Exam #2 Review Exam #2 will cover all the material that has been presented in class since Exam #1 and up through the metabolism introduction. This includes eukaryotic cell structure / function, transport, the closed system growth curve, enzymes and the introduction to metabolism. As always, it is best to begin by studying your notes and then after you feel your study is complete, take some time to look through this review. I. Eukaryotic cell structure / function A. There is a great deal of variance among eukaryotic cells - from protozoan cells to yeast cells to human cells. Fungi and protists (classically split into algae and protozoa) are eukaryotic representatives of the microbial world. B. Structure of the eukaryotic cell. 1. Cytoskeleton - provides structure and shape of cell, three components: a. Microtubules - largest element of cytoskeleton, composed of hollow cylinders of tubulin, form mitotic spindles, cilia and flagella and cell “highways”. b. Microfilaments - smallest element of cytoskeleton, composed of actin, involved in motion (pseudopod formation). c. Intermediate filaments - very stable structural element, play a supportive role, composed of proteins including keratin. Practice: Microfilaments a. are a component of the cytoskeleton. b. are long, twisted polymers of a protein called actin. c. form eukaryotic flagella. d. are made of tubulin. e. a and b f. c and d 2. Nucleus a. Bound by both an inner and outer membrane. The space between the two membranes is called the perinuclear space. The membrane has large nuclear pores through which proteins can pass (Why is this important?) b. Linear pieces of DNA are packaged by wrapping one and three quarters times around a histone octamer to form a core particle. Neighboring core particles are linked by DNA. This linker DNA associates with another histone called H1. Together, the core particle, H1 and some of the linker DNA form a nucleosome. Histones are rich in what type of amino acid? How does the charge of DNA / histones affect this packaging process? Chromatin is the complex of DNA and proteins that together form the chromosomes. How does euchromatin differ from heterochromatin? c. A region within the nucleus, called the nucleolus, is the site of ribosome assembly. Practice: The nucleus a. is a double membrane sac containing DNA as is found in eukaryotes. b. Is a single phospholipid membrane sac containing prokaryotic DNA. c. is a smaller structure contained within the eukaryotic nucleolus. d. cannot transport molecules to the cytoplasm due to the double membrane barrier. 3. The Endoplasmic Reticulum a. Rough ER - Site of synthesis of proteins targeted for the membrane, for secretion or for specific organelles. (Studded with 80S ribosomes (*60S and 40S subunits)) What is the medical importance of the fact that prokaryotes have 70S ribosomes and eukaryotes 80S? b. Smooth ER - Site of lipid and steroid hormone synthesis, location of calcium ion storage. (No ribosomes cover the surface, thus smooth). *vesicles bud off of both of these organelles carrying the recently synthesized compounds. These vesicles are targeted for the Golgi. Practice: Which one of the following would be the site of synthesis and folding, but not final modification of a protein needed outside the cell? a. The Golgi apparatus b. The mitochondria c. The smooth ER d. The rough ER 4. The Golgi apparatus - molecules from ER are further modified (e.g. addition of carbohydrate or phosphate groups). Vesicles bud off of Golgi and carry modified molecules to their destination. The Golgi has a cis and a trans face that differ substantially from one another. Practice: The Golgi Apparatus a. is the site of modification of molecules from the ER. b. has an acidic pH and is filled with hydrolytic, digestive enzymes. c. is found exclusively in plants and algae. d. is considered the “powerhouse” of the eukaryotic cell. e. both b and c 5. Lysosomes - acidic interior, filled with digestive enzymes to hydrolyze macromolecules. 6. Mitochondria - powerhouses of the cell! Practice - draw this organelle and label all parts. Where are the components of the electron transport chain? Practice - Which one of the following organelles contains its own DNA genome and 70S ribosomes? a. lysosomes b. the endoplasmic reticulum c. mitochondria Which statement/s regarding mitochondria is/are FALSE? a. Mitochondria are capable of converting CO2 into organic compounds. b. Mitochondria reproduce by binary fission. c. Nearly all eukaryotic cells contain mitochondria. d. Mitochondria contain their own DNA genome 7. Chloroplasts Practice - draw this organelle and label all parts. Where are the components of the electron transport chain? Practice - Both chloroplasts and mitochondria synthesize ATP using the electron transport chain, in what ways are these two organelles different (in terms of the origin of the electrons that fuel the electron transport chain)? Practice: Which of the following explains the origin of mitochondria and chloroplasts? a. The Chemiosmotic Hypothesis b. The Endosymbiont Theory c. The Fluid Mosaic Model d. Spontaneous generation 8. Plasma membrane In many ways the plasma membrane of a eukaryotic cell is similar to that of a prokaryotic cell (e.g Both are composed of a semipermeable phospholipid bilayer (fluid-mosaic). Both contain transport proteins. Practice - List the ways in which the plasma membrane of a eukaryotic cell is different than that of a prokaryotic cell. a. Endocytosis 1. phagocytosis - Used to engulf large particles - cell sends out long extensions called pseudopods. These surround debris and form a phagosome which fuses with a lysosome to form a phagolysosome (often termed cell eating). 2. pinocytosis a.) Macropinocytosis b.) Clathrin-dependent (Receptor mediated) c.) caveolae-forming Practice: Which statement/s is/are TRUE? a. Phagocytosis and pinocytosis are both types of endocytosis. b. Receptor mediated (clathrin-dependent) endocytosis is a type of pinocytosis. c. During phagocytosis, a phagolysosome is formed. d. During caveolae-forming endocytosis, no lysosome fusion occurs, thus many pathogens enter cells this way. e. all of the above *Remember that many pathogens exploit endocytosis to enter a host cell. b. Exocytosis 9. Flagella and cilia Practice: How are flagella different in prokaryotes and eukaryotes? ! All of the following are true of eukaryotic flagella EXCEPT a. eukaryotic flagella are composed of 9 pairs of microtubule doublets. b. eukaryotic flagella sometimes have lateral hairs called flimmer filaments. c. eukaryotic flagella are composed of a basal body, a hook and a filament. d. eukaryotic flagella function in motility by wave-like motion (base to the tip or tip to the base). Cilia a. are also called pili. b. are also called fimbriae. c. are shorter than flagella. d. move in two phases. e. a and b f. c and d *NOTE: It is a good test of understanding to compare features of prokaryotic and eukaryotic cells. Practice: Which statement does NOT correctly summarize a difference between prokaryotic and eukaryotic cells? a. The electron transport chain of aerobically respiring prokaryotic and eukaryotic cells is found across the cytoplasmic membrane. b. Whereas prokaryotes generally have a single chromosome, eukaryotes usually have more than 1 chromosome for the storage of genetic material. c. eukaryotic cells have a membrane-bound nucleus whereas prokaryotic cells have only a gel-like mass called the nucleoid. d. Whereas prokaryotic cells secrete enzymes to digest macromolecules, eukaryotes generally bring in large molecules via endocytosis. Which of the following is useful in distinguishing between prokaryotic and eukaryotic cells? a. the presence / absence of peptidoglycan b. the type of ribosomes used for the synthesis of proteins c. the presence of membrane-delimited organelles within the cytoplasm d. all of the above For the following 5 cell components, please determine whether they are generally present: a. only in prokaryotes b. only in eukaryotes c. only in bacteria d. in both prokaryotes and eukaryotes ____16) Endoplasmic reticulum ____17) A single circular chromosome ____18) N-acetylmuramic acid (NAM) ____19) diaminopimelic acid ____20) flagella V. Microbial nutrition and growth A. Uptake of nutrients (transport) The diagram below summarizes the types of transport covered. Use this to review the differences / similarities of each type of transport. Practice: Transporters using this type of transport require no energy but become saturated at high substrate concentrations. a. active transport b. simple diffusion c. facilitated diffusion d. none of the above *During what type of transport is a molecule modified as it is transported? B. Protein secretion - be familiar with the Sec-dependent pathway! C. Bacterial cells reproduce via binary fission: a parent cell replicates its DNA, elongates, a septum forms and eventually cleaves off two distinct daughter cells. With this type of growth, the increase in cell numbers is exponential. Practice: If a single cell lands on an agar plate and begins to divide, how many cells will there be after the tenth cycle of division? D. A researcher may also be interested in calculating the number of cells in a population of cells that originated from more than a single cell. The following equation can be used for this purpose and will be provided on the exam: n Nt = No X 2 where Nt = the # of cells in a population after a given time No = The original number of cells in a population n = the number of cycles of division (depends on doubling time) Practice: 100 cells of Vibrio fischeri are used to inoculate a large bottle of sterile media. If this bacteria has a doubling time of 2.5 h, how many cells are present in the culture after an overnight incubation (16 h)? C. In the lab, organisms are generally grown in closed (batch) systems (Why are these systems called closed systems??). The Growth Curve describes growth in closed systems. Please spend some time reviewing this growth curve in your notes. ! Practice: During which growth phase do cells begin to synthesize secondary metabolites in response to increasing cell population and buildup of waste products? a.