L14 - Chemolithotrophy

Question 1

What is chemolithotrophy?

Answer 1

the use of inorganic compounds as electron donors in metabolism

Question 2

What are chemolithotrophs? What are pure chemolithotrophs and what are mixotrophs?

Answer 2

organisms that obtain energy from the oxidation of inorganic compounds. pure = energy purely from inorganic. mixotroph = chemolithotrophs that require organic carbon as a carbon source

Question 3

How does different oxidation reactions exist in the environment

Answer 3

many sources of reduced molecules exist in the environment the oxidation of different reduce compounds yields varying amount of energy

Question 4

How does hydrogen (H2) oxidation work? what carries it out? what catalyses it?

Answer 4

And aerobic hydrogen oxidizing bacteria and IKEA are known to carry out hydrogen oxidation. It is catalyzed by hydrogenized enzyme and coupling it with carbon cycle allows, chemo, trophic growth.

Question 5

What is the role of hydrogenase in cellular metabolism?

Answer 5

Hydrogenase interacts with gaseous hydrogen (H₂), oxidizing it and passing electrons through cytochromes to generate energy.

Question 6

How are electrons from hydrogen oxidation used in cellular processes?

Answer 6

Electrons from hydrogen oxidation are passed through cytochromes, using NAD to reduce CO₂ and generate a proton motive force.

Question 7

How is energy generated during hydrogen oxidation?

Answer 7

The energy from hydrogen oxidation generates a proton motive force, which is used to synthesize ATP.

Question 8

Describe the oxidation of reduced sulphur compounds. Why is sulphur good for this?

Answer 8

there is a large variety of reduced sulfur compounds that can be used as electron donors since they have lot of oxidation states.

Question 9

What is the main product of this oxidation and what happens to its surroundings

Answer 9

One product of sulfur oxidation is proton H+, which lowers the pH of its surroundings.

Question 10

What is sox system?

Answer 10

oxidizes reduced sulphur compounds directly to sulphate

Question 11

Oxidation of reduced sulphur compounds is usually _____ (aerobic or anaerobic) but some organisms can use __ as e- acceptor

Answer 11

1. aerobic
2. nitrate

Question 12

What are the oxidation states of sulphur

Answer 12

-2,-1,0,-2,+6,+4,+6

Question 13

WHat is oxidized to what in Iron (Fe2+) oxidation?

Answer 13

ferrous iron (Fe2+) is oxidized to ferric iron (Fe3+)

Question 14

WHat is ferric hydroxide?

Answer 14

rust, precipitates in water and forms rust

Question 15

What is the pH at which many Fe oxidizers can grow? What is it associated with?

Answer 15

<1, acidic pollution from coal mining activities

Question 16

some _____ ____ can oxidize Fe2+ ____ using Fe2+ as an electron donor for CO2 reduction

Answer 16

anoxygenic phototrophs
anaerobically

Question 17

Fe3+ formed reacts with water to form _____ (what color is it)

Answer 17

rust (ferric hydroxide), orange

Question 18

How is Iron oxidation carried out in bacteria?

Answer 18

• Fe2+ oxidation begins extracellularly
• c-type cytochrome oxidizes Fe2+ to Fe3+
• 3- passed to rusticyanin in periplasm
• rusticyanin reduces cytochrome c and reduces cytochrome a
• cytochrome a interacts with O2 to form H2O
• ATP synthesized
• autotrophy in acidithiobacillus ferrooxidans is driven by the calvin cycle

Question 19

Examples of compounds that serve as electron donors in sulphate reduction

Answer 19

H2, organic compounds, phosphite

Question 20

How do sulphur-reducing bacteria gain additional energy?

Answer 20

through disproportionation of sulphur compounds

Question 21

Where is sulphur stored on earth? as what compounds?

Answer 21

the bulk of sulphur on earth occurs in sediments and rocks as sulphate and sulphide minerals (e.g. gypsum, pyrite). the ocean represent the most significant reservoir of sulphur (as sulphate) in the biosphere

Question 22

What are the key processes in the sulphur cycle

Answer 22

sulphide/sulphur oxidation, sulphate reduction, sulphur reduction, sulphur disproportionation, organic sulphur compound oxidation or reduction, desulphurylation

Question 23

What is the role of sulphur in proteins, and how is it assimilated?

Answer 23

Sulphur is an important element in proteins, and it is assimilated into proteins from sulphate through assimilation reactions, where sulphate is reduced to incorporate sulphur into organic compounds.

Question 24

What are desulfurization and disproportionation reactions in sulphur metabolism?

Answer 24

Desulphurization reactions result in sulphur being lost back to organic sources, while disproportionation involves the oxidation of elemental sulphur to sulphate and reduction to sulphide.

Question 25

How do bacteria manage oxidation and reduction of sulphur, and what is the significance of their cell structure?

Answer 25

Bacteria carry out both oxidation and reduction reactions simultaneously at the interface between oxic and anoxic environments. They elongate their cells, which facilitates electron transport for sulphur metabolism, including the reduction of pure sulphur to H₂S.

Question 26

What is hydrogen sulphide and how is it produced? how is it removed?

Answer 26

hydrogen sulphide is a major volatile so for gas that is produced by bacteria via sulphate reduction or emitted from Geochemical sources. It is toxic to many plants and animals and reacts with numerous metals, sulphur chemolithotrophs can oxidise sulphide and elemental sulphur at oxic/anoxic interfaces.

Question 27

How is hydrogen sulphide useful?

Answer 27

eact with metal compounds to remove metal contamniation (metal sulfides formed under redutive reactions → insoluble so its not leaked into oceans

Question 28

Organic sulphur compounds can also be metabolized by ____

Answer 28

microorganisms

Question 29

What is the most abundant organic sulphur compound in nature? where is it produced?

Answer 29

dimethyl sulphide (DMS), marine environments as a degradation product of dimethylsulphoniopropionate (algal osmolyte)

Question 30

Why is iron one of the most abundant elements on earth’s crust

Answer 30

produced by fusion in stars, iron is accumulated

Question 31

What else is present on earth’s surface, how many oxidation states does it exist in?

Answer 31

manganese can also be oxidized or reduced, exists in 2 oxidation states

Question 32

How is Fe2+ and Fe3+ turned into Fe0

Answer 32

smelting of ores

Question 33

How are oxidation and reduction reactions in the environment separated spatially?

Answer 33

Oxidation and reduction reactions are separated in the environment depending on the availability of oxygen, with oxic conditions at the top and anoxic conditions below.

Question 34

What happens under oxic conditions in the environment?

Answer 34

A: In oxic conditions, iron and manganese are oxidized, forming insoluble compounds that sink through the water column.

Question 35

What occurs in lower, anoxic conditions in the environment?

Answer 35

n anoxic conditions, reduced compounds lead to the consumption of acetate, which remains soluble and mixes with the water column, rising to the surface.

Question 36

Describe the phosphorous cycle. why is it limiting and how do we use it?

Answer 36

In the bio of fear, there exists organic and inorganic phosphates which cycles through living organisms, modern soil phosphorus is in a DNA backbone. It is very important however it is limiting in terms of its availability, so humans tend to add additional phosphorus and fertilizers to boost agricultural productivity.

Question 37

Describe the calcium cycle

Answer 37

reservoirs are rocks and oceans marina phototrophic microorganisms uses Ca2+ to form exoskeleton