Chapter 14: Metabolic Diversity of Microorganisms

Question 1

Light reaction

Answer 1

produces ATP and NADPH
- requires an electron donor from environment (water, H2S, H2)

Question 2

Dark reactions

Answer 2

reduce CO2 to cell material for growth
requires ATP and e- (NADH/NADPH)

Question 3

oxygenic photosynthesis

Answer 3

oxidation of H2O produces O2
-cyanobacteria

Question 4

anoxygenic photosynthesis

Answer 4

oxidation of H2S produces SO42-
-purple/green sulfur bacteria

Question 5

chlorophyll and bacteriochlorophyll

Answer 5

tetrapyrroles w magnesium
- different pigments allows different phototrophs to absorb different wavelengths

Question 6

photocomplexes

Answer 6

proteins housed within membranes
- reaction centers contain pigments
- antennae pigments surround and funnel light energy to rxn centers

Question 7

chloroplasts

Answer 7

in eukaryotes
- intercellular organelles containing thylakoids

Question 8

thylakoids

Answer 8

sheet-like membrane systems

Question 9

chlorosomes

Answer 9

capture low light intensities
- in anoxygenic green sulfur bacteria, filamentous anoxygenic phototrophs, & phototrophic Acidobacteria

Question 10

Carotenoids

Answer 10

widespread accessory pigment
hydrophobic
yellow, red, orange, brown, or green
absorb blue light
-quenches toxic oxygen species, prevents dangerous photooxidation

Question 11

phycobiliproteins

Answer 11

the main light-harvesting systems of cyanobacteria and red algae chloroplasts
- red/blue-green tetrapyrroles: “bilins” bound to proteins
pro: integrated into cytoplasmic membrane
purple bacteria: chromatophores/lamellae
cyanobacteria: thylakoids

Question 12

phycoerythrin

Answer 12

absorbs ~550nm (red)

Question 13

phycocyanin

Answer 13

absorbs ~620 nm (blue)

Question 14

noncyclic photophosphorylation

Answer 14

e- do not circle back and reduce NADP+ to NADPH

Question 15

cyclic photophosphorylation

Answer 15

occur if cell requires less NADPH to produce more ATP

Question 16

autotrophy

Answer 16

CO2 is reduced and assimilated into cells
- in phototrophs: often called “dark rxn”

Question 17

Calvin Cycle

Answer 17

Requires:
6 CO2
CO2 acceptor
12 NADPH
18 ATP
RuBisCO
phosphoribulokinase

To make 1 Glucose

Question 18

carboxysomes

Answer 18

inclusions containing and improving efficiency of RubisCO in many autotrophs
- increase CO2 concentration (instead of O2)
-250 RubisCO/carboxysome

Question 19

Reverse Citric Acid Cycle

Answer 19

aka reductive TCA cycle
used by green sulfur bacteria (and some chemoautotrophs)
more efficient:
4 NADH
2 reduced ferredoxins
10 ATP

Question 20

Hydroxypropionate Cycle

Answer 20

2 CO2
6 H
3 ATP
into glycoxylate

Question 21

Nitrogen fixation

Answer 21

atmospheric gaseous N2 -> ammonia NH3
- no eukaryotes fix nitrogen
16 ATP

Question 22

nitrogenase

Answer 22

enzyme complex composed of dinitrogenase and dinitrogenase reductase
-inhibited by oxygen

Question 23

Ways of protecting nitrogenase from oxygen

Answer 23

oxygen-retarding slime layer
removal by respiration
anoxic heterocyst formation

Question 24

Assaying nitrogenase

Answer 24

acetylene reduction
-nitrogenases reduce other triply bonded compounds, including acetylene, to form ethylene

Question 25

assimilative reduction

Answer 25

consumes energy ie. NO3-, SO4-, and CO2 reduction for new sources of N, S and C for new cell material

Question 26

dissimilative reduction

Answer 26

conserves energy product of reduction is a small molecule that is excreted (N2, H2S, CH4) - only in anaerobic respiration

Question 27

H2 oxidation

Answer 27

H2 + 1/2 O2 -> H2O very exergonic, can be coupled to ATP synthesis catalyzed by hydrogenase

Question 28

H2 bacteria

Answer 28

most are chemoorganotrophs CO2 fixed by Calvin Cycle

Question 29

Oxidation of Sulfur compounds

Answer 29

H2S, S0, S2O3- (SO3 2- common) in stages, first produces S0 (deposited in cell as an energy reserve) produces H+ (acidifies environment) Sox system

Question 29

facultative chemolithotrophs

Answer 29

repress synthesis of Calvin cycle and hydrogenase enzymes when organics present catalyzed by hydrogenase

Question 29

Sox System

Answer 29

oxidizes reduced sulfur compounds directly to sulfate 4 key proteins: SoxXA, SoxYZ, SoxB, SoxCD

Question 30

sulfur-oxidizing microbes that store sulfur granules lack _______

Answer 30

SoxCD (sulfur dehydrogenase)

Question 31

chemoautotrophs

Answer 31

aerobes oxidizing ferrous iron at low pH Fe2+ -> Fe3+

Question 32

ferrous hydroxide

Answer 32

Fe3+ + 3 H2O = Fe(OH)3 + 3 H+ insoluble, precipitates in water, driving down pH

Question 33

Bioleaching

Question 34

Assimilative sulfur metabolism

Answer 34

incorporation of sulfate for biosynthetic purposes to make cysteine, methionine, and other organosulfur compound

Question 35

Dissimilative sulfur metabolism

Answer 35

use of sulfate as an electron acceptor for energy conservation and production of large amount of H2S (excreted)

Question 36

Sulfur reduction

Answer 36

1 ATP/SO4- reduced to HS- e- transport reactions lead to PMF formation

Question 37

methanogenesis

Answer 37

biological production of methane catalyzed by strictly anaerobic Archaea (methanogens) - form of anaerobic respiration reduction of CO2by H2 to form CH4 NEEDS TRUE ANOXIC CONDITIONS

Question 38

methanogens

Answer 38

present in freshwater sediments, sewage sludge digesters, bioreactors, animal intestines

Question 39

C1 carriers

Answer 39

coenzyme in methanogenesis - carry C1 units along path of enzymatic reduction (methane, methanol, etc.)

Question 40

methanogenesis coenzymes

Answer 40

Coenzyme M (last step) Coenzyme F430 (last step-not a carrier) Coenzyme F420 (Flavin derivative, fluoresces @420 blue-green) Coenzyme B (terminal step, catalyzed by methyl reductase enzyme complex)

Question 41

methylotrophs

Answer 41

oxidize methane (+ other C1 organic compounds) as electron donors

Question 42

aerobic methane oxidation

Answer 42

CH4 -> CH3OH -> CH2O -> HCOO- -> CO2

Question 43

serine pathway

Answer 43

acetyl-CoA synthesized from CH2O and CO2 needs 2 NADH and 2 ATP

Question 44

ribose monophosphate pathway

Answer 44

all carbon derived from CH2O (no NADH) 1 ATP per glyceraldehyde -3-phosphate(G-3-P) synthesized reversal of glycolysis produces glucose

Question 45

anaerobic oxidation of methane (AOM)

Answer 45

can occur by an association (consortium) of 2 organisms: sulfate-reducing bacterium (SRB) and Archaea

Question 46

RuBisCO

Answer 46

active in carboxysome very low affinity for CO2 compared to O2