Chapter 4 Cell Structure and Function PDF

LECTURE PRESENTATIONS For BIOLOGY, TWELFTH EDITION Sylvia S. Mader, Michael Windelspecht Michael Windelspecht Chapter 4...

LECTURE PRESENTATIONS For BIOLOGY, TWELFTH EDITION Sylvia S. Mader, Michael Windelspecht Michael Windelspecht Chapter 4 Cell Structure and Function Lectures by Dr. Qaisar Mahmood, PhD Erin Barley Copyright © McGraw-Hill Education  Chapter Outline 4.1 Cellular Level of Organization 4.2 Prokaryotic Cells 4.3 Introduction to Eukaryotic Cells 4.4 The Nucleus and Ribosomes 4.5 The Endomembrane System 4.6 Microbodies and Vacuoles 4.7 Energy-Related Organelles 4.8 The Cytoskeleton Copyright © McGraw-Hill Education  4.1 Cellular Level of Organization The cell is the smallest unit of living matter. The link between cells and life became clear to microscopists during the 1830s. The work of Schleiden, Schwann, and Virchow helped in creating the cell theory. It states that Cells are the basic units of structure and function in organisms. All organisms are composed of cells. All cells come only from preexisting cells because cells are self-reproducing. Copyright © McGraw-Hill Education  Cell Size Cells size range from far smaller than 1millimeter (mm) to one micrometer (μm) in diameter. Because of their size, very small biological structures can only be viewed with microscopes. Why are cells so small? Cell is a system by itself; it needs a surface area large enough to allow adequate nutrients to enter and for wastes to be eliminated. Small cells are likely to have an adequate surface area for exchanging molecules. As cell increase in size, the surface area becomes inadequate to exchange the materials that the volume of the cell requires. Copyright © McGraw-Hill Education  Cell Size surface‑area‑to‑volume ratio requires that cells be small. Large cells – surface area relative to volume decreases which also decreases the efficiency of transporting materials in and out of the cell. Small cells – larger surface-area-to-volume ratio is advantageous for exchanging molecules. Copyright © McGraw-Hill Education  Surface-Area-to-Volume Relationships Dividing a large cube into smaller cubes provides a lot more surface area per volume. This relationship is called the surface-area-to-volume-ratio. As cell size decreases from 4cm3 to 1 cm3 , the surface – area-to-volume-ratio increases. Copyright © McGraw-Hill Education  Sizes of Various Objects The unassisted human eye can usually see macroscopic organisms and a few large cells. Microscopic cell are visible with the light microscope, but not in much detail. An electron microscope is necessary to see organelles in detail and to observe viruses and molecules. In metric system, each higher unit is ten times greater than the preceding unit.(1 m = 102 cm = 103 mm = 106 µm = 109 nm). Copyright © McGraw-Hill Education Two different types of cell exist in nature  4.2 Prokaryotic Cells Lack a membrane-bound nucleus. Structurally smaller and simpler than eukaryotic cells (which have a nucleus). Prokaryotic cells are placed in two taxonomic domains: Bacteria Cause diseases but are also environmentally important as decomposers. Can be useful in manufacturing products and drugs. Archaea Live in extreme habitats like hot springs and salt lakes. Two prokaryotic domains are structurally similar but biochemically different. Copyright © McGraw-Hill Education  The Structure of Prokaryotes Extremely small: 1–1.5 μm wide and 2–6 μm long Occur in three basic shapes: Spherical coccus Rod-shaped bacillus Spiral spirillum (if rigid) or spirochete (if flexible) Copyright © McGraw-Hill Education  The Structure of Prokaryotes Prokaryotic cells lack membrane-bound organelles, as well as a nucleus. Their DNA is located in a region called a nucleoid. Copyright © McGraw-Hill Education  The Structure of Prokaryotes In bacteria, the Cell Envelope includes the plasma membrane, the cell wall, and the glycocalyx. Plasma membrane is a phospholipid bilayer with embedded proteins. The plasm membrane has the important function of regulating the entrance and exist of substance into and out of the cytoplasm. Regulating the flow of materials into and out of the cytoplasm is necessary in order to maintain its normal composition. Copyright © McGraw-Hill Education Plasma Membrane  The Structure of Prokaryotes In prokaryotes, the plasma membrane can form internal pouches called (mesosomes). Mesosomes most likely to increase surface area for the attachment of enzyme that are carrying on the metabolic activities. Cell wall maintains the shape of the cell, even if the cytoplasm should happen to take up an abundance of water. The cell wall contains peptidoglycan. Copyright © McGraw-Hill Education  The Structure of Prokaryotes Cell Envelope also includes: Glycocalyx is a layer of polysaccharides that lies outside of the cell wall in some bacteria. A slime layer, not well organized and easy to remove. When layer is well organized and resistant to removal is called a capsule. Copyright © McGraw-Hill Education  Prokaryotic Cytoplasm Cytoplasm Semi-fluid solution composed of water, organic and inorganic molecule encased by plasma membrane. Organic molecules are a variety of enzymes, which speed the many types of chemical reactions involved metabolism. Nucleoid is a region of cytoplasm that contains the single and circular DNA molecule. (Prokaryotes have a single and coiled chromosome). Plasmids are extrachromosomal pieces of circular DNA. Ribosomes are tiny structures in the cytoplasm that synthesize proteins. Copyright © McGraw-Hill Education  Prokaryotic Cytoplasm Some prokaryotes carry out metabolism in the same manner as animals (ingest other organism), but cyanobacteria (blue-green bacteria) are capable of photosynthesis in the same manner as plants. These organisms live in water, ditches, on building, and on the bark of trees. Their cytoplasm contains extensive internal membranes called (Thylakoids). Thylakoids where chlorophyll and other pigments absorb solar energy for the production of carbohydrates. Copyright © McGraw-Hill Education  External Structures of Prokaryotes Flagella – provide motility Consists of filament, hook and basal body Can rotate at 360 degree The number and position of flagella can be used to distinguish different types of prokaryotes. e.g., vibrio cholera (1), Spirilla spp (tufts at one or both ends) Copyright © McGraw-Hill Education  External Structures of Prokaryotes Fimbriae are small, bristle-like fibers that sprout from the cell surface. They are not involved in locomotion; they are involved in attaching prokaryotes to a surface. Conjugation pili are rigid, tubular, structures used by prokaryotes to pass DNA from cell to cell. Prokaryotes reproduces asexually by binary fission, but they can exchange DNA by way of the conjugation pili. Copyright © McGraw-Hill Education  4.3 Introduction to Eukaryotic Cells Eukaryotic cells, like prokaryotic cells, have a plasma membrane composed of a phospholipid bilayer with embedded proteins. separates the contents of the cell from environment regulates that passage of molecules into and out of the cytoplasm. What distinguishes eukaryotic cells from prokaryotic cells: Eukaryotic cells are also much larger than prokaryotic cells. Presence of membrane-bound nucleus that houses DNA. Presence of internal membrane-bound compartments, organelles which: Perform specific functions. Isolate reactions from other reactions Copyright © McGraw-Hill Education  Introduction to Eukaryotic Cells There are two classes of organelles. Endomembrane system Organelles (endoplasmic reticulum (ER), and Golgi apparatus) that work together and communicate with one another by means of transport vesicles. Via membrane channels. Via small vesicles. Energy-related organelles Mitochondria and chloroplasts. Independent and self-sufficient. Copyright © McGraw-Hill Education  Animal Cell Anatomy Copyright © McGraw-Hill Education  Plant Cell Anatomy Copyright © McGraw-Hill Education  Structure of a Eukaryotic Cell Plant and animal cell diagrams are generalized for study purposes. Understanding of the cell structure and function will help you when you study the function of specialized cells. Specialized cells may have more or fewer copies of organelles, depending on their functions. Example: Liver cells, which detoxify drugs, have more smooth endoplasmic reticulum than other cells. Example: Nerve cells, which carry electrical impulses across long distances, have more plasma membrane. Copyright © McGraw-Hill Education  Structure of a Eukaryotic Cell The cell is a system of interconnected organelles that work together to metabolize, regulate, and conduct life process. Example: Nucleus is a compartment that houses genetic material and eukaryotic chromosomes and contain hereditary information. It communicates with ribosomes in the cytoplasm. Copyright © McGraw-Hill Education  Structure of a Eukaryotic Cell Production of specific molecules takes place inside or on the surface organelles by enzymes embedded in the organelle's membranes. These products are then transported around cell by transport vesicles. Membrane sacs that enclose the molecules and keep them separate from the cytoplasm. Vesicles move around using cytoskeleton network. Cytoskeleton is protein fibers are like railroad tracks, which maintains cell shape and assists with cell movement. Copyright © McGraw-Hill Education  Structure of a Eukaryotic Cell Plant cells, fungi, and many protists have cell walls. Plant cell walls contain cellulose, a structural polysaccharide, and, therefore, has a different composition from the bacteria cell wall. Copyright © McGraw-Hill Education  4.4 The Nucleus and Ribosomes The Nucleus It is generally appearing as oval structure located near the center of most cells. The nucleus is the commend center of the cell. Some cells such as skeletal muscle cells, can have more than one nucleus. Separated from cytoplasm by nuclear envelope. Consists of double layer of membrane (inner and outer). Nuclear pores permit exchange between nucleoplasm and cytoplasm Its size sufficient (100 nm) to permit the passage of ribosomal subunits and mRNA out of nucleus into the cytoplasm, and the passage of proteins from the cytoplasm into the nucleus. Copyright © McGraw-Hill Education  The Nucleus The interior of the nucleus contains chromatin in semifluid matrix nucleoplasm. Chromatin looks grainy, but actually it is a network of strands that condenses and undergoes coiling into rodlike structure called chromosome. It contains nucleic acids and proteins. Chromosomes are formed during cell division. Chromosomes are carriers of genetic information. This information organized on the chromosome as genes, the basic unit of heredity. Three types of RNA are produced in the nucleus: rRNA, mRNA, and tRNA. Dark nucleolus composed of rRNA. rRNA joins with proteins to form subunits of ribosomes. Copyright © McGraw-Hill Education  Anatomy of the Nucleus Copyright © McGraw-Hill Education  Ribosomes Ribosomes are particles where protein synthesis occurs in the cell. Consist of a large subunit and a small subunit (subunits are made in nucleus), each comprised of a mix of protein and rRNA, are necessary components of a functional ribosome. In eukaryotes, ribosomes are 20 nm by 30 nm. And in prokaryotes they are slightly smaller. The number of ribosomes in a cell varies depending on its functions; for example, pancreatic cells and other glands have many ribosomes because they produce hormones that contain proteins. May be located: On the endoplasmic reticulum (thereby making it “rough”), or Free in the cytoplasm, either singly or in groups, called polyribosomes. Copyright © McGraw-Hill Education  Ribosomes In the process of transcription and translation: In nucleus , the information within a gene is copied into mRNA, which is exported into the cytoplasm via nuclear pore. Ribosomes receive the mRNA with a coded message from DNA with the correct sequence of amino acids to make a particular protein. Proteins synthesized by cytoplasmic ribosomes are used in the cytoplasm; and those synthesized by attached ribosomes end up in ER. What causes a ribosome to bind to the endoplasmic reticulum? Copyright © McGraw-Hill Education  Ribosomes Binding occurs only if the protein being synthesized by a ribosome begins with a sequence of amino acids called a single peptide. The signal peptide binds a particular (signal recognition particles, SRP), which then binds to a receptor on the ER. Once the protein enters, the ER, an enzyme cleaves off the signal peptide, and the protein ends up within the interior of ER, where it folds into its final shape. The sequence of DNA being transcribed into mRNA, and in turns being translated into a protein, occurs in all living cells, the DNA-mRNA-protein sequence of events is termed the central dogma of molecular biology Copyright © McGraw-Hill Education  Function of Ribosomes Copyright © McGraw-Hill Education  4.5 The Endomembrane System Series of intracellular membranes that compartmentalize the cell This system compartmentalizes the cell so that particular enzymatic reactions are restricted to specific regions and overall cell efficiency is increased. Consists of: Nuclear envelope Membranes of endoplasmic reticulum Golgi apparatus Several types of Vesicles Transport materials between organelles of system Copyright © McGraw-Hill Education  Endoplasmic Reticulum ER is consisting of a complicated system of membrane channels and saccules (flattened vesicles) and is physically continuous with the outer membrane of the nuclear envelope. The ER consists of rough ER and smooth ER, which have different structures and functions. Regardless of functional differences, both rough and smooth ER form vesicles that transport molecules to other parts of the cells, notably Golgi apparatus. Copyright © McGraw-Hill Education  Endoplasmic Reticulum Ribosomes are present on rough ER, which consists of flattened saccules, but not on smooth ER, which is more tubular. Copyright © McGraw-Hill Education  Endoplasmic Reticulum Rough ER  Studded with ribosomes on cytoplasmic side, giving it the capacity to produce proteins.  Inside its lumen, the rough ER allow protein to fold and take on their final three-dimensional shape.  It contains enzymes that can add sugar chains to protein to form glycoproteins that are important in many cell function. Smooth ER  It is continuous with the rough ER and dose not have attached ribosomes  Synthesis of lipids In testes, testosterone (steroid hormone) is produced by smooth ER.  Site of various synthetic processes, detoxification, and storage In the liver, smooth ER help detoxify drugs and alcohol. Copyright © McGraw-Hill Education  The Golgi Apparatus The Golgi apparatus is named for Camillo Golgi.  Consists of 3 to 20 flattened, slightly curved saccules  Appearance can be compared to a stack of pancakes  Processes, packages and secrets modifies proteins and lipids with “signal” sequences Receives protein-filled vesicles from rough ER and lipid-filled vesicles from smooth ER on cis (or inner) face After modification, prepares for “shipment” and packages proteins and lipids in vesicles that leave Golgi from trans (or outer) face  Some transported to locations within cell  Some exported from cell (secretion, exocytosis)  Others returned to ER or merged with plasma membrane Copyright © McGraw-Hill Education  Golgi Apparatus The Golgi apparatus is a stack of flattened, curved saccules. It processes proteins and lipids and packages them in transport vesicles that either distribute these molecules to various locations within the cell or secrete them externally. Copyright © McGraw-Hill Education  Lysosomes Lysosomes are membrane-bound vesicles (not found in plants)  Produced by the Golgi apparatus  Contain powerful hydrolytic digestive enzymes and are highly acidic ( act like our stomach) Digest large molecules into simpler subunits Recycle cellular resources (destroy nonfunctional organelles and portions of cytoplasm). White blood cells have a greater proportion of lysosomes than other cells, because they engulf pathogens and digestion them in lysosomes. Copyright © McGraw-Hill Education  Lysosomes Several human lysosomal storage diseases are due to a missing lysosomal enzyme. Tay-Sachs (missing enzyme digests a fatty substance that helps insulate nerve cells and increases their efficiency. Gene therapy restores missing enzyme to cells and may be able to treat Tay-Sachs disease. Copyright © McGraw-Hill Education  Lysosomes Lysosomes are bud of the Golgi apparatus in cells, are filled with hydrolytic enzymes that digest molecules and parts of the cell. Here a lysosome digests a worn mitochondrion and a peroxisome. Copyright © McGraw-Hill Education  Endomembrane System Summary Proteins produced in rough ER and lipids from smooth ER are carried in vesicles to the Golgi apparatus. The Golgi apparatus modifies these products and then sorts and packages them into vesicles that go to various cell destinations. Secretory vesicles carry products to the membrane where exocytosis produces secretions.  Example: Mammary glands produce milk and pancreas produces digestive enzymes. Lysosomes fuse with incoming vesicles and digest macromolecules. Copyright © McGraw-Hill Education  Endomembrane System Copyright © McGraw-Hill Education  4.6 Microbodies and Vacuoles Microbodies contain specialized enzymes to perform special metabolic function. Example: Peroxisomes  Like lysosomes. Membrane-bounded vesicles. Enclose enzymes that are involved in the breakdown of fatty acids. Enzymes are synthesized by free ribosomes. As the enzyme of peroxisomes oxidize fatty acids , they produce (H2O2),toxic substance. Contain an enzyme called catalase that immediately breaks down H2O2 to water and O2 by catalase. Lake of peroxisomal membrane protein results in adrenoleukodystrophy (ALD), producing neurological damage. Copyright © McGraw-Hill Education  Plant Cell Peroxisome Peroxisomes contain one or more enzymes that can oxidize various organic substances. Copyright © McGraw-Hill Education  Vacuoles Membranous sacs that are larger than vesicles  Store materials that occur in excess  Others very specialized (contractile vacuole) (some protists) that ridding the cell of excess water Plants cells typically have a central vacuole  Up to 90% volume of some cells  Functions in: Storage of water, nutrients, pigments, and waste products Development of turgor pressure Toxic substances used for protection from herbivores Some functions performed by lysosomes in other eukaryotes Example: aged organelles are broken down by digestive enzymes Copyright © McGraw-Hill Education  Plant Cell Central Vacuole The large central vacuole of plant cells has numerous functions, from storing molecules to helping the cell increase in size. Copyright © McGraw-Hill Education  4.7 Energy-Producing Organelles Chloroplasts and mitochondria are the two eukaryotic membranous organelles that specialize in converting energy to a form that can be used by the cell. Chloroplasts  Some algal cells have only one chloroplast, while some plant cells have as many as a hundred. Chloroplasts are quite larger than mitochondria.  Three-membrane system  Surrounded by double membrane (inner and outer)  The double membrane encloses the semifluid stroma, which contain enzymes and thylakoids, dislike sacs formed from a third chloroplast membrane. Copyright © McGraw-Hill Education  Chloroplasts A stack of thylakoids is a granum. The lumens of the thylakoids are believed to form a large, internal compartment called the thylakoid space.  Chlorophyll (green photosynthetic pigment) and other pigments that capture solar energy are located in the thylakoid membrane (inner membranes of chloroplast)  The enzymes that synthesize carbohydrates are located outside the thylakoid in the fluid of the stroma. Copyright © McGraw-Hill Education  Structure of Chloroplast Copyright © McGraw-Hill Education  Chloroplasts Chloroplasts use solar energy to synthesize carbohydrates during photosynthesis, which serve as organic nutrient molecules for plants and all life on Earth. Photosynthesis can be represented by this equation: Solar energy + CO2 + water Carbohydrate + O2 Make plants use CO2 as only source of carbon Energy poor compounds converted to energy rich compounds. Plants, algae, and cyanobacteria are capable of conduction photosynthesis in this manner, but only plants and algae have chloroplasts, because they are eukaryotes. Copyright © McGraw-Hill Education  Chloroplasts A chloroplast is a type of plastid. Plastids are plant organelles that are surrounded by a double membrane and have varied functions. serve as sites of photosynthesis. Other types of Plastids: Chromoplasts, contain pigments that results in yellow, orange or red color. Give the color of autumn leaves, fruits, carrots and some flowers. Leukoplasts are colorless plastids that synthesize and store starches and oils. Copyright © McGraw-Hill Education  Mitochondria Contained by nearly all eukaryotic cells and all plant, algae, and animal cells Smaller than chloroplast Numbers vary with metabolic activities and energy requirements of cells (Liver cells have as many as 1,000) Contain ribosomes and their own DNA Surrounded by a double membrane (inner and outer membranes) Powerhouses of cell produce most of ATP utilized by the cell Copyright © McGraw-Hill Education  Mitochondria The inner membrane surrounds the semifluid matrix and is highly convoluted into folds called cristae that project into the matrix. Matrix is highly concentrated mixture of enzymes that breakdown carbohydrates and other molecules. These reactions supply the chemical energy needed for a chain of proteins on the inner membrane to create the condition allow ATP synthesis to take place. The entire process, which also involves the cytoplasm, is called cellular respiration, because oxygen used, and carbon dioxide given off. Copyright © McGraw-Hill Education  Structure of Mitochondrion Copyright © McGraw-Hill Education  Energy-Producing Organelles Chloroplasts use sunlight to produce carbohydrates, which in turn are used by the mitochondria. The mitochondria then produce carbon dioxide and water, which is in turn used by the chloroplasts. Copyright © McGraw-Hill Education  Cytoskeleton Copyright © McGraw-Hill Education  The Cytoskeleton The cytoskeleton maintains a cell’s shape and allows its part to move. Three types of protein components make up the cytoskeleton. They can be detected in cells using labeling and fluorescence microscopy. Copyright © McGraw-Hill Education  Centrioles Short, hollow cylinders with 9+0 pattern of microtubule are arranged in an outer ring. Composed of 27 microtubules Microtubules arranged into 9 overlapping triplets In animal cells and most protist, centrosome contains two centrioles. Centrosome is the major microtubule- organizing center for the cell. Oriented at right angles to each other Before an animal cell divides, the centrioles replicate, and the members of each pair are at right angles to one another. Then each pair becomes part of a separate centrosome during mitosis to determine plane of division. Copyright © McGraw-Hill Education  Centrioles May give rise to basal body structure that lies at the base of cilia and flagella and may direct the organization of microtubules within these structures. In other words, a basal body may do for a cilium or flagellum what the centrosome does for the cell. Copyright © McGraw-Hill Education  Centrioles Copyright © McGraw-Hill Education