Lecture 13 Metabolism III

Question 1

What are the two types of photosynthesis

Answer 1

Anoxygenic and oxygenic

Anoxygenic harvested energy from light in ocean
Oxygenic evolved from anoxygenic

Question 2

What is the significance of methanogenisis

Answer 2

Mineralization of organic matter on the subsurface
Major role in digestion process of ruminant animals
Produces biogenic methane gas from coal and oil
Anaerobic digestion to produce biogas from compost, Waste water treatment

Question 3

How does oxygenic photosynthesis work?

Answer 3

Excites chlorophyll, excites rxn centre’s with PSI AND PSII, decreasing reduction potentials

Cyclic photophosphorylation
Involves PSI and produces ATP

Non-cyclic
Involves production of reducing energy and NADPH
Electrons are donated by H2O to PSII. NADPH is used for co2 fixation

Question 4

How does anoxygenic photosynthesis work?

Answer 4

Purple non sulfur bacteria
Electron donors: H2S
Don’t have enough reducing potential too low
Reducing power must be generated by PMF

Green non sulfur bacteria
Can directly DIVERT ELECTRONS FROM FAD to NAD

Question 5

What is reverse electron transport

Answer 5

It’s a a method that’s used by anoxygenic phototrophs and chemolithotrophs to generate reducing power to produce NADPH or fadh2.
Proton gradient provides energy for reverse electron transport

Question 6

What is methanogenisis?

Answer 6

Produce methane, anaerobic process
Oxidation of h2 coupled with reduction of CO2
Key enzyme: mcr

Question 7

What is hydrogen oxidation?

Answer 7

Oxidation of H2
H2 is an excellent donor, TEA O2, enzyme is hydrogenase, can transfer electrons directly to NADP

Question 8

What is the key enzyme of ammonia oxidation?

Answer 8

AMO (ammonia monooxygenase)

Question 9

What is the specialized organelle in Annamox?

Answer 9

Annamoxosome

Protects the cell from reactive intermediates, where metabolism takes place

Question 10

What is Anammox?

Answer 10

Anaerobic ammonia oxidation
Oxidation of ammonia coupled nitrite reduction to produce N2

Beneficial process to waste water treatment! Does not require o2

Question 11

Under what conditions can FE oxidation occur?

Answer 11

Acidic and neutral
Oxygen is the TEA for acidic or nitrate for neutral

Question 12

What is the electron donor in anammox?

Answer 12

Hydrazine , it’s every electronegative and donates electrons to Fe
Intermediate of metabolism
It’s also used in rocket fuel

Very oxygen sensitive

Question 13

What are the two different functional types of nitrification ?

Answer 13

Ammonia oxidizing bacteria (AOB)

Nitrogen oxidizing bacteria (NOB)

Question 14

Which pathway is used by many strict anaerobes including methanogenisis?

Answer 14

Reductive acetyl coA pathway

Question 15

Which enzymes catalysts the addition of CO2 to RuBP in the Calvin cycle?

Answer 15

Rubisco

Question 16

What are the phases of the Calvin cycle?

Answer 16

Carboxylation, reduction, regeneration

Question 17

What is synotrophy?

Answer 17

Metabolic process in which two organisms cooperate to degrade a substance and conserve energy

Question 18

What is the purpose of the carboxyxomes in the Calvin cycle?

Answer 18

They serve to concentrate co2 in many microbes

Question 19

What is diazotrophy

Answer 19

Specific type of autotrophy, involves nitrogen fixation to make nitrogen readily available, nitrogen gas to ammonia

Free living cyanobacteria

Nitrogrenase is a key enzyme
-Oxygen sensitive

Question 20

How do aerobic nitrogen fixers manage?

Answer 20

They physically separate from oxygen rich environments, form cells

Question 21

Autotrophy C fixation

Answer 21

Assimilation of CO2 into cell material

Overall objective is to convert CO2 to glucose
Pathways: Calvin cycle, reverse TCA, reductive acetyl coA

Question 22

What happens in carboxylation

Answer 22

Rubisco catalyze the addition of CO2 to RuBP forming 2 PGA

Question 23

Reduction in Calvin cycle

Answer 23

PGA reduced to bisphosphoglycerate

Question 24

Regeneration in Calvin cycle

Answer 24

Regeneration of RuBP

Question 25

Reductive reverse tca cycle

Answer 25

Operates in certain anaerobic bacteria and archaea
Used by many chemolithotrophs
Purpose: carbon fixation in the absence of oxygen
Nadph production

Question 26

Reductive acteyl coa, energy requirements

Answer 26

In methanogens: no atp required, pmf is used to reduce fd and co2
In bacteria: nadph is used to reduce co2 1 atp is required to generate formyltetrahydrofolate

Question 27

Interspecies H2 transfer

Answer 27

A process where H2 is transferred from the syntroph to the methanogeni

Question 28

What does nitrification do?

Answer 28

Two step, oxidation of ammonia (nh4+) to nitrite (no2-) and then to nitrate (no3-)

Question 29

What do anomoxosomes do?

Answer 29

Protect cells from reactive intermediates like hydrazine (rocket fuel)

Protons accumulate within this organelle —> producing PMF
ATP synthase located on the membrane

Question 30

Compare Assimilatory (anabolism) vs Dissimilatory (catabolism) reduction

Answer 30

Assimilation
-INPUT OF ENERGY
- reduction of inorganic sources of elements into organic forms for BIOSYNTHESIS
-only enough reduction to satisfy the needs of biosynthesis

Dissimilation
- generation of ENERGY
-reduction of inorganic forms for energy production
- electron accepor gets reduced and excreted (metals, NO3, CO2)
- large amount of electron acceptor used

Question 31

(Synotrophy) Many fermentations are not thermodynamically feasible… solution?

Answer 31

shift equilibrium, remove the products! low concentration

how? couple it with a favourable one

who? 4H2 + CO2 –> CH4 + 2H2O
-130 kj/mol

makes it exergonic example
removal of the H2 product pulls ethanol fermentation to the right overall exergonic.

Question 32

Purpose of Anaerobic food webs

Answer 32

drive carbon cycling in both natural and anoxic environments.

hydrolysis –> fermentation –> terminal respiration

methane is the main product of degradation (biogas ferment waste)