The Muscle Burn: Lactic Acid Fermentation Explained

7th Grade

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| By Thames

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| Questions: 20 | Updated: Mar 8, 2026

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1. What is the primary reason your body performs lactic acid fermentation during a fast sprint?

To provide energy when oxygen levels are low

To help the lungs take in more air

To cool down the body temperature

To turn protein into sugar

To help you sleep better

If you are running very fast, then your muscles use oxygen quicker than you can breathe it in. If oxygen is missing, then the cell switches to lactic acid fermentation to keep making energy.

Explanation

If you are running very fast, then your muscles use oxygen quicker than you can breathe it in. If oxygen is missing, then the cell switches to lactic acid fermentation to keep making energy.

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About This Quiz

The Muscle Burn: Lactic ACID Fermentation Explained - Quiz

Push your muscles hard enough and they will keep contracting even when oxygen cannot be delivered fast enough to sustain aerobic respiration, and the molecule that makes that possible is lactic acid. Lactic acid fermentation explained covers how pyruvate accepts electrons from NADH during intense exercise, regenerating the NAD+ that... see moreglycolysis needs to keep producing ATP without oxygen. The same pathway that burns in your legs during a sprint also gives yogurt its tang. How well do you understand the biochemical steps of lactic acid fermentation, why it is a short-term energy solution rather than a sustainable one, and the connection between fermentation products and the foods and biotechnology applications that depend on them? see less

2. Lactic acid fermentation is a type of aerobic respiration.

True

False

If a process is "aerobic," then it requires oxygen. If lactic acid fermentation happens specifically when oxygen is not available, then it is classified as anaerobic, not aerobic.

Explanation

If a process is "aerobic," then it requires oxygen. If lactic acid fermentation happens specifically when oxygen is not available, then it is classified as anaerobic, not aerobic.

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3. The starting material for both regular respiration and ______ is a simple sugar called glucose.

If a cell needs to make energy (ATP), then it must break down a fuel source. If glucose is the most common fuel for cells, then it is the starting point for this fermentation process.

Explanation

If a cell needs to make energy (ATP), then it must break down a fuel source. If glucose is the most common fuel for cells, then it is the starting point for this fermentation process.

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4. Which of these foods is created by bacteria using lactic acid fermentation?

Yogurt

Bread

Apple juice

Steak

Popcorn

If certain bacteria eat the lactose sugar in milk and release acid, then the milk thickens and becomes tart. If this specific change occurs, then the resulting food is yogurt.

Explanation

If certain bacteria eat the lactose sugar in milk and release acid, then the milk thickens and becomes tart. If this specific change occurs, then the resulting food is yogurt.

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5. Which of the following are common products or results of lactic acid fermentation in a cell?

ATP (energy)

Lactic acid

Carbon dioxide gas

Oxygen

Glucose

If the cell breaks down glucose without oxygen, then it produces a small amount of energy and the chemical byproduct lactic acid. However, unlike yeast, this specific process in muscles and yogurt bacteria does not produce carbon dioxide gas.

Explanation

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6. When lactic acid builds up in your muscles, it often causes a temporary ______ sensation.

If the environment inside your muscle tissue becomes more acidic due to the waste from lactic acid fermentation, then your nerves send a signal of discomfort. If this signal is felt during exercise, then it is experienced as a "burn."

Explanation

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7. The amount of energy (ATP) produced by lactic acid fermentation is much lower than the energy produced using oxygen.

True

False

If oxygen allows a cell to fully break down sugar, then it releases a lot of energy. If lactic acid fermentation only partially breaks down the sugar, then the cell receives a much smaller "emergency" amount of energy.

Explanation

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8. In what part of the cell does lactic acid fermentation take place?

Cytoplasm

Mitochondria

Nucleus

Cell Wall

Vacuole

If the mitochondria require oxygen to function and this process happens without oxygen, then it cannot happen in the mitochondria. If the process must stay in the main jelly-like fluid of the cell, then it happens in the cytoplasm.

Explanation

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9. Why does yogurt have a sour or tangy taste?

Because of the acid produced during the fermentation process

Because of the sugar added by the bacteria

Because the milk is spoiled and rotten

Because the container is made of plastic

Because it is kept in a cold fridge

If bacteria perform lactic acid fermentation, then they release an organic acid as waste. If acids naturally taste sour to humans, then the presence of lactic acid makes the yogurt tangy.

Explanation

If bacteria perform lactic acid fermentation, then they release an organic acid as waste. If acids naturally taste sour to humans, then the presence of lactic acid makes the yogurt tangy.

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10. Bacteria like ______ are the primary organisms used by humans to turn milk into yogurt through fermentation.

If a specific group of bacteria is named after their ability to produce "lactic" acid from "bacillus" shaped cells, then that group is Lactobacillus.

Explanation

If a specific group of bacteria is named after their ability to produce "lactic" acid from "bacillus" shaped cells, then that group is Lactobacillus.

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11. Which of the following are examples of "anaerobic" activities where your body might use lactic acid fermentation?

Sprinting 100 meters

Lifting a very heavy weight

Sleeping in a bed

Walking slowly through a park

Doing a high-intensity "burst" of jumping jacks

If an activity is so intense that you cannot keep up with the oxygen demand, then it is anaerobic. Short, powerful bursts of movement fit this description, while resting or slow walking do not.

Explanation

If an activity is so intense that you cannot keep up with the oxygen demand, then it is anaerobic. Short, powerful bursts of movement fit this description, while resting or slow walking do not.

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12. After you stop exercising, your body eventually breaks down the extra lactic acid in the liver.

True

False

If the exercise ends and you breathe deeply, then oxygen returns to the tissues. If oxygen is available, then the liver can convert the waste from lactic acid fermentation back into useful molecules or energy.

Explanation

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13. How does the production of lactic acid help the process of making cheese?

It causes the milk proteins to clump together (curdle)

It makes the cheese glow in the dark

It turns the cheese into a liquid

It prevents the cheese from ever getting old

It makes the cheese taste like chocolate

If lactic acid fermentation lowers the pH of the milk, then the proteins change shape. If the proteins change shape and stick together, then the milk curdles, which is the first step in making cheese.

Explanation

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14. The term "anaerobic" literally means "without ______."

If the Greek root "an-" means without and "aer" means air/oxygen, then any anaerobic process like ______ is performed without the use of air.

Explanation

If the Greek root "an-" means without and "aer" means air/oxygen, then any anaerobic process like ______ is performed without the use of air.

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15. If a cell had plenty of oxygen available, would it normally choose to perform lactic acid fermentation?

No, because using oxygen produces much more energy

Yes, because it is faster

No, because it prefers to make carbon dioxide

Yes, because it tastes better

It depends on the time of day

If a cell is "efficient," then it wants the most energy for its effort. If aerobic respiration provides roughly 18 times more energy than lactic acid fermentation, then the cell will always choose the oxygen path if possible.

Explanation

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16. Which of these foods are often preserved using the acid from lactic acid fermentation?

Pickles

Sauerkraut

Kimchi

Fresh apples

Raw carrots

If the acid produced by bacteria makes it hard for "bad" mold and germs to grow, then it acts as a preservative. Foods like pickles, sauerkraut, and kimchi are all made by allowing this fermentation to happen under controlled conditions.

Explanation

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17. Lactic acid fermentation produces exactly 2 molecules of ATP for every 1 molecule of glucose.

True

False

If the process only goes through the initial steps of glycolysis to get energy, then it follows the math of that pathway. If glycolysis yields a net gain of 2 energy units, then that is the total produced.

Explanation

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18. While humans produce lactic acid, yeast cells produce ______ and carbon dioxide during their version of fermentation.

If different organisms have different enzymes, then they make different waste products. If yeast perform alcoholic fermentation, then they produce ethanol (alcohol) instead of lactic acid.

Explanation

If different organisms have different enzymes, then they make different waste products. If yeast perform alcoholic fermentation, then they produce ethanol (alcohol) instead of lactic acid.

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19. What is "oxygen debt"?

The amount of oxygen needed to clear out the lactic acid after exercise

The cost of buying an oxygen tank

When a cell has too much oxygen

A type of bank loan for scientists

When you hold your breath underwater

If you use up your oxygen during a sprint and rely on lactic acid fermentation, then you have a "shortage" to make up. If you huff and puff after the race to get your levels back to normal, then you are paying back your oxygen debt.

Explanation

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20. Final summary: Which statement best describes the role of lactic acid fermentation in nature?

It is a biological backup plan for making energy when oxygen is missing

It is the main way all animals breathe

It is a process that only happens in factories

It is the way plants make their food from sunlight

It is a process that destroys all energy in a cell

If the goal is survival and oxygen is the primary fuel-enhancer, then anything else is a secondary option. If fermentation allows life to continue when the primary fuel-enhancer is gone, then it is a backup plan.

Explanation

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