Biology Chapter 4: Cell Structure and Function PDF

Because learning changes everything. ® Biology Sylvia S. Mader...

Because learning changes everything. ® Biology Sylvia S. Mader Michael Windelspecht Chapter 4 Cell Structure and Function Lecture Online Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  Outline 4.1 Cellular Level of Organization 4.2 Prokaryotic Cells 4.3 Introducing 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 2  4.1 The Cell Theory 1. All organisms are formed of one or more cells. 2. Cells are the smallest and most basic units of organization in living organisms. 3. All cells arise from the division of pre- existing cells because cells are self- reproducing.  Sizes of Living Things Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 0.1 nm 1 nm 10 nm 100 nm 1 m 10 m 100 m 1 mm 1 cm 0.1 m 1m 10 m 100 m 1 km protein chloroplast plant and mouse rose animal frog egg amino cells acid virus ostrich most bacteria human egg ant egg atom blue whale electron microscope human light microscope human eye 4  Cell Size Cells range in size: 1mm to 1micrometer in diameter. Cells need a large surface area of plasma membrane to adequately exchange materials. The surface‑area‑to‑volume ratio requires that cells be small – Large cells - surface area relative to volume decreases which 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 5 Thinking about surface area to volume in a cell Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 mm 2 mm Surface area 6 ´ 1 mm2 = 6 mm2 6 ´ 4 mm2 = 24 mm2 (square mm) Volume (cubic mm) (1 mm)3 = 1 mm3 (2 mm)3 = 8 mm3 Surface area 6 24 = 3 Volume 1 8 1  Surface-Area-to-Volume Relationships One Eight Sixty-four 4- 2- 1- centimeter centimeter centimeter cube cubes cubes 1.5: 1 3: 1 6: 1  Cells Two different types: I. Prokaryotic cells II. Eukaryotic cells All Cells are made of 3 main parts: 1. Plasma membrane 2. Nucleoid (prokaryotes), Nucleus (eukaryotes) 3. Cytoplasm.  4.2 Prokaryotic Cells  Small with simple internal structure  Lack membrane bound organelles.  Have a cell envelope.  Contain a single circular strand of DNA  have a nucleoid instead of a nucleus  Enzymes that catalyze reactions are bound to the cell membrane.  Placed in two taxonomic domains, structurally similar but biochemically different: 1- Eubacteria 2- Archaea Bacteria  1- Bacteria There are 3 different shapes: Uses of bacteria: 1- Some cause disease. Ex. Tuberculosis, Tetanus, gonorrhea. 2- Important decomposers. 3- used to manufacture all sorts of products & drugs. Ex. Insulin Cyanobacteria= blue green algae, has thylakoids & are capable of photosynthesis.  Cell Envelope includes: – Plasma membrane - Phospholipid bilayer with embedded and peripheral protein Form internal pouches (mesosomes) increases SA – Cell wall - maintains the shape of the cell and is strengthened by peptidoglycan – Glycocalyx - layer of polysaccharides on the outside of the cell wall Well organized and resistant to removal (Capsule)  Prokaryotic Cytoplasm and Appendages Cytoplasm: Semifluid solution that contains water, inorganic & organic molecules (enzymes) Bounded by plasma membrane – Nucleoid is a region that contains the single, coiled DNA molecule – Plasmids are small circular rings of DNA Appendages – Flagella – provide motility like a propeller -consists of a filament, hook & basal body - number & location distinguish different types – Fimbriae – small, bristle-like fibers that sprout from the cell surface – Conjugation pili – rigid tubular structures used to pass DNA from cell to cell 12 4.3 Eukaryotic Cells, contain 1- Membrane-bound nucleus that houses DNA. 2- Specialized organelles which perform specific functions. isolate reactions from other reactions. 3- Plasma membrane which is composed of a phospholipid bilayer with embedded proteins separates cell contents from environment regulates passage of materials in and out The first two distinguish eukaryotic from prokaryotic cells Origin of the Eukaryotic Cell The fossil record suggests that the first cells were prokaryotes. Biochemical data shows eukaryotes are more closely related to archaea than bacteria. The nucleus is believed to have evolved by invagination of the plasma membrane. The invagination process also explains origins of endoplasmic reticulum and Golgi apparatus. Energy organelles, mitochondria and chloroplasts, may have originated when larger cells engulfed smaller prokaryotic cells. Eukaryotic cells would have benefited from the ability to utilize oxygen or synthesize organic food. Endosymbiotic theory is the name of the hypothesis. 14  Origin of Organelles Original prokaryotic cell DNA 1. Cell gains a nucleus by the plasma membrane invaginating and surrounding the DNA with a double membrane. Nucleus allows specific functions to be assigned, freeing up cellular resources for other work. 2. Cell gains an endomembrane system by proliferation of membrane. Increased surface area allows higher rate of transport of materials within a cell. Endosymbiotic 3. Cell gains mitochondria. Theory aerobic Ability to metabolize sugars in the presence of oxygen enables bacterium greater function and success. mitochondrion 4. Cell gains chloroplasts. Ability to produce sugars from sunlight enables greater function and success. chloroplast photosynthetic Animal cell bacterium has mitochondria, but not chloroplasts. Plant cell has both mitochondria and chloroplasts. 15  Eukaryotic Cells: Organelles Two classes of organelles: – Endomembrane system Organelles that communicate with one another – Via membrane channels – Via small vesicles – Energy related organelles : Mitochondria & Chloroplasts Independent and self-sufficient Have their own DNA. Divide on their own 16 Comparison Eukaryotic Cell Structures and Functions  4.4. Nucleus Command center of cell. Separated from cytoplasm by nuclear envelope ( phospholipid bilayer). Contains chromatin ( NA & proteins) in semifluid nucleoplasm Nucleolus is composed of rRNA Site for ribosome synthesis Nuclear pores: import proteins from cytoplasm & export mRNA and ribosomal subunits to cytoplasm.  Ribosomes  occur singly or in groups (polyribosomes)  found freely in cytoplasm or attached to the membrane of the endoplasmic reticulum (ER).  made of 2 subunits: one large (30 nm),one small (20nm). Each subunit is made of proteins and rRNA synthesized in the nucleolus.  Site of protein synthesis  The central dogma of molecular biology is the DNA-mRNA-protein sequence of events.  Ribosomes May be located: on the endoplasmic reticulum (thereby making it “rough”), or free in the cytoplasm, either singly or in groups, called polyribosomes. Information for the gene is copied into mRNA, which is exported into the cytoplasm. Ribosomes receive the mRNA with a coded message from DNA with the correct sequence of amino acids to make a protein. Proteins synthesized by cytoplasmic ribosomes stay in cytoplasm; those by attached ribosomes end up in ER. 21  Function of Ribosomes Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1. mRNA is first copied from a gene, and then it exits the nucleus through a pore complex. A ribosome attaches and begins protein synthesis, Nucleus producing a signal peptide. DNA mRNA ribosome mRNA signal peptide nuclear pore ribosomal subunits 2. Signal recognition particle 3. SRP binds to (SRP) binds to signal peptide receptor (purple); and temporarily halts protein a channel opens; synthesis. SRP leaves and mRNA allows protein signal recognition synthesis to resume; as particle (SRP) receptor polypeptide is SRP synthesized it is simultaneously 5. Ribosomal subunits Cytoplasm fed into ER. and mRNA break away. The polypeptide remains in the ER an`d folds into Endoplasmic Lumen of ER enzyme a functional protein. reticulum (ER) 4. An enzyme removes ER membrane the signal peptide from the growing polypeptide. protein Central Dogma in Biology 22  4.5 The Endomembrane System A system of membrane channels and vesicles continuous with the outer membrane of the nuclear envelope. They compartmentalize the cell Restrict enzymatic reactions to specific compartments within cell Consists of: Nuclear envelope Endoplasmic reticulum Golgi apparatus Vesicles Several types Transport materials between organelles of system Endoplasmic Reticulum Rough ER - Synthesizes proteins - Modifies and processes proteins -Adds sugar to protein to form glycoproteins Smooth ER – Synthesis of lipids – Site of various synthetic processes, detoxification of drugs, and storage – Forms transport vesicles 24  Golgi Apparatus Consists of flattened, curved saccules Resembles stack of hollow pancakes Modifies proteins and lipids with “signal” sequences Receives vesicles from 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 25  Lysosomes Membrane-bound vesicles (not in plants) – Produced by the Golgi apparatus – Contain powerful digestive enzymes and are highly acidic Digestion of large molecules Recycling of cellular resources ( dead mitochondria) Tay- Sachs disease is caused by defect in lysosomal enzyme. 27  Lysosomes A Lysosome is engulfing a dead mitochondria & a peroxisome  4.6 Peroxisomes  membrane-bounded vesicles that enclose enzymes synthesized by free ribosomes (instead of RER).  Common in cells that synthesize and break down lipids  contain enzymes that oxidize fatty acids:  RH2 + O2  R + H2O2  H2O2 (toxic) is broken down to H2O + O2 by the peroxisomal enzyme catalase.  In plants, seeds use peroxisomes to oxidize fatty acids into molecules that can be converted to sugars. Needed for seed germination  Plant Cell Peroxisome (photo): ©EM Research Services, Newcastle University  Vacuoles  In animal cells, few ( fat cells).  In protists, water regulation (contractile)  Plant cells have a large central vacuole (90% vol. of cell) filled with cell sap – Functions: Storage of water, sugar, salts, pigments & wastes Development of turgor pressure for support. Contain toxic chemicals to deter herbivores. If an organelle age, it will fuse with the vacuole that breaks it down (~lysosomes)  4.7 Energy-Related Organelles a) Chloroplasts: type of plastids found in plants, algae and cyanobacteria  contain multiple copies of the same DNA  Forms disc-like thylakoids are stacked to form grana.  Suspended in semi-fluid stroma.  Chlorophyll is located in the thylakoid membrane; while enzymes that synthesize carbohydrates located in the fluid stroma. Solar Energy 6CO2 +6 H2O  C6H12O6 + 6O2 Other types of plastids: Chromoplasts & Leucoplasts b) Mitochondria  Present in all eukaryotic cells.  Smaller than chloroplast.  Number varies depending on metabolic activity of the cell.  about the size of bacteria  Matrix contains ribosomes & DNA  power house of the cell; produces most of ATP  converts chemical energy of CHO into ATP by the process called cellular respiration. C6H12O6 +6O2  6CO2 + 6H2O + ATP (energy) Energy-Producing Organelles Figure 4.16 34  4.8 The Cytoskeleton internal skeleton maintain the shape of cell. organelles do not just drift around in the cell but are held in place by the cytoskeleton allows cell movement (cilia, flagella, crawl) allows organelle movement & organization allows cell division (centrioles, filaments) Dynamic : Assemble when Phosphatases removes PO4 from proteins Disassemble when kinases adds PO4 to proteins Cytoskeleton is composed of : Rely on actin for transfer of molecules Give strength to feathers Transfer of color pigments For camouflage a) Actin Filaments, under plasma membrane maintains cell shape.  Extremely thin filaments, like a twisted pearl necklace  Support for microvilli in intestinal cells  Intracellular traffic control For moving stuff around within cell Cytoplasmic streaming.  Function in pseudopods of amoeboid cells  Important component in muscle contraction (other is myosin, a “motor” molecule)  Important in animal cell division b) Intermediate Filaments:  8-11nm in diameter  intermediate in size  Types of fibrous polypeptides vary according to the tissue Functions: - Support nuclear envelope - Support plasma membrane & take part in the formation of cell-to-cell junctions (skin) - give great mechanical strength to skin cells ( keratin) c) Microtubules:  Hollow cylinders (=25nm)  Made of 13 rows of α,β tubulin dimers  It is under the control of microtubule  organizing center (MTOC) in centrosomes 25µm  maintain the shape of the cell 0.2-  act as tracks along which organelles can move  Interacts with “motor” molecules, kinesin and 25n dynein, to cause movement of organelles m  Mitotic “spindle” distributes chromosomes during cell division Outside the cell  Centrioles  Short hollow cylinders made of 27 microtubules.  One pair per animal cells located in the centrosome.  Oriented at right angles. 9 + 0 pattern of microtubule  Plant cells do not have triplets centrioles but MTOC.  help assemble microtubules  help in separation of chromosomes during cell division  Give rise to basal bodies of cilia  Cilia and Flagella Hair-like projections from cell surface that aid in cell movement Very different from prokaryote flagella – Inside there is a cylinder of 18 microtubules arranged in 9 microtubule pairs – In center are two single microtubules – This 9 + 2 pattern used by all cilia & flagella In eukaryotes, cilia are much shorter than flagella – Cilia move in coordinated waves like oars – Flagella move in a whiplike motion. 41  Structure of a Flagellum Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. outer Flagellum microtubule doublet radial spoke central shaft The shaft of the microtubules flagellum has a ring of nine microtubule doublets anchored dynein to a central pair of side arm microtubules. 25 nm Flagellum cross section The side arms dynein Sperm of each doublet side arms plasma are composed triplets membrane of dynein, a motor molecule. Basal body ATP In the presence of ATP, the dynein side arms reach out to their neighbors, The basal body of a flagellum has and bending occurs. 100 nm a ring of nine microtubule triplets Basal body cross section with no central microtubules. (Flagellum, Basal body): © William L. Dentler/Biological Photo Service 42