Exam 3

Question 1

doubling time (aka generation time)

Answer 1

Many microbes have incredibly short doubling times, sometimes as fast as 20 minutes. This means that a single cell could potentially multiply to over 10^14 cells in a 24-hour time-span due to their rapid reproduction

Question 2

What is the approximate doubling time of Escherichia coli (E. coli) under ideal laboratory conditions?

Answer 2

Under ideal laboratory conditions with ample nutrients and favorable temperature (around 37°C or 98.6°F), the doubling time for E. coli is approximately 20 to 30 minutes

Question 3

What are the “Big 6” essential elements required by all living things?

Answer 3

The “Big 6” essential elements are C (Carbon), N (Nitrogen), P (Phosphorus), H (Hydrogen), O (Oxygen), and S (Sulfur)

Question 4

Name some essential cations required by living organisms

Answer 4

Essential cations include Mg2+ (Magnesium), Fe2+ (Iron), K+ (Potassium), and Ca2+ (Calcium)

Question 5

What are trace metals, and why are they important for living organisms?

Answer 5

Trace metals are minute amounts of metals required in trace quantities by living organisms. They are important because they serve as cofactors for enzymes involved in specific metabolic pathways. Some examples of trace metals include cobalt, copper, manganese, molybdenum, nickel, and zinc

Question 6

Carbon is assimilated metabolically into cellular biomass by two
mechanisms:

Answer 6

• heterotrophism
• autotrophism

Question 7

How do heterotrophic microbes acquire carbon, and what do they use it for?

Answer 7

Heterotrophic microbes obtain carbon by consuming organic matter produced by other organisms. They assimilate this carbon into their cellular biomass for building and maintaining structures and use it as an energy source through metabolic processes like glycolysis and cellular respiration.

Question 8

How do autotrophic organisms acquire carbon, and what do they use it for?

Answer 8

Autotrophic organisms acquire carbon directly from carbon dioxide (CO2) through processes like photosynthesis. They utilize this carbon to build cellular biomass and produce energy, similar to heterotrophic organisms

Question 9

What percentage of global photosynthesis is estimated to be carried out by cyanobacteria

Answer 9

Cyanobacteria are estimated to be responsible for approximately 50% of global photosynthesis on Earth

Question 10

What is chemotropism, and how does it provide energy for cellular processes?

Answer 10

Chemotropism is the process by which organisms obtain energy by chemically rearranging organic compounds. It involves the breakdown of organic molecules, such as glucose, through metabolic processes like glycolysis and cellular respiration to produce ATP, which fuels cellular processes

Question 11

What is phototropism, and how does it provide energy for cellular processes?

Answer 11

Organisms use phototropism, involving light-absorbing pigments like chlorophyll, to convert light energy into chemical energy (primarily ATP) through photosynthesis for cellular processes

Question 12

How is energy used in biological systems for various cellular tasks?

Answer 12

Energy in biological systems is used immediately for tasks such as active transport, metabolism, biosynthesis, motility, and more

Question 13

What are some high-energy molecules in cells, and what is their role in energy storage?

Answer 13

High-energy molecules like ATP, GTP, NADH, NADPH, FADH2, and PEP store energy in their chemical bonds and release it when needed for various cellular functions

Question 14

How is energy stored as membrane potentials in biological systems, and what are their roles?

Answer 14

Energy can be stored as membrane potentials across cell membranes, representing differences in electrical charge. These potentials are used for tasks like nerve impulse transmission and active transport

Question 15

What is the feast-and-famine cycle, and how do microorganisms respond during the “feast” phase?

Answer 15

The feast-and-famine cycle involves fluctuations in nutrient availability. During the “feast” phase, microorganisms experience rapid growth when ample nutrients are available, often characterized by exponential population growth

Question 16

What happens to microorganisms during the “famine” phase of the feast-and-famine cycle?

Answer 16

During the “famine” phase, microorganisms face nutrient scarcity. They may enter a state of dormancy or slow metabolic activity to conserve resources and survive until nutrients become available again

Question 17

What are the key assumptions underlying exponential growth in microbial populations?

Answer 17

1. Exponential growth assumes a constant generation time (doubling time)
2. It assumes the presence of unlimited resources
3. It relies on the process of binary fission for reproduction

Question 18

What is exponential growth in microbial populations?

Answer 18

Exponential growth is a rapid and continuous increase in the population of microbes, where the number of individuals (N) at any given time is proportional to 2^n, with ‘n’ representing the number of generations. It assumes constant generation time, unlimited resources, and binary fission as key factors

Question 19

What is an example of exponential growth in the context of in vitro cultivation?

Answer 19

In vitro cultivation of bacteria is an example of exponential growth. Bacterial populations can double in size at regular intervals when provided with ample nutrients and favorable conditions in a laboratory setting

Question 20

Can you provide an example of exponential growth in natural ecosystems?

Answer 20

Invasive species, algal blooms, and populations recovering from catastrophic events in natural ecosystems can experience exponential growth under certain conditions

Question 21

What is an instance of exponential growth in the context of infectious diseases?

Answer 21

Infectious diseases can exhibit exponential growth within a susceptible population during early outbreak stages. The spread of contagious pathogens, like COVID-19, can follow exponential growth when transmission rates are high and preventive measures are not widely implemented

Question 22

What is the relationship between the growth rate (k) and generation time (g) of microorganisms?

Answer 22

The growth rate (k) and generation time (g) of microorganisms are inversely related. The relationship is expressed as g = 1/k, where faster growth (higher k) corresponds to shorter generation times (g)

Question 23

Why is rapid microbial growth (high k) desirable in biotechnology?

Answer 23

In biotechnology, rapid microbial growth is desirable to optimize high yield over short time periods, which is economically advantageous for production processes

Question 24

In the context of infectious diseases, how does the growth rate (k) of pathogens relate to disease severity?

Answer 24

Pathogens with high growth rates (high k) often lead to acute diseases with rapid onset, while those with lower growth rates (lower k) tend to cause latent diseases with prolonged incubation periods.