Glycolysis & Fermentation Quiz Questions

The Krebs cycle, also known as the citric acid cycle, is a series of chemical reactions that occur in the mitochondrion. It is an essential part of cellular respiration, where glucose is broken down to produce energy in the form of ATP. The mitochondrion is the powerhouse of the cell and is responsible for generating most of the cell's energy. Therefore, it is correct to say that the Krebs cycle occurs in the mitochondrion.

In glycolysis, glucose is broken down into pyruvate. This process occurs in the cytoplasm of the cell and is the first step in cellular respiration. During glycolysis, glucose is converted into two molecules of pyruvate, producing a small amount of ATP and NADH in the process. Pyruvate can then be further metabolized in the presence of oxygen to produce more ATP through the citric acid cycle and oxidative phosphorylation.

Before entering the Krebs cycle, pyruvate undergoes a series of enzymatic reactions to be converted into acetyl-CoA. This conversion occurs in the mitochondria and involves the removal of a carbon dioxide molecule from pyruvate, resulting in the formation of acetyl-CoA. Acetyl-CoA then enters the Krebs cycle, also known as the citric acid cycle, where it undergoes further reactions to generate energy in the form of ATP. Therefore, acetyl-CoA is the correct answer as it is the molecule that is formed from pyruvate before entering the Krebs cycle.

During glycolysis, a 6-carbon sugar diphosphate molecule, known as glucose-6-phosphate, is split into two 3-carbon sugar phosphate molecules, called glyceraldehyde-3-phosphate. This process is the first step in the breakdown of glucose and occurs in the cytoplasm of cells. The splitting of the 6-carbon sugar diphosphate allows for further processing and energy production through the subsequent steps of glycolysis. Therefore, the statement that a 6-carbon sugar diphosphate molecule is split into two 3-carbon sugar phosphate molecules during glycolysis is true.

In the electron transport chain, NADH transfers electrons along with protons (hydrogen) to the chain. This process occurs during cellular respiration, where NADH is produced in the previous steps of glucose metabolism. The electrons and protons are then passed through a series of protein complexes in the electron transport chain, ultimately leading to the production of ATP. Therefore, the statement that electrons enter the electron transport chain when NADH transfers them there along with protons in the form of hydrogen is true.

During a single glycolysis run, one molecule of glucose is broken down into two molecules of pyruvate. This process produces a net gain of 2 NADH molecules and 2 ATP molecules. The conversion of glucose to pyruvate involves several enzymatic reactions, including the production of NADH through the reduction of NAD+ and the production of ATP through substrate-level phosphorylation. Therefore, the correct answer is 2 NADH and 2 ATP.

Under anaerobic conditions, glycolysis occurs in the absence of oxygen. The end product of glycolysis is pyruvate, which is then converted to lactic acid through a process called fermentation. This allows the production of ATP to continue in the absence of oxygen. Therefore, the correct answer is lactic acid.

ATP synthase is an enzyme responsible for the synthesis of ATP. It utilizes the energy from the proton motive force, which is generated by the movement of protons across the cell membrane, to convert ADP (adenosine diphosphate) to ATP (adenosine triphosphate). This process is known as oxidative phosphorylation and occurs in the inner membrane of mitochondria in eukaryotic cells. The energy stored in ATP can then be used by the cell for various metabolic processes, such as muscle contraction, active transport, and synthesis of macromolecules.

In the Krebs cycle, also known as the citric acid cycle, the initial reaction involves the addition of a 2-carbon molecule, acetyl-CoA, to a 4-carbon molecule, oxaloacetate. This reaction forms a 6-carbon molecule, citrate, which is then further metabolized in a series of reactions to produce energy in the form of ATP. Therefore, the correct answer is that the initial reaction involves the addition of a 2-carbon molecule to a 4-carbon molecule.

The statement is false. A single "turn" of the Krebs cycle involves only two decarboxylation reactions, specifically the conversion of isocitrate to alpha-ketoglutarate and the conversion of alpha-ketoglutarate to succinyl-CoA. Therefore, the statement that it involves four different decarboxylation reactions is incorrect.

During aerobic respiration, the last carrier protein transfers a pair of electrons to oxygen. This is because oxygen is the final electron acceptor in the electron transport chain, which is the last stage of aerobic respiration. Oxygen accepts the electrons and combines with hydrogen ions to form water. This process is crucial in generating ATP, the energy currency of the cell, through oxidative phosphorylation.

A single "turn" of the Krebs cycle will yield 1 ATP, 3 NADH, and 1 FADH2. This is because during the Krebs cycle, one molecule of ATP is produced through substrate-level phosphorylation. Additionally, three molecules of NADH are generated through the reduction of NAD+ to NADH, and one molecule of FADH2 is produced through the reduction of FAD to FADH2. This ATP and the reduced coenzymes NADH and FADH2 are important in the subsequent electron transport chain, where they donate electrons and protons to generate more ATP.

The statement is false because the electron transport chain does not shuttle protons and electrons to NADH. Instead, it shuttles protons and electrons from NADH to generate ATP through oxidative phosphorylation. NADH is a product of the citric acid cycle and glycolysis, and it donates its electrons to the electron transport chain to create a proton gradient that drives ATP synthesis.

The electron transport chain in bacteria is located in the cell membrane. This is because the cell membrane is responsible for maintaining the integrity of the cell and controlling the movement of substances in and out of the cell. The electron transport chain is a series of proteins and molecules embedded in the cell membrane that help generate energy in the form of ATP. This location allows for efficient transfer of electrons and the production of ATP to support the metabolic processes of the bacteria.

Under aerobic conditions, the end-product of glycolysis is not further reduced to yield more ATP. Instead, it enters the citric acid cycle (also known as the Krebs cycle) where it undergoes further oxidation to produce ATP through oxidative phosphorylation. This process occurs in the mitochondria and is a key step in aerobic respiration. Therefore, the correct answer is False.