6. How Microbes Obtain Energy

Question 1

Glucose eventually becomes what under AEROBIC conditions? ANAEROBIC?

Answer 1

Aerobic - pyruvate

Anaerobic - lactic acid

Question 2

Important step that occurs during homolactic/heterolactic fermentation?

Answer 2

NADH oxidizes to NAD+

Question 3

Difference between homo- vs heterolactic fermetnation?

Answer 3

Homolactic = only lactate produced

Heterolactic = lactate + ethanol + CO2 produced

Question 4

Example of genus that undergoes lactic acid fermentation?

Answer 4

Lactobacillus => yogurt fermentation

Question 5

Definition of fermentation?

Answer 5

An energy yielding process in which an organic molecule is oxidized WITHOUT an exogenous electron acceptor

Question 6

During fermentation a microbe will often use _______ or a ________ derivative as the e- acceptor

Answer 6

pyruvate; pyruate acceptor

Question 7

Fermentation - 3 fates for pyruvate?

Answer 7

Lactic acid, formic acid, ethanol

Question 8

After NADH is oxidized to NAD+, where does NAD+ go?

Answer 8

Back to glycolysis to make ATP

Question 9

What molecule goes into mixed acid fermentation? Products of it?

Answer 9

Pyruvate

Ethanol, CO2, lots of mixed organic acids (succinic, formic, lactic acid)

Question 10

2 microbes that can perform mixed acid fermentation?

Answer 10

Salmonella, E.coli

Question 11

Why is fermentation NOT considered biochemical respiration?

Answer 11

No ETC used

Question 12

Fermentation - ATP is generated by ________________

Answer 12

substrate-level phosphorylation

Question 13

How do some microbes generate energy using the ETC even though oxygen is absent?

Answer 13

Use inorganic molecule other than oxygen to accept electrons

Question 14

Difference between aerobic and anaerobic respiration?

Answer 14

Aerobic - uses O2 as terminal e- acceptor

Anaerobic - DOESN’T use O2 as terminal e- acceptor

Question 15

Organisms that obtain energy and e- from reduced inorganic molecules are called __________

Answer 15

chemolithotrophs

Question 16

Why are facultative anaerobes also important in ruminant guts?

Answer 16

Use up any O2 that diffuses across rumen epithelium from the cow

Question 17

Volume of saliva cows use per day for digestion?

Answer 17

100 L

Question 18

Grass has Beta(__->__) linked glucose polymers so they must use ________ to cleave the linkages

Answer 18

B(1->4)

microbes

Question 19

Microbial enzymes that break down grass polymers?

Answer 19

Beta-amylases, cellulases, pectinases

Question 20

Ruminant guts: products of fermentation, acetogenesis, methanogenesis?

Answer 20

Fermentation: organic acids (propionic acid, butyric acid)

Acetogenesis: acetic acid, H2, CO2

Methanogensis: methane

Question 21

Energy sources for foraging ruminants?

Answer 21

Organic acids and microbial biomass from microbes

Question 22

Why is grass a poor nutrient source?

Answer 22

Mostly made of cellulose

Question 23

4 types of energy generating pathways?

Answer 23

1. Fermentation
2. Aerobic respiration
3. Anaerobic respiration
4. Chemolithotrophy

Question 24

Energy generating pathways that use sugars, amino acids, fatty acids as e- donors?

Answer 24

Fermentation, aerobic, anaerobic

Question 25

Electron acceptor(s) in each of the 4 energy generating pathways?

Answer 25

Fermentation - pyruvate/pyruv derivatives

Aerobic - O2

Anaerobic - CO2, NO3-, SO42-

Chemolithotrophy: O2, NO3-

Question 26

Important molecule that is generated as pyruvate accepts electrons from a e- donor?

Answer 26

NADH

Question 27

Electron donors in chemolithotrophy?

Answer 27

All inorganic: NH3+/H2/H2S/S0

Question 28

No oxygen is needed as a terminal e- acceptor in fermentation so they usually occur under ________ conditions

Answer 28

anoxic

Question 29

2 types of formic acid fermentation?

Answer 29

Mixed acid fermentation

Butanediol fermentation

Question 30

In mixed acid fermentation, the presence of ________ (enzyme) degrades formic acid to ____ + _____

Answer 30

formic hydrogenlyase

H2 + CO2

Question 31

In butanediol fermentation, pyruvate is converted to ______ + _________ + small amounts of organic acids

Answer 31

acetoin + butanediol