mcb exam 2 Flashcards
(24 cards)
What are the different microbial nutritional groups based on their needs for carbon and energy
- Heterotroph
- Autotroph
Hetertroph
must obtain carbon in an organic form
Autotroph
uses inorganic CO2 as its carbon source
Decomposers
metabolizing the organic dead matter of dead organisms
Saprobes
free living microorganisms that feed on organic detritus from dead organisms
Parasites
derive nutrients from the cells or tissues of a living host
Influences a hypotonic, hypertonic and an isotonic solution would have on a typical microbial cell
- Hypotonic: solute concentration of the external environment is lower than the cells internal environment
- Hypertonic: the environment has a higher solute concentration than the cytoplasm
- Isotonic: the environment is equal in solute concentration to the cell’s internal environment
Different transport mechanisms for moving substances in and out of a cell
- Simple diffusion:
- Facilitated diffusion:
- Carrier-mediated active transport:
- Group translocation:
- Endocytosis
Which transport mechanisms require the expenditure of energy in form of ATP?
- Active transport (endocytosis, group translocation, carried mediated active transport
Phases of microbial growth.
- Lag
- Log/Exponential
- Stationary
- Death
What does “doubling time” mean?
- The time required for a complete fission cycle (parent cell to two new daughter cells)
Different methods and equipment used in enumerating microbial growth
- Turbidometry: relies on the simple observation that a tube of clear nutrient solution becomes cloudy or “turbid” as microbes grow in it.
- Direct total cell count: counting the number of cells in a sample microscopically
- Polymerase chain reaction (PCR): quantify bacteria without culturing them
Lag phase
“flat period”, populations appear to not be growing or growing at a less exponential rate
Log/Exponential phase
cells reach the maximum rate of cell division. Curve increases dramatically
Stationary phase
population enter a survival mode; cells stop growing or grow slowly
Death phase
cells die at an exponential rate.
Hypotonic
solute concentration of the external environment is lower than the cells internal environment
Hypertonic
the environment has a higher solute concentration than the cytoplasm
Isotonic
the environment is equal in solute concentration to the cell’s internal environment
Simple diffusion
fundamental property of atoms and molecules that exist in a state of random motion
Facilitated diffusion
- Molecules bind to specific receptor in membrane and is carried to other side
- Molecule specific. Goes both directions
- Rate of transport is limited by number of binding sites on transport proteins
Carrier-mediated active transport
Atoms or molecules are pumped into or out of the cell by specialized receptors
Group translocation
Molecule is moved across membrane and simultaneously converted to a metabolically useful substance
Endocytosis
-(Bulk transport) Mass transport of large particles, cells and liquids by engulfment and vesicle formation
- Phagocytosis moves solids into cell; pinocytosis moves liquids into cell