Cell Structure and Function 1 Topic 5 Learning Objective After studying this topic you should be able to: Of Nuclei and Cells CEB Textbook Chapter 4, pages 54-67 Mastering Biology, Chapter 4 Understand and use the metric system. Recognise (in drawings or micrographs) and name the main characteristics that differentiate prokaryotic and eukaryotic cells. Recognise (in drawings or micrographs), describe, and understand the structure and function of the following organelles: Nucleus, Ribosomes, and all the components of the Endomembrane System. The Art of Looking at Cells Artists are often inspired by biology and biology depends on art The paintings of Wassily Kandinsky (1866-1944) show the influence of cellular forms Illustration is an important way to represent what scientists see through microscopes The anatomist Santiago Ramón y Cajal (1852-1934) was trained as an artist He drew these retina nerve cells INTRODUCTION TO THE WORLD OF THE CELL The microscope was invented in the 17th century Using a microscope, Robert Hooke discovered cells in 1665 All living things are made of cells (cell theory) 4.1 Microscopes provide windows to the world of the cell The light microscope enables us to see the overall shape and structure of a cell Image seen by viewer Eyepiece Ocular lens Objective lens Specimen Condenser lens Light source Figure 4.1A
Cell Structure and Function 2 Electron microscopes were invented in the 1950s They use a beam of electrons instead of light The greater resolving power of electron microscopes allows greater magnification reveals cellular details Scanning electron microscope (SEM) Scanning electron micrograph of cilia Figure 4.1B Transmission electron microscope (TEM) 4.2 Cell sizes vary with their function Below is a list of the most common units of length biologists use (metric) Transmission electron micrograph of cilia Figure 4.1C Table 4.2 Cell size and shape relate to function 4.3 Natural laws limit cell size At minimum, a cell must be large enough to house the parts it needs to survive and reproduce The maximum size of a cell is limited by the amount of surface needed to obtain nutrients from the environment and dispose of wastes Figure 4.2
Cell Structure and Function 3 A small cell has a greater ratio of surface area to volume than a large cell of the same shape Types of Living Things 30 µm 10 µm NON CELLULAR - Viruses PROKARYOTIC Lacks distinct nucleus (Bacteria) EUKARYOTIC Has distinct nucleus (include plant, animal, fungi and protist cells) Figure 4.3 Surface area of one large cube = 5,400 µm 2 Total surface area of 27 small cubes = 16,200 µm 2 Prokaryotic cells are small and structurally simple PROKARYOTIC CELLS (BACTERIA) Prokaryotic cells are small, relatively simple cells They lack nuclei and other membraneenclosed organelles PROKARYOTES Prokaryotes have inhabited Earth for billions of years Prokaryotes are the oldest life-forms They remain the most numerous and widespread organisms on Earth today Prokaryotes are classified into two domains, based on nucleotide sequences and other features Bacteria and Archaea Table 16.8 Figure 16.7
Cell Structure and Function 4 Prokaryotes come in a variety of shapes Spheres (cocci) are the most common Rods (bacilli) Prokaryotes obtain nourishment in a variety of ways These E. Coli colonies are growing with only glucose as an organic nutrient Curves or spirals Figure 16.9A-C Figure 16.10 Autotrophs obtain carbon from CO 2 and are of two types Photoautotrophs and chemoautotrophs Heterotrophs obtain carbon from organic compounds Photoheterotrophs and chemoheterotrophs The first cells were most likely chemoautotrophs They may have gotten their energy from sulfur and iron compounds Table 16.10 Archaea thrive in extreme environments and in the ocean Archaea live in anaerobic swamps salt lakes acidic hot springs deep-sea hydrothermal vents animal digestive systems Diverse structural features help prokaryotes thrive almost everywhere Rotating flagella aid in locomotion Plasma membrane Flagellum Cell wall Figure 16.11A, B Figure 16.12A Rotary movements of each flagellum
A prokaryotic cell is enclosed by a plasma membrane and is usually encased in a rigid cell wall Pili help cells cling to surfaces The cell wall may be covered by a sticky capsule Ribosomes Prokaryotic flagella Pili Capsule Cell wall Inside the cell are its DNA and other parts Plasma membrane Pili Nucleoid region (DNA) Figure 4.4 Figure 16.12B Endospores allow certain bacteria to survive environmental extremes in a resting stage Many prokaryotes grow in linear filaments Endospore Figure 16.12C Figure 16.12D EUKARYOTIC CELLS There are 4 main types Fungi Protists Animals Plants 4.5 Eukaryotic cells are partitioned into functional compartments All other life forms are made up of one or more eukaryotic cells These are larger and more complex than prokaryotic cells Eukaryotes are distinguished by the presence of a true nucleus (surrounded by a membrane) Eukaryotes, unlike prokaryotes, also have membrane-enclosed structures called organelles Cell Structure and Function 5
Cell Structure and Function 6 Eukarya 2.7 billion years ago Protists FUNGI Fungi Animals Eukaryotes Plants Rarely discrete cells. FUNGI Nucleus and organelles are membrane bound. Plant like but no chlorophyll. Rigid cell walls that have chitin. Heterotrophic. Fungi (yeasts, moulds and mushrooms) morels The Michigan fungus is estimated to be 1500 years old. It covers about 38 acres and weighs about 11,000 kg. Number of fungal species: about 65,000. UNICELLULAR EUKARYOTES (PROTISTS) Protists (Unicellular Eukaryotes) Are single celled eukaryotes e.g. Paramecium Found almost anywhere there is water Discrete single cells or single cells in colonies Nucleus and organelles are membrane bound. Some are autotrophic and carry out photosynthesis. Others heterotrophic (ingest food) like animals.
Cell Structure and Function 7 Protists Amoeba Tetrahymena Amoeba Giardia SEM thanks to Stanley L. Erlandsen, and Dennis E. Feely, authors of "Trophozoite Motility and the Mechanism of Attachment," in Giardia and Giardiasis, Plenum Press, 1984 Giardia lacks mitochondia, but contains two nuclei. Photosynthetic protists are called algae They include Unicellular dinoflagellates Flagellar groove Anal Pore Amoeba eats Paramecium - http://www.youtube.com/watch?v=pvoz4v699gk Flagellum Figure 16.23A Diatoms Green algae Seaweeds are multicellular marine algae These protists are multicellular photosynthetic organisms that lack the structural specializations of plants Examples include Brown algae Red algae Green algae Figure 16.23 B, C Figure 16.24A, B
Cell Structure and Function 8 Age of fossils in millions of years PALEOZOIC ERA PRECAMBRIAN ERA Brown algae seem closely related to diatoms These groups may eventually be classified with some other groups of protists in a separate kingdom Many biologists favor classifying red algae in their own kingdom Plasmodial slime molds form brightly colored supercells with many nuclei These slime molds have unicellular stages They also have stages where they exist as plasmodia, multinuclear masses of cytoplasm undivided by membranes Is Slime Mould Intelligent? - http://www.youtube.com/watch?v=exeyggxu8-8 Macronucleus Figure 16.22A, B Multicellular life may have evolved from colonial protists Multicellularity evolved independently many times Probably by specialization of the cells of colonial protists 1 2 Locomotor cells 3 Gamete Somatic cells Multicellular life has diversified over hundreds of millions of years Multicellular life first arose over a billion years ago All life was aquatic until almost 500 million years ago Multicellular organisms colonize land Diverse multicellular algae, fungi, and animals, all living in the sea Mass extinctions Earliest animals; many multicellular algae Oldest known fossils of multicellular eukaryotes (small algae) Unicellular protist Colony Foodsynthesizing cells Early multicellular organism with Later organism that specialized, interdependent cells produces gametes Figure 16.25 Figure 16.26 Earliest multicellular eukaryotes? VIDEOS ANIMAL CELLS Diversity of Protists (20 mins) http://www.youtube.com/watch?v=ln69k7lytsu
Cell Structure and Function 9 ANIMAL CELLS An animal cell Exist as part of multicellular organisms. Rough endoplasmic reticulum Smooth endoplasmic reticulum Nucleus Nucleus and organelles membrane bound. Lack cell walls (because we have skeletons). Flagellum Not in most Lysosome plant cells Centriole Ribosomes Peroxisome Heterotrophic (take in nutrients from outside/ingest food). Figure 4.5A Cytoskeleton Microtubule Intermediate filament Microfilament Golgi apparatus Plasma membrane Mitochondrion The plasma membrane controls the cell s contact with the environment Eukaryotes The cytoplasm contains organelles Many organelles have membranes as boundaries These compartmentalize the interior of the cell This allows the cell to carry out a variety of activities simultaneously REMEMBER - Cells are 3 dimensional!! PLANT CELLS
Cell Structure and Function 10 Plant cells A Plant Cell Nucleus Rough endoplasmic Ribosomes reticulum Exist as part of multicellular organisms. Nucleus and organelles membrane bound. Have cell walls (instead of skeleton). Smooth endoplasmic reticulum Golgi apparatus Microtubule Central Not in vacuole Intermediate Cytoskeleton animal filament cells Chloroplast Microfilament Cell wall Autotrophic = make their own food from raw materials. ie. Photosynthesis (using chloroplasts) Mitochondrion Peroxisome Plasma membrane Figure 4.5B A plant cell has some structures that an animal cell lacks: Chloroplasts Captures sunlight for Photosynthesis A rigid cell wall Provides structure (because plants don t have skeletons) A large vacuole Summary Questions What is the difference between a prokaryote and a eukaryote? What are the 4 main types of eukaryotic cells? What is a protist? How are plant cells and animal cells different and why? Homework Mastering Biology activity: Comparing Prokaryotic and Eukaryotic Cells Complete Bioflix study sheet: Tour of an Animal Cell, Tour of a Plant Cell and comparing Animal and Plant Cells Complete Topic 5 in Unit Assessment 1 Animal and Plant Cells - Organelles
Cell Structure and Function 11 Learning Objectives Eukaryotes Describe the structure of a generalised animal and plant cell and describe the functions of cellular components and organelles Identify the similarities and differences between plant and animal cells ORGANELLES OF THE ENDOMEMBRANE SYSTEM Imagine the cell as factory that creates a product The nucleus is the cell s genetic control center (Designer!) It is usually the largest organelle It is separated from the cytoplasm by the nuclear envelope It contains the DNA that directs the cell s activities Chromatin Nucleolus Pore NUCLEUS Two membranes of nuclear envelope The Nucleus -Composed of two concentric membranes that form the nuclear envelope. -Contains a nucleolus ROUGH ENDOPLASMIC RETICULUM Figure 4.6 Ribosomes
The Nucleolus Ribosomes (which become part of the rough endoplasmic reticulum) are produced in the nucleolus. Membranes organize the chemical activities of cells (Manager!) Membranes are selectively permeable They control the flow of substances into and out of a cell Outside cell This is where ribosomal RNA is transcribed. Cytoplasm (inside cell) Figure 5.10 The plasma membrane of an animal cell Glycoprotein Carbohydrate (of glycoprotein) Fibers of the extracellular matrix Glycolipid Nuclear Pores The nuclear envelope has pores and is continuous with the Endoplasmic Reticulum (ER) Phospholipid Cholesterol Microfilaments Proteins of the cytoskeleton Figure 5.12 CYTOPLASM (inside) Nuclear pores allow RNA and protein to move in and out of the nucleus. Endoplasmic Reticulum (ER)(Manufacturing!) Cell membrane components and materials to be exported from the cell are made here SMOOTH ER ROUGH ER Nuclear envelope Proteins are synthesised on Rough ER SMOOTH ER Ribosomes ROUGH ER Lipids (Fats) are produced on Smooth ER. In some cells, Smooth ER regulates carbohydrate metabolism and breaks down toxins and drugs Figure 4.9 Cell Structure and Function 12
Cell Structure and Function 13 The Rough Endoplasmic Reticulum (Manufacturer) makes membrane and proteins The rough ER manufactures membranes Ribosomes (the rough part) on its surface produce proteins Rough Endoplasmic Reticulum (ER) Transport vesicle buds off 4 Ribosome Sugar chain 3 Secretory (glyco-) protein inside transport vesicle 1 2 Glycoprotein ROUGH ER Figure 4.8 Polypeptide The Golgi Apparatus (Shipping out!) The Golgi apparatus consists of stacks of membranous sacs The Golgi apparatus finishes, sorts, and ships cell products These receive and modify ER products, then send them on to other organelles or to the outer cell membrane ANY CELL that secretes substances has lots of these! (e.g. glands in the pancreas and intestinal wall, salivary glands) The Golgi apparatus Golgi apparatus Receiving side of Golgi apparatus Transport vesicle from ER New vesicle forming Golgi apparatus Shipping Transport vesicle side of Golgi from the Golgi apparatus Figure 4.10 Golgi Apparatus Mitochondria (Power supply!) are the energy factories of the cell Two membranes, the inner one folded to increase surface area. Maternally inherited Contain their own DNA and replicate (possibly because they were once separate unicellular organisms) REMEMBER Cells which have high energy requirements have lots of these. E.g. Muscle cells, sperm and cells that do active transport.
Cell Structure and Function 14 Lysosomes (Cleaners!) Lysosomes are sacs of digestive enzymes budded off the Golgi LYSOSOME Nucleus digest food destroy bacteria Lysosomal Enzymes They digest the cell s food and wastes recycle damaged organelles function in embryonic development in animals Figure 4.11A Food Plasma membrane Engulfment of particle Rough ER Transport vesicle (containing inactive hydrolytic enzymes) LYSOSOMES Golgi apparatus Lysosome engulfing damaged organelle Connection: Abnormal lysosomes can cause fatal diseases Lysosomal storage diseases are hereditary They interfere with other cellular functions Examples: Pompe s disease, Tay-Sachs disease Food vacuole Digestion Figure 4.11B Plant cells A plant cell has some extra structures that an animal cell lacks: Chloroplasts Captures sunlight for Photosynthesis A rigid cell wall Provides structure (because plants don t have skeletons) A large vacuole
Cell Structure and Function 15 Chloroplasts Chloroplasts (Plant cells only) Composed of internal folded membranes where the chemical reactions in photosynthesis takes place. Using energy from sunlight to convert carbon dioxide and water to sugar (photosynthesis) Contain their own DNA and replicate by dividing Cell Wall (Plant cells only) Plant cells are supported by rigid cell walls made largely of cellulose Vacuole Walls of two adjacent plant cells PLASMODESMATA These provide support (instead of a skeleton) They connect by plasmodesmata, channels that allow them to share water, food, and chemical messages Layers of one plant cell wall Cytoplasm Plasma membrane Figure 4.19A Plant cells contain a large central vacuole Vacuoles function in the general maintenance of the cell The vacuole has lysosomal and storage functions Vacuoles Figure 4.13A Central vacuole Nucleus A review of the endomembrane system The various organelles of the endomembrane system are interconnected structurally and functionally Cells interact with their environments and each other via their surfaces (membranes) Rough ER Nucleus Smooth ER Transport vesicle from ER Nuclear envelope Transport vesicle from Golgi Golgi apparatus Plasma membrane Vacuole Lysosome Figure 4.14
Cell Structure and Function 16 Eukaryotic organelles comprise four functional categories SUMMARY - Eukaryotic organelles fall into four functional groups Table 4.20 Table 4.20 (continued) Summary Questions What are the three main differences between a plant and an animal cell? Homework Mastering Biology activity: Comparing Prokaryotic and Eukaryotic Cells Complete Bioflix study sheet: Tour of an Animal Cell, Tour of a Plant Cell and comparing Animal and Plant Cells (pge 26-30 study notes) Complete Topic 5 on Unit Assessment 1