Q7.1: An organic nutrient essential to an organism's metabolism that cannot be synthesized itself is termed a/an:

a. trace element

b. micronutrient

c. growth factor

d. mineral

c. growth factor

Many fastidious bacteria lack the genetic and metabolic mechanisms to synthesize every organic compound (amino acid, nitrogenous base, vitamins) they need for survival. Every cell needs 20 amino acids for proper assembly of protiens, but many cells cannot synthesize all of them. Those that must come from food are called essential amino acids.

Q7.2: The source of the necessary elements of life is

a. an inorganic environmental reservoir

b. the sun

c. rocks

d. the air

a. an inorganic environmental reservior

Q7.3: An organism that can synthesize all its required organic components from CO2 using energy from the sun is a 

a. photoautotroph

b. photoheterotroph

c. chemoautotroph

d. chemoheterotroph

a. photoautotroph

Autotrophs derive energy from one of two possible nonliving sources: sunlight and chemical reactions involving simple chemicals. Photoautotrophs can be oxygenic [CO₂ + H₂O uses the energy of the sun absorbed by chlorophyll and produces a (CH₂O)_n and O₂] or anoxygenic [CO₂ + H₂S uses the energy of the sun absorbed by bacteriochlorophyll and produces a (CH₂O)_n + S⁰ + H₂O; no oxygen produced].

Q7.4 An obligate halophile requires high

a. pH

b. temperature

c. salt 

d. pressure

c. salt

Most microbes live in hypotonic or isotonic habitats. Osmophiles live in habitats with high solute concentrations. Halophiles require high concentrations of salt. Obligate halophiles such as Halobacterium and Halococcus inhabit salt lakes, ponds and other hypersaline habitats. They grow optimally in solutions of 25% NaCl, but require at least 9% NaCl (combined with other salts) for growth. These archaea have significant modifications to their cell walls and membranes and will lyse in hypotonic habitats. 

Q7.5  Chemoautotrophs can survive on _____ alone.

a. minerals

b. CO₂

c. minerals and CO₂ 

d. methane

c. minerals and CO₂

Chemotrophs have adapted to the most stringent nutritional strategy on earth. ALL chemotrophs are bacteria or archaea that survive totally on inorganic substances such as minerals and gases. They require neither light nor organic nutrients in any form. They remove electrons from inorganic substances such as hydrogen gas, hydrogen sulfide, sulfur, or iron and combine them with other inorganic substances such as carbon dioxide, oxygen, and hydrogen. These reactions release simple organic molecules and a modest amount of energy to drive the synthetic processes of the cell. Chemotrophs play an important role in recycling inorganic nutrients and elements. 

Q7.6  Which of the following substances are required by ALL organisms?

a. organic nutrients

b. inorganic nutrients

c. growth factors

d. oxygen gas

b. inorganic nutrients 

In general, all living things have an absolute need for the bio-elements, traditionally listed as Carbon, Hydrogen, Oxygen, Phosphorus, Potassium (K), Nitrogen, Sulfer, Calcium, Iron(Fe), Sodium (Na), Chlorine, Magnesium and certain other elements. (CHOPKINS CaFe, NaCl Mgood) Natural organic nutrients are molecules that contain a basic framework of carbon and hydrogen. An inorganic nutrient is composed of an element or elements other than carbon or hydrogen. The natural reserviors many inorganic compounds are the mineral deposits in the water, soil, and atmosphere. [ex: metals and their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide), and water.]

Q7.7  A pathogen would most accurately be described as

a. a parasite

b. a commensal

c. a saprobe

d. a symbiont

a. a parasite

Most human infections are caused by heterotrophic microorganisms, but those having the greatest adverse impact on human health are parasites. By definition, a parasite is a microbe that invades the body of the host, uses it as a habitat and a source of nutrients, and in the process harms the host to some degree. Such parasitic microbes that grow inside sterile tissue, cause damage, and even death are also termed pathogens. 

Q7.8  Which of the following is true of passive transport?

a. it requires a gradient

b. it uses the cell wall

c. it includes endocytosis

d. it only moves water

a. it requires a gradient. For survival, cells must take nutrients from the environment INTO the cell, and transport waste OUT of the cell (back into the environment). Whatever the direction, transport occurs across the cell membrane, which is the structure specialized for this role. Diffusion is the net movement of molecules down their concentration gradient (ie: perfume in a room or sugar cube in coffee). Just by random thermal movement, the molecules will be dispersed away from an area of high concentration to an area of lower concentration until they are evenly distrubuted. Passive transport means the cell does not expend excess energy for them to function. The inherent energy of the molecules moving down a gradient does the work of transport. Two special cases are osmosis  and facillitated diffusion

Q7.9  A cell exposed to a hypertonic environment will _____ by osmosis.

a. gain water

b. lose water

c. neither gain nor lose water

d. burst

b. lose water

A cell in a hypertonic environment is exposed to a solution with a higher solute concentration than its cytoplasm. Because hypertonicity will force water to diffuse out of a cell, it is said to create a high osmotic pressure or potential. In cells with a wall, water loss causes shrinkage of the protoplast away from the wall, a condition called plasmolysis.

Q7.10  Active transport of a substance across a membrane requires

a. a gradient

b. the expenditure of ATP

c. water

d. diffusion

b. the expediture of ATP

Q7.11  Psychrophiles would be expected to grow

a. in hot springs

b. on the human body

c. at refrigeration temperatures

d. at low pH

c. at refrigeration temperatures

Q7.12  Which of the following is NOT involved in quorum sensing?

a. accumulation of inducer molecules

b. a certain level of biofilm density

c. self-monitoring

d. release of genetic material

d. release of genetic material

Q7.13  Superoxide ion is toxic to strict anaerobes because they lack 

a. catalase

b. peroxidase

c. dismutase

d. oxidase

c. dismutase

Q7.14  The time required for a cell to undergo binary fission is called the

a. exponential growth rate

b. growth curve

c. generation time

d. lag period

c. generation time

Q7.15 In a viable plate count, each _____ represents a _____ from the sample population.

a. cell; colony

b. colony; cell

c. hour; generation

d. cell; generation

b. colony; cell

Q7.16  The stage in population growth with the highest rate of cell division is the

a. stationary phase

b. lag phase

c. exponential phase

d. enlargement phase

c. exponential phase