Ch 4 Study Guide: Functional Anatomy of Prokaryotic & Eukaryotic Cells PDF

4: Functional Anatomy of Prokaryotic and Eukaryotic Cells LEARNING OBJECTIVES CHECK YOUR UNDERSTANDING 4-1 ​Compare and contrast the overall cell What is the main feature that distinguishes prokaryotes structure of prokaryotes and eukaryotes. from eukaryotes...

4: Functional Anatomy of Prokaryotic and Eukaryotic Cells LEARNING OBJECTIVES CHECK YOUR UNDERSTANDING 4-1 ​Compare and contrast the overall cell What is the main feature that distinguishes prokaryotes structure of prokaryotes and eukaryotes. from eukaryotes? 4-2 ​Identify the three basic shapes of How would you be able to identify streptococci through a bacteria. microscope? 4-3 ​Describe the structure and function Why are bacterial capsules medically important? of the glycocalyx. 4-4 ​Differentiate flagella, axial filaments, How do bacteria move? fimbriae, and pili. 4-5 ​Compare and contrast the cell walls Why are drugs that target cell wall synthesis useful? of gram-positive bacteria, gram-negative bacteria, acid-fast bacteria, archaea, and mycoplasmas. 4-6 ​Compare and contrast archaea and Why are mycoplasmas resistant to antibiotics that interfere mycoplasmas. with cell wall synthesis? 4-7 ​Differentiate between protoplast, How do protoplasts differ from L forms? spheroplast, and L form. 4-8 ​Describe the structure, chemistry, and Which agents can cause injury to the bacterial plasma functions of the prokaryotic plasma membrane? membrane. 4-9 ​Define simple diffusion, facilitated How are simple diffusion and facilitated diffusion similar? diffusion, osmosis, active transport, and group How are they different? translocation. 4-10 ​Identify the functions of the nucleoid Where is DNA located in a prokaryotic cell? and ribosomes. 4-11 ​Identify the functions of four What is the general function of inclusions? inclusions. 4-12 ​Describe the functions of endospores, Under what conditions do endospores form? sporulation, and endospore germination. 4-13 ​Differentiate prokaryotic and Identify at least one significant difference between eukaryotic flagella. eukaryotic and prokaryotic flagella and cilia, cell walls, plasma membrane, and cytoplasm. 4-14 ​Compare and contrast prokaryotic Identify at least one significant difference between and eukaryotic cell walls and glycocalyxes. eukaryotic and prokaryotic flagella and cilia, cell walls, plasma membrane, and cytoplasm. 4-15 ​Compare and contrast prokaryotic Identify at least one significant difference between and eukaryotic plasma membranes. eukaryotic and prokaryotic flagella and cilia, cell walls, 4-15 ​Compare and contrast prokaryotic Identify at least one significant difference between and eukaryotic plasma membranes. eukaryotic and prokaryotic flagella and cilia, cell walls, plasma membrane, and cytoplasm. 4-16 ​Compare and contrast prokaryotic Identify at least one significant difference between and eukaryotic cytoplasms. eukaryotic and prokaryotic flagella and cilia, cell walls, plasma membrane, and cytoplasm. 4-17 ​Compare the structure and function The antibiotic erythromycin binds with the 50S portion of of eukaryotic and prokaryotic ribosomes. a ribosome. What effect does this have on a prokaryotic cell? On a eukaryotic cell? 4-18 ​Define organelle. Compare the structure of the nucleus of a eukaryote and the nucleoid of a prokaryote. 4-19 ​Describe the functions of the nucleus, How do rough and smooth ER compare structurally and endoplasmic reticulum, Golgi complex, functionally? lysosomes, vacuoles, mitochondria, chloroplasts, peroxisomes, and centrosomes. 4-20 ​Discuss evidence that supports the Which three organelles are not associated with the Golgi endosymbiotic theory of eukaryotic evolution. complex? What does this suggest about their origin? NEW IN THIS EDITION ​Revised discussion of classification of flagella, fimbriae, pili, motility, LPS, facilitated diffusion, aquaporins, and active transport. CHAPTER SUMMARY Comparing Prokaryotic and Eukaryotic Cells: An Overview (p. 77) 1. ​Prokaryotic and eukaryotic cells are similar in their chemical composition and chemical reactions. 2. ​Prokaryotic cells lack membrane-enclosed organelles (including a nucleus). 3. ​Peptidoglycan is found in prokaryotic cell walls but not in eukaryotic cell walls. 4. ​Eukaryotic cells have a membrane-bound nucleus and other organelles. THE PROKARYOTIC CELL (pp. 77–98) 1. ​Bacteria are unicellular, and most of them multiply by binary fission. 2. ​ acterial species are differentiated by morphology, chemical composition, nutritional B requirements, biochemical activities, and source of energy. The Size, Shape, and Arrangement of Bacterial Cells (pp. 77–79) 1. ​Most bacteria are 0.2 to 2.0 µm in diameter and 2 to 8 µm in length. 2. ​The three basic bacterial shapes are coccus (spherical), bacillus (rod-shaped), and spiral (twisted). 3. ​Pleomorphic bacteria can assume several shapes. Structures External to the Cell Wall (pp. 79–84) Glycocalyx (pp. 79–81) 1. ​The glycocalyx (capsule, slime layer, or extracellular polysaccharide) is a gelatinous polysaccharide and/or polypeptide covering. 2. ​Capsules may protect pathogens from phagocytosis. 3. ​Capsules enable adherence to surfaces, prevent desiccation, and may provide nutrients. Flagella (pp. 81–82) 4. ​Flagella are relatively long filamentous appendages consisting of a filament, hook, and basal body. 4. ​Flagella are relatively long filamentous appendages consisting of a filament, hook, and basal body. 5. ​Prokaryotic flagella rotate to push the cell. 6. ​ Motile bacteria exhibit taxis; positive taxis is movement toward an attractant, and negative taxis is movement away from a repellent. ​7. ​ Flagellar (H) protein is an antigen. Axial Filaments (pp. 82–83) ​8. ​ piral cells that move by means of an axial filament (endoflagellum) are called S spirochetes. ​ 9. ​Axial filaments are similar to flagella, except that they wrap around the cell. Fimbriae and Pili (pp. 83–84) ​10. ​Fimbriae help cells adhere to surfaces. ​11. ​Pili are involved in twitching motility and DNA transfer. The Cell Wall (pp. 84-89) Composition and Characteristics (pp. 85-87) ​1. ​The cell wall surrounds the plasma membrane and protects the cell from changes in water pressure. ​2. ​The bacterial cell wall consists of peptidoglycan, a polymer consisting of NAG and NAM and short chains of amino acids. ​3. ​Penicillin interferes with peptidoglycan synthesis. ​4. ​Gram-positive cell walls consist of many layers of peptidoglycan and also contain teichoic acids. ​5. ​Gram-negative bacteria have a lipopolysaccharide-lipoprotein-phospholipid outer membrane surrounding a thin peptidoglycan layer. ​6. ​The outer membrane protects the cell from phagocytosis and from penicillin, lysozyme, and other chemicals. ​7. ​Porins are proteins that permit small molecules to pass through the outer membrane; specific channel proteins allow other molecules to move through the outer membrane. ​ 8. ​The lipopolysaccharide component of the outer membrane consists of sugars (O polysaccharides), which function as antigens, and lipid A, which is an endotoxin. Cell Walls and the Gram Stain Mechanism (p. 87) ​9. ​The crystal violet–iodine complex combines with peptidoglycan. ​10. ​The decolorizer removes the lipid outer membrane of gram-negative bacteria and washes out the crystal violet. Atypical Cell Walls (pp. 87–88) ​11. ​Mycoplasma is a bacterial genus that naturally lacks cell walls. ​12. ​Archaea have pseudomurein; they lack peptidoglycan. ​13. ​Acid-fast cell walls have a layer of mycolic acid outside a thin peptidoglycan layer. Damage to the Cell Wall (pp. 88–89) ​14. ​In the presence of lysozyme, gram-positive cell walls are destroyed, and the remaining cellular contents are referred to as a protoplast. ​15. ​In the presence of lysozyme, gram-negative cell walls are not completely destroyed, and the remaining cellular contents are referred to as a spheroplast. ​16. ​L forms are gram-positive or gram-negative bacteria that do not make a cell wall. ​17. ​Antibiotics such as penicillin interfere with cell wall synthesis.  ​17. ​Antibiotics such as penicillin interfere with cell wall synthesis. Structures Internal to the Cell Wall (pp. 89–98) The Plasma (Cytoplasmic) Membrane (pp. 89–91) ​1. ​The plasma membrane encloses the cytoplasm and is a lipid bilayer with peripheral and integral proteins (the fluid mosaic model). ​2. ​The plasma membrane is selectively permeable. ​3. ​Plasma membranes contain enzymes for metabolic reactions, such as nutrient breakdown, energy production, and photosynthesis. ​4. ​Mesosomes, irregular infoldings of the plasma membrane, are artifacts, not true cell structures. ​5. ​Plasma membranes can be destroyed by alcohols and polymyxins. The Movement of Materials across Membranes (pp. 91–94) 6​. ​Movement across the membrane may be by passive processes, in which materials move from areas of higher to lower concentration and no energy is expended by the cell. ​7. ​In simple diffusion, molecules and ions move until equilibrium is reached. ​8. ​In facilitated diffusion, substances are transported by transporter proteins across membranes from areas of high to low concentration. ​9. ​Osmosis is the movement of water from areas of high to low concentration across a selectively permeable membrane until equilibrium is reached. ​10. ​In active transport, materials move from areas of low to high concentration by transporter proteins, and the cell must expend energy. ​11. ​In group translocation, energy is expended to modify chemicals and transport them across the membrane. Cytoplasm (p. 94) ​12. ​Cytoplasm is the fluid component inside the plasma membrane. ​13. ​The cytoplasm is mostly water, with inorganic and organic molecules, DNA, ribosomes, and inclusions. The Nucleoid (pp. 94–95) ​14. ​The nucleoid contains the DNA of the bacterial chromosome. ​15. ​ acteria can also contain plasmids, which are circular, extrachromosomal DNA B molecules. Ribosomes (p. 95) ​16. ​The cytoplasm of a prokaryote contains numerous 70S ribosomes; ribosomes consist of rRNA and protein. ​17. ​Protein synthesis occurs at ribosomes; it can be inhibited by certain antibiotics. Inclusions (pp. 95–96) ​18. ​Inclusions are reserve deposits found in prokaryotic and eukaryotic cells. ​19. ​Among the inclusions found in bacteria are metachromatic granules (inorganic phosphate), polysaccharide granules (usually glycogen or starch), lipid inclusions, sulfur granules, carboxysomes (ribulose 1,5-diphosphate carboxylase), magnetosomes (Fe3O4), and gas vacuoles. Endospores (pp. 96–98) ​20. ​Endospores are resting structures formed by some bacteria; they allow survival during adverse environmental conditions. ​21. ​The process of endospore formation is called sporulation; the return of an endospore to its vegetative state is called germination. THE EUKARYOTIC CELL (pp. 98–106) THE EUKARYOTIC CELL (pp. 98–106) Flagella and Cilia (p. 98) ​1. ​Flagella are few and long in relation to cell size; cilia are numerous and short. ​2. ​Flagella and cilia are used for motility, and cilia also move substances along the surface of the cells. ​3. ​Both flagella and cilia consist of an arrangement of nine pairs and two single microtubules. The Cell Wall and Glycocalyx (p. 98) ​1. ​The cell walls of many algae and some fungi contain cellulose. ​2. ​The main material of fungal cell walls is chitin. ​3. ​Yeast cell walls consist of glucan and mannan. ​ 4. ​Animal cells are surrounded by a glycocalyx, which strengthens the cell and provides a means of attachment to other cells. The Plasma (Cytoplasmic) Membrane (p. 100) ​1. ​Like the prokaryotic plasma membrane, the eukaryotic plasma membrane is a phospholipid bilayer containing proteins. ​2. ​Eukaryotic plasma membranes contain carbohydrates attached to the proteins and sterols not found in prokaryotic cells (except Mycoplasma bacteria). ​ 3. ​Eukaryotic cells can move materials across the plasma membrane by the passive processes used by prokaryotes and by active transport and endocytosis (phagocytosis and pinocytosis). Cytoplasm (pp. 100–101) ​1. ​The cytoplasm of eukaryotic cells includes everything inside the plasma membrane and external to the nucleus. ​2. ​The chemical characteristics of the cytoplasm of eukaryotic cells resemble those of the cytoplasm of prokaryotic cells. ​3. ​Eukaryotic cytoplasm has a cytoskeleton and exhibits cytoplasmic streaming. Ribosomes (pp. 101–102) ​1. ​80S ribosomes are found in the cytoplasm or attached to the rough endoplasmic reticulum. Organelles (pp. 102–106) 1​. ​Organelles are specialized membrane-enclosed structures in the cytoplasm of eukaryotic cells. ​2. ​The nucleus, which contains DNA in the form of chromosomes, is the most characteristic eukaryotic organelle. ​3. ​The nuclear envelope is connected to a system of membranes in the cytoplasm called the endoplasmic reticulum (ER). ​4. ​The ER provides a surface for chemical reactions, serves as a transporting network, and stores synthesized molecules. Protein synthesis and transport occur on rough ER; lipid synthesis occurs on smooth ER. ​5. ​The Golgi complex consists of flattened sacs called cisterns. It functions in membrane formation and protein secretion. ​6. ​Lysosomes are formed from Golgi complexes. They store digestive enzymes. ​7. ​Vacuoles are membrane-enclosed cavities derived from the Golgi complex or endocytosis. They are usually found in plant cells that store various substances, increase cell size, and provide rigidity to leaves and stems. ​8. ​Mitochondria are the primary sites of ATP production. They contain 70S ribosomes and DNA, and they multiply by binary fission.  ​8. ​Mitochondria are the primary sites of ATP production. They contain 70S ribosomes and DNA, and they multiply by binary fission. ​9. ​Chloroplasts contain chlorophyll and enzymes for photosynthesis. Like mitochondria, they contain 70S ribosomes and DNA and multiply by binary fission. ​10. ​A variety of organic compounds are oxidized in peroxisomes. Catalase in peroxisomes destroys H2O2. ​11. ​The centrosome consists of the pericentriolar material and centrioles. Centrioles are 9 triplet microtubules involved in formation of the mitotic spindle and microtubules. The Evolution of Eukaryotes (p. 106) ​1. ​According to the endosymbiotic theory, eukaryotic cells evolved from symbiotic prokaryotes living inside other prokaryotic cells. THE LOOP Methods of action of antibiotics, discussed in Chapter 20, can be included here to illustrate differences between prokaryotic and eukaryotic cells, as well as provide clinical applications to cell structure. ANSWERS Review 1. ​ 2. ​a. ​sporogenesis ​b. ​certain adverse environmental conditions ​c. ​germination ​d. ​favorable growth conditions 3. ​ 4. ​a. ​4 ​d. ​3 ​g. ​2, 8 ​b. ​6 ​e. ​1, 5 ​h. ​7 ​c. ​1 ​f. ​3, 9 5. ​An endospore is called a resting structure because it is a method by which one cell “rests,” or survives, as opposed to growing and reproducing. The protective endospore wall allows a bacterium to withstand adverse conditions in the environment. 5. ​An endospore is called a resting structure because it is a method by which one cell “rests,” or survives, as opposed to growing and reproducing. The protective endospore wall allows a bacterium to withstand adverse conditions in the environment. 6. ​a. ​Both allow materials to cross the plasma membrane from a high concentration to a low concentration without expending energy. Facilitated diffusion requires carrier proteins. b. ​Both require enzymes to move materials across the plasma membrane. In active transport, energy is expended. c. ​Both move materials across the plasma membrane with an expenditure of energy. In group translocation, the substrate is changed after it crosses the membrane. 7. ​a. ​Diagram (a) refers to a gram-positive bacterium because the lipopolysaccharide– phospholipids–lipoprotein layer is absent. b. ​The gram-negative bacterium initially retains the violet stain, but it is released when the outer membrane is dissolved by the decolorizing agent. After the dye–iodine complex enters, it becomes trapped by the peptidoglycan of gram-positive cells. c. ​The outer layer of the gram-negative cells prevents penicillin from entering the cells. d. ​Essential molecules diffuse through the gram-positive wall. Porins and specific channel proteins in the gram-negative outer membrane allow passage of small water-soluble molecules. e. ​Gram-negative. 8. ​An extracellular enzyme (amylase) hydrolyzes starch into disaccharides (maltose) and monosaccharides (glucose). A carrier enzyme (maltase) hydrolyzes maltose and moves one glucose into the cell. Glucose can be transported by group translocation as glucose-6-phosphate. 9. ​a. ​3 ​d. ​1 ​g. ​5 ​b. ​4 ​e. ​6 ​c. ​7 ​f. ​2 Critical Thinking 1. ​Eukaryotic cells must be large enough to hold a nucleus and a mitochondrion (the minimum number of organelles). Prokaryotic cells contain molecules needed to carry on metabolic activities, but do not contain membrane-enclosed organelles, which require extra space. 2. ​Micromonas has a nucleus, one mitochondrion, one chloroplast, one Golgi complex, and one flagellum. 3. ​Like bacteria, archaea lack organelles. However, archaea also lack peptidoglycan cell walls. A more complete list of differences is in Table 10.1. 4. ​The large size of the organism caused the misidentification. Electron microscopy would reveal that this is a prokaryotic cell; chemical analysis of the cell wall would reveal peptidoglycan. 5. ​Water would passively leave the cell in a hypertonic environment. If a cell pumps K+ in, water will follow, thus preventing plasmolysis. Clinical Applications 1. ​Cell death released cell wall fragments. The gram-negative cell wall is responsible for the symptoms of septic shock. 2. ​The endospores allow survival in the presence of oxygen and during heating. 3. ​Enterobacter, Pseudomonas, and Klebsiella are gram-negative. Their cell walls contain lipid A endotoxin. 4. ​The bacteria were adhering to the inside of the pipes as a biofilm. Fimbriae and the glycocalyx allow the bacteria to adhere. 5. ​Bacterial endospores allow these bacteria to survive in products on store shelves. B. thuringiensis is sold as an insecticide, and B. subtilis as a fungicide. CASE STUDY: Coxiella burnetii Background The life cycle of Coxiella burnetii wasn’t described until 1981, although the bacterium had been recognized more than 40 years earlier. Observations made by many researchers were finally assembled to show that this bacterium has a more complex life cycle than most. See if you can propose a life cycle for this bacterium from the information provided. Coccoid and bacillary forms of Coxiella burnetii were first described in 1938. Subsequently, other this bacterium has a more complex life cycle than most. See if you can propose a life cycle for this bacterium from the information provided. Coccoid and bacillary forms of Coxiella burnetii were first described in 1938. Subsequently, other researchers described round particles that passed through bacteriological filters (0.45 µm) and were capable of infecting guinea pig cells. In 1981, electron microscopy studies of Coxiella revealed a large cell variant (LCV) and a small cell variant (SCV). The LCV has inner and outer membranes separated by a periplasm containing little peptidoglycan. The SCV lacks a periplasm and has a large peptidoglycan layer. LCVs develop a dense area in the periplasm at one end of the cell when nutrients are depleted or the pH increases. This area contains DNA and ribosomes. In one study, suspensions of C. burnetii were put in distilled water, exposed to sonication (high- frequency vibration used to disrupt cells), and incubated at 45°C for 3 hr. Only SCVs were present after this treatment. Coxiella undergo binary fission in a host cell phagolysozyme. LCVs metabolize and divide more rapidly than SCVs. Questions 1. ​Propose a life cycle for Coxiella. 2. ​Why do Coxiella show variable Gram stain results—that is, they may stain gram-positive or gram- negative? Should they be classified as gram-positive or gram-negative? 3. ​What disease does C. burnetii cause? Why can this disease be transmitted by airborne routes while other (closely related) rickettsia require insects and ticks for transmission to humans? The Solution 1. ​ 2. ​LCVs will stain gram-negative; SCVs, gram-positive. Coxiella is classified as gram-negative because the ultrastructure and chemical composition of the wall are gram-negative. 3. ​Q fever; SCVs (spores) allow this organism to survive outside a host.