Week 3 Labs Flashcards
What is osmotic balance and how is it important to cells?
ensures that optimal concentrations of electrolytes and non-electrolytes are maintained in cells, body tissues, and in interstitial fluid. Important because it maintains the cells internal environment.
What happens to many cells placed into a hypertonic enviorment?
There water content is transferred to the surrounds and they will shrivel and die.
What is pH indicator and how is it useful?
Substance that changes color based on the pH value. Useful in making differential medium as it will visually show if theres a pH change. pH decrease when fermentation occurs as it produces organic acids.
Describe the selective and differential natures of sodium chloride broth.
The selective nature comes from the increased NaCl concentration, only salt tolerant cells will grow. The differential nature comes from adding Bromocresol purple which is a pH indicator. pH above .68 is violet and below pH 5.2 is yellow.
By what mechanism do high extracellular salt concentrations kill many types of cells?
osmosis
What is a pH indicator and how does it function?
Substance that changes color based on changes in pH.pH indicators detect the presence of H+ and OH-. They do this by reacting with H+ and OH-: they are themselves weak acids and bases.
If sodium chloride broth does not change color after inoculation and incubation, how can you tell whether this is due to failure of the organisms to grow or failure to ferment the glucose?
Check for turbidity, some bacteria can grow without fermenting the glucose.
What is fermentation? How does it compare to aerobic cellular respiration?
The breakdown of sugar molecules into simpler compounds to produce substances that can be be used in making mechanical energy. Fermentation occurs in the absence of oxygen while respiration occurs in the presence of oxygen.
Why might an organism be able to ferment one sugar but not another? (For example, why might and organisms be able to ferment sucrose but unable to ferment lactose?)
The ability to ferment is based on the proteins the organism can produce. Specific transport proteins are required to move the sugars across the cell membrane and specific enzymes are required to break down the sugar.
What are some common end products of fermentation?
Acids, alcohol, carbon dioxide
What is a pH indicator and how is it useful?
pH indicator is a chemical that changes color based pH, useful because fermentation produces acids that decrease pH allowing you to observe a color change.
List the four components of a fermentation tube and describe the function of each.
specific carbohydrate, pH indicator, inverted Durham tube, nutrient broth
What feature of the phenol red manitol broth makes it complex rater than chemically defined?
Concentrations of the components are not known.
How is the ability to ferment mannitol related to an organisms genotype and phenotype?
If a phenol red mannitol broth does not change color after inoculation and incubation, how can you tell wheather this is due to failure of the organism to grow or failure to ferment the carbohydrates?
Look at the Durham tube. If gasses formed then its indicative of growth likely due to energy obtained from amino acids instead of fermentation.
