Marine Biology: Nutrient Cycling and Phototrophy

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Questions and Answers

What is the primary nutrient deficiency in high-nutrient low-chlorophyll (HNLC) regions that affects phototroph activity?

Nitrogen

Oxygen

Iron (correct)

Phosphorus

What was the primary outcome of the ocean iron enrichment experiments conducted between 1993 and 2005?

Increased ocean temperature

Decreased phytoplankton growth

Blooms of phototrophic microorganisms (correct)

Reduction in carbon sequestration

What is the general consensus among scientists regarding ocean iron fertilization for carbon sequestration?

It is effective in all oceanic regions

It is highly beneficial and necessary

It has mixed results and should be studied further

It is widely considered a bad idea (correct)

Which macronutrients are essential for phototrophs to grow in ocean ecosystems?

Nitrogen, Phosphorus, Iron Signup and view all the answers

What did John Martin famously claim regarding iron fertilization and its potential effects on climate?

It could induce an ice age Signup and view all the answers

What role does NADH serve in metabolic processes?

It acts as a diffusible electron carrier. Signup and view all the answers

Which of the following statements about respiration and fermentation is true?

Respiration occurs only in the presence of an electron acceptor. Signup and view all the answers

What is the primary energy source that drives cyclic photophosphorylation?

Light Signup and view all the answers

What is the primary mechanism through which ATP is produced in respiration?

Oxidative phosphorylation Signup and view all the answers

Which type of bacteria use REF for NADH synthesis during CO2 fixation?

Purple bacteria Signup and view all the answers

In anoxygenic photosynthesis, where does the electron cycle start and end?

The reaction center (RC) Signup and view all the answers

Which of the following is NOT a type of chemotroph?

Phototroph Signup and view all the answers

What component do green sulfur bacteria use in their electron transport chain instead of NADH?

Fd (Ferredoxin) Signup and view all the answers

What is generated during glycolysis?

ATP, pyruvate, and NADH Signup and view all the answers

What type of organisms often require external sources of electrons?

Photoheterotrophs Signup and view all the answers

In what situation is fermentation typically performed?

When an electron acceptor is not available. Signup and view all the answers

Why do some electrons leave the cycle in anoxygenic photosynthesis?

To go to NADH or Fd Signup and view all the answers

How are electrons harvested by chemolithotrophs?

Through either aerobic or anaerobic respiration. Signup and view all the answers

Which option describes organisms that utilize light for ATP but depend on organic carbon for biosynthesis?

Photoheterotrophs Signup and view all the answers

What type of phosphorylation occurs during fermentation?

Substrate-level phosphorylation Signup and view all the answers

What role do sulfur compounds play for certain organisms in this context?

They replenish the electron cycle Signup and view all the answers

What is the primary purpose of pipe vents in landfills?

To prevent the buildup of methane and explosions Signup and view all the answers

Which organism is known to oxidize sulfur in steps to produce sulfate?

Beggiatoa Signup and view all the answers

What do sulfur-oxidizing bacteria and archaea utilize to transfer electrons to the ETC?

Sox and Dsr enzymes Signup and view all the answers

Reverse electron flow is necessary because sulfur compounds have:

Less negative E values than NADH Signup and view all the answers

What is a consequence of reverse electron flow in sulfur metabolism?

Reduced ATP yield Signup and view all the answers

Sulfolobus is known for which of the following metabolic traits?

Dissolving crystalline sulfur for metabolism Signup and view all the answers

During sulfur oxidation, electrons are taken from sulfur compounds to generate:

A proton motive force for ATP synthesis Signup and view all the answers

What happens to the environment when sulfur is oxidized by certain bacteria?

It becomes more acidic Signup and view all the answers

What is the role of catalase enzyme when placed in H2O2?

It releases oxygen gas as a byproduct. Signup and view all the answers

What is the significance of cardinal temperatures for organisms?

Each organism has three specific cardinal temperatures affecting growth. Signup and view all the answers

Which adaptation helps organisms thrive at high temperatures?

More stable proteins and enzymes. Signup and view all the answers

What kind of organisms can grow in permanently frozen environments?

Psychrophiles and some algae. Signup and view all the answers

How do psychrophiles adapt to cold temperatures?

They have enzymes that are more flexible. Signup and view all the answers

Why is working with strict anaerobes challenging in labs?

They necessitate special equipment for handling. Signup and view all the answers

What characteristic distinguishes thermophiles?

They thrive in environments with high-temperature conditions. Signup and view all the answers

How do temperature extremes affect microbial growth?

They disrupt membrane stability and enzyme activity. Signup and view all the answers

What happens to organisms when they grow outside their optimum temperature range?

Their growth rate decreases. Signup and view all the answers

What type of environments do thermophilic cyanobacteria prefer?

High-temperature hotspring outflows. Signup and view all the answers

What is produced when NADH donates electrons to O2 during aerobic respiration in Escherichia coli?

Water Signup and view all the answers

Which of the following is NOT an example of anaerobic respiration?

Oxidative phosphorylation Signup and view all the answers

Why is less energy obtained when using sulfate as the electron acceptor compared to oxygen or nitrate?

Sulfate is lower on the redox tower Signup and view all the answers

What is the terminal electron acceptor in E. coli anaerobic respiration when nitrate is used?

Nitrate Signup and view all the answers

Which organism performs proton reduction and utilizes Na+ for ATP synthesis instead of H+?

Pyrococcus furiosus Signup and view all the answers

What is the key enzyme in CO2 fixation during the Calvin cycle?

Ribulose bisphosphate carboxylase Signup and view all the answers

What does the process of denitrification convert nitrate (NO3-) into?

Nitrogen gas Signup and view all the answers

How many ATP and NADH are required to synthesize one glucose molecule from six CO2 in the Calvin cycle?

18 ATP and 12 NADH Signup and view all the answers

During sulfate-reducing bacterial respiration, what is the end product often produced?

Hydrogen sulfide Signup and view all the answers

What process do some Archaea use to oxidize hydrogen and produce methane?

Methanogenesis Signup and view all the answers

Which of the following statements about chemolithotrophic metabolism is correct?

Some use inorganic chemicals for energy while utilizing CO2 Signup and view all the answers

What happens to electrons during the respiration process of hydrogen oxidation in some Archaea?

They are used to pump protons out of the cell Signup and view all the answers

How do autotrophs using the Calvin cycle ensure a high concentration of CO2 while avoiding oxygen interference?

They sequester RubisCO in carboxysomes Signup and view all the answers

Study Notes

Microorganism Growth and Metabolism

Microorganisms utilize various energy sources, categorized as either chemicals or light. Organisms using chemicals are chemootrophs, those using light are phototrophs.
Food serves two purposes: an energy source (electrons) and a biomass source (carbon, also nitrogen, phosphorous etc.). Electrons can come from organic compounds, inorganic compounds, or light. Biomass carbon sources include organic material (sugars etc.) or inorganic carbon (CO₂ or HCO₃⁻).
Bacterial cells are primarily composed of protein (55% dry weight), lipid (9.1%), polysaccharide (5%), lipopolysaccharide (3.4%), DNA (3.1%), and RNA (20.5%).
Chemotrophs employ either organic chemicals (chemoorganotrophs) or inorganic chemicals (chemolithotrophs) as energy sources. Phototrophs harness light for energy.
Oxidation-reduction reactions are crucial in transferring electrons to create energy for ATP synthesis.
ATP is the primary energy source used within cells; other compounds with phosphate bonds also have roles. Energy-rich bonds are key to ATP function.
Different substances have varying reduction potentials (E'), quantifying their ability to donate or accept electrons.
The redox tower arranges substances based on these reduction potentials and demonstrates electron flow direction, releasing energy as electrons move downhill on the tower. This electron flow from higher to lower reduction potential substances is crucial for energy transfer.
NADH is a key electron carrier in many cellular processes absorbing energy from these reactions.
Catabolic pathways (e.g., aerobic respiration, anaerobic respiration, fermentation) are diversified by the types of electron acceptors utilized.
Aerobic respiration utilizes oxygen as an electron acceptor, whereas anaerobic respiration employs alternative electron acceptors, such as sulfate, nitrate, and iron. Fermentation lacks an external electron acceptor.
Glycolysis converts glucose into pyruvate, generating ATP and NADH. ATP is made by different mechanisms, often substrate phosphorylation in fermentation versus oxidative phosphorylation in respiration.
The Krebs cycle (Citric Acid Cycle) is a central metabolic pathway that oxidizes pyruvate to CO2, producing ATP and high-energy electron carriers like NADH and FADH2.
The Electron Transport Chain (ETC) is a series of protein complexes that transfer electrons through a series of oxidation-reduction reactions, generating a proton motive force (PMF) and ultimately producing ATP (called oxidative phosphorylation).
Chemiosmosis uses the PMF to drive ATP synthesis.
During aerobic respiration, one molecule of glucose can produce approximately 38 ATP, whereas various fermentation processes generate significantly less. This difference corresponds to the energy available from different electron acceptors.
The Calvin cycle is critical for carbon fixation, converting atmospheric CO2 into organic compounds utilizing ATP and NADPH produced through light-dependent reactions.

Additional Notes

Differences in growth conditions like oxygen levels, temperature, and pH strongly shape microbial communities.
Various strategies for microbial growth classification based on oxygen needs (e.g., aerobes, anaerobes, facultative aerobes) exist. Different microbial groups require specific growth conditions.
Extremophile bacteria thrive in harsh conditions, including high temperatures (thermophiles), extremely saline environments (extreme halophiles), and acidic or alkaline conditions (acidophiles, alkaliphiles).
Microbial growth occurs through binary fission, budding, or other special cell division mechanisms.
Growth of a microbial population is expressed as generation time, the time needed for a microbial population to double in number.
Batch cultures can have different growth phases exhibiting lag phase, exponential growth phase, stationary phase, and death phase.

Other Notes

Essential factors for microbial growth include food for energy (electrons) and to make biomass(organic or inorganic carbon); also include macronutrients (N, P, S, K, and Mg). Micronutrients include trace elements and metals that act as cofactors for enzymes, along with growth factors.
Oxygen availability and reactions of O2 with redox components define different categories of organisms (aerobes, anaerobes, and facultative aerobes)
Temperatures of growth vary, from psychrophile (cold-loving) to thermophiles (heat-lovers) to hyperthermophiles.
Different pH values of growth support various categories of microorganisms.
Salt concentrations have different impacts on various microorganisms (nonhalophiles, moderate halophiles, and extreme halophiles).

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Description

Explore key concepts in marine biology related to nutrient cycling and its effect on phototroph activity in oceanic ecosystems. This quiz covers topics from iron enrichment experiments to metabolic processes essential for marine organisms. Test your knowledge on macronutrients, respiration, and the implications of ocean iron fertilization.