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Questions and Answers
What is the primary process that occurs during fermentation?
What is the role of adenosine triphosphate (ATP) in fermentation?
How does fermentation differ from aerobic respiration?
Which of the following microorganisms is known to prefer fermentation even when oxygen is present?
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What compound is produced from pyruvate during the fermentation process?
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Which of the following statements is FALSE regarding fermentation?
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What is the first step of both fermentation and cellular respiration?
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What is the primary scientific study of fermentation called?
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Which bacteria is primarily responsible for causing strep throat and rheumatic fever?
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What is the primary fermentation product of strictly homofermentative bacteria?
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Which type of lactic acid bacteria can survive in environments with 6.5% NaCl?
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What distinguishes the genera Streptococcus from Leuconostoc?
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What is the function of dextran in a medical context?
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Which of the following classes of lactic acid bacteria are recognized as forming pairs or chains?
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Which of these lactic acid bacteria is commonly used in yogurt production?
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Which species of yeast is commonly referred to as 'sugar fungus'?
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What is the primary product of lactic acid fermentation?
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Which enzyme is responsible for the conversion of pyruvate to lactic acid?
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What type of fermentation is characterized by the production of multiple end products?
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During intense exercise, what causes muscle fatigue?
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What are the two main substances produced during ethanol fermentation?
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How does lactic acid fermentation contribute to food preservation?
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Which of the following foods is NOT typically made using lactic acid fermentation?
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Which type of fermentation is primarily used in the production of sour vinegar?
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What is produced alongside carbon dioxide during the fermentation process by Saccharomyces cerevisiae?
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Which type of yeast strain is commonly referred to as top-fermenting in brewing?
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What role does temperature play in the fermentation process of Saccharomyces cerevisiae?
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What type of aromas can be produced by Saccharomyces cerevisiae during fermentation?
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What makes nutritional yeast a valuable dietary addition?
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What process occurs when Saccharomyces cerevisiae is used in winemaking?
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Which of the following vitamins is NOT mentioned as being present in Saccharomyces cerevisiae?
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What initial sugar source does yeast ferment during the bread-making process?
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What is the primary role of molds in fermented food?
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Which of the following enzymes is secreted by Aspergillus oryzae?
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During which phase do microorganisms adapt to their environment before fermentation begins?
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What happens to the growth rate of microorganisms during the Stationary Phase?
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What types of raw materials can protease decompose during fermentation?
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Which source do amylase and glucoamylase utilize for their action?
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Which of the following is NOT a typical phase of fermentation?
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What substances do small molecular sugars produced during fermentation primarily promote?
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Study Notes
Fermentation
- A metabolic process by which microorganisms, like yeasts, molds, and bacteria, transform food and beverages, enhancing flavor, preservation, and health benefits.
- Derived from the Latin verb "fervere," meaning "to boil," but fermentation occurs without heat.
- Organisms convert starch or sugars into alcohol or acid anaerobically, releasing energy
- The scientific study of fermentation is "zymology".
How Fermentation Works
- Microorganisms obtain energy from carbohydrates, primarily sugars like glucose, for their activities.
- ATP (adenosine triphosphate) provides energy to cells.
- Respiration is the mechanism by which microbes generate ATP.
- Aerobic respiration, requiring oxygen, is the most efficient ATP production method.
- Glycolysis is the initial step of aerobic respiration, where glucose is converted into pyruvic acid.
- Anaerobic respiration occurs when oxygen is limited.
- Fermentation differs from anaerobic respiration by producing various organic molecules, like lactic acid, which also generate ATP.
- Cells can switch between aerobic and anaerobic energy production depending on environmental conditions.
Process of Fermentation
- Begins with glycolysis, the same as cellular respiration, converting glucose into pyruvic acid, producing 2 ATP molecules.
- Pyruvic acid is then reduced to lactic acid, ethanol, or other products.
- NAD+ is formed during this process and recycled back in the glycolysis process.
- Fermentation happens in the absence of oxygen (anaerobic conditions) and with beneficial microorganisms like yeasts, molds, and bacteria.
- Some yeast cells, like Saccharomyces cerevisiae, favor fermentation over aerobic respiration, even when oxygen is present.
Types of Fermentation
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Lactic acid fermentation: Starches or sugars are converted into lactic acid by bacteria and yeasts, without heat.
- Lactic acid bacteria are essential for producing and preserving foods, particularly for impoverished populations.
- Creates foods like sauerkraut, pickles, kimchi, yogurt, and sourdough bread.
- Also occurs in human muscle cells during strenuous activity, causing lactic acid buildup and muscle soreness.
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Ethanol fermentation / Alcohol fermentation: Yeasts break down pyruvate from glucose metabolism, producing ethanol and carbon dioxide.
- Used in wine and beer production.
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Acetic acid fermentation: Starches and sugars from grains and fruit ferment into vinegar and condiments.
- Some bacteria produce dextran, a polysaccharide that can be used in medicine and biotechnology.
Yeast
- Saccharomyces cerevisiae is a common yeast strain used in various fermentation processes.
- In bread making, it ferments sugars in flour, producing carbon dioxide (for volume and texture) and alcohol (evaporated during baking).
- It also produces aromatic compounds contributing to bread flavor.
- Yeast is a key ingredient in brewing and winemaking, transforming barley/wheat into beer and grapes into wine.
- Different yeast strains affect flavor profiles in brewing and winemaking, including fermentation aromas (fruity, peach, rose) and varietal aromas specific to grape varieties.
- Nutritional yeast, often made from Saccharomyces cerevisiae, is used in dietary supplements, seasonings, and functional foods.
- A good source of protein, fiber, and B vitamins.
Molds
- Relatively few molds are involved in fermented food and beverages, including Actinomycetes, Mucor, Rhizopus, Amylomyces, Monascus, Neurospora, Aspergillus, and Penicillium.
- Molds produce enzymes like protease, amylase, glutamidase, pectinase, hemicellulase, and cellulase for breaking down carbohydrates and proteins.
- They contribute to flavor, texture, and nutritional value in various fermented foods.
Stages and Conditions for Successful Fermentation
- Inoculation and Lag Phase: Microorganisms are introduced to the substrate (e.g., milk, dough), and adapt to the environment before active fermentation begins.
- Exponential Growth Phase: Microorganisms rapidly multiply and break down substrates, leading to significant changes. This stage requires optimal conditions like temperature, pH, and oxygen levels.
- Stationary and Decline Phases: Growth slows down due to nutrient depletion and waste accumulation, leading to product stabilization.
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Description
Explore the fascinating process of fermentation, where microorganisms such as yeasts and bacteria transform food and beverages. This quiz delves into how these organisms convert sugars into alcohol or acid and the science of zymology. Understand the differences between fermentation and anaerobic respiration, as well as the energy production methods involved.
