High School Biology : Understanding Glycolysis

Study concepts, example questions & explanations for High School Biology

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Example Questions

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Example Question #1 : Understanding Glycolysis

Which product of glycolysis will enter the citric acid cycle?

Possible Answers:

Pyruvate

Glucose

ATP

Citric acid

Correct answer:

Pyruvate

Explanation:

The purpose of glycolysis is to generate pyruvate and NADH from glucose. The pyruvate will enter the citric acid cycle and the NADH will be used to donate a proton and electron to the electron transport chain, helping to generate the proton gradient for ATP synthesis. The first step of the citric acid cycle is the conversion of pyruvate to acetyl-CoA.

Example Question #2 : Cell Respiration

What is the primary role of lactic acid fermentation?

Possible Answers:

To create more glucose for glycolysis

To provide an intermediate for alcoholic fermentation

To create additional ATP for the cell

To provide as source of NAD+ to be used for glycolysis

Correct answer:

To provide as source of NAD+ to be used for glycolysis

Explanation:

Lactic acid fermentation occurs in the absence of oxygen, and involves an enzyme that converts pyruvate from glycolysis to lactic acid via the transfer of two hydrogen atoms from NADH and H+. The NADH is oxidized to form NAD+, a required component to catalyze glycolysis.

During anaerobic respiration the Krebs cycle and electron transport chain are not functional, leaving all cell metabolism reliant on glycolysis. Without NAD+, glycolysis would also become non-functional and cell metabolism would completely stop. Both alcoholic fermentation and lactic acid fermentation serve this purpose or replenishing glycolysis reactants, but occur in different organisms. Lactic acid fermentation is most common in animals while alcoholic fermentation occurs in unicellular organisms, such as yeast.

Example Question #3 : Understanding Glycolysis

Which of the following is produced by cellular respiration? 

Possible Answers:

Carbon monoxide

Glucose 

Oxygen 

Sulfur dioxide 

Water

Correct answer:

Water

Explanation:

Cellular respiration is the metabolic process used to generate energy, in the form of ATP, that can power cellular functions. During cellular respiration, glucose is broken down and used to generate NADP and FADH2. These molecules then donate electrons to the electron transport chain, power the proton gradient that is responsible for producing ATP through ATP synthase.

Glucose and oxygen are consumed during this process, while water and carbon dioxide are produced, along with ATP. Sulfur dioxide and carbon monoxide are not involved in the processes of cellular respiration.

Example Question #3 : Understanding Glycolysis

Which of the following molecules is not a product of glycolysis?

Possible Answers:

Pyruvate

ATP

NADH

Lactate

Correct answer:

Lactate

Explanation:

Glycolysis will split a glucose molecule into two molecules of pyruvate. This process will result in a net gain of 2 molecules of both ATP and NADH. Lactate is not a product of glycolysis, and will only be made in the event that oxygen is not available and fermentation must be used to reduce pyruvate into lactate.

Example Question #3 : Cell Respiration

Where in the cell does glycolysis take place?

Possible Answers:

The cytosol

The matrix of the mitochondria

The inner mitochondrial membrane

The nucleus

Correct answer:

The cytosol

Explanation:

Glycolysis is the first step of cellular respiration, and takes place in the cytosol. The citric acid cycle and electron transport chain are both located in the mitochondria.

Example Question #5 : Understanding Glycolysis

Which of the following statements about glycolysis are true?

Possible Answers:

At the end of glycolysis, there is a net gain of 2 ATP per glucose.

ATP in glycolysis is made via oxidative phosphorylation and ATP synthase

In glycolysis, 4 ATP were spent and 2 ATP were made.

None of these statements are true

Glycolysis takes place the mitochondria

Correct answer:

At the end of glycolysis, there is a net gain of 2 ATP per glucose.

Explanation:

In glycolysis, which takes place in the cytoplasm, 4 ATP are made and 2 ATP are spent. This means that there is a net gain of 2 ATP, which are produced via substrate level phosphorylation, which involves adding a phosphate to ADP to yield ATP.

Example Question #7 : Understanding Glycolysis

During glycolysis, what is the net gain of NADH, ATP, and pyruvate per glucose molecule?

Possible Answers:

4 NADH, 4 ATP, and 2 pyruvate

4 NADH, 2 ATP, and 1 pyruvate

2 NADH, 2 ATP, and 1 pyruvate

2 NADH, 4 ATP, and 2 pyruvate

2 NADH, 2 ATP and 2 pyruvate

Correct answer:

2 NADH, 2 ATP and 2 pyruvate

Explanation:

The overall process of glycolysis is:

The net gain of pyruvate, NADH, and ATP during glycolysis is 2 pyruvate, 2 NADH, and 2 ATP per molecule of glucose. Although the process of glycolysis yields 4 ATP, the early steps of glycolysis use 2 ATP to convert glucose into 2 phosphoglyceraldehydes (note: phosphoglyceraldehyde is a 3 carbon molecule) leading to a net gain of 2 ATP. 

Example Question #1 : Understanding Glycolysis

Which of the following reactions depicts lactic acid fermentation in animals?

Possible Answers:

Pyruvate +   Lactate + NADH + 

(under aerobic conditions)

Pyruvate + NADH +   Lactate + 

(under aerobic conditions)

Pyruvate +   Lactate + NADH + 

(under hypoxic or partially anaerobic conditions)

None of these

Pyruvate + NADH +   Lactate + 

(under hypoxic or partially anaerobic conditions)

Correct answer:

Pyruvate + NADH +   Lactate + 

(under hypoxic or partially anaerobic conditions)

Explanation:

The process of lactic acid fermentation is:

Pyruvate + NADH +   Lactate + 

(under hypoxic or partially anaerobic conditions)

Lactic acid fermentation is a biological process where pyruvate is converted into  and lactate under hypoxic conditions. It occurs in some bacterial cells, and some animal cells such as muscles. This process is catalyzed by the enzyme lactate dehydrogenase. If oxygen is present in the cell, many organisms will bypass fermentation and undergo cellular respiration.  (Fun fact: lactic acid fermentation is utilized to produce kimchi, sauerkraut, and yogurt). Animal muscle cells will undergo lactic acid fermentation, when starved of oxygen. This process is a last resort for energy and cannot be tolerated for long periods of time.

Example Question #2 : Understanding Glycolysis

Where does glycolysis take place in eukaryotic cells?

Possible Answers:

Matrix of mitochondria

Cytosol

Outer membrane of mitochondria

Inner membrane of mitochondria

The phospholipid bilayer

Correct answer:

Cytosol

Explanation:

The process of glycolysis (glucose to pyruvate) occurs in the cytosol.

Once formed, pyruvate can have numerous fates. In yeasts it can remain in the cytosol and undergo alcoholic fermentation. Pyruvate can also undergo lactic acid fermentation (under hypoxic conditions) within the cytosol of red blood cells and active muscles. Additionally, pyruvate can undergo cellular respiration in the mitochondria where it is oxidized completely into carbon dioxide and water. 

Example Question #3 : Understanding Glycolysis

Which of the following best describes where the energy comes from that drives the formation of ATP from ADP and inorganic phosphates?

Possible Answers:

Dehydroxylation 

None of these

Anabolism

Catabolism

Decarboxylation

Correct answer:

Catabolism

Explanation:

Energy from catabolism—exergonic or energy-yielding processes—is used to drive the formation of ATP from ADP and inorganic phosphate because ATP formation requires energy to be made. Catabolism is a pathway, which breaks down a larger molecule into smaller ones. Glycolysis is an example of a catabolic pathway.

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