Lecture 12: Respiration and Fermentation

Question 1

How does bacterial respiration work?

How is this different to fermentation?

Answer 1

1. Molecule X outside the cell enters and
   is oxidized = energy release
2. Molecule Y outside the cell enters
   and is reduced = energy release

FERMENTATION
1. Molecule X outside the cell enters and 
    is oxidized = energy release
2. THERE IS NO Y
3. Molecule X needs to be converted to 
    something else that can THEN be 
    reduced

Question 2

What are the three glucose metabolic pathways? What is their end products?

Answer 2

1. Glycolysis
2. Pentose phosphate pathway
3. Entner-Doudoroff pathway

“Pyruvate”
- NADPH used specifically for anabolic
reactions

Question 3

What is the result of the PPP

Answer 3

1. 2x NADPH (for synthesis)
2. glycolysis intermediates (Glyceraldehyde
   3-phosphate
3. Ribose 5-phosphate (biosynthetic
   intermediate for nucleotides)
4. Anabolic pathway compared to
   glycolysis
   a. 2 NADPH
   b. 1 ATP
   c. 1 NADH

Question 4

How is ATP generated in fermentation

Answer 4

1. No outside electron acceptors involved;
   no membrane or e- transport system req.;
   no ATP synthase needed
2. “Metabolism where E is derived from
   partial oxidation of an organic compound
   using organic intermediates as electron
   donors and acceptors
3. ALL ATP PRODUCED BY SUBSTRATE
   LEVEL PHOSPHORYLATION
   a. transfer of a Pi back onto an ADP

Question 5

How do different bacteria carry out fermentation?

Answer 5

1. Lactic acid bacteria: Gram-positive
   bacteria that ferment sugars (glucose)
   with lactic acid as major producta. lactobacilli - relatively acid tolerant
   (grow at pH4), so change the
   environment to something they can
   survive but other organisms cant.
   NON-PATHOGENIC, ACID KILLS
   OTHERS
   b. Streptococcus

Question 6

How does yeast generate energy?

Answer 6

ETHANOL FERMENTATION

1. Low [glucose], high [oxygen] = “pasteur
   effect” - fermentation suppressed
2. High [glucose], low [oxygen] = “crabtree
   effect” - aerobic respiration suppressed

2 pyruvate -> 2 acetaldehyde -> 2 ethanol

ETHANOL PRODUCTION SERVES TO KILL OTHER COMPETING BACTERIA

Question 7

What do bacteria do when there is no oxygen?

Answer 7

1. Metal respiration
2. Denitrification
3. sulphate respiration
4. fumarate respiration
5. sulphur respiration
6. methanogenesis

Question 8

What do bacteria do when there is no oxygen?

Answer 8

1. Metal respiration
2. Denitrification
3. sulphate respiration
4. fumarate respiration
5. sulphur respiration
6. methanogenesis

Question 9

How does the nitrogen cycle work?

Answer 9

1. NH4+ (organic nitrogen)
2. nitrification (NH2OH)
3. NO2- (nitrate)
4. Denitrification (NO-> N2O)
5. Fixation (N2-> NH4+) (organic)

Question 10

What are the different nitrogen cycle pathways?

Answer 10

1. Nitrification (aerobic)
   a. Nitrate to nitrite
   b. Nitrite to NO3-
2. Denitrification (anaerobic)