ESS 311 Midterm 2

Oxidation

The process of losing electrons.

Reduction

The process of gaining electrons.

How do eukaryotic organisms make energy?

Use aerobic respiration to generate energy usually by converting it to ATP.

What are autotrophs?

Organisms that get their carbon from an inorganic source.

Relationship of oxygen in autotrophs

May or may not produce or require oxygen.

What are heterotrophs?

Organisms get their carbon from an organic source.

Relationship of oxygen in heterotrophs

Aerobic requires free oxygen; anaerobic occurs in the absence of oxygen.

What is organic carbon?

C-C bonds and methane.

Photosynthesis equation

6CO2 + 6H2O + energy -> C6H12O6 + 6O2

Respiration equation

C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy

What is a redox reaction?

A reaction that has to do with electron transfer.

OILRIG

Oxidation is lost, reduction is gained.

LEO the lion says GER

Loss of electron is oxidation, gain of electrons is reduction.

Photosynthesis relationship with carbon

Converts inorganic carbon dioxide into organic carbon.

Behavior of carbon dioxide in photosynthesis

Reduced and gains electrons.

Behavior of water in photosynthesis

Oxidized and loses electrons.

What water gains in photosynthesis

Gains electrons in the form of hydrogen ions.

Respiration relationship with carbon

Oxidizes organic carbon in organisms or organic matter into inorganic carbon dioxide, releasing energy.

Behavior of oxygen in respiration

Reduced and gains electrons.

Behavior of glucose (sugar) in respiration

Oxidized and loses electrons.

Cycle of cellular respiration with oxygen (aerobic)

Glucose -> glycolysis (2 ATP) -> prep steps in cytoplasm (CO2 out) -> Kreb's cycle (CO2 out, +2 ATP) -> Electron Transport Chain (O2 in, H2O out, +34 ATP).

Cycle of cellular respiration without oxygen (anaerobic)

Glucose -> glycolysis (2 ATP) -> Fermentation (lactic acid or alcohol).

What is fermentation?

The process of making ATP without oxygen (anaerobic).

How much ATP fermentation produces

2 ATP per glucose (from glycolysis).

How fermentation produces ATP

Through substrate level phosphorylation during glycolysis, not the electron transport chain.

Process of lactic acid fermentation

Glucose -> glycolysis -> pyruvate -> reduced to -> lactate.

Products of lactic acid fermentation

Lactate (lactic acid) and NAD+. Does not release CO2.

Process of NADH during lactic acid fermentation

NADH reduces pyruvate into lactate and becomes NAD+.

Process of alcohol fermentation

Glucose -> glycolysis -> pyruvate -> converted to -> acetaldehyde -> reduced to -> ethanol.

Products of alcohol fermentation

Ethanol, CO2, and NAD+.

Process of pyruvate during alcohol fermentation

Pyruvate loses CO2 to form acetaldehyde, which is then reduced to ethanol by NADH.

Overview of lactic acid fermentation

Produces lactate, no CO2, pyruvate directly reduced.

Overview of alcohol fermentation

Produces ethanol, releases CO2, pyruvate -> acetaldehyde -> ethanol.

Common characteristics between both fermentations

Begin with glycolysis, produce 2 ATP, regenerate NAD+ so glycolysis can continue, and do not use the electron transport chain.

ATP generation in aerobic vs anaerobic respiration

Aerobic yields significantly more ATP (around 32-34 ATP) compared to anaerobic/fermentation (2 ATP).

Purpose of fermentation besides food

Creates acetate and dihydrogen which is necessary for microbial genetics.

Where lactic fermentation occurs

Soils and animal guts.

Conversion of organic acids during fermentation in microbes

Organic acids to acetate.

Product of glucose in both fermentations

Acetate.

Nutrients limited in open ocean systems

Sulfur.

Gibbs free energy (G) equation

ΔG = Gfinal - Ginitial.

When energy is provided

G final < G initial.

Negative change in G

Exergonic reaction, releases energy.

When energy is required

G final > G initial.

Positive change in G

Endergonic reaction, requires energy.

Why organic matter builds up in anoxic environments

Aerobic respiration is more efficient with oxygen, generating more ATP; anoxic environments lack this efficiency.

How oxygen relates to growth of population

Aerobic respiration yields higher energy, allowing microbes to grow faster and result in larger population size and biomass.

Exergonic process

Energy provided, negative change in Gibbs, breaks down glucose to release free energy, Gibbs products < reactants (e.g., cellular respiration).

Endergonic process

Requires energy/sunlight to generate, Gibbs products > reactants (e.g., photosynthesis).

How exergonic processes work without sunlight

Releasing stored energy from chemicals or electricity instead.

What determines the free energy released by a reaction

Surrounding conditions including substrate conditions.

What does the figure demonstrate about Gibbs free energy

How substrate and product concentrations change Gibbs free energy.

Acetogenesis below zero on graph

Exergonic, energetically favorable.

Acetogenesis above zero on graph

Endergonic, energetically unfavorable.

Characteristics of energetically favorable reaction

High reactant concentrations and low product concentrations.

Characteristics of energetically unfavorable reaction

High product concentrations and low reactant concentrations.

What happens when hydrogen concentration increases during acetogenesis

Reaction becomes less energetically favorable because hydrogen is a product.

What happens when sulfide builds up

Reaction may become less favorable or slow down.

Most to least energetically favorable for redox reactions

Oxygen is most, nitrate, manganese, iron, sulfate, CO2 is least.

Redox potential (Eh)

The measure of the overall intensity of the oxidizing or reducing conditions within a system.

How to measure redox potential

Measuring the electron flow between a reference electrode and a platinum electrode.

Properties of the bottom of a lake

Anoxic, more respiration than photosynthesis, low photosynthesis due to less light and less atmospheric circulation.

Causes of a reaction to stop

Concentration of reactants and products, buildup of products, or reactants only used once previous products are consumed.

Anoxic

Without oxygen.

Oxic

With oxygen.

Aerobic respiration metabolism

Heterotrophic, aerobic (most animals, fungi, many bacteria in soil with oxygen and sediment).

Acetate production metabolism

Autotrophic, anaerobic (bacteria in anoxic sediments and environments).

Iron oxidation metabolism

Autotrophic, aerobic (iron oxidizing bacteria in iron-rich soil ecosystems).

Denitrification metabolism

Heterotrophic, anaerobic (denitrifying bacteria in poor oxygen soil ecosystems).

Anammox metabolism

Autotrophic, anaerobic (anammox bacteria in anoxic aquatic sediments and low oxygen environments).

Sulfate reduction metabolism

Heterotrophic, anaerobic (sulfate reducing bacteria in anoxic soil ecosystems).

Acetolactic methanogenesis metabolism

Heterotrophic, anaerobic (methanogenic archaea in wetlands, swamps, lake sediments, animal guts).

Hydrogenotrophic methanogenesis metabolism

Autotrophic, anaerobic (hydrogen-using methanogenic archaea in anoxic environments).

Diffusion of components of oxygen gradient in nature

Diffuse down: oxygen, light, and heat. Diffuse up: nutrients.

Green sulfur bacteria (GSB)

Tolerate higher sulfide concentrations, do not produce oxygen.

Nitrate/nitrite reductions

Takes nitrate and creates ammonia; doesn't build up because it is a gas (heterotrophic, anaerobic).

Nitrifiers

Take ammonium and make nitrate (autotrophic, aerobic).

Relationship of iron and phosphorus in a lake

Iron binds with phosphorus near the top and sinks; once anoxic, iron reduces and releases the phosphorus which floats back to the top.

The likelihood of anoxic water

The longer water lacks light or atmosphere, the more likely it is to go anoxic.

Determining how oxic an environment is

Depends on the balance of diffusion, respiration, and sometimes photosynthesis.

Presence of oxygen in soil

Dry soil is oxic; wet soil ball is anoxic on the inside and oxic on the outside.

Oxygen properties in water

Small standing water is anoxic; moving water is oxic.

Mississippi River example

Anthropogenic excess nutrients flowing downriver cause big algal blooms and dead zones in the gulf due to lack of movement.

N fixation pathway

N2 gas converted into ammonia and ammonium by biological fixation.

Non-anthropogenic process of biological nitrogen fixation

Microbes convert atmospheric nitrogen into ammonia.

Anthropogenic process of biological fixation of nitrogen

Haber-Bosch process.

Haber-Bosch process

Humans industrially convert N2 into ammonia to make fertilizers.

Percentage of nitrogen gas in the atmosphere

Approximately 78%.

Process necessary for most organisms to use nitrogen

Must convert N2 to ammonia (NH3) or ammonium (NH4+).

Why energy is required for nitrogen fixation

Breaking the strong triple bonds in atmospheric nitrogen requires a lot of energy.

Relationship between human nitrogen fixation and eutrophication

Humans produce reactive nitrogen through the Haber-Bosch process and spread it through fertilizers, increasing nutrient runoff.

Reactive Nitrogen

Nitrogen in forms organisms can use, such as ammonia, ammonium, and nitrate.

Why nitrogen-fixing microbes need glucose/organic carbon sources

To provide chemical energy for nitrogen fixation.

Where nitrogen-fixing microbes are found

Near plant roots, which release sugars that provide microbes with energy.

Dominant nitrogen-fixing microbe in many aquatic ecosystems

Cyanobacteria.

Conditions that favor many N-fixing cyanobacteria

Warm temperatures and high light availability.

Leaching

Movement of dissolved nutrients and organic compounds out of soil or decomposing matter into the surrounding environment.

Source of dissolved amino acids in the environment

Decomposed dead matter and chemical alterations/leaching.

What leaching releases into the environment

Dissolved organic compounds, including amino acids and nutrients.

Uptake of nutrients

Absorbed by plants and algae from their environment.