Microbiology Exam 1

• What makes transport electrogenic vs. electroneutral?

  -Electrogenic: when movement of ions across a membrane results in a net charge (non-neutral charge)

  -Electroneutral: movement of ions across a membrane does not result in a net charge (neutral charge)
• What is a permease?

  substrate specific carrier protein located in the membrane
• Passive Transport


  -Simple Diffusion: uncharged, small, goes along with concentration gradient

  -Facilitated Diffusion: goes against concentration gradient (needs protein transport)
• Active Transport

  -Symport: couples molecule going unfavorably to molecule moving favorably

  -Antiport: trading molecules from inside to outside

  -ABC Transport: (ATP-binding-cassette) powered by ATP hydrolysis
• What types of compounds can diffuse across the membrane?

  -Small, non-polar molecules (O, CO2)

  -Small polar molecules (H2O, ethanol)

  -Lipids

  -Fat soluble Vitamins/alcohols
• What is the proton motive force and what can it be used for?

  Force that promotes movement of protons across membrane down the electrochemical potential gradient (Use: ATP synthesis)
• What is membrane potential?

  difference in voltage or electrical charge across the plasma membrane (between interior and exterior)
• How does a cell store energy?

  -ATP (through cellular respiration)

  -Energy Rich Molecules (glucose, fat/lipids, proteins)

  -Chemical Bonds
• Organotrophs

  obtain electrons from organic compounds
• Lithotrophs

  acquire electrons from inorganic sources
• Chemotrophs

  Organisms that get energy from chemicals taken from the environment
• Phototrophs

  organisms that get energy from light
• Autotroph

  An organism that makes its own food
• Heterotroph

  An organism that cannot make its own food.
• Provide some reasons that can explain why we have only cultured <1% of the existing microorganisms.

  Lab settings do not allow for every microbe to grow on account of:

  -Nutrient requirements are unknown

  -rely on relationships with outside sources to grow (symbiotic)

  -extremely slow growth (makes it hard for large-scale study)
• What is defined minimal media?

  contains only those compounds needed for an organism to grow
• What are: essential nutrients, macronutrients, cofactors and growth factors, and what are some examples of each?


  -Essential Nutrients: elemental compounds that a cell requires but cannot make itself

  -Macronutrients: nutrients that are required in large amounts for a cell to function (ex: Carbon, hydrogen, sulfur, oxygen, nitrogen, phosphorous)

  -Cofactors: a non-protein chemical compound that assists enzymes in their biological functions (K/Mg/Ca)

  -Growth Factors: organic molecules essential for microbial growth (Amino Acids, Purines /Pyrimidines, and Vitamins)
• Microorganisms differ from one another in the ways in which they obtain ________and ___________.

  Carbon and energy
• Chemotaxis

  movement of bacterium in response to signal (chemical or physical)
• Monotrichous

  single flagellum
• Lophotrichous


  cluster of flagella at one or both ends
• Peritrichous


  flagella all over
• What is flagella?

  Long, thin whip-like structure that helps organisms move through moist or wet surroundings
• Pilli (fimbriae)


  -Allow prokaryotes to attach to surfaces and exchange genetic material (infection)

  -evenly distributed or localized to one or both poles of the cell

  -motility, biofilm production, cell aggregation
• Magnetosomes

  membrane-bound compartments (with iron minerals) that orient themselves to earths geomagnetic field (magnetostatic bacteria)
• Storage Granules

  membrane-bounded vesicles containing condensed materials (stores carbon/energy reserves, PHA, PHB, glycogen, sulfur)
• Carboxysomes


  bacterial microcompartments (BMCs) consisting of polyhedral protein shells filled with enzymes found in cyanobacteria that enhance CO2 fixation
• Thylakoid


  folded intracellular membranes across which photosynthesis occurs (cyanobacteria)
• Describe the process of septation? Hoe does it help to determine the shape/arrangement of the cells?

  1. Selection of division site: (usually midpoint on surface)

  2. Formation of the Septum: septum is partition that forms between two daughter cells (new cell wall material and membrane)

  3. Constrictions and Separation: septum grows inward to split into two daughter cells

  4. Determines shape and arrangement of bacterial cells based on location and patterns
• When does the septum begin to form?

  Septation is triggered by the replication of the termination sequence
• Where does replication begin? What is a replisome? Why are 4 DNA polymerases at the origin of replication?

  -Origins of Replication

  -complex molecular machine that replicates DNA

  -4 are needed because they need two for leading and two for lagging strand DNA replication
• What does a signal sequence indicate? What recognizes the signal sequence?

  -Serves as a targeting signal for proteins destined toward the secretory pathway

  -recognized by the translocon during protein translocation

  -core of the signal peptide contains a long stretch of hydrophobic amino acids
• What is the significance of the coordination of transcription and translation in prokaryotes?

  -Must happen simultaneously and allows rapid protein production (reduces need to store RNA transcripts)

  -can cease productions of mRNA following rapid feedback regulation
• What is the periplasm?

  in gram-negative bacteria, it is the space between the cytoplasmic membrane and the outer membrane
• What is LPS and where is it found?

  LPS stands for lipopolysaccharide and it is found in gram-negative cell walls and is an endotoxin
• Describe the gram-negative outer membrane.

  -Contains: LPS, proteins, and phospholipids

  -relatively permeable (allows nutrients and some toxins in)

  -located in periplasmic space (between outer membrane and plasma membrane)
• What are the unique aspects of the Mycobacterial cell envelope? How can we detect it through staining?

  -waxy phenotype

  -Arabinogalactans

  -Acid-fast stain required (gram stain CANNOT penetrate membrane)

  -low membrane permeability and grows slow
• What is the S layer?

  -Protective layer (can contribute to cell shape)

  -Porous

  -made of proteins and glycoproteins

  -also found in archaea
• Why is the cell wall a good target for antibiotics? What antibiotics target peptidoglycan?

  -Human/animal cells do not have a cell wall. Targets bacterial cells without harming human/animal cells.

  -Penicillin prevents peptidoglycan synthesis by blocking the way (cock-blockers)

  -Vancomycin: prevents removal of D-alanine (end all antibiotic)
• Characterize the structure and function of the cell wall.

  -Structure: (peptidoglycan) located outside the membrane in only plants, fungi, algae, most bacteria, and archaea have cells with cell walls

  -Functions: strength, permeability, and structural support