Microbial Lifestyles and Metabolism (Dr. Kreft): Metabolism

Question 1

What trophic category are animals?

L> Do bacteria fit into this?

Answer 1

• chemotrophs
  L> they use chemical reactions as energy source, organic matter as electron source, organic matter as carbon source
• Bacteria do not fit into this ….metabolism of bacteria is far more diverse …some get electrons from inorganic compounds (H2, H2S, NH3, Fe etc)…some use CO2

Question 2

Chemotroph?

Answer 2

• energy from chemical reactions e.g. oxidation of inorganic or organic compounds

Question 3

Organotroph?

Answer 3

• electrons from organic matter e.g. sugar, amino acids, fatty acids, petroleum

Question 4

Heterotroph?

Answer 4

• Carbon from organic matter e.g. sugars, amino acids, fatty acids, petroleum etc

Question 5

Phototroph?

Answer 5

• energy from light

Question 6

Lithotroph?

Answer 6

• electron from inorganic matter

eg H2, H2S, NH3, Fe

Question 7

Autotroph?

Answer 7

C from CO2

Question 8

What trophs involve energy?

Answer 8

• Chemotroph, phototroph

Question 9

What trophs involve electrons?

Answer 9

• Organotroph

- Lithotroph

Question 10

What trophs involve carbon sources?

Answer 10

• Heterotroph

- Autotroph

Question 11

What troph are humans classified as?

Answer 11

-chemo-organo-heterotrophs

Question 12

What trophs are plants classified as?

Answer 12

• photo-lito-autotrophs

* *some phototrophic bacteria are photo-organ-hetero-trophs

Question 13

Hydrogen bacteria burn __ and use ___ as carbon source

Answer 13

• H2 and use CO2
• 2H2 + O2 –>2H2O
• • H2 is an electron donor, O2 is an electron acceptor..this respiration generates ATP…

Question 14

What trophy are Hydrogen bacteria?

Answer 14

• chemo-litho-autotrophs

Question 15

How many trophy combinations are actually possible? Can you have organo-auto or litho-hetero?

Answer 15

• 6/8
• NO neither
  L> does not make sense to use organic matter for electrons and not for carbon
  L> does not make sense to use inorganic for electrons and organic for carbon

Question 16

What are the two parts of metabolism?

Answer 16

1. Catabolism

2. Anabolism

Question 17

Explain catabolism and anabolism relationship!

Answer 17

• catabolism(breaking down) supplies anabolism( biosynthesis) with ATP, NADPH if needed (if C source more oxidized than biomass)
• carbon source + ATP= ADP + Pi –> Biomass (anabolism)
• energy source= ADP+ Pi= ATP and waste (catabolism)
• *the energy and carbon source can be the same

Question 18

What is SLP?

Answer 18

• substrate level phosphorylation

Question 19

What is ETP?

Answer 19

• electron transport chain

Question 20

Chemotrophs undergo what two kinds of metabolism??

Answer 20

1. Fermentation (aerobic sometimes, anaerobic always)

2. Respiration: aerobic and anaerobic (without presence of oxygen)

Question 21

Phototrophs undergo what two kinds of metabolism??

Answer 21

• oxygenic
• anoxygenic
• like respiration but in the pop direction

Question 22

Example of SLP?

Answer 22

• glycolysis
• Oxidation of aldehyde to acid coupled t o phosphorylation of acid…transfer of phosphor group to ADP…1 ATP formed…..stoichiometric coupling. If not enough delta g in a reaction then no ATP can be made, if too much delta G, surplus is wasted….no membranes needed
• No Fe needed

Question 23

Explain the ETP respiratory chain in Paracoccus denitrificans

Answer 23

• Complex 1 NADH DH(yields 4H)
• Complex III Cyt bc (cyt reductase) yields 4H
• Complex IV Cyt aa (Cyt oxidase) yields 2H
• Complex V ATP Synthase -> yeilds ATP and 3.3H in the cytoplasm..not the periplasm
• *ETC goes from electron donor (NADH) to electron acceptor (O2)

Question 24

Explain the basic gist of ETP

Answer 24

• needs membrane to separate charge and H
• protons are pumped out through membrane
• or n protons are consumed inside and produced outside ( outside is usually higher H concentration, more positive)
• proton motive force (pmf) has two components : pH difference and membrane potential
• requires Fe
• 10 H per 3ATP (one turn of ATP synthase)
• *1 H= 0.3 ATP

Question 25

Explain Fermentation

Answer 25

- does not need oxygen but may take place in the presence of oxygen - it is energy metabolism without using any external electron acceptors such as oxygen, nitrate, sulphate, Fe ...so only part of the substrate can be oxidized and the other part has to be reduced..no net gain/loss of electrons there needs to be a balance - most form ATP via SLP but not all - or ATP via ETP but not all

Question 26

Is fermentation life without oxygen?

Answer 26

NO

Question 27

Does fermentation not use any electron transport chains?

Answer 27

NO

Question 28

Budding yeast Saccharomyces cervisiae ferments under?

Answer 28

- aerobic conditions if glucose is in excess | * *ethanol fermentation of sugars

Question 29

Yeast ethanol fermentation yields how many ATP per glucose?

Answer 29

- 2 ....alt fermentations yield more or less (1-4 ATP) more ATP if you can get rid of electrons as H2

Question 30

Do many fermentations have branched pathways?

Answer 30

- yes - high ATP branch - low ATP branch (ATP yield variable * **many fermentations use ETP

Question 31

Explain respiration!

Answer 31

- oxidation of substrate = electron donor is coupled to reduction of external electron acceptor * *Anaerobic = various other electron acceptors (NO3, Fe3+, SO4 2-, CO2 * Aerobic = just oxygen - involves ETP and SLP - 38 ATP per glucose - needs external electron acceptor - Fe is needed for cytochromes (FeS)

Question 32

Paracoccus denitrificans is a relative of what?

Answer 32

- mitochondria

Question 33

Explain phototrophs!

Answer 33

- light driven electron transport chain to generate proton motive force which drives ATP synthesis - NADPH which can be used to reduce CO2 in the dark reaction - Photons of visible light contain 100-200kJ/mol - one single photon shifts the redox potential of (Bacterio) Chlorophyll by 1-2 V more negative

Question 34

Phototrophs: | - reserving respiration with light energy??

Answer 34

- 6CO2 +6H2O --> C6H12O6 + 6O2 delta G = +2872kJ/mol - oxidizing the reduced end products of respiration: H2O, H2S, Fe2+ - oxidizing the reduced end products of fermentation: acetate, lactate, ethanol, butyrate and hydrogen

Question 35

Phototrophs: | - explain Oxygenic

Answer 35

- H2O as electron donor --> O2 | - cyanobacteria (chloroplasts in plants are these)

Question 36

Phototrophs: | - Anoxygenic?

Answer 36

- H2S as electron donor --> SO4 2- - or H2, ethanol, butyrate ... -

Question 37

Phototrophs: - Anoxygenic L> Purple bacteria??

Answer 37

- non sulfur bacteria - use organic electron donors and carbon sources....photo-organo-heterotrophs -

Question 38

Phototrophs: - Anoxygenic? L> Purple sulfur bacteria??

Answer 38

- use H2S and S as electron donor and CO2 ( or acetate) as carbon source...photo-litho-auto-trophs (if using acetate= hetero) * *Green sulfur bacteria/