MCAT Biology : Glycolysis

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

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Example Question #1 : Biochemistry And Metabolism

Which cell in the human body only uses glycolysis for ATP production?

Possible Answers:

Neuron

Myocyte

Hepatocyte

Erythrocyte

Correct answer:

Erythrocyte

Explanation:

Erythrocytes (red blood cells) have no mitochondria, and thus cannot use oxidative phosphorylation to produce additional ATP from pyruvate derived from glycolysis.

Liver cells (hepatocytes), neurons, and muscle cells (myocytes) can derive some ATP from glycolysis, but then feed the resulting pyruvate into the Krebs cycle in the mitochondria for additional energy production.

Example Question #1 : Glycolysis

Which of the following biological processes will occur under both aerobic and anaerobic conditions in humans?

Possible Answers:

Fermentation

Glycolysis

Citric acid cycle

Krebs cycle

All of the these processes occur in both environments

Correct answer:

Glycolysis

Explanation:

The correct answer is glycolysis. Fermentation is a pathway that requires anaerobic conditions to activate. The citric acid cycle and Krebs cycle are two terms for the same process, and require aerobic conditions to proceed. Glycolysis has pathways that account for situations both in the presence and absence of oxygen.

Example Question #2 : Glycolysis

Which statement about glycolysis is correct?

Possible Answers:

Three molecules of NADH2 and one molecule of FADH2 are produced

 

Two net molecules of ATP are produced through substrate-level phosphorylation

Glycolysis cannot proceed under anaerobic conditions

Resulting pyruvate molecules are always directly incorporated into the Krebs cycle

A proton gradient is established across the mitochondrial membrane

Correct answer:

Two net molecules of ATP are produced through substrate-level phosphorylation

Explanation:

In glycolysis, four ATP molecules made from each unit of glucose, however, two ATP molecules are used during this process, so the net result of one round of glycolysis is two ATP molecules. These products are made via substrate-level phosphorylation, a process in which a phosphorylated molecule transfers its phosphate to ADP or GDP (producing ATP or GTP).

The other choices are incorrect. Three NADH2 and one FADH2 are made in one round of the Krebs cycle, not glycolysis. Glycolysis is an anaerobic process and takes place in the cytoplasm, not the mitochondria. Finally, pyruvate products do not necessarily have to enter the Krebs cycle—they can be metabolized anaerobically if insufficient oxygen is present.

Example Question #2 : Glycolysis

Which of the following is a product of glycolysis?

Possible Answers:

Glucose

Acetyl CoA

NADH

O2

GTP

Correct answer:

NADH

Explanation:

In glycolysis, one glucose molecule and two NAD+ molecules yield two molecules of pyruvate, two molecules of ATP, and two molecules of NADH.

Acetyl CoA is formed from pyruvate at the beginning fo the Krebs cycle. GTP is a product of the Krebs cycle. Oxygen and glucose are both reactants in metabolic processes that are derived from external intake (respiration and digestion).

Example Question #3 : Glycolysis

Given the process of glycolysis, which of the following would serve to allosterically inhibit the rate of glycolysis?

Possible Answers:

Increased oxygen

Increased glucose

Increased ATP

Decreased ATP

Increased fructose

Correct answer:

Increased ATP

Explanation:

The product of glycolysis is ATP, and each cycle gives a net of two ATP, thus if there were already high levels of ATP in the body, glycolysis would not have to occur as frequently since the body's energy demands are already being met. High levels of ATP would serve as an allosteric inhibitor.

Decreased ATP and increased glucose would increase the rate of glycolysis. Increased oxygen or fructose may indirectly increase the rate of glycolysis, depending on other cellular factors.

Example Question #4 : Glycolysis

Which of the following products is not created by glycolysis?

Possible Answers:

Pyruvate

ATP

NADH

Lactic acid

Correct answer:

Lactic acid

Explanation:

Glycolysis is the first step of cellular respiration. It is responsible for the production of two ATP molecules, two pyruvate molecules, and two NADH molecules. Lactic acid is a byproduct of anaerobic respiration in skeletal muscle.

Example Question #4 : Glycolysis

What is the location of glycolysis?

Possible Answers:

The outer mitochondrial membrane

The cytosol

The mitochondrial matrix

The intermembrane space

Correct answer:

The cytosol

Explanation:

The first step of respiration is glycolysis. All of the steps of glycolysis take place in the cytosol of the cell; this allows prykarotes to perform glycolysis, as well as eukaryotes.

Once pyruvate is generated from glycolysis, it is transported to the mitochondria to complete the citric acid cycle. The electron transport chain, the final step of cellular respiration, is located on the inner mitochondrial membrane, and utilizes the proton gradient in the intermembrane space.

Example Question #5 : Glycolysis

Which of the following is not true of glycolysis?

Possible Answers:

It is anaerobic

It produces four net ATP

It occurs in the cytoplasm

It produces NADH

It requires an input of ATP to begin

Correct answer:

It produces four net ATP

Explanation:

Glycolysis produces four total ATP molecules, but only produces two net ATP. The process requires an initial investment of two ATP to initiate the glycolysis pathway. By using two ATP and producing four, there is a net production of two ATP.

Glycolysis is an anaerobic process that occurs in the cytoplasm. In addition to making ATP, glycolysis also generates NADH, which goes to play a role in the electron transport chain.

Example Question #6 : Glycolysis

Which of the following is not a product in the net reaction for glycolysis?

Possible Answers:

ADP

Pyruvate

NADH

Water

ATP

Correct answer:

ADP

Explanation:

The glycolysis reaction follows two step. The initiation requires the input of two ATP, which become converted to ADP. Later in the process, however, four ADP are required to produce four ATP products. ADP is consumed in a greater quantity than it is produced, eliminating it from the net products.

Example Question #9 : Biochemistry And Metabolism

What type of enzyme is responsible for initiating the process of glycolysis?

Possible Answers:

Phosphorylase

Kinase

Hydrolase

Phosphotase

Correct answer:

Kinase

Explanation:

The initial reactants for glycolysis are glucose, ATP, ADP, and NAD+. The final products are pyruvate, ATP, ADP, and NADH. To get from glucose to pyruvate, a number of enzymes are needed. While knowing the names of each enzyme is not usually necessary, it is important to have a general understanding of the glycolytic process. The first step is phosphorylation of the reactant glucose, which is accomplished by hexokinase in most cells, and by glucokinase in the liver and pancreas specifically. The resultant glucose-6-phosphate then continues through the remaining steps in glycolysis to produce pyruvate.

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