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ESCI 111 > BioGeo Chemistry > Flashcards

BioGeo Chemistry Flashcards

1
Q

What is biogeo chemistry?

A

Is the chemistry of life and its interaction with Earth and the geological environment.

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2
Q

What is the composition of a living organism?

Hint: 5 components

A
  1. Nitrogen 3%
  2. Hydrogen 10%
  3. Carbon 18%
  4. Oxygen 65%
  5. Others (phosphorus 1%, calcium 1.5%, potassium 0.4%).

Living organisms need access to these elements in order to survive.

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3
Q

What cycle is the major cycle of forming tissues?

A

REDOX (reduction and oxidation).

Reduction = a GAIN of electrons.
Oxidation = a LOSS of electrons and is a substance binding to oxygen (e.g rusting of iron).
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4
Q

Why are redox reactions important to life?

A

Because these reactions very often produce ENERGY and organisms EXPLOIT this energy source.

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5
Q

What is photosynthesis?

A

Plants use energy from sunlight to force electrons OFF OXYGEN in H2O, forming O2.
(O2- are oxidised to O (O2), liberating free electrons).

These electrons can reduce H+ in water to H2.

The H2 can then give up these electrons (therefore, binding back to H+) to C in CO2, reducing it to GLUCOSE (CH20).

This is all driven by the sun’s energy.

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6
Q

What does light energy cause?

A

Light energy, therefore, causes oxidation of O2 and reduction of CO2.

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7
Q

What is respiration?

A

It is carbon in glucose (CH2O) being oxidised to CO2, releasing electrons.

These electrons can reduce H+ in glucose to H2.
The H2 can then give up these electrons (therefore, being oxidised back to H+) to O2, reducing it to O2- to form H20.

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8
Q

What is the respiration process used for?

A

Energy is released in the process and harnessed by metabolic processes. Used to fuel our bodies.

Energy captured by plants in the form of sunlight is then released.

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9
Q

Name the steps of the rock cycle…

Hint: from magma to magma again

A
  1. Molten rock (magma) crystallises to form IGNEOUS rock.
  2. Igneous rocks reach the SURFACE (through uplift and volcanism).
  3. Surface rocks weather, dissolve, recycle sediments.
  4. Sediments get BURIED and SUBDUCTED to form METAMORPHIC rocks.
  5. Further burial causes re-melting to form magma.

All of this takes place underground except step three.

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10
Q

How does the rock cycle have profound influences over geological timescales?

A

It has a profound influence on surface biogeochemical cycles, controlling nutrients supplies, and modulating atmosphere gases.

E.g. global productivity (especially in the southern oceans) are affected by Fe and P, C cycles (rocks) are affected by weathering, carbonate formation (which removes CO2), and volcanism (which adds CO2) and other gases (e.g. SO2 to the atmosphere. All this equals the habitability.

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11
Q

How does water evaporate?

A

Water evaporates with the tropical oceans dominating the water vapour supply budget.

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12
Q

How is water vapour dispersed relatively quickly around the globe?

A

By winds.

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13
Q

When does vapour primarily condense?

A

Vapour condenses, primarily when temperatures drop(e.g. uprising air cools) to form clouds, rain, or son (or when they move into cooler areas).

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14
Q

What do white clouds mean?

A

Clouds have a significant impact on the climate. When they are white this means there is a lot of RADIATION being REFLECTED on them.

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15
Q

What is the timescale for water in the oceans from the surface to deep to cycle?

A

1500 years.

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16
Q

What has a strong influence on the global transport of heat?

A

Because water has a huge heat capacity and latent heat of evaporation, the cycling of water has a strong influence on the global transport of heat.

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17
Q

What removes O2 from the atmosphere?

A

Plants and trees (vegetation).

O2 is removed from the atmosphere during oxidation reactions (respiration and similar reactions) and is eventually lost to the lithosphere (primarily as CaCO3).

18
Q

What adds oxygen to the atmosphere?

A
  • Photolysis
  • Photosynthesis
  • Weathering
19
Q

How much oxygen does the atmosphere contain?

A

21%

20
Q

Where is the vast majority of oxygen found?

And why is the vast majority of the oxygen cycle driven by photosynthesis?

A

The vast majority of oxygen is in the lithosphere but as silicates. However, they are released slowly due to weathering being a slow process. Therefore, photosynthesis drives much of the oxygen cycle, liberating free O2.

There is also a minor contribution from the photodissociation of N2O and H2O.

21
Q

What other cycles does the oxygen cycle interact with?

A

The hydrogen and water cycles (via H2O) and the carbon cycle (via CO2).

22
Q

How much carbon does the atmosphere contain (in ppm)?

A

400ppm.

23
Q

Where do carbon cycles take place?

A

Between the atmosphere, biosphere, ocean and sediments.

24
Q

What sphere contains the largest pool of carbon?

A

The lithosphere (80% in limestones) BUT is SLOW to exchange with other spheres.

So, of the readily-cycled carbon, the largest pool is in the DEEP OCEAN, followed by fossil carbon (fossil fuels).

25
Q

How is carbon a major energy carrier in the biosphere?

A

Plants capture energy from the sun (photosynthesis-storing solar energy), reducing CO2 to C- polymers (e.g. organic molecules). Re-oxidation of organic material (respiration) is one of the main ways that HIGER organisms obtain energy.

26
Q

What element is vigorously cycled in the biosphere with little to no net loss?

A

Carbon.

27
Q

What is the most abundant component in the atmosphere?

A

N2, Nitrogen (70%).

28
Q

Why is Nitrogen (N2) the most abundant in the atmosphere?

A

This is because there is a triple bond present between the two atoms making it hard to bream (very inert).

So, bioavailable nitrogen is often limiting.

29
Q

What is inorganic nitrogen?

A

Lightning has enough energy, and in the presence of O2 generates N-oxides (oxidised N). This is only a small contributor to bioavailable N. It is SLOW.

30
Q

What is biological nitrogen?

A

Nitrogen-fixing, organisms often use a Fe-containing enzyme to reduce N2 to NH4. This often creates an iron limitation in places (N nutrient production is restricted by bioavailable Fe).

This ammonia gets assimilated, oxidised (to nitrates and nitrites) and is vigorously recycled in the biosphere.

31
Q

What can act as an oxidising agent (in the absence of O2)?

A

NO3- can act as an oxidising agent.

So, in anoxic environments identification occurs, reducing NO3- back to N2.

32
Q

What plays no significant role in the phosphorus cycle?

A

The atmosphere

33
Q

How is phosphorus obtained?

A

Phosphorus is weathered from rocks, but slowly. The major source is the mineral apatite (Ca phosphorus). A lot of the P liberated by rocks is taken up in other minerals and isn’t bioavailable.

34
Q

How do soils lose phosphorus?

A

Soils lose phosphorus to runoff. So, P is a major bio-limiting nutrient in many systems.

35
Q

How do tectonics control the biosphere?

Hint: Influence

A

Tectonics control long (geological) timescales by influencing P availability (implicated in early O2 evolution (balance of continental weathering supporting photosynthetic life.

36
Q

What cycle is the slowest?

A

The phosphorus cycle.

Bioavailable P in the environment is vigorously recycled BUT because the rock cycle is SLOW, the P cycle is the SLOWEST.

37
Q

What has had the greatest impact on the phosphorus cycle?

A

Of all the cycles, HUMANS have perhaps had the greatest impact on the phosphorus cycle.

38
Q

What did the growing of crops use to involve?

A

The growing of crops used to involve returning organic-bound P to the soils (as mulching or manure fertiliser).

However, now the majority of material (organic) is removed from where grown and transported to cities. The resulting sewerage does NOT return to the fields but is ultimately DISPERSED into the HYDROSPHERE (as a dilute phase).

39
Q

What does dispersing sewerage (diluted) into the hydrosphere decrease and increase?

A

This decreases the fertility of soils on the LAND.

BUT increases the fertility in the OCEANS.

40
Q

What does the concept of peak phosphorus mean?

A

The concept that we might hear to depleting our readily available supplies of P.

We now try and capture the recycled P.

ESCI 111 (18 decks)

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