smaller angle of incidence ▪ Large angle of incidence ▪ Angle of refraction bends away ▪ Angle of refraction approaches from normal line (bigger angle of normal line (smaller angle of refraction) refraction) ▪ smaller refractive index (RI) ▪ Larger refractive index (RI) value value ▪ Larger value for numerical ▪ smaller value for numerical aperture (NA) as it has wider cone of light aperture (NA) as it has narrower cone of light nhi/bio411_Topic1/2015 Effect of magnification Resolution 100-200 nm (0.1-0.2 µm). Magnification 1000-1500X Resolution 0.1-2nm Magnification 1000X400-500  Electron microscopy ▪ Forms an image with a beam of electrons that can be made to travel in wavelike patterns when accelerated to high speeds. ▪ Electron waves are 100,000X shorter than the waves of visible light. ▪ Electrons have tremendous power to resolve minute structures because resolving power is a function of wavelength. ▪ Magnification between 5,000X - 1,000,000X  2 types of electron microscopes ▪ Transmission electron microscopes (TEM) ▪ transmits electrons through the specimen; darker areas represent thicker, denser parts and lighter areas indicate more transparent, less dense parts. ▪ Scanning electron microscopes (SEM) ▪ provides detailed three-dimensional view. SEM bombards surface of a whole, metal-coated specimen with electrons while scanning back and forth over it. Transmission Electron Micrograph Scanning Electron Micrograph Fluorescent microscope ▪ Modified compound microscope with high energy light source (UV light) and a filter that protects the viewer’s eye ▪ Use dyes that emit visible light when bombarded with shorter UV rays. ▪ Useful in diagnosing infections Confocal microscope Uses lasers to produce three-dimensional images of living cells and tissue slices. Optical sections of the specimen are collected by laser scanning and stored in the computer. The information from each visual plane can be viewed and reconstructed into three dimensional projections of the specimen.  Resolution 0.1-2 nm FLUORESCENT MICROSCOPES CONFOCAL MICROSCOPES Mercury lamp Laser  TECHNIQUES OF MICROSCOPY TECHNIQUE RESULTS (a) Brightfield (unstained specimen) specimen is dark and contrasted by the surrounding bright viewing field (b) Brightfield (stained specimen) nhi/bio411_Topic1/2015  TECHNIQUES OF MICROSCOPY TECHNIQUE RESULTS (c) Phase-contrast imaging methods that can be used to visualize even small differences in the refractive index within a sample. small phase changes in the light rays, induced by differences in the thickness and refractive index of the different parts of an object, can be transformed into differences in brightness or light intensity (d) Differential-interference- contrast (Nomarski) optical microscopy technique used to enhance the contrast in unstained, transparent samples nhi/bio411_Topic1/2015  TECHNIQUES OF MICROSCOPY TECHNIQUE RESULTS (e) Fluorescence combines the magnifying properties of light microscopy with visualization of fluorescence. Fluorescence microscopy is accomplished in conjunction with the basic light microscope by the addition of a powerful light source, specialized filters, and a means of fluorescently labeling a sample nhi/bio411_Topic1/2015  TECHNIQUES OF MICROSCOPY TECHNIQUE RESULTS Cilia 1 µm (a) Scanning electron microscopy (SEM) -produces a 3D image (b) Transmission electron Longitudinal Cross section microscopy (TEM) section of of cilium 1 µm -produces a 2D image cilium nhi/bio411_Topic1/2015  CELL STAINING Function: to optimize visualization of cell structures and subcellular components nhi/bio411_Topic1/2015 What is Cellular Staining? ▪ Cell staining is a technique used to better visualize cells and cell components under a microscope. ▪ Using different stains, one can preferentially stain certain cell components, such as a nucleus or a cell wall, or the entire cell. ▪ Most stains can be used on fixed, or non-living cells, while only some can be used on living cells; some stains can be used on either living or non-living cells. nhi/bio411_Topic1/2015 Why Stain Cells? ▪ Most basic reason that cells are stained is to enhance visualization of the cell or certain cellular components under a microscope. ▪ Cells may also be stained to highlight metabolic processes or to differentiate between live and dead cells in a sample. ▪ Cells may also be enumerated by staining cells to determine biomass in an environment of interest. nhi/bio411_Topic1/2015  This Giemsa stained micrograph depicts an example of a slightly acidic slide that yielded a pink coloured resultant stain. The micrograph shows malarial cells.  How Are Cells Stained and Slides Prepared? Cell staining techniques and preparation depend on the type of stain and analysis used. One or more of the following procedures may be required to prepare a sample: ▪ Permeabilization ▪ Mounting ▪ treatment of cells, generally with a ▪ involves attaching samples to a glass mild surfactant, which dissolves cell microscope slide for observation and membranes in order to allow larger analysis. dye molecules to enter inside the cell. ▪ Example cells grown on slides, loose cells applied to a slide using aseptic ▪ Fixation techniques or thin sections of tissues ▪ serves to "fix" or preserve cell or tissue morphology through the ▪ Staining preparation process. ▪ application of stain to a sample to ▪ involve several steps, example by colour cells, tissues, components, or adding chemical fixative that creates metabolic processes. chemical bonds between proteins to ▪ involve immersing the sample (before increase their rigidity. or after fixation or mounting) in a dye ▪ Common fixatives include solution and then rinsing and formaldehyde, ethanol, methanol, observing the sample under a and/or picric acid. microscope. ▪ excess dye solution is washed away nhi/bio411_Topic1/2015  TYPES OF DYE FOR STAINING A chromophore is a chemical group or molecule within a larger molecule that is responsible for its color. Chromophores are typically composed of groups of atoms with a high degree of conjugation, which allows them to absorb certain wavelengths of visible light and reflect or transmit others. This absorption of specific wavelengths gives rise to the observed color of the compound. BASIC DYE ACIDIC DYE ▪ the chromophore is a cation (positive ion). ▪ the chromophore is an anion (negative ion). ▪ Examples: ▪ Examples: ▪ crystal violet, methylene blue, ▪ stains the background instead malachite green (attracted to bacteria) (negative staining)  List of Common Stains There are several types of staining media, each can be used for a different purpose. Commonly used stains and how they work are listed below. All these stains may be used on fixed, or non-living, cells and those that can be used on living cells are noted. ▪ Bismarck Brown - colours acid mucins, a type ▪ Iodine - used as a starch indicator. When in of protein, yellow and may be used to stain live solution, starch and iodine turn a dark blue cells colour. ▪ Carmine - colours glycogen, or animal starch, ▪ Malachite green - a blue-green counterstain to red safranin in Gimenez staining for bacteria. This ▪ Coomassie blue - stains proteins a brilliant blue, stain can also be used to stain spores. and is often used in gel electrophoresis ▪ Methylene blue - stains animal cells to make ▪ Crystal violet - stains cell walls purple when nuclei more visible. combined with a mordant. This stain is used in Gram staining ▪ Neutral/Toluylene red - stains nuclei red and ▪ DAPI - a fluorescent nuclear stain that is excited may be used on living cells. by ultraviolet light, showing blue fluorescence ▪ Nile blue - stains nuclei blue and may be used when bound to DNA. DAPI can be used in living of fixed cells on living cells. ▪ Eosin - a counterstain to haematoxylin, this stain ▪ Nile red/Nile blue oxazone - this stain is made colours red blood cells, cytoplasmic material, cell by boiling Nile blue with sulfuric acid, which membranes, and extracellular structures pink or creates a mix of Nile red and Nile blue. The red red. accumulates in intracellular lipid globules, ▪ Ethidium bromide - this stain colours unhealthy staining them red. This stain may be used on cells in the final stages of apoptosis, or deliberate living cells. cell death, fluorescent red-orange. ▪ Osmium tetroxide - used in optical ▪ Fuchsin - this stain is used to stain collagen, microscopy to stain lipids black. smooth muscle, or mitochondria. ▪ Hematoxylin - a nuclear stain that, with a ▪ Rhodamine - a protein-specific fluorescent mordant, stains nuclei blue-violet or brown. stain used in fluorescence microscopy. ▪ Hoechst stains - two types of fluorescent stains, ▪ Safranin - a nuclear stain used as a 33258 and 33342, these are used to stain DNA in counterstain or to colour collagen yellow. living cells. nhi/bio411_Topic1/2015  PREPARATION OF SAMPLES Wet Mount Dry Mount allow examination of characteristics of live are made by drying & heating a film of cells: motility, shape, & arrangement specimen. Immediate observation Repeated observations Live specimen Dead specimen Temporary fixation with cover slip Permanent fixation with Stained or unstained stained Example: blood smear Example: prepared slide for pathological and biological research nhi/bio411_Topic1/2015 nhi/bio411_Topic1/2015 MICROSCOPE FIELD OF VIEW nhi/bio411_Topic1/2015 MEASURING FIELD OF VIEW nhi/bio411_Topic1/2015  SIZE OF CELLS 🞂 Why is it necessary to measure the field of view? 🞂 Cells in nature exist as different sizes nhi/bio411_Topic1/2015 TOPIC 1.3: CELL STRUCTURE & FUNCTION These basic features are shared by all cells: 1. Plasma membrane 2. Cytosol 3. Cytoplasm 4. Ribosomes 5. DNA nhi/bio411_Topic1/2015 These basic features are shared by all cells: 1. Plasma membrane: ▪ a selective barrier which encloses a cell (in plant and bacteria cells this barrier is known as a cell wall) 2. Cytosol: ▪ located inside the plasma membrane, this is a jelly-like fluid that supports organelles and other cellular components. 3. Cytoplasm: ▪ the cytosol and all the organelles other than the nucleus. 4. Ribosomes: ▪ the organelles on which protein synthesis takes place. 5. DNA: ▪ the genetic material which is contained in one or more chromosomes. nhi/bio411_Topic1/2015  DIFFERENTIAL CENTRIFUGATION The cell membrane is first ruptured to release the cell’s components by using a homogenizer. The resulting mixture is referred to as the homogenate. The homogenate is centrifuged to obtain a pellet containing the most dense organelles. Separation of cellular organelles on the basis of sedimentation rate sedimentation is typically from most to least dense organelle. nhi/bio411_Topic1/2015 CELL SIZES, SHAPES & FUNCTIONS ▪ Size of cells relate to function they serve ▪ The shapes of cells are quite varied ▪ neuron is long ▪ parenchyma is equidimensional ▪ Flexible- cell membrane ▪ rigid- cell wall nhi/bio411_Topic1/2015  10 µm 10 µm 10 µm Network of protein based fiber. Column of tubulin dimers Keratin proteins These protein are long Actin subunit Fibrous subunit (keratins coiled together) strings of monomers 25 nm connected end-to-end 7 nm 8–12 α β Tubulin nm to form a polymer. dimer  SIGNIFICANCE OF CELL SIZE Although it might seem logical for an organism to be made of one giant cell, our cells are specialized: they have unique jobs in the body. There are physiological limits to how big a cell can grow. The reason cells can grow only to a certain size has to do with their surface area to volume ratio. For example a balloon. The air inside is the volume, and the latex outside is the surface area. As a balloon gets bigger, the volume expands, but there is a limit to how big the surface area can get.  SIGNIFICANCE OF CELL SIZE Surface area is the area of the outside of the cell, called the plasma membrane. The volume is how much space is inside the cell. The ratio is the surface area divided by the volume. Surface area increases while total volume remains constant This indicates how much surface area is available compared to how big the cell is. If the surface area to volume ratio is small, the cell is very big. 5 If the ratio is big, the surface area is greater than the 1 volume, and the cell is small. 1 Total surface area [Sum of the surface areas (height × width) of all boxes 6 150 750 sides × number of boxes] Total volume [height × width × length × 1 125 125 number of boxes] Surface-to-volume (S-to-V) ratio [surface area ÷ volume] 6 1.2 6 SIGNIFICANCE OF CELL SIZE cell's efficiency depends on its size. Why??????????? nhi/bio411_Topic1/2015  SIGNIFICANCE OF CELL SIZE It matters because a cell's efficiency depends on its size. Why??????????? For example, let's consider diffusion, and note that the plasma membrane serves an important purpose here. It's the barrier of the cell and where the cell interacts with its environment. Waste diffuses out of the cell here, and important nutrients and oxygen diffuse in. The cell also receives signals from other cells about what to do, when to reproduce, and where to move. These signals must move through the interior of the cell as well. However, this is going to take much longer if the cell is large or has a small surface area to volume ratio. nhi/bio411_Topic1/2015  SIGNIFICANCE OF CELL SIZE having a small size makes cells very EFFICIENT. requires LESS energy to transport from membrane of the cell to the center. the surface area to volume ratio is very large if the cell is small. unicellular organisms are limited in size by diffusion. this surface area-to-volume ratio problem explains why there are no giant unicellular organisms, and why large organisms are composed of many small cells. nhi/bio411_Topic1/2015  CELL STRUCTURES & FUNCTION: PROKARYOTES AND EUKARYOTES Basic cellular functions Removal of wastes Continuation of life (Molecule (Reproduction) transport) Release of Energy Generation of new from food cells for growth and repair (Cellular metabolism) nhi/bio411_Topic1/2015 CELLS nhi/bio411_Topic1/2015 CELLS nhi/bio411_Topic1/2015 CELLS nhi/bio411_Topic1/2015  COMPONENTS OF CELLULAR ARCHITECTURE CELL STRUCTURE LOCATION DESCRIPTION FUNCTION Cell Wall ∙ Outer layer ∙ Support (grow tall) Plant, Fungi, & Bacteria, but ∙ Protection ∙ Rigid & strong not animal cells ∙ allows H2O, O2, CO2 to ∙ Made of cellulose diffuse in & out of cell Cell Membrane ∙ Plant - inside cell wall ∙ Support ∙ Animal - outer layer; ∙ Protection cholesterol ∙ Controls movement of All cells ∙ Double layer of materials in/out of cell phospholipids with ∙ Barrier between cell and proteins its environment ∙ Selectively permeable ∙ Maintains homeostasis Nucleus ∙ Large, oval ∙ Controls cell activities ∙ May contain 1 or more All cells except prokaryotes Contains the hereditary nucleoli ∙ material of the cell ∙ Holds DNA nhi/bio411_Topic1/2015 CELL STRUCTURE LOCATION DESCRIPTION FUNCTION Nuclear membrane ∙ Surrounds nucleus ∙ Controls movement of All cells except ∙ Double membrane materials in/out of prokaryotes nucleus ∙ Selectively permeable ∙ Clear, thick, jellylike material Cytoplasm (cytosol) ∙ Supports and protects cell All cells ∙ Organelles found inside cell organelles membrane ∙ Contains the cytoskeleton fibers Endoplasmic reticulum (ER) ∙ Network of tubes or membranes ∙ Smooth w/o ribosomes ∙ Carries materials through All cells except cell ∙ Rough with embedded ribosomes prokaryotes ∙ Aids in making proteins ∙ Connects to nuclear envelope & cell membrane nhi/bio411_Topic1/2015 CELL STRUCTURE LOCATION DESCRIPTION FUNCTION Ribosome ∙ Small bodies free or All cells attached to ER ∙ Synthesizes proteins ∙ Made of rRNA & protein Mitochondrion ∙ Peanut shaped ∙ Breaks down sugar ∙ Double membrane (glucose) molecules to All cells except prokaryotes release energy ∙ Outer membrane smooth ∙ Site of aerobic cellular ∙ Inner membrane folded respiration into cristae Vacuole Plant cells have a single, large ∙ Store food, water, vacuole ∙ Fluid-filled sacs Vacuole metabolic & toxic wastes ∙ Largest organelle in plant Animal cells have small ∙ Store large amounts of cells vacuoles food or sugars in plants Lysosome ∙ Breaks down larger food me Plant - uncommon ∙ Small and round with a molecules into smaller Animal - common single membrane molecules ∙ Digests old cell parts nhi/bio411_Topic1/2015 CELL STRUCTURE LOCATION DESCRIPTION FUNCTION Chloroplast ∙ Green, oval containing chlorophyll (green pigment) ∙ Uses energy from sun to ∙ Double membrane with make food (glucose) for inner membrane modified the plant Plants and algae into sacs called thylakoids ∙ Process called ∙ Stacks of thylakoids photosynthesis called grana & interconnected ∙ Release oxygen ∙ Gel like innermost substance called stroma nucleolus ∙ Found inside the cell's nucleus All cells except prokaryotes ∙ May have more than one ∙ Make ribosomes ∙ Disappear during cell division Golgi Apparatus ∙ Have a cis & trans face ∙ Modify proteins made by All cells except prokaryotes ∙ Stacks of flattened sacs the cells ∙ Package & export nhi/bio411_Topic1/2015 proteins  BIOGENESIS & EVOLUTIONARY ORIGIN ▪ Spontaneous generation (abiogenesis) proposed that life originated form non-living matter. Disputable!! ▪ experiments by Francisco Redi (17th Century) and Louis Pasteur (19th Century) gave rise to the theory of biogenesis. ▪ Biogenesis encompasses the theory that living things can only come from other living things. ▪ It was developed in 1858 by Rudolf Virchow as a counter-hypothesis to spontaneous generation nhi/bio411_Topic1/2015 CELL THEORY Three scientists played a role in the formation of cell theory Matthias Schleiden Theodor Schwann Rudolph Virchow CELL THEORY Three scientists played a role in the formation of cell theory: Matthias Schleiden (1804–1881) ⮚ “Plants are aggregates of fully individualized, separate beings” A German botanist CELL THEORY Three scientists played a role in the formation of cell theory: Theodor Schwann (1810–1822) ⮚ “Animals are also made up of cells and proposed a cellular basis of life” A German physician and physiologist CELL THEORY Three scientists played a role in the formation of cell theory- Introduced Biogenesis : Rudolph Virchow (1821–1902) ⮚ “Animals arise only from an animal, and plants only from a plant” A German doctor, anthropologist, pathologist, prehistorian, biologist and politician, public health advocate  CELL THEORY The Cell Theory states: All living organisms are composed of cells They may be unicellular or multicellular The cell is the basic unit of life Cells arise from pre-existing cells (They are not derived from spontaneous generation) The modern version of the Cell Theory includes the ideas that: Energy flow occurs within cells Heredity information (DNA) is passed on from cell to cell All cells have the same basic chemical composition  Conditions on early Earth made the origin of life possible Chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages: 1. Abiotic synthesis of small organic molecules 2. Joining of these small molecules into macromolecules 3. Packaging of molecules into “protobionts” 4. Origin of self-replicating molecules nhi/bio411_Topic1/2015  Conditions on early Earth made the origin of life possible Scientists think that the protobionts are the evolutionary precursors of prokaryotic cells. Protobionts may be originated as an array of microspheres of diverse organic and inorganic compounds enclosed by lipidic membranes. Proteins, carbohydrates, lipids, and other organic substances were the most important autocatalytic organic compounds.  The Endosymbiosis Theory- Lynn Margulis ▪ The oldest fossils of eukaryotic cells date back 2.1 billion years ▪ The hypothesis of endosymbiosis proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells ▪ An endosymbiont is a cell that lives within a host cell plastid is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms. Copyright © 2008 Pearson Education, Inc., Publishing as Pearson Benjamin Cummings nhi/bio411_Topic1/2015  The Endosymbiosis Theory- Lynn Margulis ▪ The prokaryotic ancestors of mitochondria and plastids probably gained entry to the host cell as undigested prey or internal parasites ▪ In the process of becoming more interdependent, the host and endosymbionts would have become a single organism ▪ Serial endosymbiosis supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events Copyright © 2008 Pearson Education, Inc., Publishing as Pearson Benjamin Cummings nhi/bio411_Topic1/2015 ENDOSYMBIOSIS THEORY Endosymbiosis came about when large cells engulfed small cells The small cells were not digested by the large cells Instead, they lived within the large cells and evolved into organelles ENDOSYMBIOSIS THEORY Key evidence supporting an endosymbiotic origin of mitochondria and plastids: ▪ Similarities in inner membrane structures and functions ▪ Division is similar in these organelles and some prokaryotes ▪ These organelles transcribe and translate their own DNA ▪ Their ribosomes are more similar to prokaryotic than eukaryotic ribosomes Copyright © 2008 Pearson Education, Inc., Publishing as Pearson Benjamin Cummings nhi/bio411_Topic1/2015 END OF TOPIC 1