31 Questions
Where do the electrons come from in microbial metabolism?
All of the above
What is the ultimate terminal electron acceptor in metabolism?
Oxygen
What is the most common source of carbon metabolism but not in phototrophs?
Glucose
During metabolism, where are reduced electron carriers such as NADH generated?
Glycolsis
Where do the electrons go in the absence of oxygen or other terminal electron acceptor?
Ethanol
What type of phosphorylation occurs during glycolysis?
Substrate level phosphorylation
What can be produced from pyruvate in fermentation?
All of the above
What are the main fermentation products mentioned in the text?
Lactic acid and ethanol
What is the utility of lactic acid in food production?
Food preservative and flavor enhancer
What specific fermentation product is mentioned in relation to Saccharomyces?
Ethanol
Which of the following is true about Lactobacillus?
All of the above
Which bacteria is responsible for the fermentation of milk into cheese?
Streptococcus
Which bacteria is responsible for the tangy flavor in sausages?
Brevibacterium
Which bacteria is added to curd to produce blue cheese?
Penicillium roqueforti
Which bacteria is responsible for the production of proprionic acid and CO2 in Swiss cheese?
Propionibacterium
What accompanies the acid production during the fermentation of sauerkraut?
Carbon dioxide
Which bacteria succeeds Leuconostoc during the fermentation of sauerkraut?
Lactobacillus
Which bacteria are homofermentative?
Lactobacillus
Which of the following is the final electron acceptor in fermentation?
Pyruvic acid
During fermentation, how many ATP molecules are produced for each molecule of glucose?
2
What happens to the excess NADH produced during fermentation?
It is recycled back to NAD+
What is the main energy generation process in fermentation?
Substrate-Level Phosphorylation (SLP)
What is the final step in yeast fermentation of glucose to ethanol?
Conversion of acetaldehyde to ethanol
What is the organism responsible for most vaginal yeast infections?
Candida albicans
What may cause a change in the normal balance of yeast cells in the vagina, leading to a yeast infection?
All of the above
What is the temperature at which Candida albicans grows as a harmless commensal?
37°C
What can enhance the adhesion of Candida albicans to denture resin?
High sugar levels in the diet
Mixed fermentation is a characteristic of which taxonomic group?
enterics
Which of the following is responsible for the distinctive flavour of Swiss cheese?
propionate
In anaerobic conditions, some cells can use fermentation to generate more glucose from glycolosis?
False
One difference between homofermenters and heterofermentors is that homofermentor:
produce just lactic acid
Study Notes
Microbial Metabolism
- Electrons in microbial metabolism come from reduced electron carriers such as NADH, which are generated during glycolysis
- The ultimate terminal electron acceptor in metabolism is oxygen (in aerobic conditions) or other electron acceptors (in anaerobic conditions)
Carbon Metabolism
- The most common source of carbon metabolism, excluding phototrophs, is glucose
Fermentation
- In the absence of oxygen or other terminal electron acceptors, electrons are passed to organic molecules, resulting in fermentation
- Substrate-level phosphorylation occurs during glycolysis
- Pyruvate can be converted to lactic acid, ethanol, or other fermentation products
- Main fermentation products mentioned in the text include lactic acid, ethanol, and CO2
- Lactic acid is used in food production, such as in yogurt and sauerkraut
- Saccharomyces is associated with ethanol production
- Lactobacillus is involved in the fermentation of milk into cheese and is responsible for the tangy flavor in sausages
- Propionibacterium is responsible for the production of propionic acid and CO2 in Swiss cheese
Fermentation Microorganisms
- Leuconostoc is involved in the fermentation of sauerkraut, succeeded by Lactobacillus
- Homofermentative bacteria, such as Lactobacillus, produce lactic acid as the only or main fermentation product
- The final electron acceptor in fermentation is an organic molecule, such as pyruvate or acetaldehyde
- 2 ATP molecules are produced for each molecule of glucose during fermentation
- Excess NADH produced during fermentation is reoxidized to NAD+
Yeast Fermentation
- Candida albicans is the organism responsible for most vaginal yeast infections
- Changes in the normal balance of yeast cells in the vagina can lead to yeast infections
- Candida albicans grows as a harmless commensal at a temperature of 37°C
- Chitin enhances the adhesion of Candida albicans to denture resin
- The final step in yeast fermentation of glucose to ethanol is the reduction of acetaldehyde to ethanol
Mixed Fermentation
- Mixed fermentation is a characteristic of the Enterobacteriaceae taxonomic group
Test your knowledge of microbial metabolism and fermentation in this quiz. Explore the catabolic diversity of prokaryotes and learn about the roles of Lactobacilli and Saccharomyces in cheese, sauerkraut, and ethanol production. Discover the key factors involved in electron transportation during fermentation.
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