BIOLOGY. A Tour of the Cell CAMPBELL. Robert Hooke (1665) Antoni van Leeuwenhoek (1674) Reece Urry Cain Wasserman Minorsky Jackson

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1 6 A Tour of the Cell CAMPBELL BIOLOGY TENTH EDITION Reece Urry Cain Wasserman Minorsky Jackson Lecture Presentation by Nicole Tunbridge and Kathleen Fitzpatrick Robert Hooke (1665) Figure 1.1 The structure of nucleic acids. Antoni van Leeuwenhoek (1674) 1

2 Figure 1.2 Reproduction of Leeuwenhoek's microscope. Lens Specimen holder Simple microscope Figure 1.3 The microbial world. "animalcules = protozoa beasties" The Cell theory All organisms are made of cells - the cell is the smallest and simplest collection of matter that can be alive - the Fundamental Units of Life Cells come from other cells Cells are usually too small to be seen by the naked eye 2

3 General rule for any microscope/detector Smaller the wavelength smaller the object you can see (small objects need small hands) Think about giant fingers and texting Figure 4.1 The electromagnetic spectrum. Smaller the object = Use smaller wavelength VIBGYOR Microscopy Light Microscopy Bright-field microscopes Simple single lense Contain a single magnifying lens Similar to magnifying glass Leeuwenhoek used simple microscope to observe microorganisms 3

4 Microscopy Microscopes are used to visualize cells In a light microscope (LM), visible light is passed through a specimen and then through glass lenses Glass lenses focuses light and enlarges and resolves objects Lenses refract (bend) the light, so that the image is magnified Light Air Magnify using lenses Glass Magnification = 50/5 = 10X Focal point 5 50 Specimen Convex lens Inverted, reversed, and Enlarged image Figure 4.5 The effect of immersion oil on resolution. Special type of objective lens = oil immersion lens Microscope objective Lenses Microscope objective Refracted light rays lost to lens Glass cover slip More light enters lens Glass cover slip Immersion oil Slide Slide Specimen Light source Light source Without immersion oil With immersion oil Increases magnification and resolution 4

5 Figure 4.4 A bright-field, compound light microscope. Line of vision Ocular lens Remagnifies the image formed by the objective lens Body Transmits the image from the objective lens to the ocular lens using prisms Arm Objective lenses Primary lenses that magnify the specimen Stage Holds the microscope slide in position Condenser Focuses light through specimen Diaphragm Controls the amount of light entering the condenser Illuminator Light source Ocular lens Path of light Prism Body Objective lenses Specimen Condenser lenses Illuminator Coarse focusing knob Moves the stage up and down to focus the image Fine focusing knob Base Three important parameters of microscopy Magnification, the ratio of an object s image size to its real size Resolution, the measure of the clarity of the image, or the minimum distance of two distinguishable points Contrast, visible differences in brightness between parts of the sample Microscopy General Principles of Microscopy Magnification (enlarge) Resolution (tell apart 2 objects close together) Contrast (Differences in intensity between two objects) 5

6 50 µm Figure 6.3ab Brightfield (unstained specimen) Brightfield (stained specimen) Staining increases contrast Figure 4.16 Simple stains. Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic 3 domains Bacteria, Archae and Eukarya Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells Protists, fungi, animals, and plants all consist of eukaryotic cells or domain eukarya 6

7 2 µm 2 µm There are 3 major types of living organisms One tree of life 3 domains Bacteria Archae Eukarya Figure 1.13 (a) Domain Bacteria (b) Domain Archaea (c) Domain Eukarya Kingdom Animalia 100 µm Kingdom Plantae Kingdom Fungi Animals: Protozoa Plants: Algae Fungi Protists All living organisms have cell(s) Some are unicellular others multicellular How many different types of cells There are only 2 types of cells Prokaryotic cells Eukaryotic cells Membrane around nucleus Membrane-bound organelles 7

8 There are 3 major types of living organisms they all have cell(s) One tree of life 3 domains Bacteria prokaryotic Archae Eukarya eukaryotic Figure 1.4 Eukaryotic cell Membrane DNA (no nucleus) Membrane Prokaryotic cell Cytoplasm Nucleus (membraneenclosed) Membraneenclosed organelles DNA (throughout nucleus) 1 µm Figure 1.4 Cells of the bacterium Streptococcus (dark blue) and two human cheek cells. Prokaryotic bacterial cells Nucleus of eukaryotic cheek cell 8

9 Prokaryotic Cells cell walls contain peptidoglycan cell walls do not contain peptidoglycan but other polymers Common Features Unicellular lack nuclei or nuclear membrane around DNA Much smaller Most have cell walls simpler Comparing Prokaryotic and Eukaryotic Cells Basic features of all cells Plasma membrane Semifluid substance called cytosol/cytoplasm Chromosomes (carry genes) Ribosomes (make proteins) Figure 6.5 Fimbriae Nucleoid Ribosomes Plasma membrane Bacterial chromosome (a) A typical rod-shaped bacterium Cell wall Capsule Flagella 0.5 µm (b) A thin section through the bacterium Bacillus coagulans (TEM) 9

10 Eukaryotic cells are characterized by having DNA in a nucleus that is bounded by a membranous nuclear envelope Membrane-bound organelles Cytoplasm in the region between the plasma membrane and nucleus Eukaryotic cells are generally much larger than prokaryotic cells Figure 6.8a Flagellum Centrosome ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER Nuclear envelope Nucleolus Chromatin NUCLEUS Plasma membrane CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Ribosomes Microvilli Golgi apparatus Peroxisome Mitochondrion Lysosome Figure 6.8b NUCLEUS Nuclear envelope Nucleolus Chromatin Rough ER Smooth ER Ribosomes Golgi apparatus Central vacuole Microfilaments CYTOSKELETON Microtubules Mitochondrion Peroxisome Plasma membrane Cell wall Wall of adjacent cell Plasmodesmata Chloroplast 10

11 BioFlix: Tour of a Plant Cell BioFlix: Tour of an Animal Cell Ribosomes: Protein Factories Ribosomes are complexes made of ribosomal RNA and protein Ribosomes carry out protein synthesis in two locations In the cytosol (free ribosomes) On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes) 11

12 Figure 6.10 Ribosomes ER 0.25 μm TEM showing ER and ribosomes Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER Large subunit Small subunit Diagram of a Computer model ribosome of a ribosome Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell The endomembrane system consists of Nuclear envelope Endoplasmic reticulum Golgi apparatus Lysosomes Vacuoles Plasma membrane These components are either continuous or connected via transfer by vesicles Figure 6.15 Nucleus Rough ER Smooth ER cis Golgi trans Golgi Plasma membrane 12

13 The Endoplasmic Reticulum: Biosynthetic Factory The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER Smooth ER, which lacks ribosomes Rough ER, whose surface is studded with ribosomes Figure 6.11 Smooth ER Rough ER Nuclear envelope Smooth ER Rough ER ER lumen Cisternae Ribosomes Transport vesicle Transitional ER 0.20 μm Figure 6.11a Smooth ER Rough ER 0.20 μm 13

14 Functions of Smooth ER The liver is involved in detoxification of The smooth ER many poisons and drugs. Synthesizes lipids Which Metabolizes structures carbohydrates is primarily involved in this process and, therefore, abundant in Detoxifies drugs and poisons liver cells? Stores calcium ions Functions of Rough ER The rough ER Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) Distributes transport vesicles, secretory proteins surrounded by membranes Is a membrane factory (proteins) for the cell The Golgi Apparatus: Shipping and Receiving Center The Golgi apparatus consists of flattened membranous sacs called cisternae Functions of the Golgi apparatus Modifies products of the ER Manufactures certain macromolecules Sorts and packages materials into transport vesicles (sorting/packaging factory) 14

15 Figure 6.12 Golgi apparatus cis face ( receiving side of Golgi apparatus) Cisternae Secretory vesicles special vesicles trans face ( shipping side of Golgi apparatus) e.g. lysosome, vacuoles Figure 6.15 Nucleus Rough ER Smooth ER cis Golgi trans Golgi Plasma membrane Lysosomes: Digestive Compartments A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes work best in the acidic environment inside the lysosome Hydrolytic enzymes and lysosomal membranes are made by rough ER and then transferred to the Golgi apparatus for further processing 15

16 Some types of cell can engulf another cell by phagocytosis; this forms a food vacuole A lysosome fuses with the food vacuole and digests the molecules Lysosomes also use enzymes to recycle the cell s own organelles and macromolecules, a process called autophagy Figure 6.13 Nucleus 1 μm Vesicle containing two damaged organelles 1 μm Lysosome Digestive enzymes Plasma membrane Lysosome Food vacuole (a) Phagocytosis: lysosome digesting food Digestion Mitochondrion fragment Peroxisome fragment Peroxisome Lysosome Mitochondrion Vesicle (b) Autophagy: lysosome breaking down damaged organelles Digestion Tay-Sachs disease is a human genetic abnormality - a rare inherited disorder that progressively destroys nerve cells in brain and spinal cord. The most common form of Tay-Sachs disease becomes apparent in infancy. Infants with this disorder typically appear normal until the age of 3 to 6 months, when their development slows and muscles used for movement weaken. Affected infants lose motor skills such as turning over, sitting, and crawling. 16

17 In Tay-Sachs disease neurons becoming clogged with very large, complex, undigested lipids. Which cellular organelle must be involved in this condition? Lysosomes lack an enzyme called beta-hexosaminidase A Vacuoles: Diverse Maintenance Compartments Vacuoles are large vesicles derived from the ER and Golgi apparatus Vacuoles perform a variety of functions in different kinds of cells Food vacuoles are formed by phagocytosis Contractile vacuoles, found in many freshwater protists, pump excess water out of cells Central vacuoles, found in many mature plant cells, hold organic compounds and water 17

18 Figure 6.14 Central vacuole Cytosol Nucleus Central vacuole Cell wall Chloroplast 5 μm Concept 6.5: Mitochondria and chloroplasts change energy from one form to another Mitochondria are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP Chloroplasts, found in plants and algae, are the sites of photosynthesis Mitochondria: Chemical Energy Conversion Mitochondria are in nearly all eukaryotic cells They have a smooth outer membrane and an inner membrane folded into cristae The inner membrane creates two compartments: intermembrane space and mitochondrial matrix Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix Cristae present a large surface area for enzymes that synthesize ATP 18

19 Figure 6.17a Mitochondrion Intermembrane space Outer membrane DNA Free ribosomes in the mitochondrial matrix Inner membrane Cristae Matrix (a) Diagram and TEM of mitochondrion 0.1 μm Chloroplasts: Capture of Light Energy Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae Figure 6.18a Ribosomes Stroma Inner and outer membranes Granum DNA Thylakoid Intermembrane space (a) Diagram and TEM of chloroplast 1 μm 19

20 Chloroplast structure includes Thylakoids, membranous sacs, stacked to form a granum Stroma, the internal fluid The chloroplast is one of a group of plant organelles, called plastids The Evolutionary Origins of Mitochondria and Chloroplasts Mitochondria and chloroplasts have similarities with bacteria Enveloped by a double membrane Contain free ribosomes and circular DNA molecules Grow and reproduce somewhat independently in cells These similarities led to the endosymbiont theory The endosymbiont theory suggests that an early ancestor of eukaryotes engulfed an oxygen-using nonphotosynthetic prokaryotic cell The engulfed cell formed a relationship with the host cell, becoming an endosymbiont The endosymbionts evolved into mitochondria At least one of these cells may have then taken up a photosynthetic prokaryote, which evolved into a chloroplast 20

21 Figure 6.16 Endoplasmic reticulum Nuclear envelope Ancestor of eukaryotic cells (host cell) Nucleus Engulfing of oxygenusing nonphotosynthetic prokaryote, which becomes a mitochondrion Engulfing of Mitochondrion photosynthetic prokaryote Chloroplast At least Mitochondrion one cell Nonphotosynthetic eukaryote Photosynthetic eukaryote Centrosomes and Centrioles In animal cells, microtubules grow out from a centrosome near the nucleus In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring Figure 6.22 Centrosome Centrioles Microtubule 0.25 μm Longitudinal section of one centriole Microtubules Cross section of the other centriole 21

22 Video: Cytoplasmic Streaming Video: Chloroplast Movement Cytoplasmic streaming is a circular flow of cytoplasm within cells This streaming speeds distribution of materials within the cell In plant cells, actin-myosin interactions and sol-gel transformations drive cytoplasmic streaming 22