Fermentation & Respiration Processes

During fermentation, what molecule donates electrons to pyruvate?

NADH (or NADPH)

What are the common byproducts of fermentation?

Alcohols, carboxylates, hydrogen (H2), and carbon dioxide (CO2)

Do fermentation processes produce extra ATP beyond glycolysis?

No, they primarily regenerate NAD+ for continued glycolytic metabolism.

How do microbes adapt to limited ATP production in fermentation?

By consuming large amounts of substrates and excreting large volumes of byproductsto optimize energy extraction and maintain metabolic functions.

What type of phosphorylation generates ATP in glycolysis?

Substrate-level phosphorylation

Besides ATP, what other intermediates are produced during glycolysis? 

Water (H2O) and phosphoenolpyruvate (PEP)

What does alcoholic fermentation produce?

Ethanol and carbon dioxide (CO2)

What does homolactic fermentation produce?

2 lactic acid

What does ethanolic fermentation produce?

2 ethanol and 2 CO2

What does heterolactic fermentation produce? 

1 lactic acid, 1 ethanol, and 1 CO2

What are the products of mixed-acid fermentation?

Acetate, formate, lactate, succinate, ethanol, H2 and CO2

What does the Phenol Red Broth test detect?

The fermentation of sugars

What does the Sorbital MacConkey Agar test differentiate?

Pathogenic E.coli O157:H7 (fails to ferment sorbitol) from nonpathogenic strains.

What does a red color in the Methyl Red test indicate? 

Mixed-acid fermentation pathway (pH < 4.4)

What does a yellow color in the Methyl Red test indicate?

Not a mixed-acid fermentation (pH > 6.2)

What does the Voges-Proskauer test detect?

Butylene glycol fermentation and acetoin production

What indicates a positive Voges-Proskauer result?

Deep red color

What indicates a negative Voges-Proskauer result?

a copper color

Why do cells need energy?

To build structures from simple molecules

What are the main carriers in metabolism?

ATP, NADH, and FADH2

What are the three main types of catabolic pathways?

Fermentation, respiration, and photoheterotrophy

Which catabolic pathway concludes glucose catabolism without an electron transport chain? 

Fermentation

What does the Entner-Doudoroff pathway produce?

1 ATP, 1 NADH, and 1 NADPH

What does the pentose-phosphate pathway produce?

2 NADH and ribose-5-phosphate

What happens to pyruvate before entering the TCA cycle?

It is converted into acetyl-CoA by the pyruvate dehydrogenase complex.

What is produced during the conversion of pyruvate to acetyl-CoA? 

1 NADH and 1 CO2 per pyruvate

What is the overall function of the TCA cycle?

To oxidize pyruvate to CO2 and generate NADH/FADH2 for the electron transport chain

What types of molecules can enter central metabolism as carbon sources?

Polysaccharides, carbohydrates, lipids, and aromatics

When is the glyoxylate bypass used?

When glucose is scarce; microbes metabolize acetate or fatty acids

What are the advantages of the glyoxylate bypass?

Minimizes CO2 loss and produces 2 NADH and 1 FADH2

Why is the glyoxylate shunt important for Mycobacterium tuberculosis?

It allows persistence in host tissues by enabling long-term survival in macrophages

What does the TCA cycle begin with? 

The formation of acetyl-CoA from pyruvate

Where does the TCA cycle occur in prokaryotes and eukaryotes?

Prokaryotes: Cytoplasm

Eukaryotes: Mitochondria

How does acetyl-CoA enter the TCA cycle? 

by combining with oxaloacetate to form citrate

What enzyme complex catalyzes the conversion of pyruvate to acetyl-CoA?

Pyruvate Dehydrogenase Complex

How many ATP are generated per NADH in prokaryotes (theorectical yield)?

2.5 ATP

How many ATP are generated per FADH2 in prokaryotes (theorectical yield)?

1.5 ATP

What is the theorectical maximum ATP yield per glucose?

38 ATP in prokaryotes and 36 ATP in eukaryotes.

Why is there variation in ATP yield among bacteria?

Depends on oxygen availability and carbon source availability

What can prokaryotes use as terminal electron acceptors besides oxygen? 

metals, oxidized ions of nitrogen and sulfur

In what environments does anaerobic respiration occur?

environments lacking oxygen, such as wetland soil and the human digestive tract

What is the transition step?

pyruvate converted into acetyl-CoA before entering the citric acid cycle.

How many total electron carriers are produced per glucose? (Before ETC)

10 NADH ( 2 glycolysis + 2 transition + 6 TCA) 

2 FADH (TCA)

From the transition step, how many NADH are generated? 

2 NADH ( 1 pyruvate= 1 NADH, so 2 pyruvate = 2 NADH)

From the TCA cycle, how many electron carriers are generated?

6 NADH and 2 FADH2 (the TCA cycles twice for each glucose molecule)

In F1F0 ATP synthase, where is F0 located and what does it do?

embedded in the membrane and pumps proteins

In F1F0 ATP synthase, where is F1 located and what does it do?

Protrudes in the cytoplasm and generates ATP

What powers ATP synthase? 

The proton motive force (PMF)

How many protons are pumped per NADH and per FADH2?

NADH: 10 protons

FADH: 6 protons

How many ATP does 1 NADH yield and 1 FADH2 yield?

NADH: 2.5

FADH2: 1.5

How many ATP are generated from substrate-level phosphorylation? 

4 ATP

How many ATP are generated from oxidative phosphorylation? 

34 ATP

What is the theoretical maximum ATP yield per glucose in prokaryotes?

38 ATP

What is the theoretical maximum ATP yield in eukaryotes?

36 ATP