Microbiology Study Guide Unit 2
Define metabolism: The sum of all biological chemical reactions inside a cell or organism Differences in catabolism and anabolism: Catabolism is an enzyme-regulated chemical reaction that releases energy. Complex organic compounds such as glucose, amino acids, glycerol and fatty acids are broken down into simpler ones. The energy of catabolic reactions is used to drive the anabolic reactions. Anabolism is also enzyme regulated but requires energy for taking the simpler broken down components from the catabolism phase and building them into complex molecules such as starch, proteins and lipids What is the role of ATP?
ATP is the driving force for catabolic and anabolic reactions. ATP stores energy that is produced from the catabolic reactions which is later released to drive the anabolic reaction and other cellular work. ATP is stored energy in cells (phosphate groups held together by high energy reacting bonds) ATP is required for synthesis and some of the energy is given off as heat What are enzymes and their components? Enzymes are biological catalysts (substances that speed up a chemical reaction without themselves being permanently altered) Components:
Apoenzyme is the protein portion of an enzyme. Inactive by themselves, must be activated by cofactors Cofactor- non protein portion (IE: ions of iron, zinc, magnesium and calcium) ****If the cofactor is an organic molecule, it is called a coenzyme Holoenzyme- The apoenzyme+cofactor forms the holoenzyme. It is the active enzyme. If you remove the cofactor, the apoenzyme will not function. **Cofactors may assist the enzyme by accepting atoms removed from the substrate or by donating atoms required by the substrate. Substrate=the specific substance that an enzyme will act on) **The crucial function of enzymes is to speed up biochemical reactions at temperatures that are compatible with the normal functioning of the cell. What are metabolic pathways? The sequence of enzyme catalyzed chemical reactions within a cell. What is the Kreb’s cycle? A pathway that converts two-carbon compounds to CO2, transferring electrons to NAD+ and other carriers; also called tricarboxylic acid (TCA) cycle or citric acid cycle A series of biochemical reactions in which a large amount of potential chemical energy stored in acetyl CoA is released step by step.
In the cycle, a series of oxidations and reductions transfer that potential energy in the form of electrons to electron carrier coenzymes (mostly NAD+). The pyruvic acid derivatives are oxidized and the coenzymes are produced. Kreb’s cycle is for lipid catabolism. Glycerol is converted into dihydroxyacetone phosphate (DHAP) and catabolized via glycolysis and the Kreb’s cycle. Fatty acids undergo beta-oxidation, in which carbon fragments are spit off two at a time to form acetyl CoA which is catabolized by Kreb’s cycle.
What is glycolysis? **Glycolysis creates to ATP molecules The main pathway for oxidation of glucose to pyruvic acid: Glycolysis is usually the first stage in carbohydrate catabolism. This occurs from the oxidation of glucose to pyruvic acid. Most microorganisms use this pathway and it occurs in most living cells. The term “glycolysis” means the splitting of sugar. The sugars are oxidized, release energy and then their atoms are rearranged to form 2 molecules of pyruvic acid. **Glycolysis does not require oxygen!
Explanation of cellular respiration: Cellular respiration takes place after the glucose is broken down in pyruvic acid which is then channeled into the next step of either fermentation or cellular respiration. Cellular respiration is defined as the ATP-generating process in which most molecules are oxidized and the final electron acceptor is (almost always) an inorganic molecule. **operates via an electron transport chain * Aerobic respiration the final electron acceptor is O2 Anaerobic respiration the final electron acceptor is an inorganic molecule other than O2 What is an electron transport chain and why is it important? It is a system in which electrons pass through a series of different electron carriers to molecules or oxygen or other oxidized inorganic and organic molecules. The process occurs in the plasma membrane of the prokaryotes and in the mitochondrial membrane of eukaryotes. What is microbial growth? It is the growth in numbers of populations or an increase in the number of cells
What are three physical requirements of microbial growth? PH, temperature and moisture Define psychotrophs: Are cold loving microbes, will usually be found growing in the refrigerator such as listeria (20-25oC) How does PH affect growth? Certain bacteria thrive in a specific PH environment. Acidophiles like a PH of 5. 4 or below whereas Neutrophiles (most human pathogens) prefer a more neutral environment (5. 5-7. 5 PH) Define halophiles: Extreme halophiles (obligate halophiles) are microbes that require a high salt concentration that is required for growth.
Faccultative halophiles (most common) are microbes that do not require high salt concentrations for growth but can tolerate high salt solutions. How does osmotic pressure effect microbial growth? Microorganisms obtain most of all their nutrients in solutions surrounding water; therefore water is required for growth. They are composed of 80-90% water. High osmotic pressures have the effect of removing vital water from a cell. If a microbe is in a solution in which the concentration of solutes is higher than in the cell, the microbe is in a hypertonic environment which will create pressure on the cell.
It will crush the cell causing the cells water to push out through the plasma membrane into the high solute concentration. What are some chemical requirements for microbes? Carbon- one of the most important for microbes next to water because it is the structural backbone Nitrogen- it is required for protein synthesis (requires some sulfur), also needed for DNA or RNA synthesis (needs some phosphorous) Vitamins and minerals- needed for essential function of enzymes, usually as co-factors. What are some organic growth factors?
Essential organic compounds an organism is unable to synthesize are known as organic growth factors. They must be directly obtained by the environment. One group of organic growth factors is vitamins for human. What is a media? A media is a nutrient prepared for the growth of microorganisms. In the lab we use nutrient broths and nutrient agars. What are canophiles? Canophiles (aerobic bacteria) are microbes that grow better at high CO2 concentrations. Low oxygen high CO2 conditions resemble those found in the intestinal tract, digestive tract and other body tissues where pathogens grow.
Why is a selective media desireable? Because a selective media will suppress the growth of unwanted bacteria while encouraging the growth of the desired microbes. How do prokaryotes reproduce? Reproduce by binary fission (most common) while others may go through a “budding” process 2 Categories used to control microbes (physical and chemical) Physical: Heat (dry heat such as flame or in hot ovens) heat will denature the protein causing the proteins shape to change making it no longer usable by the organism.
Or (moist heat) such as with an autoclave which will force steam inside of the organism very quickly and cause it to break down Chemical: surfactants such as soaps which will work as a binding agen to the microorganism causing it to break off and be rinsed off or phenols which will disrupt the cell membrane or denature the protein therefore disrupting protein synthesis What are physical methods to control microbes? * Heat (dry and moist heat) * Cold * Radiation * Membrane filtration * Drying * Osmotic pressure What are the most common and effective ways of controlling microbes?
An autoclave machine that utilizes heat, steam and pressure to kill microbes and their endospores in about 15 minutes (prions are not killed) Is it more effective to control or kill microbes? It is more effective to control the microbes because we can study live bacteria, but not if they are dead Why would we want to control microbial growth? Controlling microbes can prevent infections and food spoilage Compare and contrast chromosomes in prokaryotes and eukaryotes: Prokaryotes have 1 chromosome (only one allele)
Eukaryotes have 2 chromosomes (2 alleles) DNA is not always the genetic material. What are the exceptions? How could mutations give rise to new alleles of a gene? How does translation differ from transcription? Transcription in the synthesis of a complementary strand of RNA from a DNA template Translation is the protein synthesis that involves decoding of nucleic acid and converting the information into the language of the proteins What are the differences between the leading and lagging strand?
Leading strand gets replicated sequentially and gets filled first. The lagging is the strand that gets replicated sporadically based off of what is left. What are three types of RNA and what do they do? Messenger RNA (mRNA): carries genetic information from the nucleus to the cytoplasm. Transfer RNA (tRNA): transfers the necessary sequence by carrying the code. Ribosomal RNA (rRNA): helps in synthesis of proteins. Explain mutations: A mutation is the change in the base sequence of DNA. Some mutations are bad such as when the gene for an enzyme mutates.
The enzyme encoded by the gene may become inactive or less active because its amino acid sequence has changed. But a mutation can also be beneficial such as when an altered enzyme encoded by the mutant gene suddenly has new or enhanced activity that will benefit the cell. List and discuss common mutagens: Define genetic engineering: Manufacturing and manipulating genetic material in vitro also called recombinant DNA (rDNA ) What is recombinant DNA? A DNA molecule produced by combining DNA from two different sources. Exchange of genes between two DNA molecules) **Contributes to a populations genetic diversity (source of variation in evolution) What are three processes involved in making recombinant DNA? Transformation in Bacteria Conjugation in bacteria Transduction in bacteria What is a restriction enzyme? An enzyme that cuts double stranded DNA at specific sites between nucleotides Pg. 249 What is conjugation? The transfer of genetic material from one to another involving cell to cell contact What is a plasmid? A small circular DNA molecule that replicates independently of the chromosome
